Mungbean (Vigna radiata) is a fast-growing, warm-season legume crop that is primarily cultivated in developing countries of Asia. We constructed a draft genome sequence of mungbean to facilitate genome research into the subgenus Ceratotropis and to enable a better understanding of the evolution of leguminous species. The draft genome sequence covers 80% of the estimated genome, of which 50.1% consists of repetitive sequences. In total, 22,427 high confidence protein-coding genes were predicted. Based on the de novo assembly of additional wild mungbean species, the divergence of what was eventually domesticated and the sampled wild mungbean species appears to have predated domestication. Moreover, the de novo assembly of a tetraploid Vigna species (Vigna reflexo-pilosa var. glabra) provided genomic evidence of a recent allopolyploid event. To further study speciation, we compared de novo RNA-seq assemblies of 22 accessions of 18 Vigna species and protein sets of Glycine max and Cajanus cajan. The species tree was constructed by a Bayesian Markov chain Monte Carlo method using highly confident orthologs shared by all 24 accessions. The present assembly of V. radiata var. radiata will facilitate genome research and accelerate molecular breeding of the subgenus Ceratotropis.

The purposes of this research project are to identify quantitative trait loci (QTLs) associated with yield-related traits using a recombinant inbred line (RIL) population derived from a cross between a high-yield soybean genotype SS0404-T5-76 and Daewonkong and to develop high-yield soybean and lodging-resistant sprout soybean cultivars. For development of DNA markers and identification of functional sequence variations, firstly, whole genome of five soybean genotypes, Sinpaldalkong 2, SS2-2, Pungsanamulkong, SS0404-T5-76 and Daewongkong, were sequenced using Illumina Hi-Seq technology. SS2-2 is a EMS-induced mutant of Sinpadalkong 2. SS0404-T5-76 showing high-yield is a F8 RIL derived from a cross of Pungsanamulkong x SS2-2. Daewonkong is a elite cultivar with high-protein. Furthermore, to construct a genetic linkage map, we are advancing F4 lines of SS0404-T5-76 x Daewonkong by single seed-descent. Secondly, we developed high-protein and high-yield soybean lines and lodging-resistant sprout lines. Area-adaptability tests of these promising lines are performing in three different locations including Jeju, Naju, and Suwon. Based on the results of area adaptability tests, we are planing to conduct cultivar registration of the promising soybean lines.

Phomopsis seed decay (PSD), primarily caused by Phomopsis longicolla, is a major contributor to poor soybean seed quality and significant yield loss, particularly in early maturing soybean genotypes. However, it is not yet known whether PSD resistance is associated with early maturity. This study was conducted to identify quantitative trait loci (QTLs) for resistance to PSD and maturity time using a recombinant inbred line (RIL) population derived from a cross between the PSD-resistant Taekwangkong and the PSD-susceptible SS2-2. Based on a genetic linkage map incorporating 117 simple sequence repeat markers, QTL analysis revealed two and three QTLs conferring PSD resistance and maturity time, respectively, in the RIL population. Two QTLs (PSD-6-1 and PSD-10-2) for PSD resistance were identified in the intervals of Satt100-Satt460 and Sat_038-Satt243 on chromosomes (Chrs) 6 and 10, respectively. These QTLs do not overlap with any previously reported loci for PSD resistance in other soybean genotypes. Two QTLs explained phenotypic variances in PSD resistance of 46.3% and 14.1%, respectively. Among three QTLs for maturity time, two (Mat-6-2 and Mat-10-3) were located at positions similar to the PSD resistance QTLs. The identification of the QTLs linked to both PSD resistance and maturity time indicates a biological correlation between these two traits. The newly identified QTLs for resistance to PSD associated with maturity time in Taekwangkong will help improve soybean resistance to P. longicolla.

Phytic acid, myo-inositol (1, 2, 3, 4, 5, 6)-hexakisphosphate, is a material that plants store phosphorus in seeds. Phytic acid is classified as an antinutrient because of indigestibility. Non-ruminant animals, such as human and swine, excrete unavailable phytic acid. The unavailable phytic acid run off to ground water, river, sea, causing eutrophication as a factor. Accordingly, low-phytic acid crops draw the attention due to both nutritional and environmental reasons. Using more than 900 Glycine accessions including G. max, G. soja and G. gracillis, colormetric method was applied for detecting low-phytic acid mutant. Two hundred fifty accessions were screened by the colormetric method so far, but no mutant was identified. Screening of mutants with the rest 710 accessions is in progress. MIPS1 (D-myo-inositol 3-phosphate synthase) is considered as gene related to phytic acid content in soybean. Also, lpa1 (Zea mays low phytic acid 1) known as controlling phytic acid content in maize was recently reported that homologs of lpa1 were responsible for phytic acid content in soybean and located on linkage groups L and N (Chromosomes 19 and 3). After primers were designed from these three candidate genes for phytic acid content, identification of genes responsible for low phytic acid and investigation of genetic variation among 960 accessions will be performed as further study.

