HYPHAL MORPHOLOGY ASSOCIATED WITH STRAIN INSTABILITY IN THE COMMERCIAL MUSHROOM, AGARICUS-BISPORUS

Light microscopy was used to examine the morphology of surface hyphae of strains of Agaricus bisporus that form ''fluffy'' or ''stromatal'' sectors on agar medium or in grain culture. Although differences were found between normal (U1 strain) and some sectoring isolates in the me an distance from the hyphal apex to the first branch, and in average i nternode length, these differences were not consistent under different growth conditions. Fluffy and stromatal isolates did show a high freq uency of hyphae with irregular branching patterns. A correlation betwe en high prevalence of hyphae with certain types of branching patterns and the ability to form sectors in grain culture was also observed in 35 single-basidiospore isolates derived from mushrooms produced by nor mal and sectoring cultures. It is suggested that the ability of any su bculture to form a sector may depend on the prevalence of aberrent hyp hae in the initial inoculum.