Smoothleaf and Hirsute Cottons: Response to Insect Pests and Yield in Arizona

Abstract

Hirsute and semi-smoothleaf (sm3 allele) cultivars and smoothleaf (Sm3 allele) isolines of cotton, Gossypium hirsutum L., were exposed to natural populations of insect pests for three seasons at Tempe, Ariz. Duplicate experiments in 1981 and 1982 included seven hirsute and one semi-smoothleaf cultivar and the respective smoothleaf isolines. From these experiments, we selected two hirsute cultivars and smoothleaf isolines, and re-evaluated them in 1983. Mean percent seed damage caused by pink bollworm, Pectinophora gossypiella (Saunders), and mean seed cotton yield were not significantly different in the hirsute cultivars and smoothleaf isolines. Two hirsute cultivars and one smoothleaf isoline, however, had less seed damage than their opposite counterparts. One hirsute and one semi-smoothleaf cultivar yielded more seed cotton than the respective smoothleaf isolines. Mean number of abscised squares (flowerbuds), used as an index of plant bug (primarily Lygus hesperus Knight) damage, was significantly higher on the smoothleaf isolines, whereas mean number of “horseshoes” caused by the cotton leafperforator, Bucculatrix thurberiella Busck, was significantly lower on the smoothleaf isolines. The lack of resistance to pink bollworm and susceptibility to Lygus spp. of the smoothleaf isolines led us to decide not to incorporate Sm3. into our breeding stocks. On the other hand, we are incorporating sm3 because it confers no extra susceptibility to Lygus spp. and seems to impart some resistance to the sweetpotato whitefly, Bemisia tabaci (Gennadius).