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Epidemiology of Fusarium fruit and stem rot of greenhouse grown sweet pepper Smudja, Mirej
Abstract
Spore monitoring, using Burkard Continuous Recording Air Samplers, in Lower Mainland commercial pepper crops during three different growing seasons strongly suggests that ascospores of Nectria haematococca are both the primary and secondary inoculum. Fusarium solani spores were seldom detected and apparently play a minor role, if any, in the spread of Fusarium fruit and stem rot. No ascospores could be detected in monitored greenhouses upon completion of the end-of-season cleanup procedures indicating that detectable spore inoculum was not being carried over from one growing season to the next in commercial greenhouses. In "clean" greenhouses, which obtained seedlings produced by one propagator, high ascospore levels were detected with the introduction of the new crop. No symptoms were observed on the new seedling plants but perithecia of N. haematococca were observed on the surface of the rockwool cubes in which the seedlings were growing. Spores trapped from these perithecia were pathogenic to pepper seedlings and caused typical fruit rot in pathogenicity tests. Thus, rockwool cubes contaminated during propagation are one way of introducing the fungus into "clean" commercial greenhouses. Under controlled conditions of temperature and relative humidity (RH) ascospore discharge from moistened diseased fruit tissues was not inhibited by RH as low as 51% (the lowest tested). Ascospore discharge from air-dried diseased fruit tissue occurred only at RH >95%. Temperatures in the range of 15 to 30°C were not inhibitory for ascospore discharge, however, maximum discharge occurred at the lowest temperature tested (15°C). Ascospores discharged onto glass slides maintained at 55-60% RH (typical RH observed during the cleanup) survived from 6 to 18 days, depending upon temperature. Under "typical" greenhouse conditions ascospores remained viable on glass slides for up to 12 days. Ascospore germination occurred at all temperatures tested (15-30°C), but germination was greater and occurred more quickly at higher temperatures. Substantial ascospore germination occurred only during prolonged periods (8-12 h) of very high (>98%) relative humidity. Therefore, although perithecia of N. haematococca maybe present on the cubes from the early stage of the growing cycle, losses due to Fusarium fruit and stem rot will depend on the greenhouse climate management. Ascospore discharge from the rockwool cubes, which are constantly saturated with nutrient solution, can occur independent of ambient RH. Therefore, aggressive climate management, which avoids extended periods of high RH, apparently reduces disease by preventing ascospore germination rather then preventing ascospore discharge.
Item Metadata
Title |
Epidemiology of Fusarium fruit and stem rot of greenhouse grown sweet pepper
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
1999
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Description |
Spore monitoring, using Burkard Continuous Recording Air Samplers, in Lower
Mainland commercial pepper crops during three different growing seasons strongly suggests
that ascospores of Nectria haematococca are both the primary and secondary inoculum.
Fusarium solani spores were seldom detected and apparently play a minor role, if any, in the
spread of Fusarium fruit and stem rot. No ascospores could be detected in monitored
greenhouses upon completion of the end-of-season cleanup procedures indicating that
detectable spore inoculum was not being carried over from one growing season to the next in
commercial greenhouses. In "clean" greenhouses, which obtained seedlings produced by one
propagator, high ascospore levels were detected with the introduction of the new crop. No
symptoms were observed on the new seedling plants but perithecia of N. haematococca were
observed on the surface of the rockwool cubes in which the seedlings were growing. Spores
trapped from these perithecia were pathogenic to pepper seedlings and caused typical fruit rot
in pathogenicity tests. Thus, rockwool cubes contaminated during propagation are one way
of introducing the fungus into "clean" commercial greenhouses.
Under controlled conditions of temperature and relative humidity (RH) ascospore
discharge from moistened diseased fruit tissues was not inhibited by RH as low as 51% (the
lowest tested). Ascospore discharge from air-dried diseased fruit tissue occurred only at RH
>95%. Temperatures in the range of 15 to 30°C were not inhibitory for ascospore discharge,
however, maximum discharge occurred at the lowest temperature tested (15°C). Ascospores
discharged onto glass slides maintained at 55-60% RH (typical RH observed during the
cleanup) survived from 6 to 18 days, depending upon temperature. Under "typical" greenhouse conditions ascospores remained viable on glass slides for up to 12 days.
Ascospore germination occurred at all temperatures tested (15-30°C), but germination was
greater and occurred more quickly at higher temperatures. Substantial ascospore germination
occurred only during prolonged periods (8-12 h) of very high (>98%) relative humidity.
Therefore, although perithecia of N. haematococca maybe present on the cubes from the
early stage of the growing cycle, losses due to Fusarium fruit and stem rot will depend on the
greenhouse climate management. Ascospore discharge from the rockwool cubes, which are
constantly saturated with nutrient solution, can occur independent of ambient RH.
Therefore, aggressive climate management, which avoids extended periods of high RH,
apparently reduces disease by preventing ascospore germination rather then preventing
ascospore discharge.
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Extent |
6370656 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-06-15
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Provider |
Vancouver : University of British Columbia Library
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Rights |
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.
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DOI |
10.14288/1.0099330
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
1999-05
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Item Media
Item Citations and Data
Rights
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.