Evidence of asexual recombination in Rhynchosporium secalis

Three single-spore isolates of Rhynchosporium secalis that differed in their α-esterase and β-glucosidase isozyme patterns were inoculated as two mixtures, each of two isolates, on to seedlings of the susceptible barley cultivar Maris Mink. Approximately 100 single-spore isolates were taken from mature lesions produced by each mixture. These were subjected to polyacrylamide gel electrophoresis and the gels were stained for α-esterase and β-glucosidase. Parental types only were produced by one of the isolate mixtures. However, one of the 10 lesions examined for the second mixture produced nine isolates with a novel combination of isozymes, indicating that some form of asexual recombination had occurred. The use of isozymes as a natural marker system for the detection in vivo of asexual recombination in pathogenic fungi is discussed.