Validation of QTLs for Soybean Cyst Nematode Resistance in Two Inter-specific Soybean Populations.

Soybean Cyst nematode (SCN) (Heterodera glycines Ichinohe) is the most damaging soybean pest world-wide. Glycine soja, the soybean's wild ancestor, may provide sources of new minor and major resistance genes that could help in developing more diverse SCN resistant varieties. In a previous study, novel quantitative trait loci (QTLs) associated with SCN resistance were identified on LG I, K and O in a population derived from the cross between Glycine max NKS08-80 and Glycine soja PI 464925b. In order to validate these QTLs and study the linkage relationship between loci that confer resistance to SCN, two inter-specific soybean recombinant inbred line (RIL) populations (P2 and P4) were studied. The P2 population consisted of 121 F2:5 lines derived from the cross between NK S08-80 and PI 458536 and the P4 population consisted of 209 F2:3 lines derived from the cross between OAC Shire and PI464925B. Phenotyping results showed SCN resistance data of each population were normally distributed. Extreme genotypes were found in both populations indicating transgressive segregation. For P2, the parent PI458536 was highly resistant and 74% of the RILs showed some level of resistance. For P4, 6% of the RILs were moderately resistant, although neither parent was resistant. Parents were screened with 92 SSR markers previously linked to SCN resistance and 52 and 65 polymorphic markers were found between the parents of P2 and P4 respectively. Currently, RILs from both populations are being genotyped with the polymorphic SSR markers to identify QTLs conferring resistance to SCN. The analysis of QTLs will generate new knowledge about the contribution of novel SCN resistant alleles coming from G. soja. On the other hand, effective and stable QTLs in Glycine soja will facilitate soybean breeding efforts to incorporate novel sources of SCN resistance and to improve our understanding of its inheritance in the wild germplasm.