Reaction of Trifolium subterraneum genotypes to different isolates of Kabatiella caulivora

Abstract

Single spore isolates of Kabatiella caulivora were derived from infected plant material collected at a number of locations over a wide area in the south-western coastal region of Western Australia. An experiment was conducted to compare the reactions of three resistant Trifolium subterraneum genotypes to infection at the cotyledon stage by 18 isolates. Significant differences in severity of damage to the unifoliate leaf were observed between host genotypes and isolates. The host x isolate interactions were, however, not significant. In a second experiment the reactions of two resistant and two susceptible genotypes to five isolates were compared. Significant host-genotype differences were observed in both cotyledon and unifoliate leaf damage. Isolate differences were only significant in the case of cotyledon damage. Again, no significant host x isolate interaction. was detected. Procedural problems associated with the preparation of conidial suspensions of single spore isolates of Kabatiella caulivora are discussed with particular reference to accurate measurement of disease reaction.