"Land and Food Systems, Faculty of"@en . "DSpace"@en . "UBCV"@en . "Baker, Robert Arnold"@en . "2012-03-01T20:57:54Z"@en . "1952"@en . "Master of Science - MSc"@en . "University of British Columbia"@en . "A study involving variation in strains of the potato scab organism as isolated from a soil in British Columbia is reported. Associated with this is a study of soils from scab-free and scab-infested areas.\r\nExchange capacity and related studies of a number of soil samples indicate a trend toward higher average exchange capacity, higher average exchange calcium and higher average calcium-potassium ratios in the samples from scab-infested areas. There is also a trend toward higher organic matter content and lighter soil textures in the scab-producing soils. In spite of these trends no definite correlations can be established under the method of soil sampling adopted.\r\nThirty-four strains of Streptomyces scabies isolated from diseased White Rose tubers grown on the ranch vary markedly in cultural characteristics and in pathogenicity. The effect of hydrogen ion concentration on four of these strains shows a positive correlation between pH, amount of growth and hydrogen ion concentration up to the optimum pH of 7 to 8 and beyond this range a negative correlation exists. The inhibiting acid pH is 3.4 for two strains and between 4.0 and 5.5 for the other strains. The limiting alkaline pH appears to be beyond pH 11.6.\r\nMicrophotographs of the Streptomyces scabies show typical open spirals and chains of conidia 0.5 to 1.0 microns in diameter.\r\nScab control measures conducted in pots in the greenhouse and using a severely scab-infested soil sample from the ranch indicate no control by mercuric chloride applications. Applications of sulphuric acid, sulphur and calcium hydroxide indicate that a pH of 8.0 or greater is an effective but not complete control. An acid pH of 5.0 gives less control than pH 8.0 and more acidic reactions give even less control. The applications of these necessary to effect control are too high to be of practical value.\r\nThe fungicidal effect of compound P-162 as determined under laboratory procedures is no indication of its efficacy in the field or greenhouse. Laboratory technique indicates that most strains are completely inhibited at 100 to 230 parts per million of compound P-162 while in the greenhouse tests 40 parts per million proved effective in giving partial control. The practical value of P-162 in the field is as yet to be determined since its commercial value and its usefulness as a control measure in the field is unknown."@en . "https://circle.library.ubc.ca/rest/handle/2429/41072?expand=metadata"@en . "STREPT0EYCE3 SCABIES AUD-ITS HABITAT by ROBERT, ARNOLD. BAKER A THESIS SUBMITTED' IN PARTIAL MJLPILMEOT OF THE- RE^UIREMEBTS: FOR THE DEGREE OF MASTER. OF SCIENCE. IN AGRICULTURE i n the Department of Agronomy (S o i l s ) C-,y 1 We accept t h i s thesis as conforming to the standard required: from candidates f o r the degree- of MASTER. OF SCIENCE IN AGRICULTURE Member\u00C2\u00AE of the Department of Agronomy ( S o i l s ) THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 1952 STREPTOMYCES SCABIES AND ITS HABITAT (Abstract) A study involving v a r i a t i o n i n strains of the potato scab organism as i s o l a t e d from a s o i l i n B r i t i s h Columbia i s reported. Associated with t h i s i s a study of s o i l s from scab-free and scab-infested areas. Exchange capacity and related studies of a number of s o i l samples indicate a trend toward higher average exchange capacity, higher average exchange calcium and higher average calcium-potassium r a t i o s i n the samples from scab-infested areas. There i s also a trend toward higher organic matter content and l i g h t e r s o i l textures i n the scab-producing s o i l s . In spite of these trends no d e f i n i t e correlations can be established under the method of s o i l sampling adopted. Thirty-four strains of Streptomyces scabies i s o l a t e d from diseased White Rose tubers grown on the ranch vary markedly i n c u l t u r a l c h a r a c t e r i s t i c s and i n pathogenicity. The e f f e c t of hydrogen ion concentration on four of these str a i n s shows a posi t i v e c o r r e l a t i o n between pH, amount of growth and hydrogen ion concentration up to the optimum pH of 7 to \u00C2\u00A3 and beyond t h i s range a negative c o r r e l a t i o n . e x i s t s . The i n h i b i t i n g acid pH i s 3.4 f o r two s t r a i n s and between 4.0 and 5.5 f o r the other s t r a i n s . The l i m i t i n g a l k a l i n e pH appears to be beyond pH 11.6. Microphotographs of the Streptomyces scabies show t y p i c a l open s p i r a l s and chains of conidia 0.5 to 1.0 microns i n diameter. Scab control measures conducted i n pots i n the greenhouse and using a severely scab-infested s o i l sample from the ranch indicate no control by mercuric chloride a p p l i c a t i o n s . A p p l i -cations of sulphuric a c i d , sulphur and calcium hydroxide indicate that a pH of $.0 or greater i s an e f f e c t i v e but not complete control. An acid pH of 5.0 gives less control than pH 8.0 and more a c i d i c reactions give even le s s c o n t r o l . The applications of these necessary to e f f e c t control are too high to be of p r a c t i c a l value. The f u n g i c i d a l e f f e c t of compound P-162 as determined under laboratory procedures i s no i n d i c a t i o n of i t s e f f i c a c y i n the f i e l d or greenhouse. Laboratory technique indicates that most strains are completely i n h i b i t e d at 100 to 230 parts per m i l l i o n of compound P-162 while i n the greenhouse tests 40 parts per m i l l i o n proved e f f e c t i v e i n giving p a r t i a l control. The p r a c t i c a l value of P-162 i n the f i e l d i s as yet to be determined since i t s commercial value and i t s usefulness as a control measure i n the f i e l d i s unknown. . ACKNOWISDGMENTS: The writer wishes, to; express h i s appreciation to Dr. D.G. L a i r d and Dr. C.A. Howies of the Dept. of Agronomy ( S o i l s ) , U.B.C-. f o r t h e i r encouragement, h e l p f u l c r i t i c i s m s and the use of laboratory f a c i l i t i e s . Sincere appreciation i s expressed to Dr. RJS;. litz;patr.ick and. Dr. IT..S-. Wright of the Dominion Slant Pathology Laboratory and to Dr.- W\u00C2\u00BBC. Gibson of the Grease C l i n i c Research Unit f o r the use of photographic equipment. The. author also, wishes to acknowledge the help of Mr. L. Gilmore and the. operators of Richmond Farms, Soda Creek, B.C'., i n the c o l l e c t i o n of s o i l samples and providing the data r e l a t i v e to the hiatdry, climate and a g r i c u l t u r a l practices on the farm. F i n a l l y the author wishes, to express h i s appreciation to his. wife who not only a s s i s t e d m a t e r i a l l y but also, put up with his. idiosyncrasies during the course of t h i s atudy. TABLE 03? CONTENTS INTRODUCTION I REVIEW OF LITERATURE; 3 The causative agent of common potato scab 3 V a r i a t i o n within strains of Strepto-myces scabies. 4 Presence of Streptomyces scabies i n the s o i l . 5 The e f f e c t of pathogen on the host. 6 Control measures 7 Dips 7 Breeding for resistance to scab 8 Influence of s o i l organic matter and \u00E2\u0080\u00A2j microbial populations. 9 E f f e c t of. s o i l moisture, aeration and temperature. 10 EXPERIMENTAL 12 History of the area 12 The s o i l s under study 15 Chemical study of s o i l samples 16 Buffer capacity of s o i l sample XVIII 20 B a c t e r i o l o g i c a l counts of s o i l samples. 23 Streptomyces studies 25 I s o l a t i o n of strains of Streptomyces scabies^ 25 Proof of i d e n t i t y of the streptomyces i s o l a t e s 27 Greenhouse pathogenicity t r i a l s 29 R e i s o l a t i o n of the inoculated organisms 34 I s o l a t i o n from the tubers. 34 I s o l a t i o n from the quartz sand 34 Morphology of the Streptomyces scabies i s o l a t e s 35 S u s c e p t i b i l i t y of s t r a i n s to hydrogen ion concentration 36 Methods for control of scab incidence 46, Influence of s o i l r eaction 47 E f f e c t of increased aeration 52 E f f e c t of mercuric chloride 54 Influence of Compound P~l62 55 E f f e c t of P-162 on Streptomyces scabies s t r a i n s under study. 56 Greenhouse t r i a l s with P\u00C2\u00BBl62 6 l SUMMARY AND CONCLUSIONS 63: BIBLIOGRAPHY APPENDIX I \u00C2\u00AB- Micro- photographs of representative Isolates of Streptomyces scabies, str a i n s under study. APPENDIX I I - Composition, of media used i n t h i s study. TABLES Table I Table II Table. I l l Table IT Table. V Table VI Table: VII Table VIII Table IX Base exchange analyses of s o i l samples 18 Total counts of fungi, bacteria and. actinomycetes of s o i l . samples 24 Cu l t u r a l i d e n t i f i c a t i o n , of Streptomyces scabies isolates; 28 Streptomyces i s o l a t e s grouped . according to type of l e s i o n 31 I n i t i a l and f i n a l pH. of medium i n which Streptomyces. scabies strains are grown for. 21 days, at 27\u00C2\u00B0C. 39 The e f f e c t of. s o i l reaction i n the control of common potato scab, $1 The e f f e c t of s o i l r e a c t i o n and aeration i n the control of common potato scab 53 E f f e c t of. mercuric chloride In the control of common potato scab 55 The f u n g i s t a t i c and fungi-c i d a l e f f e c t of Compound: P-162 on Streptomyces scabies i s o -l a t e s 59 Table X E f f e c t of Compound P-162 as a control f o r common potato scab 62 FIGURES F i g * 1 Richmond Farms, Soda Creek, 14 B.C.. F i g . 2 Sulphuric acid buffer, curve of sample; No* XVIII. 21 F i g . 3 Calcium hydroxide buffer curve of sample No. XVIII.. 22 F i g . 4 The e f f e c t of hydrogen Ion concentration, on. Streptomyces. scabies s t r a i n 27* 41 Fig.. 5 The effect of hydrogen ion concentration on Streptomyces scabies s t r a i n 33\u00E2\u0080\u00A2- 42 F i g i 6 The ef f e c t of. hydrogen ion concentration on Streptomyces scabies s t r a i n 39 \u00E2\u0080\u00A2 43 F i g . 7 The ef f e c t of hydrogen ion concentration on Streptomyces scabies s t r a i n 48* 44 F i g . 8 The e f f e c t of hydrogen ion concentration on Streptomyces scabies eastern s t r a i n . 45 F i g . 9 Typical samples of tubers with r a t i n g they were given. 48 1. INTRODUCTION \"Common scab 1 1 of the potato had been recognized for many years, p r i o r to the turn of the present century yet l i t t l e or no attention had: been focused upon i t . This, i s apparent from a statement by Bolley (7) who reported i n 1893:-At present**.the disease i s so common an accompaniment of the crop that l i t t l e attention, seems to be given the matter i n the making of s a l e s . Scabbed and f a i r skinned potatoes are bought and sold as i n d i f f e r e n t l y as are large: and small eggs* The only point markedly noticeable i s that, when there i s a, chance f o r the exercise of choice, the smooth product i s always selected.. Despite: t h i s obvious lack of i n t e r e s t , an awaken-ing to the seriousness of the disease was becoming apparent during the f i r s t decade of the present century, but the pro-blem was not squarely faced, i n the United States nor i n Can-ada, u n t i l about 1918 and 1919 r e s p e c t i v e l y . During these years both countries established potato grades which were based on a number of factors including s i z e , and freedom 1 2 from blemishes* This provided the stimulation necessary to focus the attention of research workers on potato scab con-trol.,, but the problem i s s t i l l f a r from being s a t i s f a c t o r i l y solved. Potato scab has, u n t i l recently, been of minor importance i n B r i t i s h Columbia but with the? extension of ^ commercial potato production into many areas- of the I n t e r i o r i t s control i s becoming a problem of major Importance. Iso-lated instances of serious scab i n f e c t i o n have been reported and one of these, from the Cariboo, has prompted the study reported at t h i s time. S o i l i s the natural, habitat for the organism r e s -ponsible f o r potato scab, and yet, some s o i l s produce scab when planted to. potatoes while others do not, even on the one ranch and within a l i m i t e d area. S o i l differences are therefore being investigated, as are stra i n s of the organism and the response: of these to various, treatments. 