Flooding due to excess soil water is the second most damaging constraint on crop growth, after drought, and affects about 16% of the cropped areas worldwide. Improvement of crop tolerance to flooding stresses will bring great benefits to crop producers, especially of regions where soil drainage is either impractical or impossible. In Missouri, Arkansas, and Mississippi, about half of the soybean acreage (approximately 5 million acres) is affected by waterlogging annually, causing a reduction in yield by 25%. Flood-tolerant soybean, therefore, would be highly beneficial to soybean producers. In collaboration with Dr. J. Grover Shannon, at MU, and Dr. Tara Vantoai, USDA-ARS, we are characterizing genetic variations in waterlogging tolerance in soybean germplasm and developing recombinant populations for QTL mapping. Our long-term goals are to elucidate signaling and metabolic pathways and uncover regulatory elements unique to flood-tolerant responses (candidate genes) under specific environmental conditions.