Inheritance of cytoplasmic-virescent cyt-V and dense-glanding dg mutants in American pima cotton

Morphological mutants of cotton (Gossypium spp,) have been used extensively in genetic mapping studies and in several instances have proven useful in agronomic improvement efforts. This investigation was conducted to determin e the inheritance, allelism, and linkage associations of two spontaneous mu tants found in plants of American Pima (G, barbadense L,) cotton. The two m utants were crossed to the normal phenotype cultivar PS-6 and to several ge netic marker stocks, Appropriate F-1, F-2 and BC populations were created f or analyses of inheritance and linkage studies. Analyses of F-1 nd F-2 popu lations of a virescent mutant indicated that it is inherited as an extranuc lear factor. Expression of the mutant is transient, being strongest in the first true leaf after germination and fading by the fourth or fifth true le af. It is proposed that the mutant be designated cytoplasmic-virescent and be assigned the gene symbol cyt-V. Analyses of F-1, F-2, and BC populations of a second, juvenilely expressed, densely glanded mutant indicated that i t is inherited as a single, recessively expressed gene. Tests for associati on of the dense glanding trait with 13 other mutant markers produced no evi dence of linkage. Linkage tests with two markers, T-1 and ms(13), were inco nclusive. Expression of the dense glanding mutant is confined to expanding leaves and internodes, and to bracteoles, Expression is strongest in the fi rst and second apical leaves, and fades by the fourth or fifth leaf, The de signation dense-glanding and gene symbol dg are assigned to the mutant.