Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/20/2002
Publication Date: 1/3/2003
Citation: CHUNG, J.I., OLSEN, H.L., GRAEF, G.L., STASWICH, P.E., LEE, D.J., CREGAN, P.B., SHOEMAKER, R.C., SPECHT, J.E. THE SEED PROTEIN, OIL, AND YIELD QTL ON SOYBEAN LINKAGE GROUP I. CROP SCIENCE. 2003. v. 43. p. 1053-1067. Interpretive Summary: Soybean is a major source of dietary protein for livestock and an increasing number of humans. Soybean is also the number one source of edible oil. Unfortunately, as breeders increase levels of protein, seed yield and seed oil production decreases, and vice versa. In this study the authors examined the genetic basis for this negative correlation. The authors determined that gene(s) may exist on one soybean chromosome that minimizes the negative correlation between oil and yield, and protein production. These gene(s) may play a role in allocation of the energy captured by photosynthesis. This information may lead the way for scientists to better understand why it is difficult to increase protein production and yield at the same time. This in turn may result in higher yields of high quality soybeans.
Technical Abstract: Variation in soybean [Glycine max (L.) Merrill] seed protein is negatively correlated with seed oil and yield. Our goal was to examine the genic (i.e., QTL) basis for these correlations. Seventy-six F5-derived RILs from a mating of a high protein (ca. 480 g kg-1) G. max accession PI 437088A with the high-yielding cultivar Asgrow A3733 (ca. 420 g kg-1) was evaluated in a 2-replicate, 6-water level experiment conducted for two years. The RILs were genotyped with 329 RAPDs, 103 SSRs, and four other markers, creating a 2943-cM genetic map of 35 LGs that, based on SSR homology, aligned with the 20 known soybean LGs. The phenotypic regression of RIL protein and oil on yield generated linear coefficients of ca. -2.6 and +1.6 (i.e., a ratio of ca. ¿1.6). A seed protein, oil, and yield QTL mapped to a LG-I interval flanked by the SSRs Satt496 and Satt239, close to the intervening RAPD OPAW13a. The additive effect of the PI 437088A allele on protein and oil was +1.0 and -0.6 % (i.e., a ratio of ca. ¿1.6), and on yield was -154 kg ha-1. A 1.6 protein / oil exchange ratio is significantly less than the calorific-based ratio of 2.0. A genetic diversion of photosynthetic carbon from 1.0 units of seed oil to 1.6 (instead of 2.0) units of seed protein should free up carbon and/or energy for extra seed dry matter. However, genetic improvement in seed protein (at the expense of oil) almost invariably leads to lower seed yield, suggesting that the energy needed for protein synthesis and deposition into the soybean seed have been significantly underestimated.