Some Loci Affecting Fiber Traits Are Linked to the Pilose Locus

R. H. Kloth


Pilose (T(1)), a dominant marker in upland cotton, has been associated with high micronaire measurements and short fibers. Pilose was, thereby, considered pleiotropic on micronaire and fiber length. However, a pilose-expressing line with a low micronaire value was recently identified. This finding does not support pleiotropy between T(1) and fiber traits, but is indicative of linkage between pilose and loci influencing fiber characteristics. To understand the relationship between T(1) and fiber traits, a pilose line was crossed to two t(1)t(1) lines with standard fiber characteristics. One hundred forty nine F2-derived F3 lines were developed from one cross and 60 F2-derived F3 lines from the other. Eight fiber traits (elongation, maturity, micronaire reading, perimeter, 2.5 % and 50 % span length, strength, and wall thickness) were measured. Segregation was normal, as indicated by allelic frequencies of 0.5 for T(1) and t(1), and segregation ratios of 1 : 2 : 1 for marker genotypes. The association of homozygous T(1) lines with fiber of low micronaire values was again observed. Linkage between T(1) and loci affecting elongation, micronaire, perimeter, 2.5 % span length, strength, and wall thickness was found, as well as significant additive and non-additive gene effects for each of these traits at the marker locus. The pilose marker accounted for 10 to 75% of the phenotypic variation associated with each trait. In conclusion, the t(1) locus is liked to numerous loci that influence fiber traits, and this linkage has been misinterpreted as pleiotropy in the past.

Reprinted from Proceedings of the 1994 Beltwide Cotton Conferences pg. 707
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998