GENETIC-VARIATION AND SEGREGATION OF DNA POLYMORPHISMS IN BOTRYTIS-CINEREA

Genetic variation among eight Dutch strains and two Italian monoascosp ore strains of Botrytis cinerea has been studied by RAPD analysis. Of the 139 RAPD markers scared, 74 markers were present in all strains, w hile 65 markers showed polymorphisms. Computer analysis of these data showed a high similarity (ranging from 0.83 to 0.94) for each pair of strains. A similarity coefficient of 0.99 was found for two Dutch stra ins isolated from different hosts in 1986 and 1990. To study the segre gation of polymorphic markers in the progeny, crosses were performed b etween Dutch strains and Italian strains. These crosses revealed the p resence of either one or both mating types in the Dutch strains. Of ea ch successful cross, the total progeny was collected from ten complete asci of which the ascospores were released in an ordered way. Morphol ogical characteristics and fungicide resistance in cultures of such an ordered collection of progeny regularly revealed an aberration in spo re order within an ascus. RAPD analysis of the progeny emphasized this phenomenon. In the segregation analysis of DNA polymorphisms in the p rogeny, cross SAS405 x Bc7 was analyzed. Most of the RAPD markers test ed segregated in a normal Mendelian ratio of 1:1. Several unexpected p henomena were observed: two markers, derived from parent SAS405, segre gated in a 1:0 ratio; three markers, originating from parent Bc7, were absent in the progeny; and two markers, not scored in the parental st rains, segregated in a 1:1 ratio in the progeny. These observations ar e discussed in view of the multinucleate, heterokaryotic nature of B. cinerea and its unknown ploidy level.