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Genetic studies in the genus coprinus McClaren, Milton


In this study, inter- and intraspecific matings were made between mycelia of different species in the genus Coprlnus. The species studied were: C. comatus (Schum.) Fries, C. micaceus (Bull.) Fries, C. domesticus (Pers.) Fries, C. macrorrhizus (Pers.) Rea, C. myceliocephalus Lange, C. narcoticus, Fries, C. Patouillardii Quel., C. lagopus Fries, and C. picaceua (Bull.) Fries. Matings were carried out using both heterothallic and homothallic species. The cultural characteristics of all species were studied and described following growth on semisynthetic solid culture media. The results of the inter- and intraspecific crosses were assessed by microscopic observations of the area of contact between paired species and by further growth and examination of the mycelia and fruit bodies arising from inocula taken from the contact area. Mycelial macerates as well as plug inocula were employed in the study. Chemical monokaryotization techniques were applied to the homodikaryotic mycelium of C. myceliocephalus. Hyphal fusions or anastomoses were not observed in the confrontation of non-compatible mycelia of the same species. This observation was true in pairings of monokaryophase x monokaryophase, dikaryophase x dikaryophase, and monokaryophase x dikaryophase, involving mycelia of the same species. Close contact, taking the form of hyphal coils or hyphal "knots," was observed in pairings of compatible monokaryophases. Similar contact was obtained between hyphae of two different isolates of the homothallic species, C. Patouillardii, but no cytoplasmic continuity could be seen between the paired mycelia. Apparent cytoplasmic continuity and hyphal contact was established in crosses between the dikaryophases of C. micaceus and C. comatus and C. macrorrhizus and C. narcoticus. In addition, similar relationships including hyphal contact and cytoplasmic continuity were observed between mycelia of the homothallic species. C. myceliocephalus and C. Patouillardii. No nuclear transfer was observed between these different species. The cultural characteristics of mycelium subsequently isolated from the cross of C. micaceus x C. comatus and C. myceliocephalus x C. Patouillardii were significantly altered from those of the original species. The linear growth rate was increased in both cases. In addition, changes in coloration and mycelial form were observed. The mycelium arising from the cross of C. narcoticus x C. macrorrhizus was identical in every respect to that of C. macrorrhizus alone. No evidence of the growth of C. narcoticus could be seen in mycelium arising from this cross. All other species crosses studied revealed no anastomoses or formation of clamp connections following mating. Three monokaryotic isolates were obtained from the treatment of the homodikaryophase of C. myceliocephalus. Two of these isolates were obtained following sixteen weeks growth on medium containing .002 M sodium arsenate, while the third was isolated after three weeks growth on liquid medium containing 0.5% cholic acid. Cytological examination of the mycelia of the three isolates showed them to be monokaryotic and all three isolates lacked clamp connections. The clampless isolates produced no fruit bodies in culture on any medium, while the original isolate readily fruited on supplemented malt agar or on oat agar. Pairings of the isolates in all possible combinations resulted neither in mating nor in clamp connection formation. The stability and distinctiveness of cultural characteristics recommended their use in any future monographic studies of this genus. The presence of hyphal interactions, including hyphal continuity between different species, suggested the need for the examination of interspecific crosses for evidence of mating other than clamp connection formation. Homothallic and heterothallic species should be considered in studies of interspecific mating. Putative hybrid mycelia were produced from matings between different species. The absence of fruit body formation by these mycelia prevented demonstration of their hybridity in this study. The recovery of clampless, monokaryotic mycelia from the homodikaryon of C. myceliocephalus suggested that this species was secondarily homothallic.

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