| Abstract: | Ninety F-2:3 progeny from a cross of resistant cultivar Peking and susceptible Essex and near-isogenic lines, NC55, and Lee, were employed in transmission, bulk, and segregation analyses to identify molecular markers associated with resistance to soybean cyst nematode (SCN) race 3. SCN bioassays were performed in a greenhouse using a race 3 isolate. Progeny response to SCN was characterized by Female Index (FI). Three morphological traits, 108 restriction fragment length polymorphisms (RFLPs), and 400 random amplified polymorphic DNAs (RAPDs) were employed. The i locus for seed coat color showed highly significant association with resistance to race 3 SCN (R-2=0.25, P = 0.0001). Two independently inherited RFLP markers, pA 136 and pA635, (linkage groups A and C, of the USDA-ARS/ISU soybean RFLP map) and three RAPD markers, E01c (LG A), G15d (LG F), and S07a (LG A), explained 32.5% of the total phenotypic variation for SCN response in F-2 progeny. Two-way ANOVA indicated significant interaction of i locus with pA136, pA635, S07a, and E01c (P=0.0001) suggesting that a quantitative trait locus (QTL) on LG A interacts with other QTLs for SCN resistance in the genome. The dominant QTL was localized 0.6 cM from i locus using MAPMAKER/QTL 1.1. Twenty-six combinations of the identified molecular markers were used in selection for SCN resistance. Combination of 4 markers (pA 136, S07a, G15d, and E01c) explained 67 % of total variation among selected resistant and susceptible individuals. |