3 2. REVIEW OF LITERATURE. The causative agent of common potato scab. Thaxter (103) i n I89O was the f i r s t to isolate; and prove the pathogenicity of the organism responsible f o r common potato scab. He named h i s Isolate Oospora scabies and gave a short description of i t s , morphology and i t s e f f e c t on the potato tuber. The present nomenclature of \"Streptomyces scabies\" came about i n two d i s t i n c t steps. F i r s t , Gussow (35) i n I.914 recognized the: s i m i l a r i t y between Oospora scabies of Thaxter and the Actinomyces bo v i s of Harz. Since Harz 1 generic name had precedence Gusaow placed the scab organism with the Actinomyces. Waksman and He n r i c i (108) were r e s -ponsible f o r the change of nomenclature from Actinomyces to Streptomyces. Their change; was. necessitated by the r e a l i z a -t i o n that Actinomyces bovis d i f f e r e d from the other members of t h i s genus both p h y s i o l o g i c a l l y and morphologically and since, as. already mentioned,, Actinomyces bovis had precedence the new. generic name of Streptomyces was adopted. Thus the organism responsible f o r the production of potato scab eame to be known as Streptomyces scabies (Thaxter) Waksman and He n r i c i * The genus i s described as being s t r i c t l y aerohic and composed of true mycelium, that m u l t i p l i e s by chains of conidia from a e r i a l hyphae* 4 . V a r i a t i o n within strains, of Streptomyces scabies* It has become obvious that many st r a i n s of Strepto- myces scabies ex i s t i n t h e i r natural environment, the s o i l * Both Waksman Cl06) and G i l l e s p i e (29) have pointed out the v a r i a b i l i t y of di f f e r e n t s t r a i n s i n t h e i r tolerance to a c i d i t y * Waksman found that, while some strains f a i l e d to grow, i n a r t i f i c i a l media of PH5*6* others grew slowly at PH4*8* G i l l e s p i e observed the same type of EH v a r i a t i o n when using t a r t a r i c a c i d to increase the hydrogen i n con-centration of h i s medium. & pos i t i v e tyrosinase reaction i s given as a distinguishing c h a r a c t e r i s t i c of Streptomyces scabies yet Waksman (106)= i n 1922 claimed that not a l l strains of the organism do produce a brown pigment i n t y r o s i n . This l a t t e r f a c t has also been observed by D o u g l a s 1 ^ 1952. M i l l a r d and Barr (74J, i n England proved that the v a r i a b i l i t y of the pathogen makes i t s e l f apparent i n the type of lesions produced by i n d i v i d u a l s t r a i n s . Thus, they showed that eleven d i f f e r e n t strains produced varying types of scab le s i o n s and only one of the eleven produced the same type of l e s i o n as Thaxter*s o r i g i n a l i s o l a t e . P h y s i o l o g i c a l and morphological variations existed between a l l these st r a i n s * Schaal (90) concludes that new p a r a s i t i c races of Streptomyces scabies may a r i s e from variants produced either Personal communication. 5. i n the s o i l or on the tuber. Leach et a l . (53) observed that whereas a potato var i e t y may be r e s i s t a n t to one s t r a i n of Streptomyces scabies, another s t r a i n w i l l produce severe scabbing on that same tuber v a r i e t y . For instance, Cayuga potatoes, a normally scab-resistant v a r i e t y , have been shown to be severely scabbed by two d i f f e r e n t s t r a i n s of Streptomyces scabies (41). Thomas (104) observed that s i x physiologic races of Strepto- myces scabies varied markedly i n t h e i r pathogenicity on ten d i f f e r e n t potato v a r i e t i e s . Bresence of Streptomyces scabies i n the s o i l . Pratt. (82) and Lutman (58). have presented evidence showing that the scab organism Is Inherent, i n some s o i l s and not necessarily brought i n through the introduction of d i s -eased tubers. They planted scab-free, d i s i n f e c t e d tubers on v i r g i n s o i l and harvested severely scabbed erops. Further observations by Lutman (59) indicate that scab w i l l return a f t e r f i v e to s i x years of continuous potato cropping on land previously under a varied, nineteen-year r o t a t i o n of crops other than potatoes. M i l l a r d (73) on the other hand found severe scab i n the f i r s t potato crop grown on land that had been i n permanent pasture f o r the previous f i f t y years. That the actinomycetes spores and mycelium may exist i n a. viable state over a period of years i s indicated by Lutman (6l) who reported the presence of such spores and mycelium i n the i n t e r i o r of thoroughly disintegrated potato humus a f t e r a. period of three to seven years.-The e f f e c t of pathogen on the host. The outward appearances of the scab pustules or lesions are well known, but the port of entry of the actino-mycete and i t s subsequent a c t i o n on the tuber are not too c l e a r . Both Fellows (24) and Lutman (56), are of the opinion that i n f e c t i o n of the tuber occurs through the stomata at the time of t h e i r conversion to l e n t i e e l s . At t h i s point i n tuber development the epidermis of the new and incompletely-formed corky layer i s ruptured to expose the parenchyma c a l l s underneath. Fellows found that i n f e c t i o n occurred only at the a p i c a l or growing end of the tuber. H i s t o l o g i c a l sections of these infected tubers showed that the e f f e c t of the a c t i n o -mycete filaments extended along the phellogen of the c e l l s of the subepidermal layer, by way of the middle l a m e l l a which became thickened and darkened* Lutman has concluded that the actual scab of.the diseased tuber i s due to the hypertrophy of the c e l l s of the cork cambium. The condition i s always accompanied, i n deep scab, by an abnormal inereaae i n the c e l l s of that layer, due to the continued regeneration of the cork cambium layer from the outer c e l l s of the starch parenchyma. The c e l l s of the hypertrophicd area are greatly thickened due to t h e i r suberisa-t i o n * I h i l e comparing susceptible and r e s i s t a n t v a r i e t i e s of tubers Lutman ('57) observed that r e s i s t a n t russet v a r i e t i e s were characterized by close-textured l e n t i c e l s p a r t l y buried under the skin surface and f i l l e d with small c e l l s that some-what protected the tuber from i n f e c t i o n . Darling (19) con-firmed Lutman*s observation, and further found that, i n the case of r e s i s t a n t v a r i e t i e s , the periderm was. suberized ear-l i e r and extended further into the l e n t i c e l s . Thus there resulted a shorter i n f e c t i o n period and greater protection of the underlying meristematic tissues from the i n f e c t i n g a c t i n o -mycete. Hot only does Streptomyces seabies a f f e c t the tuber but i t also causes necrotic lesions on the potato stems. This has been demonstrated by Hooker (38), Hooker and Kent (40) and by Lutman (.62). Although the potato i s the main host f o r the patho-genic Streptomyces scabies, i t i s not the only plant that i s infected by the organism. Hooker (38) reported that a single culture of Streptomyces scabies that caused root necrosis on potato s i m i l a r l y affected seedlings of barley, oats, onion, tomato, egg plant, squash, red beet, carrot, parsnip and Lima bean. Lefebv.re C54);\u00C2\u00BB too, has reported the presence of Streptomyces scabies on radish grown i n Alaska. Control measures. Dips. The e a r l i e s t control measure against potato scab was the use of H d i p a % . or a d i s i n f e c t i o n of the seed tubers. B o l l e y 8 . (7) i n 1893 recommended the use of b i c h l o r i d e of mercury at a. 311000 d i l u t i o n . He found mercuric chloride more e f f e c t i v e than either Bordeaux mixture or potassium sulphide. In 1898 Garman (28) i n Kentucky stated that corrosive sublimate was e f f e c t i v e as a control,, while formol was r e l a t i v e l y i n e f f e c -t i v e . Work by Jones (46), Coons, (16)> Blodgett and Howe (6) and Cairns: (10) indicated, that formaldehyde and mercuric chloride were e f f e c t i v e c o n t r o l measures. These were superior to a v a r i e t y of organic and inorganic compounds tested at varying concentrations. Contrary to the above, Sanford (87) reported absolutely no control from the use of seed tuber disin f e c t a n t s i n f i e l d t r i a l s on severely infected s o i l * Breeding for resistance to scab. Lutman (57) and Darling (19) have observed that russet potato v a r i e t i e s appear more r e s i s t a n t to scab i n f e c -t i o n than smooth-skinned potatoes. They at t r i b u t e d t h i s ad-vantage to the nature of the l e n t i c e l s of the russet v a r i e t y . Darling concludes from h i s progeny breeding tests that the occurrence of r e s i s t a n t seedlings and t h e i r breeding behaviour may r e s u l t i n the development of scab-resistant v a r i e t i e s of commercial value. Krantz and Side (50) i n 1941 confirmed Darling*a observations and conclusions. On the other hand Morris and Afanasiev (77) reported that, of twenty-six potato v a r i e t i e s tested i n Montana, only f i v e produced over f i f t y percent.healthy tubers. Of these f i v e v a r i e t i e s , two v a r i e t i e s produced over ninety percent scab-free tubers and none showed 100% resistance. In t h i s connection, and as already discussed, i t i s in t e r e s t i n g to observe that a potato v a r i e t y may be r e s i s t a n t to one s t r a i n of Streptomyces scabies and susceptible to another. Influence of s o i l organic matter and m i r c r o b i a l populations. M i l l a r d (73) showed that scab may be i n h i b i t e d by l i b e r a l applications of green manure to the s o i l . By way of explanation he assumed that scab organisms; l i v e saprophytically on organic matter so long as i t i s present. When t h i s source of food i s depleted, the organism attacks the potato para-s i t i c a l l y . In l a t e r work with Taylor (75) however, he modi-f i e d his. ideas and concluded that the b e n e f i c i a l e f f e c t of green manuring i s due to suppression of Streptomyces scabies by the increased numbers of bacteria and other actinomycetes observed to exercise an i n h i b i t o r y influence on Streptomyces scabies. The lack of control by s o i l organic matter as observed i n some circumstances was. explained as being due to a high degree of a c i d i t y suppressing b a c t e r i a l numbers, and yet, M i l l a r d i n a previous paper (.73) reported that the scab organism i s absent from peat s o i l s of a low PH. In c o n t r o l l e d laboratory experiments Goss (32) found that severity of scab was; correlated with amount of inoculum i n the s o i l and the amount of inoculum was1 affected by degree of competition of other s o i l microorganisms. He found that manure f i l t r a t e s , contained organisms i n h i b i t o r y to 10 hi s s t r a i n of Streptomyce s s c ab i es: but a pure s t r a i n of Streptomyces praecox was. i n e f f e c t i v e * Other, workers ( 4 , 89) nave shown that additions: of soybeans, rye, and clover: a l l a i d i n reducing scab at s o i l reactions, optimum f o r Streptomyces scabies a c t i v i t y * The con-t r o l e f f e c t has been attributed to b i o l o g i c a l changes p a r t i s c u l a r l y i n the rhizosphere. Lochhead (55) bas indicated that the percentage incidence as well as. t o t a l numbers of sapro-phytic actinomycete3 antagonistic to Streptomyces scabies are greatly increased i n the rhizosphere, of potatoes grown on a soybean-cover-crop-treated s o i l * In f i e l d experiments Goss and, Afanasiev (33) found long rotations more e f f e c t i v e than short rotations i n reducing scab* In a four year r o t a t i o n with potatoes i n the l a s t year, manure had no e f f e c t when applied at the beginning of the. r o t a -t i o n . When the manure was applied i n the year of potato p l a n t -ing, both y i e l d and scab increased., but percentage scab a c t -u a l l y decreased. E f f e c t of s o i l moisture, aeration and temperature* A l l m icrobiological l i f e i s affected by conditions of moisture, aeration and temperature, and Streptomyces scabies i s no exception.* Jones and McKinney (47) suggested that per-haps temperature was. a factor i n producing scab-free potatoes under f i e l d conditions. They observed that i n c e r t a i n areas i n Europe where temperature was. generally cooler than i n potato 11 scab, areas, of the United States, clean potato crops could be produced continuously on the same p l o t . Their observations l e d them to conclude that there was a greater prevalence of scab i n Wisconsin during the warm summers than i n northern Maine where cool summers predominated.. Goss (32) however, i n controlled experiments, found that temperatures: ranging from below 22.\u00C2\u00B0C to 30\u00C2\u00B0C had no ef f e c t on the severity of scab i n u n s t e r i l i z e d s o i l s , yet s t e r i l i z e d s o i l s inoculated with Streptomyces scabies showed l e s s scab at temperatures below 22\u00C2\u00B0C than at higher temperatures* I f One may assume that cool summers, and greater p r e c i p i t a t i o n go, together, then the: work of M i l l a r d (73) and Sanford (84, 85 > 88) may better explain, the preliminary ob-servations; of Jones, and McKinney. M i l l a r d and Sanfiord showed that 'scab i s more prevalent i n dry s o i l s than i n wet ones;: for example, s o i l s at 12^ and 18^ moisture gave severely scabbed, tubers while, s o i l s at 28^ moisture gave almost 100% clean tubers. Sanford found no apparent temperature ef f e c t at 14\u00C2\u00B0C and 22\u00C2\u00B0C. The conclusions drawn are that moisture clogs the pores of the s o i l , reduces: aeration and i n h i b i t s the pathogen*s a c t i v i t y * On the other hand, and based on the work of Dippenaar (88)- and Goss (32), the moisture e f f e c t may be due to a greater antagonistic population i n the wet s o i l s * Both Dippenaar and Goss found a higher percentage of a c t i n o -myces, than bacteria, i n dry s o i l s while, i n the wet s o i l s the bacteria predominated* 12 3. EXPERIMENTAL The Cariboo country, p a r t i c u l a r l y that portion-l y i n g between Williams. Lake and Quesnel, holds; promise of becoming an important seed potato producing area,. There i s , however, one factor m i l i t a t i n g against the success of the venture and that i s the prevalence of common potato scab* I t s presence on the s o i l s of Richmond Farms,, which are l o c -ated adjacent to the Prince George Highway a few miles north of Soda. Creek, has necessitated the abandonment of White Rose as a va r i e t y f o r t h i s ranch. S o i l from badly infected f i e l d s ; on thi s ranch was chosen for the 3tudy reported at t h i s time* History of the Area* The area was, home steaded i n 1859 and u n t i l 1946 was u t i l i z e d primarily for stock graaing on the slopes while; the f l a t s were retained permanently for a l f a l f a , hay production. In 1946, 16 acres of White Rose and Netted Gems were planted i n f i e l d s 12, 13 and 14 as shown on map* Excellent y i e l d s resulted with both v a r i e t i e s but the White Rose potatoes; Jgrown on the slopes were severely scabbed* Nevertheless the newly broken area planted: i n 194?