Effects of cucumber genotype on the induction of resistance to powdery mildew, Sphaerotheca fuliginea, by 2, 6‐dichloroisonicotinic acid

Abstract

Conspicuous differences in inducibility of resistance to powdery mildew between susceptible and partially resistant cucumber cultivars were found when 2, 6‐dichloroisonicotinic acid (INA) was used as a model substance. In the partially resistant cv. Flamingo, EC50 was approximately 0·25 mg/1. In the susceptible cvs Corona and Lange Groene Gigant it was approximately 6mg/1. In greenhouse experiments with cv. Flamingo, powdery mildew could be well controlled with fortnightly applications in doses as low as 0·5 mg/1. The effect was highly cumulative.