Identification of a QTL associated with tolerance of soybean to soil waterlogging

Soil waterlogging is a major environmental stress that suppresses soybean [Glycine mar (L.) Merr.] growth and yield. Our objective was to identify quantitative trait loci (QTL) associated with the tolerance of soybean to soil waterlogging. We subjected 208 lines of two recombinant inbred (RI) populations, 'Archer' X 'Minsoy' and 'Archer' X 'Noir I', to 2 wk of waterlogging when the plants were at the early flowering stage. The control plants were not flooded. The experiment was conducted in three environments: Columbus, OH, in 1997 and 1998 and Wooster, OH, in 1998. We identified a single QTL, linked to marker Sat_064, from the Archer parent which was associated with improved plant growth (from 11-18%) and grain yields (from 47-180%) in waterlogged environments. This highly significant QTL (P = 0.02-0.000001) was identified in both RI populations and at both Columbus 1997 and 1998 environments, but not at the Wooster 1998 environment. The differences in soil type and flooding treatment (stagnant versus moving water) could have contributed to the lack of QTL identification at the Wooster 1998 environment. The Sat_064 QTL was uniquely associated with waterlogging tolerance and was not associated with maturity, normal plant height or grain yields. The Sat_064 marker maps close to the Rps4 gene for Phytophthora (Phytophthora sojae M.J. Kaufmann & J.W. Gerdemann) resistance; however, since Archer does not contain the Rps4 resistance allele, it is probably not a disease tolerance QTL. Near isogenic lines with and without the Sat_064 marker have been developed and are being field tested under waterlogging conditions to confirm the association of the QTL with the tolerance of soybean to waterlogging stress.