Normal vs. Okra Leaf Yield Interactions in Cotton. I. Performance of Near‐Isogenic Lines from Bulk Populations1

Abstract

Okrale af (L2°,L2°) cottons, Gossypium hirsutum L ., have several advantages over normal leaf cottons, but are rarely used commercially because they usually carry approximately a 5% ield disadvantage. Okrale leaf cottons usually have been developed by the back cross method, which presumably places Okra leaf in a physiological background better suited to the normal leaf phenotype. This study was designed to determine if the 5% yield differential could be reduced or eliminated by the use of a different breeding method. ‘Stoneville 7A’ Okra leaf (nectariless) was crossed with ‘Carolina Queen’ (smoothleaf) and ‘Deltapine 5540‘ to produce CQ and DPL populations. From each cross, 50 heterozygous (L2°,l2) F7 plants were selected and near‐isolines of Okra and normal were developed. In 1981, the normal leaf strains average 1068 kg ha−1 lint and the Okra leaf strains average 1015 15kg ha−1 lint, a significant difference. Strain ✕ leaf type interactions were significant for both populations. In 1982, we grew the two highest yielding strains, the five Okra leaf strains that outyielded their normal leaf near‐isolines, and the five normal leaf strains that outyielded their Okra leaf near‐isolines in 1981. Our selection objectives were achieved with the DPL but not with the CQ population in 1982. Okra leaf selections in DPL background yielded 7% more lint than their normal leaf near‐isolines, whereas ‘Stoneville 213’ normal leaf yielded 10% more lint than its backcross‐derived(BC3) Okra leaf isoline. The 1982 DPL and CQ yield patterns were verified with four selection planted at two dates in 1983. Soil type in 1981 and 1982 was a Dubbs silt loam(finesilty, thermic Typic Hapludalfs), and in 1983 was a Dundee silty clay(fine‐silty, mixed, thermic Aeric Ochraqualfs). The results from the three experiments imply that certain populations have the genetic potential of producing Okra leaf cottons with higher yielding ability than that of normal leaf ones.