\u00C2\u00BB including a l l of or parts of f i e l d s 4 to< 11. i n c l u s i v e showed no evidence of s,cab. The h i s t o r y of the area for the. ensuing three years may be best expressed by indi c a t i n g the ro t a t i o n used which Reference Figure- I , Map of Richmond,Farm. 13. i s as follows:-l s t year - oats seeded to a l f a l f a . 2nd year - a l f a l f a . 3rd year - a l f a l f a , cut for hay and the aftermath turned under. 4th year - potatoes 5th year - potatoes or ro t a t i o n repeated. In June 195\u00C2\u00B0\u00C2\u00BB when s o i l samples; were secured for study, the f i e l d s were under the following, crops:-F i e l d 4 (east h a l f ) - oats H 4 (west h a l f ) - potatoes \u00E2\u0080\u00A2* 5 - oats \" 6. ~ oats \u00E2\u0080\u00A2\"\u00E2\u0080\u00A2 7 - a l f a l f a . \" 8 - potatoes 9 - a l f a l f a F i e l d s 12, 13 and 14- a l f a l f a , , timothy and clover mixture and no longer included i n the r o t a t i o n be-cause of th e i r high scab i n f e c t i o n . F e r t i l i z e r s are applied by placement at the time of the potato, planting. In 1949, 400 pounds per acre of 6-30-15 was applied to a l l f i e l d s . In 1950,the Netted Gems received 600 to 700 pounds per acre of 2\u00C2\u00ABl6-6 while the White Rose: received fOO, pounds per acre of 4-10-10* Potato tops are burned as soon as. possible a f t e r removal of the crop* The f i e l d s are furrow i r r i g a t e d two or three- times, during the growing season, the f i r s t i r r i g a t i o n usually Fig.. 1. Plan of Richmond. Farms,, Soda Greek,. B.C. Key: - a) - F o o t of slope \"**)' Approx. scab boundary - east side, i s scabby area. c) - D i r e c t i o n of slope dJI -XVII- Location and numbering of s o i l samples m e ) l - 14 - Operators numbering of f i e l d s with acreages:. 15* occurring i n mid or late J u l y . The source of i r r i g a t i o n i s McLeese Lake situated i n the adjacent h i l l s some three miles away. While no accurate records are available on the climate of the area, a. few general observations on p r e c i p i t a -t i o n and temperature may be made. The annual p r e c i p i t a t i o n averages from 14 to 16 inches, the large proportion of which occurs, as r a i n which i s f a i r l y well d i s t r i b u t e d throughout the year. Summer temperatures average. 70 to 75\u00C2\u00B0^' with few ex- \u00E2\u0080\u00A2 tr.emes of 92.\u00C2\u00B03?. Spring f r o s t s continuing u n t i l the end of May or beginning of June determine- i n large measure the time- of planting* Occasional, night frosts; hare been noted during summer months. The s o i l s under study. Potatoes grown on ce r t a i n areas, of the ranch are more, subject to scab than those grown elsewhere on the farm,, hence i t was. reasoned: that s o i l differences may account for the variations i n scab prevalence. With th i s i n mind s i x samples of s o i l from non-scabby areas, and eleven samples from scabby areas were c o l l e c t e d f o r laboratory study.. Reference to P i g . I w i l l disclose the approximate locations from which these seventeen samples were taken. S o i l sample XVIII was, c o l l e c t e d by the farm opera-tors from f i e l d s 12: and 14 i n July 1951. Total sample weighed 2-500 pounds and on a r r i v a l at the. greenhouse was thoroughly mixed to ensure homogeneity of sample, and then spread out to 16 a i r dry.. Chemical study of s o i l samples* Total exchange capacity and exchangeable bases; were determined by the ammonium acetate method of Schollenberger and Simon; (92)\u00C2\u00BB while organic matter was; determined by the wet combustion potassium dichrornate method of Peach et a l . (81)* Soil. pH*s were determined: on the Beckman Model G- pH meter foX-lowing A.O.A.C. procedures: and textures; were done manually and confirmed by Mr. A* Tzogoeff of the S o i l Survey D i v i s i o n of the Dominion Experimental Farms Service at the University of B r i t i s h Columbia* For convenience the r e s u l t s of the foregoing analyses, as given i n Table I, are arranged with the s i x scab-free samples,\" I, I I , I I I , V, VI and VII,. followed by the data on scab\u00E2\u0080\u0094infested samples* The r e s u l t s do not appear to indicate any outstanding differences between the scab-free and scab-infested samples. However i n analyzing these r e s u l t s the method of sampling must be borne i n mind. Extremes, of v a r i a t i o n that occur may have been smoothed out had a composite sample been taken from each f i e l d . This was not done and hence variations that exist within a. single f i e l d are made apparent. Thus, the method of sampling may explain why one, or even two or three, samples vary markedly, from the rest of the samples, within the scab-free or scab-In-fested, areas. Textures indicate that the non scabby samples are heavy textured, except sample VTI, while the scabby samples are 17. l i g h t textured with the exception of sample XI I I . While e v i d -ence i s not forthcoming that texture i s a decisive f a c t o r In the incidence: of scab yet the fact that the: causative organism i s an obligate aerobe suggests:, at l e a s t , that the difference i n aeration between heavy and l i g h t soils, may be a f a c t o r . Support f o r t h i s reasoning comes from Sanford (84) who con-cluded that excess moisture i n the s o i l , at the time of tuber formation reduces aeration, thus c u r t a i l i n g actinomycete a c t i v i t y , and reducing the l i k e l i h o o d of tuber i n f e c t i o n * S o i l reaction shows no s i g n i f i c a n t differences:, the f i r s t s i x samples of Table: T, representing non-scabby s o i l s , have a. pH. range of 6\u00C2\u00BB4 to 7*2 while- the other twelve samples range from pH: 5\u00C2\u00BB5 t\u00C2\u00A9 7*2* S i m i l a r l y , organic matter does not appear to have exerted any influence on scab i n f e c t i o n . While the range i s s l i g h t l y higher i n the scab-infested s o i l s , being from 5*11# to 10.84^ as compared to 4.02^ to 6.58^ f o r the clean soils.,, s t i l l there are s i x samples of the former s o i l s that show organic matter contents: lower than the two highest of the scab-free s o i l s . Since no hydrogen was indicated i n the ammonium ace-tate s o l u t i o n a f t e r the s o i l s had. been leached,, and since sodium was not determined quantitatively, the difference between the t o t a l exchange capacity and the sum of the determined cations, calcium, magnesium and potassium, is, included as hydro-gen plus sodium* I t w i l l also be noted that samples IX, XV\" and XVII indicated no hydrogen plus; sodium and t o t a l s of calcium, Table I Base exchange analyses of s o i l samples Sample Texture pH % ' To t a l exchange Ca Mg K H Ratio of No. Organic capacity-m.e./ plus CatK Matter 100 gms. oven- Ha dry s o i l m.e./lOO gms. oven-dry s o i l . I Clay 6.8- 5*73 24*83 12.42 5*06 5*51 1*84 2.25:1 I I Clay 61.6 4.02 19*31 9.96 4*82 4.34 0.19 2*3:1 I I I Clay 6.6 4*75 22.62 12.64 5*31 3.84 Q.83 3.3:1 ( s i l t y ) 51.60 - \u00E2\u0080\u00A2 V H 6.4 6.58 17*86 7*61 5*87 20.26 3:1 VI B 6.5 6.58 63*80 I9.88 8*69 6.78 28.44 2*9:1 VTI Gravelly 7\u00C2\u00BB\"2. 5*54 28.40 14.56 6*85 6.45 0.54 2*2:1 Loam .' IV Loam 6*3 7*95 33*59 18.38 -5*75 8.63 0.83 2:1 VIII - Gravelly 7*1 7*25 32.21 17.48 6.23 8.32 0.18 211 Loam IX Loam \"6.6 6*9.0 24.41 18.52 5*01 3*41 5*4:1 X Gravelly \u00E2\u0080\u00A25*5 6008- 28.80 14.08 4.80 1.98 7.94 7:1 Loam \u00E2\u0080\u0094 \u00E2\u0080\u00A2 XI Sandy 6.5 7*83. 29.74 18.74 6.90 3*09 1.01 6:1 Loam 5.73 0.06 . 17:1 XII 7*2 6.82 29*39 22.30 1.30 XIII S i l t y c l a y 6.3 5*11 27.64 15.50 6.83 2.32 2:*99 6.6 s i Loam -5:1 XIV Loam( s i l t y ) 6.2 5*67 33*30 19.52 7.01 3*82 2*95 XV Si It-Loam 6.6 5*89 24.65 16*88 6.89 7*36 2*3:1 XVI Lsamfsilty) 6.3 5.14 32.40 16.66 6.89 8.49 O.36 2:1 XVII Loam 6.6 6.06 20.6G. 12*48 5*07 3*54 3*5:1 XVIII Loamc, 6.6 10.84 47.40 26.07 11.00 9*05 1.28 3:1 19. magnesium and potassium exceeded the t o t a l exchange capacity* This difference i s probably due to soluble salts- being present i n the s o i l independent of the exchange complex. As i s evid-ent from the data there is; a. wide range i n t o t a l exchange capa-c i t y . This may be due i n part at l e a s t to the fact that each s o i l sample represents that from a single l o c a t i o n rather than a composite i n order to bring out the v a r i a t i o n e x i s t i n g i n the s o i l for each area. Samples from the scab-free area i n d i -cate a range i n exchange capacity from 19*3 m.e/iOQ gms.; to: 63.8 while the scab Infested samples present present a. much narrower range and l y i n g within that already-noted. -. . I t -..is con-cluded, therefore,, that exchange- capacity of these s o i l s i s not related to incidence of scab. v > Individual cations of the exchange complex indicate a s i m i l a r s i t u a t i o n . A review of the work of Schroeder and Albrecht (93) indicates that with a calcium potassium r a t i o of approximately one ecab incidence i s at i t s lowest. Using hydrogen saturated clays and then adjusting calcium potassium l e v e l s to between 0 and 100 m i l l i e q u i v a l e n t s , Schroeder and Albrecht found that* irrespective of pH l e v e l , less scab occurred when Ca.K was at 60.50 m i l l i e q u i v a l e n t s than at the r a t i o s 0:50, 100:50, 60:10 or 60:100. Gries et a l . (34) found a s i m i l a r e f f e c t , but the scab incidence depended upon which cation was controlled i n 20. order to reduce the r a t i o . They found that reducing the calcium potassium r a t i o by increasing potassium and holding calcium constant increased scab while i f potassium was held constant; and calcium decreased to reduce the r a t i o , scab de-creased. The calcium potassium r a t i o s recorded i n Table I are a l l greater than 1:1. Although higher r a t i o s tend to predominate; i n scabby samples, s t i l l there are those samples which show a r a t i o comparable to the r a t i o s recorded for the non-scabby s o i l s . Hence i t must be concluded that the calcium potassium r a t i o has, not exerted any s i g n i f i c a n t e f f e c t on scab incidence i n these f i e l d s . Buffer capacity of s o i l sample XVIII. Since s o i l sample XVIII was to be used for exten-sive greenhouse studies a. knowledge of i t s buffering capacity was; e s s e n t i a l . The buffer curves, as presented i n Pigs. 2 and 3, were prepared by shaking 10 gram samples of the s o i l with a l i -quots of 0.4 H-H2SO4 or 0.04 N-ea(pH) 2 made up. to a t o t a l v o l -ume of 100 mis. The samples were: shaken on the r e c i p r o c a l shaker f o r 2 hours and then l e t stand 48 hours. At the end of t h i s time the pH*s of the suspensions were determined on the Beckman Model G pH meter, and these results plotted against weight of acid or base required to a t t a i n that, pH. Thus the amount of aci d or base required for a desired pH i n any desired g i g . 2. Sulphuric a c i d buffer curve of Sample Ho. XVIII H 23 weight of s o i l may be r e a d i l y calculated. A. c r i t i c a l examination of the buffer curves shows that while the s o i l i s s l i g h t l y buffered i n the range pH 9.0 to 10.4, the aci d curve shows no buffering e f f e c t u n t i l pH 3 i s reached. Under these conditions one should expect r e l a -t i v e l y consistent greenhouse or f i e l d r e s u l t s provided the ac i d or base added i s i n a reactive form. B a c t e r i o l o g i c a l counts of s o i l samples. B a c t e r i a l counts were made on a l l samples by the p l a t e - d i l u t i o n technique* Suitable d i l u t i o n s were plated using glucose peptone agar adjusted to pH4*5 f o r the fungi counts and sodium albuminate agar adjusted to pH6.8 f o r the ba c t e r i a l and actinomycetes counts. An endeavour was made to separate actinomycetes and b a c t e r i a a f t e r a seven days i n -cubation period, but such a separation i s sometimes d i f f i c u l t i n borderline cases. Where any doubt existed the colony was placed with the ba c t e r i a . The r e s u l t s , as expressed i n Table I I , are as d i f f i - * c u l t to analyze as were the re s u l t s f o r exchange capacity* A l l counts average higher i n the scabby s o i l s than i n the non-scabby s o i l s . This i s p a r t i c u l a r l y apparent, i n the case o f the fungi but not as noticeable for the bacteria and strepto-myces* However -both high and low counts occur i n both s o i l s and ranges are s i m i l a r * Insofar as the ratio, of one species to the other i s concerned, the bac t e r i a actinomycetes ratio i s 24 Table I I . T o t a l counts of f u n g i , bacteria, and actinomycetes per gram of s o i l IV VIII IX X XI XII XIII XIV XV XVI XVII XVIII Sample No* of No* of No. of No. fungi bacteria actinomycetes x 10,000 x 10,000 x 10,000 I 1.3 173 40 II 1*3 16 o 30 III 1.2 80 30 V 2*9 7\u00C2\u00A9 26 VI 4-3- 800. 