Analyses of a Dominant Male‐Sterile Character in Upland Cotton. II. Genetic Studies1

Abstract

A plant in an okra leaf, frego bract, nectariless strain of upland cotton (Gossypium hirsutum L.) had one branch bearing male‐sterile flowers. Crosses between male‐sterile and male‐fertile plants resulted in populations segregating 1:1 for fertile and sterile plants. Populations from selfed F1 and F4 fertile plants contained only fertile plants. These data suggested that a dominant gene controlled the sterility expression. Viability tests disclosed that a few viable pollen grains were produced in male‐sterile flowers. Six male‐sterile plants produced self‐pollinated seed; the resulting progenies gave a ratio of one sterile to one fertile plant, rather than 3:1 as expected. It was theorized that the pollen grains carrying the dominant gene for male sterility were less competitive than pollen grains carrying the recessive allele or non‐viable. Testcross populations of sterile plants in the F2 generation segregated 1 fertile:1 sterile, indicating that no plant was homozygous dominant for male sterility. Cytological observations had revealed that the new dominant gene differed from Ms4 and Ms7, is microsporogenesis breakdown. The gene symbol Ms10 is proposed for this new dominant gene conditioning male sterility.