Pink Bollworm Resistance, Lint Yield, and Lint Yield Components of Okra‐Leaf Cotton in Different Genetic Backgrounds1

Abstract

The two leaf (L) types, Okra leaf [2(L02)] and normal leaf, from seven genetic backgrounds (G) of cotton, Gossypium hirsutum L., were subjected over two seasons (Y) to natural populations of pink bollworm (PBW), Pectinophora gossypiella (Saunders), at Tempe, AZ. In other experiments, one of the seven Okra‐leaf strains and an Okra‐leaf cultivar, ‘Gumbo 500’, were compared with ‘Stoneville 213’, a normal‐leaf cultivar, for one to three seasons. Objectives of this study were to determine whether (i) L interacted with G or Y for seed damage caused by PBW, for lint yield, or for earliness; and (ii) yield of Okra‐leaf strains could be increased by selecting for improved yield components. An important goal is to determine whether PBW‐resistant, Okra‐leaf cottons will yield as much lint as normal‐leaf cottons in stressful environments. In the leaf shape‐genetic background experiments, significant L ✕ G and Y ✕ G interactions were detected for seed damage by PBW, but not for lint yield or earliness. Mean yield per plant and percent seed damage for the seven normal‐leaf cultivars were significantly higher than those of the Okra‐leaf strains, 36.0 vs. 30.7 g/plant, and 17 vs 14%, respectively. Okra‐leaf strains were not significantly earlier than normal‐leaf cultivars. Examination of lint yield components suggested that selection for lint per seed, a highly heritable trait, should increase lint yields of some Okra‐leaf cottons. However, bolls per plant, expected to have low heritability, was the main yield component that limited tint yield of most of those cottons. The Okra‐leaf strains and cultivar, when compared to Stoneville 213, generally had less seed damage and yielded less lint. An exception was in 1985, when Gumbo 500 did not yield significantly less lint than Stoneville 213. In a preliminary experiment in 1985, two Okra‐leaf advanced breeding stocks outyielded the normal‐leaf counterparts by 23 and 18%, respectively.Results thus show that Okra‐leaf breeding stocks in certain genetic backgrounds have a modest level of resistance to PBW and also may yield as much or more lint than do normal‐leaf cultivars. However, the inconsistent response of some Okra‐leaf cottons emphasizes the importance of comparing those cottons with normal‐leaf cultivars over a range of environments.