300, VII 4 .6 320 100 1*6 20.0 2 .0 2 .6 42*6. 31*3 17.0 8.3 13.3 39-0 36*3 17*0 i l l 170 200 90 470 150 210 233 42 60 53 36 130 53 1\u00C2\u00B0 83: 370 850 143: 130 250 the only one that i s similar throughout. The somewhat higher fungi counts i n the scab-infested s o i l s makes any r a t i o involving t h i s species lower when computed for those s o i l s . Although no d e f i n i t e c o r r e l a t i o n exists between numbers of fungi, bacteria or actinomycetes and scabby or non-scabby samples* t h i s does not preclude the p o s s i b i l i t y that organisms have no e f f e c t i n the control of scab i n these f i e l d s . However, to adequately determine whether or not antagonistic effects are: present would require extensive studies of the physiology of the numerous groups of organisms, present, and a. comparison of the b a c t e r i a l equilibriums i n 25. the: various s o i l samples* A study based on the n u t r i t i o n a l requirements of the various* groups, of organisms and a com-parison of the \"Bacterial. Balance Index\"\" as formulated by Loch'head (55) may be ind i c a t i v e of the b i o l o g i c a l d i f f e r -ences between scab-infested and scab^free s o i l s and explain t h e i r proximity to one another. Streptomyces- Studies. I s o l a t i o n of st r a i n s of Streptomyces: scabies. Infected tubers were c o l l e c t e d from the 195\u00C2\u00A9 crops grown on the s o i l s already reported, upon* These, i s o l a t e d tubers represented those, with severe deep le s i o n s , small sur-face lesions-, or simple r us setting of the skin. - They were stored a t 40\u00C2\u00B0F u n t i l required f o r study. In preparation for i s o l a t i o n of the organism, sur\u00C2\u00AB-face of the tuber was. thoroughly cleaned with soap and water* Following this,, treatment with hydrogen peroxide as recom-mended by Shapovalov (94): or with mercuric chloride as. recom-mended by Ken Knight and Muncie (49) proved i n e f f e c t i v e i n eliminating contaminants such as. fungi: when concentration of disinfectant had been increased to the point where contam-inants ceased to appear the scab organism had also been des-troyed. The detergent \"Tide* was, f i n a l l y adopted f o r remov-ing contaminants; from the surface of the tubers. Scabby 26. portions were; s l i c e d off. the tubers: by means' of a s t e r i l e , s c a l p e l and placed i n tubes, of s t e r i l e , water* These were macerated by means of a, s t e r i l e , glass rod and the suspension plated i n the usual manner. A number of d i f f e r e n t media were used f o r plating;: these included nutrient agar, potato dextrose agar, a. t h i n glucose agar* sodium asparaginate g l y -c e r o l agar, asparagin glucose agar j egg albumen agar and s o i l extract agar. No one medium however was, markedly superior to the others* The plates were incubated at 27\u00C2\u00B0C and aft e r seven days sixteen streptomyces-like isolates: were picked. Later twelve a d d i t i o n a l colonies were picked from smeared p l a t e s . Another procedure involving the use of * T i d e w followed by submerging the tubers, for three minutes i n a one to one P e r f e x - s t e r i l e water s o l u t i o n (100) resulted i n an a d d i t i o n a l twenty three i s o l a t i o n s . Thus f i f t y - o n e i s o -l a t i o n s i n a l l were made from the various media and held f o r further study. A l l . i s o l a t e s were seeded on sodium asparaginate gly c e r o l agar slopes and incubated at 27\u00C2\u00B0C. Upon preliminary examination following seven days incubation, t h i r t y four isolates, appeared as t y p i c a l streptomyces, i.e.,. growth was of a. tough leathery consistency, a. white to grey a e r i a l mycelium was apparent, and most i s o l a t e s gave? evidence of a yellow-brown to. brown pigment. Por purposes of comparison a. s t r a i n of the organism, 2?. Streptomyces scabies, was obtained from J.K. Richardson, of the Dominion Plant; Pathology Laboratory,, St. Catharines, Ontario'. This organism had, been is o l a t e d from a potato scab l e s i o n and had been proven to have strong p a r a s i t i c c a p a b i l i t i e s . Proof of identjly of the streptomyces i s o l a t e s . The description of Streptomyces scabies as; pre-sented by Bergey (8) served as a. basis f o r i d e n t i f i c a t i o n of i s o l a t e s . Cultural, c h a r a c t e r i s t i c s of the 35 i s o l a t e s were observed on nutrient agar, glucose asparagin agar and t y r o s i n agar, and i n mannitol yeast extract asparagin f l u i d medium and litmus, milk. The i s o l a t e s were also tested for the hydrolysis of starch and the reduction of n i t r a t e s to n i t r i t e s . The data are presented i n Table III and are r e -potted as ^positive\",, negative results; being l e f t blank. A \" p o s i t i v e * report r e l a t i v e to each medium indicates that the i s o l a t e conforms to the growth characteristics; which may be described as follows:-Litmus milk - brown r i n g with greenish tinge; coagulated;, peptonized with alka-l i n e reaction. Tyrosin agar - tyrosinase reaction positive with grey-white a e r i a l mycelium. Starch agar - thin, transparent spreading growth. Starch, i s hydrolyzed. N i t r i t e s produced from n i t r a t e s . Brown soluble pigment formed. The two main tests f o r the; separation of Streptomyces 28. Table I I I . C u l t u r a l i d e n t i f i c a t i o n of actinomycetes i s o l a t e s . &. a Production of pigment on; o o M 8 \u00E2\u0080\u00A2 C bOH bp O OJ H fl H p , *H ctf +3 M a 0) M a o -P bp a) >>jd 4^ Pi O to -H win 3 c 3 m \u00E2\u0080\u00A2 o u \u00E2\u0080\u00A2<-{ u ' \u00C2\u00ABH +s aj h to P M 3 -H *d .\u00C2\u00A3 g o o cs u u vi e ra u 8 u H f jCfl ; !tJ \u00C2\u00A3} 0 0 + 3 o d \u00C2\u00BB CO +>bD CO +\u00C2\u00BB cs oa ' > > 01 W ^ H EH CU saj 08 [2. J * ft \u00C2\u00AB i o f M - pcj 1 2 3: 4 I 9 10; 11. 12 13 ^ 16 17 22. 27 30 31 32 33 34 35 37 38 39 41 45 47 48 49 .50 51 E . I . Notes:- (1) See context for int e r p r e t a t i o n of data. (2) n E . I . M i s the i s o l a t e obtained from Plant Pathology Laboratory, St. Catharines,, Ontario. pes. p o s p o s p o s p o s p o s p e s pos . p o s POS: p o s pos. p o s p o s p o s p o s pos p o s p o s p o s pos. p o s p o s pos pOS p o s pos p o s p o s pos; pos. p o s p o s p o s pos. pos. pos. pOS: POS p o s pes. pos . p o s p o s pos. p o s p o s pos:. pos. pos; POS. pos. pos. POS:. p o s pos p o s p o s p o s pos : p o s p o s pos; p o s POS: p o s p o s p o s POS: p o s pos; p o s pos p o s p o s p o s pos p o s p o s p o s p o s p o s p o s p o s g o s p o s pos. pos . pos ; p o s p o s p o s p o s p o s p o s pos. p o s p o s POS p o s p b 3 POS: p o s p o s p o s pOS; p o s p o s p o s p o s p o s p o s p e s p o s p o s p o s p o s p o s pos pos. p o s pos p o s p o s p e s p o s pos p o s : POS p o s p o s p o s p o s POS: p o s p o s pos p o s p o s p o s p o s p o s p o s p o s p o s p o s p o s p o s p o s p o s p o s p o s p o s w p o s pos; pos pos: p o s p o s pos p o s p o s p o s p o s pos, p o s 29. scabies from other species are a p o s i t i v e tyrosinase reaction and the production of a brown rin g on milk. Bergey states that a posit i v e tyrosinase reaction i s the primary separatpry feature. A review of Table I I I reveals that a l l isolates: under study were t y r o s i n p o s i t i v e and one h a l f produced: the t y p i c a l brown r i n g i n milk and reduced n i t r a t e but not nec-e s s a r i l y the same ones. A l l but eight hydrolyzed starch. While only three Isolates showed \" p o s i t i v e \" i n every respect, i t i s concluded from the c u l t u r a l data.submitted that the 35 i s o l a t e s are t y p i c a l Streptomyces scabies or variants of the same. Afanasiev ( l ) , Douglas of Ontario A g r i c u l t u r a l College and the Dominion Plant Pathology Laboratory at St. Catharines have shown that strains of the scab- organism are not consistent i n a l l c u l t u r a l c h a r a c t e r i s t i c s . Greenhouse pathogenicity t r i a l s . White Rose seed pieces aft e r submerging f o r 15 minutes i n 1::1000 mercuric chloride, solution were planted i n quartz sand i n 8-inch pots previously treated! with 1:500 s o l u -t i o n of mercuric; c h l o r i d e . While the quartz sand, was not s t e r i l i z e d i t was tested f o r the presence of actinomycetes with negative results,. Por inoculation purposes, the t h i r t y - f i v e i s o l a t e s were grown i n 3,0 mis. of mannitol yeast extract asparagin 30. f l u i d medium.. Before using, the culture f l a s k s were shaken to break up the mycelial mat as much as; possible. The. whole, medium plus, growth,- was: then added to the surface of a. pot and a l i g h t watering was: given to f a c i l i t a t e washing the growth into the region of tuber formation. Inoculum was added to the plants 28, 45 and 65 days a f t e r planting.. While a. single pot was used f o r each i s o l a t e under study t h i r t e e n check pots were d i s t r i b u t e d throughout the greenhouse, as a precautionary measure i n case of need.. Nutrient, solutions containing magnesium sulphate, potassium chloride, ammonium n i t r a t e , monocalcic phosphate and ferrous sulphate were added, to a l l pots, once every two weeks-. Extreme caution was exercised to guard against organisms being carried from pot to another* Water was. added approximately efrery other day s u f f i c i e n t to maintain the t u r g i d i t y of the plants* At the time of watering the greenhouse f l o o r s were thoroughly dampened to keep dust at a. minimum* For the control, of insect pests:, and p a r t i c u l a r l y white f l i e s , the greenhouse section was. treated twice during the growing season with Para,-thion* Fourteen weeks after planting the tubers were harvested and the presence or absence of scab lesions recorded* At the same time a. sample of the quartz sand surrounding the roots and zone of tuber formation was taken i n s t e r i l e p e t r i p l a t e s . Owing to 31 the small size of the tubers i t was. sometimes d i f f i c u l t to d i s t i n g u i s h t y p i c a l scab l e s i o n a . Where this, d i f f i c u l t y existed i t was assumed that the tubers were free of severe scabbing and they were described as having \" a t y p i c a l small spots\". The number of tubers per plant ranged from 6 to 23 with an average of 12 per pot* Examination of the tubers revealed that there was a side range i n pathogenicity of the various i s o l a t e s tested. They may be c l a s s i f i e d into 3 categories; as follows, 1) those producing russetting and a t y p i c a l extremely small ( l cm. or l e s s i n diameter) l e s i o n s . -2) those producing russetting and t y p i c a l scab lesions; of a diameter exceeding 1 mm. but not exceeding 3 mm. i n diameter,. 3) , those i s o l a t e s producing t y p i c a l lesions of 2 mm. or greater diameter and producing a deep corky type of l e s i o n of no determinate shape. A. grouping of the Organisms i n accordance with the type of lesions produced i s presented i n Table IV: Table XV. Streptomyces Isolates grouped according \u00E2\u0080\u00A2 to type of l e s i o n Category Isolate 1 I, 2, 5, 8 , 11, 12, 13, 30, 51* 2 3., 4, 6, 7, 10i, 15, 16, 22, 31, 32, 33, 35, 38, 41, 47, 49, 50-3 9, 17, 27, 34, 37, 39,. 4 5 , 48, Eastern s t r a i n . 