Identification of quantitative trait loci for resistance to soybean cyst nematode race 3 in soybean

With the advent of molecular marker techniques such as RFLP and RAPD, it became possible to identify and localize QTLs and to investigate the types and gene effects attributed to QTLs. This study was conducted; (1) to identify and localize QTLs for SCN race 3, (2) to identify the magnitude and mode of inheritance for each QTL, and (3) to identify the best combinations of QTLs. Twelve markers (7 RAPD, 4 RFLP, and I morphological trait) were significantly (P＜0.05) associated with resistance to SCN race 3. We identified 3 QTLs were mapped to two linkage groups (LGC-3 and LGC-7). Our results indicated that MAPMAKER/QTL analysis allowed more stringent determination of association of molecular makers with resistance to SCN race 3 than by univariate regression analysis. The mode of inheritance for each QTL was 2 dominant and 1 recessive. Two pairs of flanking makers (pA85 and pA170B, B01 and pA 226B) and unlinked RAPD marker (N11¹) were used for multiple regression analysis. The highest variation for SCN response (26.1%) was explained by the marker combinations of pA85, pA170B, B01, amd N11¹. Our results necessitate identification of the remaining QTLs in order to explain larger portion of phenotypic variation in soybean.