Transmission of PsV-F and PsV-S Mycoviruses during Conidiogenesis of Penicillium stoloniferum

Abstract

SUMMARY: Levels of both fast and slow Penicillium stoloniferum virus (PsV-F and PsV-S) were evaluated in single conidial isolates of P. stoloniferum NRRL5267. Approximately 7 % (3/43) of a random population of conidia from a culture of P. stoloniferum contained no PsV-F, while other conidia produced cultures with various levels of PsV-F. The greatest variation in PsV-F levels was observed in single conidial isolates from cultures that contained low to intermediate levels of virus, i.e. 11 to 25 E 1cm 260 units per g dry weight of mycelium. The least variation was seen in isolates from a culture with a high PsV-F level (37 E 260 units per g dry weight of mycelium). Two of the original 43 single conidial isolates contained no detectable PsV-F or PsV-S. Of the second-generation single conidial isolates from an original PsV-S+ PsV-F- isolate, 6 % failed to show detectable PsV-S. PsV-F levels of cultures remained constant throughout a series of transfers when the inoculum was a mixture of conidia and mycelium. The presence of PsV-F at different levels, or its complete absence, did not affect fungal biomass, conidium size, morphology or viability. The results are discussed in terms of how conidiogenesis may influence the transmission or persistence of PsV-F and PsV-S during morphogenesis.