32 In respect to the check pots, those grown i n the immediate v i c i n i t y of the inoculated pots showed, occasional evidence of russetting and a few tubers showed the, a t y p i c a l small spots. However the check pots: set out at a. distance from th4 inoculated pots gave clean tubers i n a l l cases. These results, provided further evidence that no; pathogenic strains of actinomycetes were present i n the quartz sand, nor were any disease-producing organisms present i n the tap water used f o r watering. These pathogenicity studies, provide further evid-ence that the 35 i s o l a t e s represent s t r a i n s of Streptomyces scabies, however there i s a, wide range i n pathogenicity, as observed i n Table IV. Nine of the 35 s t r a i n s demonstrated d i s t i n c t l y weak pathogenicity while nine were highly patho-genic. Even within each of the foregoing groups there i s a lack of uniformity i n respect to c u l t u r a l c h a r a c t e r i s t i c s as i s evident, from further reference to Table I I I . This v a r i a -tion,however, i s quite i n l i n e with the evidence appearing i n the l i t e r a t u r e . Afanasiev ( l % for instance i n 1937* when studying the comparative physiology of 2$ i s o l a t e s , 7 of which were pathogenic, found that a l l the pathogenic strains and three of the IS saprophytes produced melanin i n the presence of t y r o s i n plus, an a d d i t i o n a l nitrogen source. Taylor and Decker (102) i n 1947 studied the c u l t u r a l 33. c h a r a c t e r i s t i c s of 143 s t r a i n s of actinomycetes;. They found that a b i l i t y to produce t y p i c a l scab lesions on tubers cor-re l a t e d p e r f e c t l y with the production of a dark brown ring of surface growth i n separated milk with or without i n d i c a t o r . The Dominion Plant Pathology Laboratory at St. Catharines showed that 38 out of 39 s t r a i n s producing a brown r i n g on milk were pathogenic, while only one of 30 non-brown r i n g producers was mildly p a r a s i t i c . It was further indicated that tyrosinase reaction positive strains, are brown r i n g p o s i -t i v e and that negative s t r a i n s are also brown r i n g negative. Douglas of the Ontario A g r i c u l t u r a l College, however, has i n d i -cated that pathogenic strains are not necessarily both brown ring p o s i t i v e and tyrosinase r e a c t i o n p o s i t i v e but may be nega-t i v e to one t e s t and. positive to the other. Saprophytic strains on the other hand are negative for both tests; i n the large majority of cases. A l l the i s o l a t e s i n this, study gave a p o s i t i v e t y r o -sinase reaction and a l l but one of the strongly p a r a s i t i c s t r a i n s gave a brown r i n g positive test i n milk. Those i s o l a t e s of medr ium pathogenicity, designated as tt2tt gave variable r e s u l t s i n the milk. Eight of those isolates' were positive brown rin g and nine were negative. Three is o l a t e s recorded as m i l d l y p a r a s i t i c showed po s i t i v e t e s t s on both milk and t y r o s i n . Thus both the s l i g h t v a r i a b i l i t y and the uniformity of these two. tests and t h e i r c o r r e l a t i o n to pathogenicity i s borne out. 34. R e i s o l a t i o n of the inoculated organisms. I s o l a t i o n from the tubers. A representative tuber was selected from each group of potatoes from each pot f o r r e i s o l a t i o n of the pathogen with which that p a r t i c u l a r pot was inoculated. The technique f o r t h i s i s o l a t i o n was s i m i l a r to that previously described, and the t h i n glucose agar was used f o r the p l a t i n g . Where t y p i c a l lesions occurred an i s o l a t e similar to the inoculant was i s o -l a t e d . S i m i l a r i t y was based, on character of growth on nutrient agar, i n litmus milk and on ty r o s i n agar. Thus iCochs postulates have been ca r r i e d to t h e i r fulfilment by, a) i s o l a t i o n of pathogen from host, b) i n f e c t i n g host, with i s o l a t e , and 1 c) r e i s o l a t i o n of same pathogen from the host infected i n (>);. Repeated attempts to i s o l a t e streptomyces from russetted areas or from the a t y p i c a l small spots were unsuccess-f u l . However, as Goss (32) observed, russetting is. a super-f i c i a l form of scab from which i t i s d i f f i c u l t to i s o l a t e actinomycetes. I s o l a t i o n from the quartz sand. R e i s o l a t i o n of the streptomyces i s o l a t e s from the quartz sand was r e a d i l y accomplished at a. d i l u t i o n of 1:100,000. The t h i n glucose agar was used, as the i s o l a t i o n medium. Cultures of the colonies picked from these plates were tested f o r growth 35* characteristics, en nutrient agar, i n litmus milk, and on t y r o s i n agar and compared to both the Isolates from the tubers and the o r i g i n a l inoculum. In only two cases* was there a lack of complete c o r r e l a t i o n . The inoculum of i s o l a t e s 5 and 10 as i s o l a t e d from the quartz sand gave a t y p i c a l r e s u l t s i n litmus milk and on t y r o s i n agar although they d i d produce brown p i g -ment In nutrient agar. Morphology of the Streptomyces scabies i s o l a t e s . Although morphology of organisms, i s not an end i n i t s e l f , s t i l l i t i s an a i d i n the- c l a s s i f i c a t i o n and character-i z a t i o n of many forms of microbiological l i f e . With t h i s i n mind, s l i d e s were prepared a f t e r the technique of Skinner et a l . (95) but with some modifications. Drawn out glass tubing of c a p i l l a r y size and held with p a r a f f i n wax on the s l i d e was used as a support upon which to r e s t the cover g l a s s . A drop of mannitol yeast extract asparagin agar was run under the cover glass, allowed to s o l i d i f y and then a drop of growth suspension added. The prepared s l i d e s were then placed on a piece of \u00C2\u00ABZ B-shaped s o l i d glass rod i n a s t e r i l e p e t r i p l a t e . S u f f i c i e n t s t e r i l e water was added to the plate to maintain a moist atmosphere but not flood, the entire bottom of the p l a t e . The s l i d e s were incubated at 27 \u00C2\u00B0G for at l e a s t s i x weeks. The nature of the medium was such as to prolong the vegetative period of growth without producing f r u i t i n g bodies, hence the long incubation period. As the s l i d e s dried somewhat, 36. conditions became l e s s conducive to vegetative growth and spores began to appear i n ever increasing numbers. \"Spores'1 here may be defined as. those peculiarities of growth which are evident at the ends of the a e r i a l hyphae. These may take a number of forms aa ao ably demonatrated for numerous streptomyces by Brechaler (21) . Generally the sporea of Streptomyces scabiea are long or short chalna of round c o c c i -l i k e forms at the ends of the a e r i a l hyphae. Occasionally s p i r a l forms are evident but they are not formed as extenaively as the spore chaina. Recording the r e s u l t s by means of microphotographic techniques proved t a be an excellent procedure p a r t i c u l a r l y where the conidia-Iike forms appeared. However there was one d i s t i n c t diaadvantage i n that, due to depth of focua, i t was d i f f i c u l t and sometimea impoaaible to get good picturea of s p i r a l forma. Some of these pictures with short descriptions are presented i n Appendix I . S u s c e p t i b i l i t y of atraina. to hydrogen ion concentration. Four of the culturea i a o l a t e d i n t h i a work, and the eastern s t r a i n were chosen for more extenaive atudy. The eaatern i 8 o l a t e was chosen f o r comparison purposes while the other four i a o l a t e a , 27, 33, 39 and 48 were aelected on the baala of t h e i r pathogenicity and t h e i r c h a r a c t e r i a t i c reaemblance to Strepto-myces scabies on various culture media. It i a believed that 37 the l a t t e r four i s o l a t e s are representative of the s t r a i n s causing scab i n the area under study. Thirty ml., portions of mannitol yeast extract asparagin f l u i d medium was dispensed into 12!?-ml erlenmeyer f l a s k s and s t e r i l i z e d . A f t e r s t e r i l i z a t i o n the pH of the i n d i v i d u a l f l a s k s was adjusted with s t e r i l e aliquots of either Q;.04H-H 2S\u00C2\u00A94 or 0.02 B-Ca(OH)2\u00E2\u0080\u00A2 The: f i v e I s o l a t e s under study were grown f o r seven days on mannitol yeaat extract asparagin agar slopes and then 5 mis., of d i s t i l l e d water was added to them. The surface of the growth was l i g h t l y scraped with a flamed loop, the tube agitated, and the suspension added to t h e e f l u i d medium. D i l u t i o n plates of several of these suspensions indicated that s l i g h t l y over f i v e b i l l i o n spores were added per f l a s k and that the inoculum was. reasonably constant f o r a l l f l a s k s . A l l f l a s k s including con-t r o l s of no inoculum were incubated at 27\u00C2\u00B0C f o r 21 days.. At the end of 21 days the growth was f i l t e r e d off by means of sintered glass f i l t e r s ; and dried to constant weight atlI.0\u00C2\u00B0C. The pH of the medium and the percent l i g h t transmittancy as determined with a Ho. 425-B f i l t e r i n the Fisher electrophoto-meter, were both recorded at t h i s time. For graphical presenta-t i o n the photometer reading was, subtracted from 100 and pl o t t e d as \"Intensity of Pigmentation\" rather than n%. l i g h t transmitted.\" jghls had the e f f e c t of inverting the curve and i t was f e l t that 38* by so doing a. better representation of pigment production as related to weight of growth would be given* The i n i t i a l and f i n a l pH of the various media are presented i n Table V* The data tend to confirm Waksman's (105) observa-tions that most strains of Streptomyces scabies, tend to adjust reaction of t h e i r environment i n the d i r e c t i o n of optimum for t h e i r growth* Thus, a d i s t i n c t l y a c i d medium becomes less a c i d i c and a. d i s t i n c t l y a l k a l i n e medium becomes less a l k a l i n e * Since no analyses were done on the medium the precise nature of the changes responsible f o r the a l t e r a t i o n s i n pH are not known* However Waksman (I07) states that since the a c t i n o -mycetes; prefer proteins, to carbohydrates as. a source of energy, ammonia, i s r a p i d l y produced* With protein as the only carbon source ammonia might accummulate to the point where the medium would become too a l k a l i n e for growth* Even when a suitable carbohydrate energy source i s added and acid i s produced, prob-ably a l a c t i c , the tendency i s always toward a maximum a l k a l i n i t y of. pH 8*6 to 8*8* Presumably any acid produced that w i l l tend to. buffer against ammonium i s decomposed to 0:02 a n d H 2 G 3 0 that i t s buffering capacity i s l o s t * Although the foregoing may explain a change of pH from a c i d i c to a l k a l i n e i n the present instance, i t does not explain: a reaction change from extremely alkaline to l e s s a l k a l i n e , Both the phenomena may be explained on the basis of decar-boxyllation. and deamination of the protein i n the media* Since 39 Table Y. I n i t i a l and f i n a l pH of medium i n which. Strepto- myces scabies strains are grown for 21 days at 2 7\u00C2\u00B0C ~ I n i t i a l F i n a l pH of medium o f pH s t r a i n indicated 27 33 39 4-8 E.I, 2.00 2.00 2.05 2.00 2.00 2.00 2.50 2.5a 2.60 2.60. 2.50 2.50 3.OO 3.00 3.05 3.10, 3*05 3..10 3.40 3.40 3.50 3.50 3*45 3.50 4.00 \u00C2\u00A3.00 4.20 4.10 7.20 5.5O 7.00 6.20 6.50, 7.10 7.60 7.IO 6.90 7.60 7.60 8.05 7.50 7*70 7.70: 8.00 , 7.00 8.10 7.30 8.65 8.10 8.10. 7.90 8.00. 8.30 9.00 8.30 8.30 8.10 8.30 8.6O. 9*85 ' 8.30 8.50 8.30 8.40. 8.60 11.60 8.20 8.70 7.90. 8.20: 8.70; ^ Contaminated with f u n g i . decarboxylation accurs i n an acid medium the r e s u l t is, a loss; of CO2 from the medium and a greater concentration of -HEL^groups to increase a l k a l i n i t y . Deamination on the other hand w i l l r e -place decarboxyllation when the environment i s a l k a l i n e . Thus a loss of NH3 r e s u l t s , -GOOH groups become more concentrated and the. pH. becomes less a l k a l i n e . While t h i s s i t u a t i o n holds as a general r u l e i n b a c t e r i a l metabolism, s t i l l actinomycetes. may prove the exception. It contradicts- Waksman1s statements that deamination occurs at a pH of 6 .8 , and that ammoniacal nitrogen w i l l be present i n the medium at this, pH. Further, i t infers, that the change i n reaction i s due, not only to the accumulation of a basic compound but also to the loss of an a c i d i c component of that, compound. S i m i l a r l y the change of pH on the alkaline 40:. side i s due both to a loss of an a l k a l i n e component and an accumulation of an a c i d i c compound. From Figs*. 4 , 5\u00C2\u00BB 6 and 7\u00C2\u00BB a n d 8 , c a n be seen the graphic relationships between pH, growth and pigment production. Generally, there i s a positive; correlation, between pH, weight of growth and i n t e n s i t y of pigment to a. maximum and then a negative c o r r e l a t i o n occurs.. This i s p a r t i c u l a r l y apparent f o r Strepto- myces. 33, 4 8 , and the eastern c u l t u r e . Streptomyces 27 and 39 however show a secondary peak i n growth a f t e r a decrease. The i n t e n s i t y of pigmentation does hot show the same trend for these l a t t e r two s t r a i n s . It i s possible that these two st r a i n s are more r e s i s t a n t to the e f f e c t of pH than are st r a i n s 33, 48 and the eastern i s o l a t e . This i s borne out by the greater t o t a l growth at any s p e c i f i c pH f o r strains 27 and 39. The f a c t that pigment i n t e n s i t y did not increase to a second peak fo r 27 and 39 appears to indicate that there; i s a closer r e l a t i o n s h i p be-tween pigment and pH than between growth and pigment. The optimum pH f o r strains 39,, 48 and the eastern c u l -ture i s between pH 7 and 8 . This also holds f o r s t r a i n 27 i f the second growth increase is. neglected. S t r a i n 33 however shows a s l i g h t l y higher optimum between pH 8.6 and 9 . The f i r s t four organisms confirm Waksman1 s observation (.105) that the optimum pH i s 7*8 to. 8 . In the same work Waksman states that the l i m i t i n g hydro-gen ion concentrations are at pH 5 a n a - 9> However: both 27 and the eastern i s o l a t e show r e l a t i v e l y extensive growth at pH 4 . In the case of st r a i n s 33, 39 and 48 however, the l i m i t i n g pH is. between 41. F i g . 4. The effect of Hydrogen ion concentration on growth and pigmentation. Crosses (x) i n d i -cate growth and c i r c l e s (o) r e -present i n t e n s i t y of pigmentation. 