Identification of QTL(s) associated with resistance to sudden death syndrome (SDS) in soybeans

Abstract

Sudden Death Syndrome (SDS), caused by Fusarium virguliforme has been recognized to be one of the top four loss-causing diseases for soybeans (Glycine max L .Merr.) on a worldwide basis. By 2007, more than twenty QTLs providing resistance to SDS causing isolates were reported in eight different recombinant inbred line (RIL) populations grown in the Southern United States. This study was conducted to examine the Northern germplasm for SDS resistance. The objectives were to (1) establish a screening method for SDS of soybeans that provides informative phenotypes for both root resistance and foliar resistance (2)estimate the number, genetic positions and genetic effects of QTL involved in resistance under greenhouse and field conditions (3) determine the proportion of the genotypic variance explained by all detected QTL (4) to compare our results with those of other studies and (5) to draw conclusions about the prospects of utilizing marker-assisted selection (MAS) for increasing the level of resistance to SDS in the Northern germplasm. An RIL population of 230 F5 derived F12 lines developed from `Minsoy' x `Noir1' was evaluated in the greenhouse and field with three varying procedures. Foliar and root rot SDS damage was assessed using a visual rating scale. Seven QTLS were detected for foliar resistance on chromosomes one, three, four, five, six and fifteen (D1a, N, C1, A1, C2, and E, respectively) with a total of 79.27% of genetic variance explained. Two QTLs were detected for root rot resistance on chromosomes two and three (D1b and N, respectively) with a total of 21.1% of genetic variance explained. A number of the intervals were associated with previous reported SDS resistant QTLs; however, it appears that several of the QTLs are novel. Further research should be conducted to confirm the new locations.