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Penetrance of Genes Associated with Genes for Incompatibility

Claude L. Rhyne, Jack C. Carter


Cultivars cross with incompatible cottons producing hybrid seed that are lethal. Incompatibles have gene le1 of a wild Ecuadorian and the independently inherited Le2dav of wild diploid Gossypium 2D3. Even if these genes are extant in Upland background, they carry associated genes of the donor species. Among these are tufting of seed but breeders have selected for n1 that confers fuzzy seed. The F1 of a naked seed le1 N1 stock x the Stoneville 907 cultivar Le1 Le2 was challenged by an incompatible yielding viable that were naked seeded except one non-naked. An earlier attempt had yielded one non-naked. Together, le1 n1 recombination was 3.8 cM. The recombinant produced seed ranging from a low grade tufted to uniformly fuzzy, indicating a range in expressivity of the le1 n1 / le1 tufting phenotype. Advancing the genotype resulted in S1 and S2 that were uniformly fuzzy, nectariless gland-free and pollen fertile. This infrequent event localized recombination rendering the genotype gl2 le1*n1 ne1 Ms8. The genotype was combined with Le2dav - Ne2 Ms9. Since Le2dav was associated with Ne2 and recombined with ms9 the order of genes is similar to those of the le1 n1 recombinant. The gene at the N2 locus is similar to the gene of fuzzy seeded cultivers. Inheritance and expressivity of genes for tufting was investigated showing a range in fuzz amount and location on seed. Evidence for complementary genes at independent loci and for a gene of variable expression was obtained. Phenotype tufted at the tip deteriorated to bare spots on seed otherwise fuzzy in individual plants, even if the common expression of the heterozygote was a barren seed with a green tuft of fuzz at the small end. Other non-hirsutum genes of the linkage group, Ms11 le1 tufting Ne1 also varied in expressivity.

Reprinted from Proceedings of the 1996 Beltwide Cotton Conferences pp. 619 - 622
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998