Studies On Natural Variation, Germplasm Exploration And Genetic Improvement Of Male Sterility In Soybeans

Male sterility in crops has been utilized in development of hybrid cultivars and population improvement, and also in the researches on the mechanism of plant developmental and reproductive biology. Some soybean cytoplasmic-nuclear male sterile (CMS) lines and nuclear male-sterile (NMS) mutants have been obtained, but the efficiency of seed increase and hybrid seed production of CMS lines is still a barrier to commercial utilization of heterosis due to pollination problem, and related basic research is necessary. Discovery and development of new male-sterile lines will be an effective approach to improve the fertility and outcrossing ability of soybean. The objectives of this thesis were to detect, identify and develop new CMS and NMS lines from soybean landraces, hybrid populations and induced mutation progenies, respectively, to reveal their male and female fertility, pod-set situation and genetic characteristics, and to reveal the natural variation of male sterility in soybean. The main results were as follows:1. Total nineteen sterile lines were identified and evaluated from 8327 soybean landraces and 414 hybrid populations. Most of these sterile lines might be natural mutants according to their similar morphological and agronomical performances to their corresponding parents. The natural mutation rate of sterility was estimated as 0～1.87×10 from five cultivars with large population size. The results indicated that there existed certain amount of natural variation and mutants in sterility which were feasible to be obtained through natural variation selection and could be used as elite sources for further research on development and reproductive biology as well as in breeding programs of soybeans.Six male and female performance types were identified according to the male and female fertility of 19 sterile lines from natural variation and five from induced mutation. It included : ① seven lines with male-sterile and female-fertile (MS-FF) type, and three lines, NJS-3H, NJS-4H, NJS-8H, had good outcrossing ability, ② three lines with male-sterile and female partially sterile (MS-FPS) type, ③ two lines with male-sterile and female-sterile (MS-FS) type, ④ two lines with male partially sterile and female fertile...