Genetic study and validation of molecular markers associated with cyst nematode in soybean populations.

To meet the need of new food-type soybean cultivars with resistance to soybean cyst nematode (SCN), this work aimed to select superior progenies and to estimate genetic parameters in two soybean populations F2:3, F3:4 e F4:5 originated from crosses between genotypes type food x grain type. The evaluated traits were: height of plants at maturity (APM), height of first pod insertion (AIV), lodging (AC), agronomic value (VA), number of pods per plant (NV), number of days to maturity ND), number of branches (NR), number of nodes (NN), weight of 100 seeds (PCS) and grain yield per plant (PG). The experimental design used was the augmented blocks and the statistical analyses were performed using mixed model REML/BLUP. The genetic parameters estimates indicated a high genetic variance in the population, the heritability presented was high for most of the evaluated traits and the coefficients of environmental variation were mostly low. In addition, the identification of molecular markers of the microsatellite type (SSR) associated with resistance to SCN (race 3). This step was performed using F2 progenies of the crosses between grain type soybean x food type, which were previously phenotyped for resistance to NCS. Two pairs of SSR primers flanking 2 genes associated with resistance to the SCN were identified, with Satt275 and Satt309 on chromosome 18 linked to the rhg1 gene and two on chromosome 8, Sat_162 and GMES6186, associated with the Rhg4 gene. Together, these markers can be used effectively in the assisted selection of higher progenies for resistance to NCS. (AU)