Effect of Heterozygous and Heterogenous Populations of Normal and Okra Leaf Cottons on Yield

William R. Meredith, Jr.


 
ABSTRACT

One of the major problems confronting breeders evaluating the yield of genotypes is the presence of large genotype X environment interactions (G X E). From a theoretical viewpoint, heterozygous and heterogenous populations are expected to be more stable in their producing ability and thus have smaller G X E than homozygous and homogenous populations. To test this hypothesis in cotton, isogenic populations of normal, okra leaf, and their F1 and F2 hybrids from eight cultivars were grown in 12 environmental regimes. The 32 isogenic populations were grown in two years, 1979 and 1980; two planting dates, April and May; and three seeding rates, 10, 20 and 30 seed/m- on 1m row.

The lint yield response of the four isogenic genotypes interacted with years, planting dates, years X planting dates, years X cultivars, and years X planting dates X seeding rates. The greatest interacting factors were years and years X planting dates with F = 12.2 and 5.7, respectively. Okra leaf produced significantly higher lint yields (77 kg/ha) than normal for the May 1979 plantings, but produced significantly less for the April 1979 and May 1980 plantings, yielding 57 and 88 kg/ha less than normal for the respective regimes. Significant positive dominance (F -midparent) of 68 kg/ha was detected for the April 1980 planting but significant negative dominance of 44 kg/ha was detected for the May 1979 plantings. The F2 yield was significantly lower, -40 kg/ha, than expected on the basis of the performance of its individual genotypic components [F2-(F1 + midparent)/2] for both 1979 plantings. In 1980 the F2 yielded 29, and significantly, 43 kg/ha more than expected for the April and May plantings, respectively. In addition, the F2 yield regression for environmental yield index was 0.85 and significantly lower than the regression coefficient for the other three genotypes which averaged about 1.05. Thus, F2 populations yield better than expected in the low yielding environments and less than expected in high yielding environments. This study indicated F2 populations were more stable in yield performance than their isogenic homozygous and homogenous normal and okra leaf parents, and also more stable than their heterozygous and homogenous F1 parents.



Reprinted from Proceedings of the 1983 Beltwide Cotton Production Research Conference pg. 109
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998