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 determine the inheritance, allelism, and linkage associations of two spontaneous mutants found in plants of American Pima ( G. barbadense L.) cotton. The two mutants were crossed to the normal phenotype cultivar PS‐6 and to several genetic marker stocks. Appropriate F 1 , F 2 , and BC populations were created for analyses of inheritance and linkage studies. Analyses of F 1 and F 2 populations of a virescent mutant indicated that it is inherited as an extranuclear factor. Expression of the mutant is transient, being strongest in the first true leaf after germination and fading by the fourth or fifth true leaf. It is proposed that the mutant be designated cytoplasmicvirescent 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 it is inherited as a single, recessively expressed gene. Tests for association of the dense glanding trait with 13 other mutant markers produced no evidence of linkage. Linkage tests with two markers, T 1 and ms 13 , were inconclusive. Expression of the dense glanding mutant is confined to expanding leaves and internodes, and to bracteoles. Expression is strongest in the first and second apical leaves, and fades by the fourth or fifth leaf. The designation denseglanding and gene symbol dg are assigned to the mutant.