ÃÞ »¨ ѧ ±¨ Cotton Science 2008£¬20(6)£º452-459
Genotypic Resistance of F1 Cotton Hybrids by Inoculation with Different Virulent Isolates of the Fungus Verticillium Dahliae Klebahn Abstract£ºThe plant pathogen Verticillium dahliae causes severe cotton loss in Uzbekistan. To create cotton varieties that are resistant to the more virulent races of V. dahliae , we wanted to determine genotypic resistance of varieties and lines of cotton to more virulent isolates of different geographic populations of the fungus V. dahliae isolated from different cotton varieties in Uzbekistan, and determine the inheritance of wilt resistance with hybrids of the first generation to various isolates of V. dahliae . We found that the highest wilt resistance was observed in the variety §° mad and lines L-44, L-408, L155 and L-1708 to the isolates 28, 30, 32, 36, 40 and 44. They exhibited hypersensitivity when the pathogen was inoculated into the plant, but they did not display external symptoms of wilt. Wilt resistance of hybrids of the first generation as determined by inoculation with the isolates of V. dahliae was inherited according to the type of super dominance and dominance toward the resistant or susceptible parent independent from the method used to determine the disease index. Also intermediate inheritance was observed. The degree of dominance depended on the combinational ability of parents and genotype reaction of F1 hybrids when pathogens were introduced into the plant, and also on the virulence of the isolates found in different varieties of cotton from different soil-climatic regions. The varieties with the highest phenotypic wilt resistance (i.e., tolerance) were §° mad, §³-5621 and lines L-44 and L-1708. Among hybrids, the hybrid combinations L-155 ¡Á§³-5621 and L1708 ¡Á§³-5621 had the highest phenotypic wilt resistance. The degree of tolerant resistance to wilt varied from 50 £¥ to 80%. Genetic control of resistance to V. dahliae isolates and F1 hybrids was characterized by negative and positive super dominance, dominance toward the best or the worst parent and intermediate inheritance. The hybrid combinations L-155 ¡Á§³-5621 and L-155¡ÁL-44 had the best combinational wilt resistance toward the V. dahliae isolates studied, as compared to other hybrid combinations with the maternal forms §°mad,§³-8284 and L-408.
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