Plant Genome IV Conference Plant Genome IV Conference
Severe soybean (Glycine max (L.) Merr.) yield losses occur due to the disease sudden death syndrome, caused by Fusarium solani (Mart.) Sacc. f. sp. phaseoli (Burk.) Snyd. & Hans., type A. Selection for partial SDS resistance is the most economic control measure for protecting yield in pathogen infested fields. This study was undertaken with adapted soybean germplasm to identify and characterize loci underlying yield and useful field resistance to SDS. Four separate chromosomal segments were found to be strongly associated with mean SDS DI across 5 locations (P < 0.001). The four loci were stably associated with SDS resistance within each of five SDS pathogen infested locations (p < 0.007). Three of the four loci associated with SDS resistance were also associated with mean yield. However, the yield association was only significant in three of five environments. No additional QTL were detected with a major effect on yield (R2 < 0.05, P M 0.02) that were not associated with SDS. Yield and SDS resistance are imperfectly correlated (R = 0.6). Therefore, we conclude that QTL for yield separate from SDS resistance exist but are much weaker than the SDS/yield associated QTL in this progeny population. Two of the four loci are closely linked to QTL conditioning SCN race 3 resistance, one of these may be pleiotropic. Jointly, the four quantitative trait loci (QTL) accounted for about 65% of total phenotypic variability in mean DI, 50% in mean DS, 35% in mean yield and 25% in SCN resistance. Selection for the SDS resistance QTL may allow efficient selection of resistant genotypes with good yield potential in SDS pathogen infested fields.