Quantitative trait loci affecting cotton fiber are linked to the t1 locus in upland cotton
1995
Kloth, R.H. (United States Dept. of Agriculture/Agricultural Research Service, Stoneville, MS (USA). Jamie Whitten Delta States Research Center)
Pilose (T1), a dominant marker in upland cotton, has been associated with coarse, short fibers. Pilose was, thereby, considered to be pleiotropic on fiber fineness and length. However, a pilose-expressing line with a fiber of average fineness was recently identified. This finding does not support pleiotropy between T1 and fiber traits, but is indicative of linkage between pilose and loci influencing fiber characteristics. To understand the relationship between T1 and fiber traits, a pilose line with short, coarse fiber was crossed to two tltl lines with standard fiber characteristics. One hundred and forty-nine F2-derived F3 lines were developed from one cross, and 60 F2-derived F3 lines from the other. Seven fiber traits (elongation, maturity, micronaire reading, perimeter, 2.5% span length, strength, and wall thickness) were measured. Segregation was normal, as indicated by allelic frequencies of 0.5 for T1 and t1, and segregation ratios of 1:2:1 for marker genotypes. The association of homozygous T1 lines with fibers of average fineness was again observed. Linkage between T1 and loci affecting micronaire, perimeter, 2.5% span length, strength, and wall thickness was found in both populations. Significant additive and non-additive gene effects for each of these traits at the marker locus were found as well. The pilose marker accounted for 10-75% of the phenotypic variation associated with each trait. In conclusion, the t1 locus is linked to numerous loci that influence fiber traits, and this linkage has previously been misinterpreted as pleiotropy.
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