Searching for resistance sources to Verticillium wilt of cotton in seedlings from Gossypium spp.

WOS: 000397202600004Verticillium dahliae is a major wilt pathogen impacting cotton production in Turkey. Isolates of V. dahliae can be characterized as defoliating (D) or nondefoliating (ND) pathotypes based on symptom expression in cotton. Currently there are no fungicides identified that can manage this pathogen. Host resistance is the most economical and environmentally friendly means to manage this disease. Cotton genotypes, comprising the main cultivars and some breeding lines available in Turkey, were evaluated under controlled conditions for resistance to verticillium wilt. To establish adequate conditions for resistance expression, experiments examining isolate pathogenicity and the most appropriate inoculum concentration were carried out first. Based on the obtained data, 10 cultivars were then inoculated with D and ND pathotypes by the "pot immersion" method at 10(6) conidia/mL inoculum concentration and the plants were evaluated considering both internal and external disease symptoms. Plants were scored on a 0 to 4 scale for above-ground symptoms (0 = healthy; 4 = dead plant) ca. two weeks after inoculation. Significant differences in resistance level were observed among the genotypes (p < 0.05). The cultivar Maydos Yerlisi had the lowest level of wilt, with a mean rating of 1.0. The cultivar Nazilli NDT-15 had the strongest wilt, with a mean rating of 3.3. These results suggest that 'Maydos Yerlisi' can be used in cotton breeding programs to develop resistant varieties to V. dahliae