INDUCTION TO RESISTANCE TO CROWN RUST IN OAT

Induction of resistance to crown rust, caused by Puccinia coronata Cda . var. avenae Frazer et Led., occurred in seedlings of three genetic l ines of oats (Avena sativa L.) inoculated sequentially with one of thr ee inducer-challenger combinations of the pathogen. There was signific ant reduction in both the number of pustules per leaf and the weight o f urediospores harvested in all three host genotypes tested. There wer e highly significant differences between individual spore harvests cor related with age of the pustules. Development of telia by the challeng er was found to occur considerably later, and was less intense, when t he challenger was inoculated alone in contrast to treatments in which the challenger followed pre-inoculation with the inducer. There was no correlation between the numbers of resistant and susceptible lesions within the range of inoculum density used in these experiments.