The knowledge of origin and evolution of cultivated soybeans is one of the basic issues in both biology and agronomy of the crop. In order to investigate the nuclear and cytoplasmic genetic diversity, geographic differentiation and genetic relationship among geographic ecotypes of cultivated (Glycine max) and wild (G. soja) soybeans, the allelic profiles at 60 nuclear simple-sequence repeat (nuSSR) loci and 11 chloroplastic SSR (cpSSR) loci evenly distributed on whole genome of 393 landraces and 196 wild accessions from nation-wide growing areas in China were analyzed. (i) The genetic diversity of the wild soybean was obviously larger than that of the cultivated soybean, with their nuSSR and cpSSR alleles as 1067 vs. 980 and 57 vs 44, respectively. Of the 980 nuclear alleles detected in the cultivated soybean, 377 new ones (38.5%) emerged, while of the 44 chloroplastic alleles in the cultivated soybean, seven new ones (15.9%) emerged after domestication. (ii) Among the cultivated geographic ecotypes, those from southern China, including South-Central China, Southwest China and South China possessed relatively great genetic diversity than those from northern China, while among the wild geographic ecotypes, the Middle and Lower Changjiang Valleys wild ecotype showed the highest genetic diversity. (iii) The analysis of molecular variance, association analysis between geographic grouping and molecular marker clustering and analysis of specific-present alleles of ecotypes demonstrated that the geographic differentiation of both cultivated and wild soybeans associated with their genetic differentiation, or in other words, had their relevant genetic bases. (iv) The cluster analysis of all accessions clearly showed that the wild accessions from Middle and Lower Changjiang Valleys and South-Central & Southwest China had relatively small genetic distances with all cultivated accessions. The UPGMA dendrogram among geographic ecotypes further showed that the genetic distances between all cultivated ecotypes and the Middle an
WEN ZiXiang, ZHAO TuanJie, DING YanLai & GAI JunYi Soybean Research Institute of Nanjing Agricultural University
Soybean mosaic virus （SMV）, a member of the genus Potyvirus, is a major pathogen of soybean plants in China, and 16 SMV strains have been identified nationwide based on a former detailed SMV classification system. As the P3 gene is thought to be involved in viral replication, systemic infection, pathogenicity, and overcoming resistance, knowledge of the P3 gene sequences of SMV and other potyviruses would be useful in efforts to know the genetic relationships among them and control the disease. P3 gene sequences were obtained from representative isolates of the above-mentioned 16 SMV strains and were compared with other SMV strains and 16 Potyvirus species from the National Center for Biotechnology GenBank database. The P3 genes from the 16 SMV isolates are composed of 1041 nucleotides, encoding 347 amino acids, and share 90.7-100% nucleotide （NT） sequence identities and 95.1-100% amino acid （AA） sequence identities. The P3 coding regions of the 16 SMV isolates share high identities （92.4-98.9% NT and 96.0-100% AA） with the reported Korean isolates, followed by the USA isolates （88.5-97.9% NT and 91.4-98.6% AA）, and share low identities （80.5-85.2% NT and 82.1-84.7% AA） with the reported HZ 1 and P isolates from Pinellia ternata. The sequence identities of the P3 genes between SMV and the 16 potyviruses varied from 44.4 to 81.9% in the NT sequences and from 21.4 to 85.3% in the AA sequences, respectively. Among them, SMV was closely related to Watermelon mosaic virus （WMV）, with 76.0-81.9% NT and 77.5-85.3% AA identities. In addition, the SMV isolates and potyvirus species were clustered into six distinct groups. All the SMV strains isolated from soybean were clustered in Group I, and the remaining species were clustered in other groups. A multiple sequence alignment analysis of the C-terminal regions indicated that the P3 genes within a species were highly conserved, whereas those among species were relatively variable.
Soybean seed storage protein is one of the most important plant vegetable proteins, and β subunit is of great significance to enhance soybean protein quality and processing property. F2 segregated population and residual heterozygous lines（RHL） derived from the cross between Yangyandou（low level of β subunit） and Zhonghuang 13（normal level of β subunit） were used for mapping of β subunit content. Our results showed that β subunit content was controlled by a single dominant locus, qBSC-1（β subunit content）, which was mapped to a region of 11.9 cM on chromosome 20 in F2 population of 85 individuals. This region was narrowed down to 2.5 cM between BARCSOYSSR_20_0997 and BARCSOYSSR_20_0910 in RHL with a larger population size of 246 individuals. There were 48 predicted genes within qBSC-1 region based on the reference genome（Glyma 1.0, Williams 82）, including the two copies of β subunit coding gene CG4. An InDel marker developed from a thymine（TT） insertion in one copy of CG4 promoter region in Yangyandou cosegregrated with BARCSOYSSR_20_0975 within qBSC-1 region, suggesting that this InDel marker maybe useful for marker-assisted selection（MAS）.
