Effects of Okra‐Leaf, Frego‐Bract, and Smooth‐Leaf Mutants on Pink Bollworm Damage and Agronomic Properties of Cotton1

Abstract

Eight isolines of cotton, Gossypium hirsutum L., which carried all possible combinations of Okra leaf (L°2), frego bract (fg), and Smooth leaf (Sm2) vs. their normal‐leaf and normal‐bract equivalents in the La 71‐7 (a Stoneville) background, were grown in replicated experiments for 3 years in Arizona in insecticide‐free environments. Percentage of seed damage caused by pink bollworm (PBW), Pectinophora gossypiella (Saunders), and 11 agronomic properties were studied.Mean seed damage in the Okra‐leaf isolines was 82% of that in the corresponding normal‐leaf lines, a significant reduction. The Okra‐leaf isolines were comparable to the normal‐leaf types in agronomic properties. Their only negative effect was an 8% lower lint yield (which was significant). Okra leaf interacted with frego bract only for boll size and with Smooth leaf only for seed index. Okra leaf interacted with years for seed damage because the Okra‐leaf isolines had 76% as much damage as the normal‐leaf stocks in 1979, but 85% as much in 1978 and 88% as much in 1980. Seed damage in the frego‐bract isolines was not significantly different from that in its normal‐bract counterparts. Frego bract interacted significantly with Smooth leaf for lint percent and with years for seed damage, total lint yield, bolls/plant, boll size, lint percent, and plant height. When closely examined, the interaction for seed damage suggested that frego bract afforded a slight advantage during the years when seed damage was relatively high. However, deficiencies in numerous agronomic properties (including a 24% lint yield reduction) and the five year ✕ agronomic property interactions offset any advantages in reduced seed damage afforded by frego bracts. Smooth‐leaf isolines unexpectedly displayed more seed damage than the hirsute‐leaf lines. Smooth‐leaf isollnes were also inferior to the hirsute‐leaf types in all agronomic properties except seed index and displayed significant interactions between years and percent lint yield at second and third harvest, total lint yield, bolls/plant, and date of first flower. For PBW resistance and agronomic performance, Okra leaf appears to have value, frego bract does not, and Smooth leaf must be reevaluated.