Thrips (Thysanoptera: Thripidae) Tolerance in Cotton: Sources and Heritability

Thrips (Thysanoptera: Thripidae) resistance or tolerance in cotton, Gossypium hirsutum L., is often associated with extreme pubescence. This is undesirable because hairy (pubescent) plants tend to have more trash in harvested lint which reduces the price received by growers. Two other possible sources of resistance include gossypol and thick lower epidermal cells, the latter has been found in G. barbadense L. Five G. barbadense genotypes were mated in a North Carolina Design II to 4 upland cultivars to evaluate combining ability. In addition, 90 converted racestocks were screened for tolerance to thrips. Experiments were designed to evaluate tolerance or resistance by comparing plots with and without thrips. Two G. barbadense parents had tolerance to thrips while two upland cultivars also exhibited tolerance. In the F₁ generation, general combining ability was significant for thrips damage ratings among the G. barbadense parents. In the F₂ generation, all characters exhibited specific combining ability. Thus, non-additive genetic variance predominates measures of thrips tolerance.