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 lines of oats (Avena sativa L.) inoculated sequentially with one of three inducer-challenger combinations of the pathogen. There was significant reduction in both the number of pustules per leaf and the weight of urediospores harvested in all three host genotypes tested. There were highly significant differences between individual spore harvests correlated with age of the pustules. Development of telia by the challenger was found to occur considerably later, and was less intense, when the 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.