Wednesday, November 7, 2007
278-9

Yield of Slow-Wilting Soybean Breeding Lines in High- and Low- Yielding Environments in the Southern USA.

Philippe Rzewnicki1, Thomas Carter2, Larry Purcell3, Pengying Chen3, H.R. Boerma4, and Thomas Sinclair5. (1) USDA-ARS Plant Science Research Unit, 11210 Crestmont Dr, Raleigh, NC 27613, (2) USDA-ARS, 3127 Ligon St., Raleigh, NC 27607, (3) University of Arkansas, Fayetteville, AR 72704, (4) University of Georgia, Athens, GA 30602, (5) University of Florida, Gainesville, FL 32611-0965

Drought is a major limitation to soybean yield in the USA. However, slow-wilting germplasm has been identified which shows promise in combating this problem. Through two cycles of breeding, the slow-wilting trait was transferred to two maturity group VII soybean breeding lines. NXX traces 25% of its pedigree to slow-wilting PI 416937. NXX also traces 25% of its pedigree to the same PI plus an additional 25% to slow-wilting NTCPR94-5157, an adapted breeding line from the USDA soybean breeding program at Raleigh. These breeding lines were entered into the USDA southern regional soybean trials and evaluated for yield in a total of 23 environments during 2004-2006. Mean yield of the slow-wilting breeding lines (Group A) was calculated as deviation from the mean of all other entries in the test (Group B) and graphed against Group B means. Results indicated that the yield of the slow-wilting lines was numerically equal to the Group B mean when the Group B mean was 38 bu/ac or greater (mean of 14 tests). Yield of the slow-wilting lines was greater than Group B lines when the Group B mean fell below 38 bu/ac (mean of 9 tests).The yield benefit of the slow-wilting lines was more pronounced as the yield of Group B declined. Mean yield advantage in lower-yielding environments was 6 bu/ac. These results suggest that economic value of the slow-wilting trait is quite large and that it may be protective over a wide range of low-yielding environments. Breeders should consider slow-wilting as a priority trait in cultivar development.