Genetic Analysis And QTL Mapping Of Soybean Seed Size And Shape Traits In Four Related Recombinant Inbred Line Populations

The seed size and shape are very important target traits of soybeans for breeding, and they are also closely related to the yield and appearance quality. It is of great value for soybean high-yield breeding to study the variation of seed morphology traits.reveal the genetic basis of seed size and shape of soybeans, and mine the valuable and stable QTL. In this study, four related recombinant inbred line （RIL） populations （RIM6T, RIZM6, RIM6W, RILM6） from the crosses between Meng 8206 and four diverse parents, Tongshanhuangdou （（?））, Zhengyangpingdinghuang （（?））, Wsb （（?））, Linhehuangdou （（?）） were offered by National Center for Soybean Improvement, in Nanjing Agricultural University. Field experiments in two sites were conducted in 2012, The objective is to reveal the genetic analysis and QTL （quantitative trait locus） mapping of 100-seed weight and seed shape traits in these population, and to obtain useful information and materials for further researches on elite gene discovery and utilization. The main results are as follows.1. Variance analysis showed that there were differences in all seven traits, including 100-seed weight, seed length, seed width, seed thickness, seed length/width, seed length/ thickness, seed width/thickness, in four RIL populations in both Fengyang city of Ahhui province and Pukou district of Jiangsu province. The values of broad heritability of 100-seed weight were all above 85% in all populations, the values of broad heritability of seed length, seed width, seed thickness, seed length/width, seed length/thickness were all above of 80% in four populations. The broad heritability of seed thickness was all above 72% and that of seed width/thickness was all above 65% in four populations. The heritability was high in the four tested populations.2. According to the results of segregation analysis method of the mixed major genes and polygenes inheritance model, The 100-seed weight traits of RIM6T population in two test sites and of RIZM6 population in FengYang site fitted E₁₇ model （2 major genes+ polygenes+complementary role）, and those of RIZM6 and RILM6 in JiangPu site followed E₁₉ （2 major genes+polygenes+inhibition） model. The 100-seed weight traits of RIM6W population in Jiangpu and of RILM6 group in Fengyang fitted E₁₈ （2 major genes+polygenes+overlapping role） model, however, that of RIM6W in JiangPu followed the C₂ （polygenic） model. Except grain length might be controlled by 2 major genes （B model）,2 major genes+polygenes （E model） and polygenes （C model）, other seed shape traits were controlled by polygenes （C model）.3. By using the high-density genetic maps of RIM6T, RIZM6, RIM6W and RILM6 populations, the QTL mapping of 100-seed weight, seed length, seed width, seed thickness, seed length/width, seed length/thickness, seed width/thickness of 4 RIL populations in two sites were analyzed by software Windows QTL Cartographer V2.5. The results showed that 9 and 11 QTL conferring seed morphology-related traits were detected in RIM6T population in two sites, and located on seven linkage groups （Al linkage group etc.）. A total of 30 and 28 QTL controlling seven seed morphology-related traits were mapped in RIZM6 population in two sites, and located on 18 linkage groups. Total 42 and 31 QTL for seven seed morphology-related traits were found in RIM6W population in two sites, and located on 15 linkage groups. Nine and ten QTL for seven seed morphology-related traits were found in RILM6 population in two sites, and located on seven linkage groups （A2 linkage group etc.）. The contribution rate of 57 loci in all QTL surpassed 10%. Among them, the contribution rate of qSL/SW-5-1 and qSWT-14-2 in RIM6T in JiangPu site reached to 20.73% and 24.46%. The "repeatable" QTL in two sites were summerize. There were five QTL of 100-seed weight trait detected in two planting sites, including three named as qSWT-5-1, qSWT-5-12 and qSWT-12-1 in RIM6T population, qSWT-7-1 in RILM6 qSWT-17-1 in RIM6W. Ten QTL of seed shape trait were detected in two planting sites. There were two QTL, qSW-8-1 and qSW-13-1, for seed width and one for seed thickness trait named qST-13-1. in RILM6 population. In RIM6W population, each of the seed width trait, seed length/width trait, seed length/thickness trait and seed width/thickness trait has also been found each of four QTL named qSW-17-1, qSL/SW-2-1, qSL/ST-2-1 and qSW/ST-11-1.was found to control seed width, seed length/width, seed length/thickness and seed width/thickness trait respectively. Three QTLfor seed length/width trait, which named qSL/SW-5-1, qSL/SW-13-3, and qSL/SW-15-1 were also detected in RIZM6 population in two sites.