Submitted to: Journal of Heredity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 8, 2002
Publication Date: October 30, 2002
Citation: Turley, R.B., Kloth, R. H. 2002. Identification of a Third Fuzzless Seed Locus in Upland Cotton (Gossypium hirsutum L.). The Journal of Heredity. 93(5):359-364. Interpretive Summary: The "naked seed" mutations in cotton can be used as a tool to better understand the development of cotton fiber. There are two types of cotton fiber which develop on cottonseeds. The lint fibers begin to develop at flowering and grow to lengths of approximately an inch. A second round of fiber development occurs about seven days after flowering. These are fuzz fibers and are short and have no economical value. During the development of cotton fiber, "Naked seed" lines are characterized by the presence of lint fibers (economically valuable), but which lack fuzz fibers. We have found a new variable (gene) involved in expressing the "naked seed" mutation in one of the lines used in this study. We have designated this new gene n3, and found that it is also required for the expression of the fiberless trait in cotton (no lint or fuzz). With this new gene n3, and the other two "naked seed" genes, N1 and n2, we have a better understanding gof what is required for production of cotton fiber. Once their identities are known, strategies can be developed, and tested, to increase lint percent or other aspects of fiber quality. With the recent report of a yield plateau in cotton, increasing lint percent, or any other component of yield, is vital to improving the American cotton industry.
Technical Abstract: Segregating populations were developed to evaluate the expression of the fuzzless seed alleles, N1 and n2. Accession 143 of the Mississippi Obsolete Variety Collection (MOVC) carries the n2 locus which is recessive to the seed fuzz phenotype. Data from the F2, BC1F1, F2:F3, and BC1F2 populations of DP 5690 X 143 fit a two loci model for expression of the recessive fuzzless seed phenotype. Expression of the n2 locus required a second recessive locus which we have designated n3. The dominant N3 allele found in DP 5690 reverses the expression of the fuzzless seed phenotype in homozygous n2 plants. Accession 243 of the MOVC carries the N1 locus which is dominant to the presence of seed coat fuzz. No variation from expected ratios occurred when the 243 X DP 5690 cross segregated in the F2, BC1F1, F2:F3, and BC1F2 populations. The N3 allele had no apparent effect on the expression of the N1 locus. In a cross between accessions 243 X 143 a wide evariation in the lint percent of individual plants was observed, including lines which were completely devoid of lint and fuzz fiber (fiberless). A line was derived from an individual fiberless plant which was designated MD 17 fiberless. In a cross between DP 5690 X MD 17 fiberless, we demonstrated that three alleles, N1, n2 and n3, were involved in the expression of the fiberless phenotype. The involvement of n2 and n3 in the expression of the fiberless phenotype was demonstrated in the F2 progeny of the cross between MD 17 fiberless X 143. This was the first demonstration that N1, n2 and n3 epistatically interacted to produce fiberless seed.