42 . F l g * 5* The effect of Hydrogen ion concentration on growth and pigmentation. Crosses (x) i n d i -cate growth and c i r c l e s (o) r e -present i n t e n s i t y of pigmentation. Fig\u00C2\u00BB 6> The effect of Hydrogen ion concentration on growth and pigmentation. Grosses (x) i n d i -cate growth and c i r c l e s (o) r e -present intensity of pigmentation. 44. F i g * 7\u00C2\u00BB The e f f e c t of Hydrogen ion concentration on growth and pigmentation. Crosses (x) i n d i -cate growth and c i r c l e s (o) r e -present intensity of pigmentation. 4\u00C2\u00A3. a\u00C2\u00BB The e f f e c t of Hydrogen ion concentration on growth and pigmentation. Crosses (x) i n d i -cate growth and c i r c l e s (o) r e -present intensity of pigmentation. 46. 4 and 5-5 and so quite possibly these three organisms, would have been i n h i b i t e d at about, a. pH of 5'. Although i n h i b i t i o n i s indicated on the a l k a l i n e side complete i n h i b i t i o n has not been attained even at pH 11*6. Physiological differences between the f i v e strains are borne out by the varying amounts, of growth and the varying pigment i n t e n s i t i e s at s p e c i f i c pH*s. These differences? are also evident i n the fact that the i n h i b i t o r y a c i d pH i s not. the same f o r a l l s t r a i n s . Methods for Control of Scab Incidence. The s o i l used for the following greenhouse studies has been discussed i n a previous section of t h i s paper. The White Rose var i e t y of potato, was used for a l l gfeenhouse t e s t s . The tubers, f o r planting were supplied by Dr- N.S. Wright of the Dominion Plant Pathology Laboratory, University of B r i t i s h Columbia, and so far as could be ascer-tained, were; free of scab, flea, beetle,, or other common potato diseases. As a further, precaution a l l tubers were submerged fo r 1$ minutes i n a Ls 100.0 solution of mercuric chloride. The knife used f o r cutting the seed pieces waa dipped, into 1:1000 mercuric chloride solution prior to each i n d i v i d u a l cut. Seed pieces were planted immediately a f t e r c u t t i n g . Individual tubers of the crop were rated for scab 47. using the most seriously scabbed tubers, which occurred i n the checks, for comparison and giving them a r a t i n g of B3 , r :\u00C2\u00BB Scab-free tubers were rated as no\u00C2\u00B0 while ratings of \" l w and tt2M were accorded tubers showing a scab incidence between the two ex-tremes. P i g . 9 shows the extent of scab at each i n d i v i d u a l r a t i n g . Only those spots showing black on the photograph are actual scab l e s i o n s . As. an i n d i c a t i o n of the severity of scab under each treatment, every tuber harvested from that set of pots was. assigned a r a t i n g . A l l tuber ratings for that t r e a t -ment were then averaged and recorded as a whole number and dec i -mal f r a c t i o n . Also recorded was the percentage tubers harvested from a p a r t i c u l a r treatment that showed any scab at a l l i r r e g a r d -l e s s of s e v e r i t y . This fi g u r e , expressed as a percent was con-sidered to be the prevalence of scab under that treatment. Influence of s o i l reaction. With the i n i t i a l work of G i l l e s p i e (29) i n 1918 and Waksman (105, 106): i n 1919 and 1922, an aspect of scab control was presented that has. continued to the present time. The above workers found that i n culture media Streptomyces scabies (termed Actinomyces chromogenus by G i l l e s p i e ) was i n h i b i t e d at a pH of 5.0 or lower. Supporting evidence to the e f f e c t that scab may be controlled at a pH of $.2. or lower i s presented by Martin (66, 67), Cook and Houghland, (13) and Cook and Nugent (14, 15). The f i e l d observations of G i l l e s p i e and Hurst (30). and of Blodgett and Howe (6) based on surveys of d i f f e r e n t areas help to confirm the f e a s i b i l i t y of c o n t r o l l i n g scab through 48. TUBER RATING FOR S C A B F i g * 9 Typical samples of tubers given rating as indicated 49. lowering of .pK. On the contrary the findings of Raedar (83)', Dippenaar (20), Taubenhaus (98) and Schaal (91) indicate that an a p p l i c a t i o n of sulphur f a i l e d to. prevent scab.. I t should be borne i n mind, however, that i n these cases the desired pH of 5\u00C2\u00BB2 or lower was not always reached. Eddins (22), Muncie et a l . (78): and Larson et a l . (51) found that although a pH of 5.2 controlled scab, y i e l d was adversely a f f e c t e d . For t h i s study three series of 12-inch pots each containing 10 pounds of s o i l were set up i n t r i p l i c a t e for each treatment. One series involved additions, of HgSO^at rates to provide a. range i n pH from 2 .5 to 5 i n c l u s i v e at 0.5 pH i n t e r v a l s . The H2SO4 was applied at a concentration of 6 normal and at rates calculated from the. a c i d buffer curve of figure 2. A second series covered the same pH range with sulphur as, the amendment. The t h i r d series involved: the addi t i o n of Ca(OH) 2 i n varying amounts to provide a pH range o.f 8 to 10 i n c l u s i v e , applications: being calculated from the base buffer curve of figure 3 . The check consisted of the untreated s o i l of pK 6 . 6 . For details, aa to precise amount of amendment added i n each case and the r e l a t i o n of this, to the ultimate pH of the s o i l , see Table VI. At harvesting, 90 to 100 days a f t e r p l a n t i n g , the tubers were rated f o r scabbiness, and s o i l samples were taken from the region of tuber development for pH determinations. Y i e l d was low r 5o. and size, was small, no more than give tubers being taken from any one pot and the average diameter being 3/4 inch. The r e s u l t s presented i n Table VI indicate that the desired pH has been given by the H2SQ4 and sulphur additions as calculated from the aci d buffer curve of F i g . 2. This may be expected i n the case of treatment of s o i l with 6H H2SO4 which has hydrogen ions immediately a v a i l a b l e to replace exchangeable bases. Sulphur however i s an insoluble element that requires\u00E2\u0080\u00A2 oxidation to H2SO4 before i t s a c i d i c e f f e c t becomes; apparent. That t h i s reaction must have occurred i s evident from the data, so one may conclude that s u l f o f y i n g organisms are abundant and active i n t h i s s o i l . The Ca(0H)2 additions have not shown the same desirable results,. This Is not unusual since the Ca(0H) 2 would be r a p i d l y converted to the even more insoluble GaCO^ on being added to the s o i l . Calcium i n the l a t t e r form i s going to act slowly and over an extensive period, of time before the desired pH w i l l be apparent. The extent of scab control i a obvious from the r e s u l t s . Some; control has been exercised by almost a l l amendments, at 1 least insofar as severity of scab i s concerned. The same cannot be said f o r scab prevalence since many cases occur where scab i s less severe but a l l tubers have been infected. This s i t u a t i o n i s p a r t i c u l a r l y apparent i n the case of the H2SO4 and sulphur additions. With these two amendments too, better control i s 51 Table VT. The ef f e c t of s o i l r eaction i n the control of common potato scab. Desired. PH Amendment used Ap p l i c a t i o n lbs/ac. , pH \u00E2\u0080\u00A2\u00C2\u00BB at .harvest Tuber r a t i n g * 2.5 3-0 3*5 4.0; 5*0. H 2 S 0 4 51,938 36,856 28,366 21,574 . 11.586 2.8 3*1 4*06 5*40 4.96 no germinat ion 0.75(100^} 1.75(100^) 1.20 (80%) 1.00(100^) 2.5 3*0; 3*5 4.0 5*0 Sulphur 16,958 12,090 9,150 7,180 3,590; 2*9 3.55 3*05 4.20 5*05 3.00(100^) 2.10(100^) 1.90(100^) 0.83 ( 8 \u00C2\u00AB 0.60 (60^) 6.8 Check aw 6.8 2.60(100^) 8.0 8*5 9*0 10.0 Ca(OH) 2 2,880 5,200 8.490 19,190 7.36 7*73 7*82 8.11 1.70 (80%) 0.50 (50^) 0.83 (66^1 -0.14 (.14\u00C2\u00A7\u00C2\u00A3) See context for explanation of tuber r a t i n g s . indicated at pH 5 than at lower pH*a. The Ca(0H) 2 applications show a straight l i n e r e l a -tionship between amount of appl i c a t i o n , or pH, and both severity; and prevalence of scab. This treatment also indicates better r e s u l t s than the two acid treatments.. A second greenhouse experiment waa set up i n a simi-l a r manner to the f i r s t and included the three lowest a p p l i c a -tions of acid, the four lowest applications of sulphur, and the three highest applicationa of calcium. The reau l t s of this, e x p e r i ment, given i n Table VII, indicate the same trends as are appar-52. ent i n the f i r s t experiment although a c t u a l f i g u r e s may vary s l i g h t l y . E f f e c t of increased aeration. In order to observe the ef f e c t of increased aeration and permeability of the s o i l , sawdust and peat additions were made to pots as set up i n the second experiment. One serie s of pots received two inches of cedar sawdust of no d e f i n i t e s i z e and thoroughly mixed with the s o i l . A second s e r i e s of pots received peat, applied and mixed i n the same fashion as the sawdust. Observation of the plants throughout the experiment indicated no differences i n top growth between s o i l alone, s o i l plus sawdust and s o i l plus peat. The same holds true i n the case of scab control and pH changes, as indicated i n Table V I I . While a few i s o l a t e d cases are apparent where s l i g h t differences do occur, the data are comparable. The r e s u l t s of these experiments on the e f f e c t of r e a c t i o n have confirmed the r e s u l t s of Menzies (76) who found excellent scab c o n t r o l at a. pH of 8 or greater. And they have, at least p a r t i a l l y , confirmed the work of those researchers who lowered pH. i n order to control scab. The difference, of Course, i s i n the fact that scab appeared to become more severe at pH*s lower than 5*0* This factor p a r t i c u l a r l y , contradicts the findings of Oswald and Wright (80) who found better scab control at pH 4 .2 than at pH 5\u00C2\u00BB2. 53 Table. TIL E f f e c t of s o i l r e a c t i o n and aeration i n the control of common potato, scab* Desired Amendment Applica-? pH used t i o h lbs/ac. pH at harvest Tuber r a t i n g 3t -p CQ to 3 (A o EJ ^ o H H s ; H (3 H ca w ft <1> CM c3 H H H H \u00E2\u0080\u00A2r-( \u00E2\u0080\u00A2H b 6 ,b o to to CO -p td td 3 a s \u00E2\u0080\u00A2H b coi in P i 0) H 3*5 H2S04 28.366 3.7 4 .2 4*1 1.42 1.52 i .5 .4 -4.6 70% 4.0 21,574 4 .3 4.3 1*37 100% 1.25 80^ 1.40 73% 1 5.0 11,586 4.9 5.2 4.8 1.10 1.20 0.98 100^ 100$ 92^ 3*0 Sulphur 12,090 3.4 3*0 3.1 2.3 2.1 2.2 10 100^ 100^: 3*5 9,150 3*5 3*3 3*5 2.0 1.17 0.80 IQQ%: 83^. 61% 4.0 7,180 3*8 3*8 4.0 1*7 l - t -100^ 1.0 100^ 83^ 5.0 3,590 4*7 4*7 4.7 0*9 0.82 0.87 7A% 82^: 63^-6.8 Check 6.8 6*7 6 .3 \u00C2\u00A3*8 2.7 2.6 100^ 100^ 100% 8.5 Ga(OH) 2 5200 7*5 7*7 7*5 1.7 1*57 1.54 8490 82^ 89^ 9.0 8.2 810 8.0 0.85 0.45 0.80 8.1 64^ 4 3 * 70% 10 . 0 19190 7*9 8.3 0.10 0.15 0.25 10%' i5\u00C2\u00A3 12^; K See context f o r explanation of tuber r a t i n g 54 E f f e c t of mercuric c h l o r i d e . As: i s the case i n the adjustment of pH f o r scab con t r o l , variable r e s u l t s have been reported concerning the a p p l i c a t i o n of mercury compounds f o r control of scab. Martin (69) i n 1931 reported control of scab by mercurial applications i n one part of Hew Jersey and four years l a t e r (70) he reports increased scab, due to mercurial a p p l i c a -tions, i n a d i f f e r e n t part of the same sta t e . Under Long: Island conditions, Cunningham (17) and Cunningham and Wessels (18) report good control apply-ing yellow oxide of mercury or mercuric chloride at the rate of 4 pounds per acre, while Taylor (99) and Taylor and Blodgett (.101) observed more severe scab through mercuric chloride additions i n western Hew York. Similar r e s u l t s are apparent throughout the l i t e r a t u r e . While one group of workers achieves, a control i n one area another group f i n d increased seabbiness. with the same amendments in another Qn the basis of t h i s controversial data, an experi-ment was set out to test the'efficacy of mercuric Chloride as a scab control measure on the s o i l used i n this, study. Applications were made at the rates of 5, 10, 15 and 20 pounds per acre with the s a l t being added to the pots i n solu-t i o n to ensure a, thorough d i s t r i b u t i o n . 