A screening technique for detecting levels of resistance in cucumber (Cucumis sativus L.) to belly rot induced by Rhizoctonia solani Kuehn

Abstract

A procedure for detecting cucumber fruit resistance to belly rot induced by Rhizoctonia solani is described. Inoculum in an unsterilized soil, naturally infested with Rhizoctonia solani Kuehn, AG-4, was increased by placing whole cucumber fruit in contact with the moistened soil until the fruit rotted. The screening technique required a uniformly controlled soil environment, with an inoculum density of 30 propagules/100 gm soil, a temperature of 30°C, and 12% moisture. Fruit to be screened were placed on the prepared soil and a PVC film cover maintained soil moisture during the three day screening. Soil depth, ranging from 1.5 to 4.0 cm in the screening chamber, did not affect infection nor did disturbing the fruit daily during screening. Attached fruit were shown to be more susceptible to belly rot than detached fruit, and fruit grown on turgid plants were more susceptible than fruit which had developed on wilted plants. Genetic resistance was correlated with tough skin in some breeding lines.