VIEW ARTICLE

Metabolic Nature of the Infection-Limiting Effect of Heat on Bean Anthracnose. J. E. Rahe, Departments of Biochemistry and Botany & Plant Pathology, Purdue University, Lafayette, Indiana 47907, Present address of senior author: Department of Biological Sciences, Simon Fraser University, Burnaby 2, British Columbia; J. Kuc, Departments of Biochemistry and Botany & Plant Pathology, Purdue University, Lafayette, Indiana 47907. Phytopathology 60:1005-1009. Accepted for publication 27 January 1970. DOI: 10.1094/Phyto-60-1005.

Colletotrichum lindemuthianum, the causal agent of bean anthracnose, does not grow at temp above 32 C. The disease is also heat-sensitive. Thermal sensitivities of conidia, appressoria, and infection hyphae on etiolated bean hypocotyls, and conidia and mycelia on agar were investigated. The infection-limiting effect of heat treatment reflected deleterious effects of heat on conidia and appressoria, but mycelium on agar was not killed by five times the duration of heat treatment that prevented further development of infection hyphae in the host. Infection-limiting heat treatment of infected plants induced protection against subsequent infection by the same race of the fungus; but previously uninfected plants were more susceptible after heat treatment. The response of previously infected and uninfected plants to a varietal-nonpathogenic race of C. lindemuthianum was not affected by heat treatment. We conclude that heat treatment of the host-fungus complex prevents further development of the pathogen via initiation of a response that also protects the host against subsequent infection.