Resistance in Susceptible Maize to<i>Helminthosporium carbonum</i>Race 1 Induced by Prior Inoculation with Race 2

Abstract

Inoculation of leaves of susceptible maize genotypes with the nonpathogenic race 2 of Helminghosporium carbonum at least 10 hr before inoculation with the pathogenic race 1 prevented development of large lesions typical of the susceptible reaction. Appressorium formation, penetration, and hyphal growth by the pathogen were decreased. Addition of HC-toxin (the host-specific toxin produced by pathogenic race 1) to the race 1 challenge inoculum abolished the resistance induced by race 2 (...)