Construction, Analysis And Application Of Mungbean Gentic Linkage Map

Genetic linkage maps are important for genetic studies. However, mungbean [Vigna radiata (L.) Wilczek], one of the important protein sources for the Asia population, is much lagged in genetic research. SSR marker has been popular in developing genetic linkage maps for diverse species. However, the development of SSR primers in mungbean falls behind too. In the present study, we evaluated the transferability of SSR markers into mungbean from 4 relatives, and used the polymorphic transferable SSR markers in constructing mungbean linkage map. Based on the integrated linkage map, the bruchid-resistance locus and the QTLs for seed weight and other eight important agromomic traits were analyzed. In addition, the integrated map for mungbean was compared with the map published for Azuki bean (Vigna angularis) based on common SSR markers. The results are as follows:1. A total of 597 pairs of SSR primers from related species were evaluated for their transferability and polymorphism in mungbean. In total, 128 (65%) of the azuki bean SSRs, 43 (72%) of the blackgram's, 117 (40%) of the common bean's, and 13 (30%) of the cowpea's could generate clear PCR products and 107 pairs were polymorphic. A new genetic linkage map was constructed with 186 markers (98 SSRs, 76 RFLPs, 3 RAPDs, and 9 STSs), including 12 linkage groups, covering a total length of 1 896.0 cM, and the average distance between markers is 10.2 cM.2. As previously reported, a major locus resistant to bruchid was mapped on linkage group I9. And 5 SSR markers from common bean were integrated to the target region, among which C220 was closely linked to it with a genetic distance of about 2.6 cM; 36 common SSR markers were used for comparative mapping for mungbean and azuki bean. And a high level of homology was observed between the two genomes based on the syteny of common markers in linkage maps.3. Additive and epistatic effects of QTLs for 9 important agronomic traits were evaluated based on the information obtained in 3 or 4 sites. Totally, 33 additive QTLs and 10 pairs of epistatic QTLs were detected. The QTLs distributed on 10 linkage groups, except the linkage group 3C and N. The additive QTLs explain the phenotypic variations ranging from 1.1% to 29.8% and 5 QTLs were above 10%. The epistatic QTLs explain the phenotypic variations ranging from 2% to 7.9%. The results also indicate that both the additive effects and epistatic effects are sometimes subjected to environmental modifications.