Analyses of a genic male-sterile mutant in soybean
Reid G. Palmer
A new genic male-sterile mutant in soybean was characterized genetically, developmentally, and molecularly. This mutant is controlled by a single recessive gene, which is not allelic to six previously identified soybean genic male-sterile mutants: ms1, ms2, ms3, ms4, ms5, or ms6. No linkage was detected between the male-sterile gene and flower color (W1 locus), or between the male-sterile gene and pubescence color (T1 locus). Developmental and enzymatic studies showed that sterility was caused by retention of the callose walls, which normally are degraded by callase ([beta]-1,3-glucanase) at the late tetrad stage. Molecular markers linked with the male-sterile gene were identified by using an F2 population of 111 individuals. Analysis revealed that the male-sterile locus, designated 'ms' was located on linkage group D1b of the USDA/ARS/ISU soybean molecular genetic map. The availability of linked DNA markers will facilitate the genetic analysis of the male-sterile gene in relation to soybean breeding programs, and will be a starting point for the isolation of the ms gene by map-based cloning. Another gene, root florescence (Fr1) segregating in the F2 population was mapped by bulked segregant SSR analysis. Fr1 was mapped on linkage group K, flanked by Satt337 and Sat-044. Fr1 previously was mapped on linkage group 12 of the classical genetic map. Thus classical genetic linkage group 12 has been correlated to linkage group K. Twelve classes of [beta]-1,3-glucanases were cloned and sequenced. Members of 11 classes mapped at 34 loci on 5 different linkage groups using an F2 population of 56 individuals. Northern blot analyses performed on total RNA from root, stem, leaf, pod, flower bud, and hypocotyl, using the different classes of [beta]-1,3-glucanase as probes, indicate tissue specific expression patterns. Sglu7 is expressed in the flower buds. According to expression pattern, phylogenetic studies, and in situ mRNA localization studies (in situ mRNA localization is in a separate manuscript not included in the dissertation), Sglu7 is the candidate gene that encodes [beta]-1,3-glucanase expressed in the anther tapetum and involved in male sterility.