[Mapping of five genes resistant to SMV strains in soybean]

Soybean mosaic virus (SMV) is one of the most prevalent pathogens that impact the soybean world widely. Previous reports showed that most of the resistances were controlled by one pair of dominant genes. In this study, a soybean RIL population NJRIKY derived from Kefeng 1 x Nannong 1138-2 was used to study the inheritance of resistance to five SMV strains (Sa,Sc-8, Sc-9, N1, and N3) and mapping of resistant genes. Kefeng 1 is resistant to all five SMV strains while Nannong 1138-2 is susceptible to all five SMV strains. The parents and RIL populations were planted in green house and five SMV strains were inoculated on different populations. The results showed that each ratio of the number of resistant families to that of susceptible families was consistent with 1:1 for the five strains. This indicated that the resistance to each of the five strains was controlled by one dominant gene, respectively. RFLP and SSR markers were used to analyze the RIL population, Mapmaker/Exp 3.0b was used to study the linkage between markers and the resistant genes. Through linkage analysis, Rsa was found linked Rn1, Rn3 and Rsc9 with 21.4 cM, 23.5 cM and 35.3 cM, Rsc8 was found to be linked only Rn1 with 35.8 cM. Multi locus analysis showed that the order and intervals of the five resistance genes were Rsc8-35.8 cM-Rn1-10.3 cM-Rn3-21.5 cM- Rsa-35.8 cM-Rsc9. According to the result of RFLP and SSR analysis, a genetic map was constructed which consisted of 256 markers that covered 3050.9 cM and converged into 22 linkage groups. The five resistance genes were mapped on the linkage group N8-D1b + W. The RFLP markers A691T, K4771, LC5T were found linked to the resistant genes Rn1 and Rn3 with distances of 15.04 cM, 17.82 cM, 15.37 cM, 16.14 cM, 17.82 cM, 16.58 cM.