55 From the results:, Table VIII, i t i s obvious that no control has occuned. Table VII I . E f f e c t of mercuric chloride i n the control of common potato scab. Rate of \u00E2\u0080\u00A2 Tuber r a t i n g a p p l i c a t i o n \u00E2\u0080\u0094 \u00E2\u0080\u00A2 Severity of Prevalence of scab; scab 5 1.78 100% 10 2.55 100^-15 2.50 10.0^ 20 2.70 90^ See. context f o r explanation of tuber rating;. Ken Knight (48) showed that, whereas; mercuric chloride would control strains of Streptomyces scabies from one part of the country, i t increased seabbiness. i n the case of s t r a i n s from some other region. He explains that i n cases where the s t r a i n of Streptomyces. scabies vigorously r e s i s t s the e f f e c t of HgCl2, susceptible organisms i n the s o i l are reduced i n numbers thereby permitting the. i n f e c t i n g organism to multiply to a marked degree. Influence of Compound B-162. With the development of innumerable organic f u n g i -cides i t was natural that some attention should, be directed toward potato scab control by these compounds. Michaelson et a l . (72) tested the e f f e c t of 2-4>dichlorophenoxyacetic 56. acid on s i x physiologic strains of Actinomyces scabies, at various hydrogen ion concentrations.. They found that the organisms: could: be i n h i b i t e d i n culture by the ac i d , ester and s a l t forms of 2-4:-\u00C2\u00A9 at concentrations, as low as, 56 parts per m i l l i o n . Garber- et al.. (27) found that pentachloro-phenoxyacet.ic a c i d was. f u n g i s t a t i c f o r one s t r a i n of Strepto-myces, scabies at 32 to 500 parts per m i l l i o n and f u n g i c i d a l at 1000 and 2000 parts, per million.. No e f f e c t was indicated at 0 to 16 parts per m i l l i o n , growth was l i m i t e d at 32 to 64 parts per m i l l i o n and i n h i b i t e d at 125 parts per m i l l i o n . The f i e l d a p p l i c a t i o n of pentachlorophenoyacetic acid has indicated i n h i b i t i o n or growth prevention of Streptomyces scabies, at applications of I and 10 pounds: per a c r e . More scab-free tubers and shallower scab pustules indicated, some c o n t r o l . The Julius Hyman Co. of Denver Colorado (.44) have recently developed, a. chlorinated hydrocarbon which they de-signate as Compound P-162.. Company l i t e r a t u r e dealing with t h i s compound indicates that Streptomyces scabies, i s Inhibited by concentrations as low as 0.4 to 0.6 parts per m i l l i o n of P-162 i n culture medium,, while, f i e l d applications of 40 pounds per acre of the compound show excellent control of common scab i n Colorado. E f f e c t of P-162 on Streptomyces scabies st r a i n s under, study. In order to determine the f u n g i s t a t i c and f u n g i -c i d a l effectiveness of P-162', a series of d i l u t i o n plates 57. were; prepared, ranging from 0 to 2000. ppm. Mannitol yeast extract asparagin agar was used\", as the. growth medium and. was quant i t a t i v e l y dispensed i n tubes before s t e r i l i z a t i o n . Because of the highly v o l a t i l e nature of P-162 i t could not be s t e r i l i z e d , and. had. to, be added, by pi p e t t e i n approximate quantities to each Individual plate at the time of pouring. Even t h i s technique must have resulted i n the loss of a degree of effectiveness of the P-162 for i t s odor was quite noticeable when added to the f l u i d agar-. A f t e r s o l i d i f i c a -t i o n the plates; were streaked with the streptomyces i s o l a t e s . Check plates were carr i e d throughout.. Since compound P - l62 i s almost insolu ,ble i n water the i n i t i a l concentration, i s made up with acetone. One gram of P-162. i n 100 mis of acetone gives a. concentration of 10,000 parts, per m i l l i o n of t o t a l compound. However since P-162 i s only 90.8^ pure the necessary adjustment was made to give the required parts- per m i l l i o n . A l l plates were incubated at 27\u00C2\u00B0C for 14 days and then observed for amount of growth* On a l l plates where growth did not. occur a smear, was. taken and sown onto mannitol. yeast extract asparagin agar, slants, to determine whether the i n h i b i t i o n had been f u n g i s t a t i c or f u n g i c i d a l . The slants were then observed for growth after- 21 days Incubation at 27\u00C2\u00B0C. The r e s u l t s as. presented i n Table IX are s e l f explana-tory.. The majority of organisms have been i n h i b i t e d at 9O..8 to 227 parts per m i l l i o n . Only nine organisms, have withstood a greater than 227 parts per m i l l i o n concentration, none have withstood 1000 parts, per million,, and only five -have been i n h i b i t e d at concentrations less than 9O..8 parts, per m i l l i o n * Streptomyces 47 was most susceptible, to the com-pound while 35 was the most r e s i s t a n t . These r e s u l t s are similar to those of Garber et a l . (27) who tested the f u n g i s t a t i c and f u n g i c i d a l pro-p e r t i e s of pentachlor.ophenoxyac.etic a c i d . Garber. et a l . found, no v i s i b l e e f f e c t at 0 to 16 parts per m i l l i o n , l i m i t e d growth at 3 2 and 64 parts, per m i l l i o n and i n h i b i t i o n at. 125 parts per m i l l i o n . The a c i d proved to be. f u n g i s t a t i c at 32! to 500 parts per m i l l i o n and f u n g i c i d a l at 1000 and 2000 parts per million.. Garber*s. tests- were c a r r i e d out on four d i f f e r e n t species, of organisms including one 3train of Streptomyces scabies. The; J u l i u s Hyman CO. i n t h e i r Release. No. 4 claim that 0.4 to 0.6 parts per million, was i n h i b i t o r y for the p a r t i c u l a r Streptomyces scabies culture they tested. Their technique using a. f l u i d medium and keeping the tubes, of sown medium completely a i r t i g h t i s superior to adding the P-162 to- f l u i d agar i n plates since greater control, i s exercised over the actual concentration i n each d i l u t i o n . As previously mentioned the concentration of a c t i v e P-162. must have been decreased to some extent i n pouring the agar plates used by the w r i t e r . However i t is: f e l t that t h i s loss: would not be s u f f i c i e n t to account for the tremendous discrepancy between the J u l i u s Hyman r e s u l t s and those recorded i n Table IX. \ Table IX. The f u n g i s t a t i c and f u n g i c i d a l e f f e c t of P-162. \u00E2\u0080\u009E ' D i l u t i o n - parts per million. Org. -- - \u00E2\u0080\u00A2 \u00E2\u0080\u00A2\u00E2\u0080\u00A2 -No. 0 0.4^4 0.908 2.27 4.54 9.O8 13.62 22.7 45.4 68.1 90.8 227 454 681 908 1 +++ +++ 4+4 4 4 4 T T T +4+ 4 4 4 4 4 4 4++ +44 c i \u00E2\u0080\u0094 2 11 Ifc \u00E2\u0080\u00A2t it It m It it, \u00C2\u00BB i t at c i 3 tt II II tt n tt It 11 it i t +4 c i 4 i i It It tt i t i t It tt lb \u00E2\u0080\u00A2It* H. c i 5 it tt It 11 i t 115 tt tt?. It +4 4 c i 6 it It II; i t It: It It tt It + St c i 7 m tt It 11? Ifc It tt- 11? tte i t at c i 8 tt Ifc tt t t ti- It l t it. It ++ 4 c i 9 i t It' Ifc Its l t tt tt tfe tt It: 11 4 at 10 it It It II* It It tfe i t t t It tt c i 11 ifc tl? It It tt It i t It tl\u00C2\u00BB tfe at c i 12 Ifc m tr- It It lb m Iti 4 at at c i 13 \u00C2\u00BB Ifc ifc ite It It It? tfe It. at c i - -15 tt It? it i t It It It, i t It + s t c i 16 tt tt it lt< It It It i t It tfe S t at c i 17 m Wr- li- Its lb It It Its It 4 4 S t at c i 22 ite l t Ite tfe tt It It It tt S t S t c i 27 \u00C2\u00BB It It It It It It tfe It 4 4 4 ++4 c i 30 it= lb ifc It It It: It H; tt' tt It at st 31 i t i t I t It- It Hi 4 4 4 + at at c i 32 11, It it i t tt It It 11 It It +4 c i 33 Its It! tt? it? It tt It tti Ifc It tt 4 4 34 tt tt i t It It 4 c i 35 Ifc Ifc tt \u00C2\u00ABs It It +++ 4 4 4 44+ + 4 ++ + 37 . It\" tt: t t It It 44- 4 c i 38 tt tt; lis tt It +4+ 4 4 4 4 4 4 4 4 4 at at c i 39 Ifc It It Ifc tt? i t i t It* at St c i CI c i c i at c i CJl Table IX. - Continued. The fu n g i s t a t i c and f u n g i c i d a l effect of P-162 D i l u t i o n -.parts per m i l l i o n . Org. ' Ha. 0 0.54 0.908 2.27 4.54 9.08 13.62 22.7 45.4 68.1 90.8 227 454 681 908 41 t+4 +V4 4 4 * a t S t c i 45 Ite It* H i It: <\u00C2\u00A54 4 4 -4- c i 47 \u00C2\u00BB lb c i 48 ti- +\u00E2\u0080\u00A2* 4 4 +4 4- c i 49 i t lt ft tt- 4 4 * +44 44 S t c i 50 i t : It; tt: lift Ife 44- 44- 4 S t c i 51 11 Ms tt> it It vllt 4 4 4 4 4 4 +44 4 4 S t c i E . I . u It: II? It: 4+ 44 44 4/ S t c i Noter- l ) The four d i l u t i o n s greater than 1000 p.p.m. and up to 2000 p.p.m. are not shown because obviously they are fungicidals 2); \u00E2\u0080\u00A2at*\" - f u n g i s t a t i c 3) \u00C2\u00B0ci M - f u n g i c i d a l 4) 4, ........ least, growth ......more growth 4+4, ......most growth and comparable, to checks. 61, Since approximately 100 parts per. m i l l i o n i s the i n h i b i t o r y concentration for the organisms reported upon at t h i s time, the loss would hare to amount to over 99$ of active compound to duplicate the 0.4 to. 0 .6 parts per m i l l i o n i n h i b i t o r y concentration claimed by the J u l i u s Hyman Go* The fact that this, i s an a r b i t r a r y procedure only i s admitted by the Ju l i u s Hyman Co. when they state that i t requires,40 pounds per acre to control scab i n the f i e l d . I f this, difference between laboratory r e s u l t s and f i e l d r e -sul t s i s due to loss of active compound by v o l a t i l i z a t i o n , then we can assume that there i s a loss amounting to 97% to 9&%. Reviewing the data as presented i n Table IX, In the l i g h t of a. 9&% loss due to v o l a t i l i z a t i o n , an i n h i b i t o r y concentration of 100 parts, per m i l l i o n would, a c t u a l l y amount to I .36 parts per. m i l l i o n . This concentration i s i n closer agreement with the, company's results, than the data submitted at t h i s time. Greenhouse t r i a l s with P\u00C2\u00AB\u00C2\u00BBl62. A greenhouse experiment was l a i d out involving: applications of 20, 40, and 80 pounds per acre to pots con-t a i n i n g 10; pounds, of s o i l . The compound was: applied i n emul-sion form as. recommended by the company. That compound P-162 may have p o s s i b i l i t i e s as a scab control measure on Richmond Farms i s apparent from the 62 r e s u l t s shown i n Table X. Table. X. E f f e c t of. compound. P-162 as a. control for common potato scab,. 4 Tuber r a t i n g * A p p l i c a t i o n lbs/ac. pH of s o i l at harvest Intensity of scab Prevalence of scab 20. 4.0 80 6.7I 6.70 2.20 1.12 0.45 100% Q7% 45% See context for explanation of, tuber rating.. Thus an a p p l i c a t i o n of P-162 at 80 pounds per acre gives the same control as pH 4 to 5 or\" pH 7.5 to 8 , and at a much lower, a p p l i c a t i o n of amendment than i s nec-essary i n the case of the adjustment of pH.. It i s possible that a. s l i g h t l y higher rate of a p p l i c a t i o n of P-162. would have given complete control of common potato scab i n t h i s s o i l . 63. 4.-\u00C2\u00BB SUMMARY AND CONCLUSIONS. Soils; on one part of a ranch i n the Cariboo demon-strated potato scab of high i n t e n s i t y while those on another part of the same ranch f a i l e d to demonstrate the presence of scab even when a scab sensitive v a r i e t y of potato was: grown. With the method of f i e l d sampling, adopted, laboratory studies of these soils; revealed no consistent differences i n respect t o : -1.) Base exchange involving t o t a l exchange capacity,, degree of base saturation, percent or. proportion of the. various cations and calcium potassium r a t i o , 2) Hydrogen ion concentration,. 3) Organic matter content. 4) S o i l s i n scab-free areas, were predominately clays while with few exceptions, the s o i l s with a high evidence of scab were loams or of lighter, texture.. Thus texture or aeration may be a. factor determining the incidence of scab. 5). B a c t e r i a l counts of scab-infested and scab-free s o i l s showed a higher average of bacteria,, actinomycetes and p a r t i c u l a r l y fungi i n the scab infested samples. The significance of t h i s has. n\u00C2\u00AEt been determined.. 6) T h i r t y four strains of Streptomyces scabies were i s o l a t e d from White Rose, tubers grown on the ranch under .64. study. These isolates, were compared with a s t r a i n i s o -l a t e d by the Dominion Plant Pathology laboratory at St -Catharines, Ontario.. C u l t u r a l c h a r a c t e r i s t i c s of the t h i r t y f i v e strains conformed reasonably well t o descriptions outlined i n Bergey's Manual of Determinative Bacteriology. Four of the st r a i n s answered exactly to Bergey's descriptions i n the tests, c a r r i e d out.., The production of pigment i n t y r o s i n medium and the production of a brownmng i n milk are-accepted, as r e l i a b l e diagnostic tests for separation of. pathogenic and saprophytic s t r a i n s . A l l strains, produced a, brown pigment i n t y r o s i n agar while only nineteen pro-duced a. brown ring; i n litmus \"milk.. When added, to quartz, sand i n which White Rose potato plants were: growing, nine strains; produced mild scab^ seventeen produced moderately severe scab and nine produced severe acab lesions, on the tuber crop. Except i n two cases the organism was r e i s o l a t e d from both the quartz sand and the. new tubers, thus 33; of the i s o l a t e s conformed to Koch's postulates. Va r i a t i o n i n response to hydrogen ion concentra-t i o n was investigated using f i v e s t r a i n s only. The r e s u l t s indicated::-a) Optimum pH range varied with s t r a i n between pH 7 and 8 . b) The s t r a i n s without exception demonstrated a b i l i t y to adjust pH. of medium to a more suitable l e v e l . c) A d e f i n i t e c o r r e l a t i o n existed between pK of medium, 65. amount, of growth and pigment produced* d) C r i t i c a l pH for 3 strains, was above pH 4 while the other two. did not succumb u n t i l about a pH of 3.4. Morphological studies disclosed the reproductive bodies, as s p i r a l s and chains, of c.onidia. which are t y p i c a l of Streptomyces scabies. The t h i r t y f i v e strains,of Streptomyces scabies varied In t h e i r resistance to the effect of compound P - l 6 2 . One s t r a i n was; i n h i b i t e d at 2.27 parts, per m i l l i o n of P-162 while another was. r e s i s t a n t up to. 908 parts per m i l l i o n of the compound.. The majority of. the i s o l a t e s were: completely i n h i b i t e d at concentrations of P-162 ranging from 90.8 to 227 parts per m i l l i o n . Scab control, measures,, using a severely sicab\u00E2\u0080\u0094infested s o i l from the ranch and White Rose seed potatoes, c a r r i e d out i n the greenhouse gave the following r e s u l t s : a.) mercuric chloride applied at 5, 1QV 15 ahd 20 lbs/ac was. ineffective.. b) Sulphuric a c i d applied at. f i v e levels, ranging from 11,500 to 51\u00C2\u00BB000 lbs/ac. and to give a pH range from 5.0 to 2.5 showed best control at 11,500 lbs/ac or pH 5. c) Sulphur applied at f i v e l e v e l s ranging from 3,600 to 17,000 lbs/ac and to give a. pH range from 5 to 2..5 showed best- control at, pH 5* d) Calcium hydroxide applied a t four l e v e l s ranging from 2880 to 19,190. lbs/ac and to give a pH range from 66. 