Tolerance of Glabrous and Pubescent Cottons to Tarnished Plant Bug1

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Abstract
Lint yields of glabrous cottons (Gossypium hirsutum L.) are frequently lower than those of pubescent cottons. Since glabrous cottons might be more sensitive to tarnished plant bugs [Lygus lineolaris (Palisot de Beauvois)] than are pubescent cottons, we investigated the association between plant bugs and reproductive development of glabrous and pubescent cottons. Greenhouse evaluations were conducted in 1975 and 1977 with two plant bug nymphs per five plants. In the first test, reduction of flower buds by the plant bugs was 74% for four glabrous cottons, but was only 15% for two pubescent cottons. Similarly, in the second test, these reductions were 78 and 33% for five glabrous and two pubescent cottons, respectively.We also needed to develop a method for detecting tolerance that was not associated with pubescence. Thirty hybrids were produced by crossing the cultivar ‘Carolina Queen’ and its glabrous (Sm2Sm2) isoline to 15 tester parents. Each tester parent and its two hybrids were grown in the field in two bisect regimes. In one, plant bug infestations were minimized with early‐season use of insecticides, while in the other infestations were encouraged by growing mustard (Brassica juncea L. Czern. & Coss.) nearby. Yields were decreased by the plant bug enhancement; yields of glabrous hybrids were reduced by 239 kg/ha while those of pubescent hybrids were reduced by only 163 kg/ha. Tolerance to plant bugs was observed in eight of the parental lutes, but only hi two of the Sm2sm2 hybrids. One of these hybrids, with ‘Timok 811’ as a parent, was itself hirsute; the other had a high terpenoid nectariless strain, HG‐BR‐8N, as a parent.These data demonstrate that glabrous cottons are more sensitive to plant bugs than are pubescent cottons. They also indicate that possibly detection of germplasm tolerance to plant bugs can be facilitated through field evaluations of Sm2sm2 hybrids.

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