VARIATION IN SYMPTOMS OF CERCOSPORA-ARACHIDICOLA ISOLATES ON SOME GROUNDNUT GENOTYPES

Cercospora arachidicola Hori., causal agent of early leaf spot of grou ndnut has been reported to have developed tolerance to benomyl fungici des in field. Some research reports also indicated marked decrease in host resistance to this disease when cultivars are grown in different geographical regions. Knowledge of pathogen variability is crucial for a successful resistance-breeding programme. Early leaf spot symptoms produced by eight isolates of the causal agent were compared on a set of four cultivated groundnut genotypes as part of investigations on pa thogenic variation in C. arachidicola. Genotypic variation and isolate differences were observed for symptom characters, infection frequency and lesion size. The genotypes have potential for use in a host diffe rential set for separating pathotypes of the early leaf spot pathogen.