Responses of field-grown cotton cultivars to fusarium wilt, bacterial blight and verticillium wilt

Abstract

Responses of 24 cotton cultivars (Gossypium hirsutum L.) to Fusarium wilt, bacterial blight and Verticillium wilt were studied in the State of Oklahoma, U.S.A., in 1979. An irrigated experiment was pIanted in a soil naturally infested by the Fusarium wilt pathogen, and the plants were evaluated at the 90th-day stage for vascular and foliar symptoms of the disease. To evaluate responses to bacterial blight, three field experiments were planted, and the plants were artificially inoculated with two pathogen races and a mixture of such races. Plants were scored for reaction fifteen days later. Responses to Verticillium wilt were determined right before harvest, in two irrigated experiments planted under natural infestation conditions. The highest level of tolerance to Fusarium wilt was presented by the cultivar IAC RM 4 SM 5, from Brazil, followed by 4 F, from Pakistan, Acala SJ-5, from the U.S.A., Minas D. Beja, from Brazil, and C-4727, from the USSR. The most tolerant accesions to bacterial blight were: CA (68) 41, from Ugan.