Inheritance of fiber length mutants of upland cotton and relationships among lint yield, fiber quality, and economic indices
The narrow germplasm base of upland cotton iGossypium hirsutum L.) varieties grown on the Texas High Plains has historically been limited by relatively poor fiber quality. Prior work at Texas Tech University identified two chemically induced mutants (TTU 202 and TTU 271) that appeared to carry at least one partially dominant gene that increased fiber length. In 1998, a series of eight crosses were made with these two mutant lines and four established commercial cultivars (SC 9023, Holland 338, Explorer and Atlas) to determine the effectiveness of selection for fiber quality, lint yield and gross return in the segregating populations. Narrow-sense heritabilities, correlation coefficients and parent-offspring regression coefficients for HVI fiber quality, lint yield, loan value and gross return were also estimated. From their performance in the F3 and F4 generations, 56 lines that were among the top 25% for various indices were selected for: (1) superior fiber quality, lint yield and gross return (24 lines); (2) good fiber quality (11 lines); and (3) high lint yield and gross return (21 lines). These lines were advanced to the F5 generation where individual plants will be selected for additional testing. Parent-offspring Regression coefficients generated in this study showed that micronaire, fiber length, uniformity, and strength could be predicted from parental performance, while, loan value, lint yield and gross return could not be consistently predicted from the parental generation. In the F3 versus F2 generations, the highest narrow-sense heritability estimates were found in length (h^ 2n.s. = 0.10 to 0.59) and strength (h^ n.s. = 0.06 to 0.58). Micronaire, uniformity and loan value had heritability estimates ranging from h^ n.s. = 0.00 to 0.25. In the F4 versus F2 generation, fiber length had the highest heritability estimates (h^2 n.s. = 0.04 to 0.70). The heritability estimates of micronaire, uniformity, strength, and loan value ranged from h^2 n.s. = 0.00 to 0.28. In the F4 versus F3 generations, length had the highest heritability estimates (h n.s. = 0.33 to 0.76). Micronaire, uniformity and strength had intermediate heritability estimates (h^ n.s. = 0.05 to 0.66), while loan value, lint yield and gross return had low heritability estimates (h^ n.s. = 0.00 to 0.16). Results of individual correlation analyses on all crosses, the parent varieties and a collection of commercial cultivars showed there was a positive and significant correlation between lint yield and gross return (r = 0.86** to 1.00**). The impact of fiber length on loan value; strength on loan value; micronaire on loan value; length on strength; micronaire on length; and micronaire on strength had a wide range of variation in the correlation coefficients. The correlation and for loan value on gross return; fiber length on gross return; strength on gross return; micronaire on gross return; lint yield on loan value; fiber length on lint yield; strength on lint yield; and micronaire on lint yield, were mostly negative and inconsistent. The cross of SC 9023 X TTU 202 was the only cross to show a positive, significant correlation between fiber length and gross return (r = 0.37**) and fiber length on lint yield (r = 0.25**). These results indicate that selection in crosses between commercial cultivars and two enhanced fiber mutants evaluated in the study could improve fiber quality, lint yield and gross return in High Plains Cotton. The heritability estimates of micronaire, fiber length, uniformity, and strength show potential for improvement of these traits through selection. The highly positive, significant correlations showed that lint yield was the most important factor in determining gross return; fiber length and strength were the most important factors in determining loan value.
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