Genetic Analysis of a Morphological Mutant in Cotton.

A spontaneous mutant discovered in a commercial variety of Upland cotton (Gossypium hirsutum L.) was selected and further characterized. This study was conducted to examine the inheritance and linkage associations of this unique morphological mutant. Plants with this mutation show a range of phenotypes. There is no expression in the seedlings. The mutant phenotype is characterized by smaller, misshapen bracts; a wide range of vigor; and abnormal stature. The mutant was crossed to the Upland cotton genetic standard, TM-1 and to the multiple dominant marker line, T586. F₁, F₂, and BC populations were developed to facilitate inheritance and linkage analyses. Segregation from crosses between the new mutant and the normal type indicated that the mutant phenotype is inherited as a single, dominantly expressed gene. Linkage tests with nine dominant marker loci indicated significant associations at two of the loci, pilose (T₁) and pollen color (P₁). There was 13.94% recombination between the mutant and T₁, and 30.52% recombination between the mutant and P₁. Thus, the linkage associations are not an artifact of excessive recombination. This new mutant is linked about 14 crossover units from T₁ on linkage group IV.