Relationship Between Field and Greenhouse Ratings for Tolerance to Verticillium Wilt on Cotton1

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Abstract
Greenhouse evaluations of tolerance to Verticillium wilt, caused by Verticillium dahliae Kleb., in cotton, Gossypium hirsutum L, have been used in the past; however the relationship between field and greenhouse evaluations for the disease is not clear. In the present study, 48 cultivates and breeding lines of G. hirsutum were evaluated following induced infection by stem or root inoculation in the greenhouse and natural infection under field conditions (Exeter loam soil; Fine‐loamy, mixed, thermic Typic Durixeralfs). Highly significant differences were observed among genotypes in both greenhouse and field experiments, and broad‐sense heritability estimates were comparable, 0.70 and 0.74 for field and greenhouse, respectively. There was good agreement between field ratings and greenhouse reactions following stem inoculation; phenotypic and genotypic correlations were 0.72 and 0.86, respectively. There was essentially no relationship between field ratings and greenhouse reactions following root inoculation. Selection for wilt tolerance on the basis of field evaluations may result in later maturing plants and reduced lint yield since these characters appear to be associated with tolerance. However, greenhouse screening, which uses young plants, may avoid these correlated responses to selection. Greenhouse evaluation of Verticillium wilt tolerance may be used with confidence in selection programs for disease tolerance.