Resistance Induced by Race 1 ofColletotrichum trifoliito Race 2 in Alfalfa Resistant to Race 1

Publisher Website
Google Scholar
Abstract
Alfalfa plants resistant to race 1 but susceptible to race 2 of C. trifolii could be protected from race 2 when needle-inoculated with mixtures of races 1 and 2. Dilution was not a factor because race 2 alone at 1 .times. 106 conidia/ml was pathogenic but the race 2 component in the mixture at 4 .times. 106 conidia/ml was relatively, or usually, completely nonpathogenic. In spray-inoculation experiments, most cv. Arc seedlings were protected from race 2 by prior inoculation with race 1. The survival rate of ''Arc'' seedlings inoculated with a mixture of races 1 and 2 was much higher than that of seedlings inoculated with race 2 alone. Analysis of plants capable of being protected from race 2 in mixtures, or by protective sprays with race 1, demonstrated race 1 resistance was a requirement for the race 2 protection phenomenon to be operative.