The 117 soybean cultivars were collected from nine provinces in Korea, and various seed quality traits along with isoflavone contents were evaluated to elucidate their relationship. The 100-seed weight of the black soybean (31.2 g) was significantly higher (p<0.05) than yellow soybeans (28.6 g). The composition of genistein, daidzein, and glycitein accounted for 75.8, 22.8, and 1.4 % of total isoflavone in yellow soybean cultivars, while their compositions in black soybeans were 58.5, 39.7, and 1.8%, respectively. The mean contents of total isoflavone in yellow and black soybean were l,561.6~mug~;g-1~;and~;l,018.3~mug~;g-1 . The isofalvone content showed significant variation among cultivars when classified by the seed size. In the yellow soybeans, total isoflavone content was higher in small size soybean cultivars (1,776.0~mug~;g-1) and medium size soybean cultivars (1,714.3~mug~;g-1) compared to large size ones (1,518.5~mug~;g-1) . Genistein content was proved as the major factor determining the relationship between isoflavone content and 100-seed weights (r =-0.206*). Daidzein and glycitein, however, showed no significant relationship with the 100-seed weights. Isoflavone content was not significantly correlated with color parameters L (lightness) and a (redness) values, but color parameter b (yellowness) was positively correlated with glycitein (r=0.264*) in the yellow soybeans, while its negative correlation between daidzein (r=-0.245*) and total isoflavone (r=-0.256*) were observed in black soybeans. However, these findings suggested that the seed color value may not serve as an effective parameter for estimating the isoflavone intensity of the soybeans. Variation of protein and lipid contents between yellow soybeans (n=58) and black soybeans (n=59) was relatively stable, however, protein and lipid contents have no significant relationship with isoflavone content.

This study was carried out to know the variation of soybean seed proteins, 11S and 7S globulins, and their amino acid compositions among different colored soybean varieties, 'Danbaegkong' (yellow), 'Pureunkong' (green) 'Jinyulkong' (brown), and 'Geoumjeongkong l' (black). Soybean seed proteins showed a wide range in molecular size, but the electrophoresis patterns of total seed protein subunits showed a similarity among different colored soybean varieties. Amino acid compositions of total seed proteins were similar for all soybean varieties tested. However, soybean varieties showed low composition rates in sulfur containing amino acids. The composition rates of cysteine and methionine in the 11S globulins were higher than those of total seed proteins and 7S globulins. Glutamic acid and glycine were higher in the 11S and 7S globulins than those of total seed proteins. However, the levels of methionine and phenylalanine are high in the 11S globulins, but those of valine and lysin are slightly lower than the 7S globulins. By using HPLC, we tried to analyse the soybean seed proteins. The 11S globulin was composed of 10 major peaks whereas the 7S globulin was composed of 4 major peaks. The composition rates of 11S related proteins have a tendency to increasing during the maturing whereas those of 7S related proteins have a tendency to decreasing. Composition rates of each peaks among different colored soybean varieties suggested that soybean seed proteins are varied, although they showed similarity in the electrophoresis patterns, and understanding of this characteristics is important for the utilization of soybeans.

Small seed size is one of the major traits of soybean cultivars for sprouts with regard to high sprout yield. This study was conducted to identify quantitative trait loci (QTL) for seed size and weight in a set of F 6 seeds of 89 lines derived from a cross between 'Pureunkong', a soybean cultivar developed for sprouts and 'Jinpumkong 2', a soybean cultivar with no beany taste in seed due to the lack of lipoxygenases. The genetic map of 25 linkage groups with a total of 98 markers including RFLP, RAPD, SSR and classical markers was constructed from this F/sbu 5/-derived population and was used for QTL analysis. 'Pureunkong' was significantly smaller (P＜0.01) than 'Jinpumkong 2' in seed size and seed weight. Genetic variation was detected and transgressive segregation was common in the population for these traits. Seven DNA markers including opT14-1600 in LG A2, opF02-400 in LG B2, Satt100, opC09-700, opG04-730 and opQll-650 in LG C2, and opY07-1100 ＆ 1000 in LG(unknown) were significantly associated and accounted for 4.7 to 10.9% and 5.1 to 10.1 % of the phenotypic variation in seed size and seed weight, respectively. 'Pureunkong' alleles increased seed size and seed weight at the all four significant marker loci on the LG C2. These marker loci in LG C2 were closely linked and were presumed to be a single QTL. Overall, at least three independent QTLs from 3 linkage groups (A2, B2, and C2) were putatively involved in the control of seed size and seed weight.

The objective of this study was to develop a linkage map of soybean under the genetic background of Korean soybean. A set of 89 F/sub 5/ lines was developed from a cross between 'Pureunkong', which was released for soy-bean sprout, and 'Jinpumkong 2', which had no beany taste in seed due to lack of lipoxygenase 1, 2, and 3. A linkage map was constructed for this population with a set of 113 genetic markers including 7 restriction fragment length polymorphism (RFLP) markers, 79 randomly amplified polymorphic DNA (RAPD) markers, 24 simple sequence repeat(SSR) markers, and 3 morphological markers. The map defined approximately 807.4 cM of the soybean genome comprising 25 linkage groups with 98 polymorphic markers. Fifteen markers remained unlinked. Seventeen linkage groups identified here could be assigned to the respective 13 linkage groups in the USDA soybean genetic map. RFLP and SSR markers segregated at only single genetic loci. Fourteen of the 25 linkage groups contained at least one SSR marker locus. Map positions of most of the SSR loci and their linkages with RFLP markers were consistent with previous reports of the USDA soybean linkage groups. For RAPD, banding patterns of 13 decamer primers showed independent segregations at two or more marker loci for each primer. Only the segregation at op Y07 locus was expressed with codominant manner among all RAPD loci. As the soybean genetic map in our study is more updated, molecular approaches of agronomically important genes would be useful to improve Korean soybean improvement.