Theor Appl Genet (2009) 119:587–594 DOI 10.1007/s00122-009-1068-4 123 ORIGINAL PAPER Polygenic inheritance of canopy wilting in soybean [Glycine max (L.) Merr.] Dirk V. Charlson · Sandeep Bhatnagar · C. Andy King · JeVery D. Ray · Clay H. Sneller · Thomas E. Carter Jr. · Larry C. Purcell Received: 17 December 2008 / Accepted: 9 May 2009 / Published online: 27 May 2009  Springer-Verlag 2009 Abstract As water demand for agriculture exceeds water availability, cropping systems need to become more eYcient in water usage, such as deployment of cultivars that sustain yield under drought conditions. Soybean culti- vars diVer in how quickly they wilt during water-deWcit stress, and this trait may lead to yield improvement during drought. The objective of this study was to determine the genetic mechanism of canopy wilting in soybean using a mapping population of recombinant inbred lines (RILs) derived from a cross between KS4895 and Jackson. Canopy wilting was rated in three environments using a rating scale of 0 (no wilting) to 100 (severe wilting and plant death). Transgressive segregation was observed for the RIL popu- lation with the parents expressing intermediate wilting scores. Using multiple-loci analysis, four quantitative trait loci (QTLs) on molecular linkage groups (MLGs) A2, B2, D2, and F were detected (P · 0.05), which collectively accounted for 47% of the phenotypic variation of genotypic means over all three environments. An analysis of the data by state revealed that 44% of the observed phenotypic vari- ation in the Arkansas environments could be accounted for by these QTLs. Only the QTL on MLG F was detected at North Carolina where it accounted for 16% of the pheno- typic variation. These results demonstrate that the genetic mechanism controlling canopy wilting was polygenic and environmentally sensitive and provide a foundation for future research to examine the importance of canopy wilt- ing in drought tolerance of soybean. Introduction Agriculture accounts for approximately 70% of water usage globally, and 40% of crop hectarage is grown on irrigated soils (IPCC 2001). With the increasing impact of global warming and rising human population, scientists expect an increased demand on water supply in the form of irrigation world-wide (IPCC 2001). Some agricultural regions where water supply is currently plentiful may experience decreases in water availability as a result of more frequent drought episodes, or they may become too arid for agricul- tural production. With these challenges to water availabil- ity, agriculturalists will need to adopt eYcient management strategies that reduce the amount of water necessary for crops and/or increase a crop’s eYciency for using water. Drought-tolerant cultivars will be an important compo- nent of future water management strategies in agriculture, Communicated by F. Muehlbauer. D. V. Charlson · S. Bhatnagar · C. A. King · C. H. Sneller · L. C. Purcell (&) Department of Crop, Soil, and Environmental Science, University of Arkansas, Fayetteville, AR 72704, USA e-mail: lpurcell@uark.edu J. D. Ray USDA-ARS, Crop Genetics and Production Research Unit, Stoneville, MS 38776, USA T. E. Carter Jr. USDA-ARS, Department of Crop Science, North Carolina State University, Raleigh, NC 27695, USA Present Address: S. Bhatnagar Monsanto Company, Leesburg, GA 31763, USA Present Address: C. H. Sneller Department of Horticulture and Crop Science OARDC, The Ohio State University, Wooster, OH 44691, USA