averaged, on a 130 g kg Ϫ1 seed moisture basis, a seed yield of 2401 kg ha Ϫ1 , a seed protein content of 354.1 g Soybean [Glycine max (L.) Merr.] seed protein is negatively correkg Ϫ1 , and a seed oil content of 185.6g kg Ϫ1 (Hurburgh, lated with seed oil and often with yield. Our goal was to examine the 2001). These statistics indicated that 67.25 kg of the crop basis for these correlations at a quantitative genetic locus (QTL) level.could be processed into 19.7 kg of 48% protein meal Seventy-six F 5 -derived recombinant inbred lines (RILs) from the matproduct and 4.90 kg of oil product.ing of the high-protein (480 g protein per kg seed) G. max accession PI 437088A with the high-yield cultivar Asgrow A3733 (420 g kg Ϫ1 Soybean protein and oil contents in various regions seed protein content) were evaluated in six irrigation treatments (i.e., of the USA can deviate significantly from the foregoing 100, 80, 60, 40, 20, and 0% replacement of weekly evapotranspiration national averages. Some of that geographic variability loss) of a two-replicate experiment conducted for 2 yr. The RILs were arises from meteorological events that, in any given genotyped with 329 random amplified polymorphic DNAs (RAPDs), season, randomly affect some regions but not others.
simple sequence repeats (SSRs), and four other markers, creatingFor example, high temperatures during soybean seed a 2943-centimorgan (cM) genetic map of 35 linkage group (LGs) that, development can elevate seed oil (Howell and Cartter, on the basis of SSR homology, aligned with the 20 known soybean 1958), while severe drought can depress seed protein LGs. The phenotypic regression of RIL protein and oil on yield re-(Specht et al., 2001). Other geographic variability arises vealed respective linear coefficients of Ϫ2.6 and ϩ1.6 percentage from region-specific climatic parameters. Notably, seed points per kg ha Ϫ1 (a protein/oil exchange ratio of Ϫ1.6). A seed protein is typically lower in the northwestern than in protein, oil, and yield QTL mapped close to RAPD marker OPAW13a southeastern soybean-growing states. In 2001, that rein a small LG-I interval that was flanked by the SSR markers Satt496 gional difference spanned 3 percentage points, the and Satt239. The additive effects of the PI 437088A allele on seed protein, oil, and yield were a respective ϩ1.0 and Ϫ0.6 percentage largest ever observed in 17 yr of survey data (Hurburgh, points (a protein/oil ratio of Ϫ1.6) and Ϫ154 kg ha Ϫ1 . Given that the 2001). Processors may not be able to derive the valuable genetic-based protein/oil exchange ratio of 1.6 is smaller than the 2.0 48% soybean meal if the soybean seed has too low of a calorific-based oil/protein ratio, one might expect the remaining 0.4 protein content. To offset this geographical disadvantage, units of carbon and/or energy to be made available for other seed breeders developing high yielding cultivars adapted to dry matter. However, yield almost invariably falls when seed protein northern and western production regions must practice is genetically ...
