Correlation and QTL Analysis of Seed Yield, Protein and Oil Content in a Recombinant Inbred Population of Soybean.

Soybean seeds contain high levels of protein and oil useful for human consumption. Increased seed yield, protein and oil content are the main objectives of soybean breeding.  The objectives of this study were to explore the underlying relationships among these traits by traditional correlation analysis and QTL-based analysis.  A recombinant inbred population was evaluated for seed yield, protein and oil content in five environments over three years.  A genetic linkage map was constructed with 710 polymorphic DNA markers and three GmFAD3 genes.  There were highly significant differences within the population for all traits.  The coefficient of correlation based on average data over five experiments was -0.539 between yield and protein, 0.230 between yield and oil, and -0.477 between protein and oil, respectively.  In total, 41 QTL for the three traits were detected.  The QTL on linkage groups D2 (Chr 17), E (Chr 15), I (Chr 20) and K (Chr 9) for yield, protein and oil, the QTL on linkage groups B1 (Chr 11), C1 (Chr 4), D1b (Chr 2) and N (Chr 3) for protein and oil, and the QTL on linkage group O (Chr 10) for oil and yield, were in the same region or situated in close proximity to one another (<5cM apart), suggesting that these QTL might have pleiotropic effects.  These QTL exhibited opposite effects on yield and protein or protein and oil in most cases.  The QTL for yield and oil on linkage groups K and O exhibited opposite effects but the effects of the QTL on linkage groups D2, E and I were similar in direction.  This molecular information may provide a better understanding of the relationships among seed yield, protein and oil content, and may also be useful for breeding higher yield and better quality soybean varieties.