GENETIC DIVERSITY IN W-TYPE AND R-TYPE POPULATIONS OF PSEUDOCERCOSPORELLA-HERPOTRICHOIDES BASED ON DNA RESTRICTION-FRAGMENT-LENGTH-POLYMORPHISMS

Thirty-seven isolates of Pseudocercosporella herpotrichoides belonging to W-type and 31 isolates belonging to R-type were analysed for DNA r estriction fragment length polymorphisms (RFLPs). They represent diver se geographic origins and different phenotypes related to sensitivity to fungicides. Total DNA digested with EcoR1 was hybridized with 22 ra ndom DNA probes from a P. herpotrichoides EcoRI-restricted DNA library . Four probes showing polymorphisms among isolates within W-type and R -type and generating a total of 44 RFLPs were retained for cluster ana lysis. Two main groups were distinguished corresponding to W- and R-ty pes. The genetic diversity among isolates was greater for the W-type t han for the R-type. Using a mitochondrial DNA probe from a known R-typ e isolate, four and three distinct EcoRI-restricted mitochondrial DNA patterns were identified in W- and R-type isolates, respectively. The variability of profiles within each pathotype confirmed a higher degre e of polymorphism in the W-type.