8 to 10 gave an actual pH range from 7*4 to 8.1 and showed best control at 19, 190 lbs/ac or pH 8 . 1 . e}: Sawdust and peat applied to increase aeration had no e f f e c t on size of tubers, y i e l d , or control of scab. f ) Compound P>l62 applied at 20, 40 and 80 lbs/ac showed best control a t 80 lbs/ac. g) It may be concluded that of a l l the amendments studied, calcium hydroxide at 19, 190 lbs/ac gave the best c o n t r o l . This was followed i n turn by P-162 at 80 lbs/ac, sulphur at 3,.6'0Q lb3/ac, s u l -phuric a c i d at 11,500 lbs/ac and with mercuric chloride giving no c o n t r o l . 1 67 BIBLIOGRAPHY Afanasiev, M*M*Comparative physiology of Actinomyces i n r e l a t i o n to. potato scab, Neb. Agr\u00C2\u00BB Exp. St a. Res. B u l l * 92, 2. Artachwager,. E., Studies; on the potato tuber> Jour* of Agr. Res* 27*809-836, 1924. 3* Assoc rn of O f f i c i a l A g r i c u l t u r a l Ghemists, O f f i c i a l and tentative methods of a n a l y s i s j o f the Assoc*n of O f f i c i a l A g r i c . Chemists* 6th edV* Wash-ington \u00C2\u00BB 1945* 4. Atkinson, R.G* and Rouatt, J.W.* The ef f e c t of the incor-poration'of c e r t a i n cover crops on the micro-f l o r a of potato scab infested s o i l , Abstract i n Proceedings of Phytopathology Society, 16\": 15, 1949. 5* Blodgett, E*lff. and Cowan, E.K., Relative e f f e c t s of c a l -cium and a c i d i t y of the s o i l on the occurrence of potato scabAmer.- Pot. Jour * 12*265**274, 1935 c i t e d i n eunningham* H.S. and Wessela, P\u00C2\u00BBH., C o n t r o l l i n g common scab of the potato on Long Island by the- addition of mercury com-pounds and the r e l a t i o n of s o i l reaction to the treatment, N*Y> State Agr* Exp* Sta. B u l l * 685:1-20, 1939* 6* Blodgett, E.M* and Howe*.F\u00C2\u00BBB*\u00C2\u00BB Factors influencing the occurrence of potato scab in_Hew; York,, C o r n e l l Univ. Agr* Exp* Sta* B u l l . * 581.1-12, 1933. 7\u00C2\u00BB Bolley, H.L.. Prevention of. potato scab, N. Dak. Agr. Exp. Sta. 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Edson, H.A. and Shapdvalov, M\u00C2\u00BB, Potato stem l e s i o n s . Jour, of A g r. Resv 14:213,-219, 1918. 2-4. Fellows, H., R e l a t i o n of growth i n the potato tuber to the potato scab disease, Jo\u00C2\u00BBir. of Agr. Res.32. 25\u00C2\u00BB Fred, E.B. and Waksman, S,A.,, Laboratory manual of general microbiology, Hew York, McGraw H i l l , 26. Frutchey, C.Wv and Muhcie, J.H., S o i l treatment with mercurials for c o n t r o l of potato scab, Mich. Agr. Exp. Sta. Quar. B u l l . 16:259-263. 1934. 27. Garber * R.H., SchaaL, L.A., and^ Fults:, J.L., The selec-t i v e a c t i o n of pentachlofophenoxyacetic acid against\" Streiptomyces scabies tTilaxfr.,)' Waksman and H e n r i c i i n culture media, Phytopathology 41.991-996, 1951. 28. Gammaih. S\u00C2\u00BB,^ Potato scab experiments, Kentucky State C o l l . Agr. Exp. Sta. B u l l . 81.5-11, 29\u00C2\u00BB G i l l e s p i e , L . J . . 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H.G.lt.> The balance of caleiumand potassium i n r e -l a t i o n to clubroot of;cabbage and potato scab* Pnytopathology 3 4 . 1 0 0 1 , 1944. 3 5\u00E2\u0080\u00A2 Gussow, K.T*, The systematic p o s i t i o n of the organism of the common potato scab * Science, '\u00E2\u0080\u00A2 F.S*. 39* 4 3 I A 9 1 4 . / 36* Ralstead. B.D*. Experriment avg i t h potatoes, It.-J * Agr* Exp. Sta* Ann* Rpt. 18 ( 1 8 9 7 ) * 276-284, I 8 9 8 . 37 \u00E2\u0080\u00A2 Hildebrand* A* A., McEeeni - W.E*, _ and Koch, L.W., Row Treatment of s o i l with tetramethylthiuram disulphide for control '\u00E2\u0080\u00A2\u00E2\u0080\u00A2of Blacicroot of sugar beet seedlings. I . Greenhouse Tests, Cdn. Jour, o f Res. 2 7 * 2 3 - 4 3 , 3 8 * Hooker, W.J., Parasitism of Actinomyces scabies on various plants. Phytopathology 37*10> I 9 4 f * 39> Hooker, W.J.. A technique for observing tuber enlarge-ment and scab development i n potatoes, Phytopathology 40*390. 1950. 40. Hooker* \u00C2\u00A5.J. and Kent,, G.C., Stem necrosis of potatoes caused; by :j\u00C2\u00A3tctinemyeea scabies, Phytopathology 37*10, 41. Hooker. W.J. and Peterson, G.E., A s t r a i n of Strepto-myces scabies p a r a s i t i z i n g Cayuga potatoes i n Iowa. Plant Disease Reporter. 3 3 * 2 8 2 , 1949 . 42. Hooker, W.J. and Sass* JwE.; Evidence of p a r a s i t i c a c t i v i t y \";of Actinomyces scabies \u00C2\u00A9n seedling roots, (AbstractJ Phytopathology 38*14, I 9 4 8 . 4 3 * Hooker,. W*J\u00C2\u00BB and Page, 0*T\u00C2\u00BB, Potato tuber growth and scabinfectien* (Abstract I Phytopathology 41* 17* 1951. 44. Hyman* J u l i a s and Co., Plant' P/athglogy Release Ho., 4 . Denver 1 . Colorado, 1 9 5 2 * \" 45* Jones, A.F.. The histogeny of potato scab, Ann* App. B i o l . 18*313-W. 1 9 3 1 . ~ 71 46. Jones, L.R., Potato scab, Vermont State Ag* Ex. S t a . B u l l . 28* 2 8 - 3 0 , 1892. 47* Jones* L.R. and FofTi nfiey, E*H\u00C2\u00BB\u00C2\u00BB Influence of s a i l temperaturev&n patato scab. Phytopathology I927V 76. Menzies, J.D., Potato scab control with calcium compounds, Phytopathology 40:968, 1950. 77* Morris, H.E. and Afanasiev, M.M., Testing of d i f f e r e n t potato v a r i e t i e s for t h e i r resistance to scab i n Montana, Phytopathology; 40t.968, 1950. 78. Muncie, J.H., et\u00C2\u00BBal., The effect Of sulphur and acid f e r -t i l i z e r on incidence of potato scab, Amer. Pot. Jour. 21:293-304, 1944. 79. Orellano, Rodrigo, Actihomyces and bacteria antagonistic to Actinbmyces scabies, (Abstract), Phyto-pathology 37:17. I.947. 80. Oswald, J.W. and Wright, B.W., l i e l d ; c o n t r o l : of potato scab i h ' e a l i f o r n i a * f Abstract): Phytopathology 41:29, 1951. 81. Peach, M., Alexander, l . T . , Dean, L.A., and Reed, J.F., Methods of s o i l a n a l y a i 8 for s o i l - f e r t i l i t y investigations;, Washington, D.G.. U.S. Dept. of Agr., 1947\u00C2\u00BB 82. Pratt, O.A., S o i l fungi i n r e l a t i o n to diseases of the I r i s h potato i n Southern Idaho, Jour. Agr. Res. I3:!7^100;, 1918. 83.,Raeder, J.M., Preliminary reaulta with the use of sulphur for the control of potato scab- i n Idaho, Phytopathology 13*512, 1934. 74 84* Sanford,.G/*BV*;- TSe'-relasfctOiB of s o i l moisture to the development of common scab of potato, Phyto- pathology 13:231-236, 1923*. 85* Sanford, G*B*, Some factors- influencing the' develop-ment of potato scab, (Abstract)} Phy topathology 14 : 5 8 , 1924* 8 6 * Sanford, G.B*, Some facto r s affexiting the pathogenicity of Actinomyces scabies:, Phytopathology 16:525-Sanford, G.BV, On trea t i n g potatoes f o r the control of common scah, S c i * Agr* 13:364-373* 1933* 88* Sanford, G.B., Common scab of potatoes i n dry and wet s o i l s , S c i * Agr*. 25 :533-536. 1945* 89\u00E2\u0080\u00A2 Sanford, G.B.-, S o i l borne diseases i n r e l a t i o n to the microflora associated with various crops and s o i l amendments, S o i l S c i * 6 l :9 i -21 1946. 90* Schaal,. L.A., Variations and physiologic s p e c i a l i z a -tions i n the common scab fungus (Actinomyces scabies), Jour, Afer* Res. 69:169-186, 1944T\" 91* Schaal, L.A., Seed and s o i l treatment f o r control of potato) scab, Amer. Pot. Jour. 23:163^17^1946. 9 2 . Sehollenberger^ C. J . and Simon, R.H., Determination of exchange capacityand exchangeable-bases; i n soil-ammonium acetate method, S o i l S c i . 59 : 93* Schroeder, R*A* and Alb*echt> \u00C2\u00A5.A., Plant n u t r i t i o n and the hydrogen ion I I Potato scab, S o i l S c i . 94*. Shapovalov, M.,, E f f e c t of temperature oh germination and growth of the common potato scab organism, Jour, of Agr. Res. 4 :129-135. 1915. 95* Skinner, C.E., Emmons, C;.W* and Tsuchiga, H*M*, Henrici's Molds1,1 Yeasts- and Actinomyces , New York*, John Wiley and Sons, 1947* 96* Statutes of Canada, 1918, Ch* 29,. sec* 337A. Stuart,,. \u00C2\u00A5., The Potato.. New York,, J.B. l i p p l n c o t t , 75 98* Taubenhaus, J . 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Taylor, C.F. and Decker, A c o r r e l a t i o n between pathogenicity a n d c u l t u r a l c h a r a c t e r i s t i c s i n the genus Actinomyces* Phytopathology 37: 49-58, 1947*. 103. Thaxter, R*, The potato scab; Conn. Agr. Exp. Sta. Rpt. PP* 3^4, bl-95, 153-161, I891. 104. Thomas, W.D., Growth and Varia t i o n of s i x physiologic races of Actinomyces scabies on di f f e r e n t culture mediae Phytopathology 37*319*331, 1947. 105* Waksman, S*A\u00C2\u00BB, C u l t u r a l studies of species Actinomyces, S o i l S c i . 8:71-207, 1919* \" \u00E2\u0080\u00A2 ' 106* Waksman, S*A*, The infIiience of s o i l r e a c t i o n upon the growthof Actinomyces causing potato scab, S o i l S c i . 14:61-79, 1922. 107. Waksman, S.A*, The Actinomycetes, Mass*, Chronica. Bbt-anica, Co*, 1950* 108\u00E2\u0080\u00A2 Waksman, S.A. and H e n r i c i , A.T., The nomenclature and c l a s s i f i c a t i o n of the Actinomycetes, Jour. Bact. 64:337-341, 1943. 109* Weindling, R.\u00E2\u0080\u009E Mi c r o b i a l antagonism-and disease c o n t r o l , S o i l S c i . 61:23-30, 1946. APPENDIX I MICROPHOTOGRAPHS OP REPRESENTATIVE ISOLATES Magnification i s X440. APPENDIX II Constitution of the media used i n t h i s study Sodium Albuminate Agar 12.-5 gm 10.0 \" 0*5 B 0.2 \u00C2\u00BB trace 0.25' gm 1000 ml 12.5 gm: 1.0 w 0.5 n 100 ml 90.0 ml x Stock solut i o n of s o i l e x t r a c t . This i s prepared by heating 1000 gm. of garden s o i l with 1000 ml of tap water i n the autoclave, for 30 minutes. A small amount of. CaCO^ i s added and the whole f i l t e r e d through a double paper, f i l t e r . . The tu r b i d f i l t r a t e should be poured back onto the f i l t e r u n t i l i t comes through c l e a r . Asparagin-Glucose- Agar-Agar 15.O gm Glucose 10.0 \" Asparagin 0.5 \" Dlpotassium phosphate 0.5\" w D i s t i l l e d water 1000 ml Peptone Glucose Acid Agar Agar 25.0 gm Monopotassium phosphate 1.0 w Magnesium sulphate 0.5 w Peptone 5.0 * Glucose 10.0 *\u00E2\u0080\u00A2 Water. 1000 ml Reaction. pH 3\u00C2\u00AB8 to 4.0 Sodium Asparaginate-Glycerol Agar. Agar Glucose Dlpotassium phosphate Magnesium sulphate F e r r i c sulphate Egg albumen (powdered) Water, d i s t i l l e d Reaction i s about 7.2\" S o i l extract Agar Agar Glucose Dlpotassium phosphate-S o i l extract (stock) Tap water Reaction should be. pH 6.8 Constitution of the media used i n t h i s study Sodium. Asparaginate Glycerol Agar Agar Gl y c e r o l Dipotassium phosphate Sodium asparaginate: Water-Reaction approximately pH 7\u00C2\u00BB 15.0 gm 10.0 , f c 1.0 * 1.0 lOOp, ml Potato; Dextrose Agar Peeled; potatoes Glucose Agar Tap\"water .7 1000 ml Reaction i a pH 6.8 The potatoes; are cut into small cubes to which 350 ml of water i s added, and. the whole steamed f o r three quarters of. an hour. The extract i s s t r a i n e d through fine: muslin without, squeezing the pulp. The other nutrients are; dissolved i n 350 ml of water which Is then added to the potato extract, and. the whole, steamed for three, quarters of an hour.. The mixture- i s then made up to bulk, standardized and f i l t e r e d , a f t e r which the agar i s added.. Mannitol Yeast. Extract Asparagin Agar Agar 15.O gm Mannitol Asparagin. Yeast Extract Dipotassium phosphate Magnesium sulphate Ferrous sulphate D i s t i l l e d , water Reaction i s pH 6.8 to 7 10.0 * 0.5 * 0.5\" m 0.5 * O.2.5 gm trace 2000 ml Tyrosin agar-Agar Glucose Tyrosin Yeast Extract (or KNO3) Dipotassium phosphate D i s t i l l e d water Reaction adjusted to pH 6.8 15.O gm 10.0 W: 2.0. \u00E2\u0080\u00A2 2.0 * 0.5 * 2000; m2 Constitution of the media, used i n t h i s study Hit rate; Sucrose- Agar. Agar. 15\u00C2\u00BB\u00C2\u00B0 gm Sodium: nitrate: 2 .0 \" Dlpotassium phosphate 1.0 * Magnesium sulphate 0 . 5 * Potassium: chloride 0 .5 m Ferrous sulphate trace Sucrose 3 0 . 0 gin D i s t i l l e d water. 1000 ml Reaction approximately pH 7 Starch Agar Soluble, starch 2 .0 gm Dipotassium phosphate 0..5 * Magnesium sulphate 0.2: tt; Galeium chloride 0 .05 gm Sodium n i t r a t e 0 .05 n Asparagin V 0.05 \" Ferrous sulphate trace Washed agar. 2 0 . 0 gm D i s t i l l e d water 1000 ml Reaction adjusted to pH 6 .8 Thin Glucose Agar Agar; 15.0 gm Glucose 1.0 , , : Monopotassium phosphate , 0 .1 U l Sodium n i t r a t e 0 .1 f t i Potassium chloride 0 .1 m Magnesium sulphate 0 .1 * D i s t i l l e d water 1000 ml Reaction adjusted to pH 6 .8 "@en . "Thesis/Dissertation"@en . "10.14288/1.0106599"@en . "eng"@en . "Soil Science"@en . "Vancouver : University of British Columbia Library"@en . "University of British Columbia"@en . "For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use."@en . "Graduate"@en . "Streptomyces scabies and its habitat"@en . "Text"@en . "http://hdl.handle.net/2429/41072"@en .