LOCALIZED INFECTION WITH TOBACCO NECROSIS VIRUS PROTECTS CUCUMBER AGAINST COLLETOTRICHUM-LAGENARIUM

A cultivar of cucumber susceptible to C. lagenarium race 1 was systemically protected against disease caused by the fungus by prior infection with tobacco necrosis virus (TNV). Infection of 1 cotyledon with the virus protected the opposite cotyledon and the 1st true leaf against disease caused by a subsequent infection with C. lagenarium. Autoclaved sap from TNV-infected plants or sap from non-inoculated plants did not elicit protection. Infection with the virus prior to infection with C. lagenarium reduced the number and size of lesions caused by the fungus at low spore concentrations, but was less effective against higher spore concentrations. The number of lesions formed on a TNV-infected cotyledon was not affected by prior infection of the opposite cotyledon with TNV or C. lagenarium.