Inheritance of Leaf Pubescence in Upland Cotton

~ ~ zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Pubescence and lint percentage. . . . . . . . . . . . . . . . . . . . . Pubescence and lint index, . . . . . . . . . . . . . . . . . . . . . . . . Pubescence and seed index. . . . . . . . . . . . . . . . . . . . . . . . . Pubescence and bolls per pound. . . . . . . . . . . . . . . . . . . . Pubescence and upper-half mean (fiber length). . . . . . . Pubescence and Presslev index (fiber strenath) . . . . . . . . LMOST all varieties of American Upland cotton A have an appreciable amount of pubescence on the lower surface of the leaves. This hairiness is an important factor influencing the grade of the lint, as it causes particles of dead leaves to adhere to the fiber and become included in the lint sample. As a result, varieties with a relatively low degree of pubescence generally produce a better grade of lint, particularly when the cotton has been harvested mechanically. Simpsonl studied the inheritance of a highly pubescent type which he designated T611. In crosses with Acala 5675 and Stoneville 17, the F, was intermediate and evidence of segregation for a single pair of factors was obtained in F, and F3. The gene for abnormally high pubescence was found to cause an appreciable reduction in lint length. It was not associated with seed index, lint percentage, lint index, and lint strength. Considerable interest has been shown recently in the variety Delta Smooth Leaf as a source of nonpubescent leaves in cotton breeding programs. The leaves of this variety are not completely smooth, but the small degree of pubescence present is of little consequence. This paper presents a summary of the inheritance of degree of leaf pubescence in the F, of a cross involving Delta Smooth Leaf and Stoneville 2-B, an Upland variety with a normal degree of leaf hairiness. Results from classifying plants of each parent and the F, are presented in Table 1. Seven classes, differentiated on the basis of degree of pubescence on the lower surface of mature leaves, were recognized in the classification. These were designated as 1, 1+, 2, 2+, 3, S+, and 4.‘Class 1 represents the smoothest leaf condition found in the populations, and Class 4 includes the most pubescent types that occurred. The data in Table 1 reveal that 28 of the 29 plants of the Delta Smooth Leaf parent were placed in Classes I , I+, or 2, with Class 1 as the modal class, All plants of the Stoneville parent were placed in Classes 3, 3+, or 4, Class 3 being the modal class. The 222 F, plants were distributed in Classes 1, 2, 2+, 3, and 3’. In spite of the number of classes found in F,, there is a suggestion