Introgression of a High Protein Allele into an Elite Soybean Cultivar Results in a High-Protein Near-Isogenic Line with Yield Parity

Soybean (Glycine max [L.] Merr.) meal is the largest source of protein meal with essential amino acids. Soybean seed protein is negatively correlated with both yield and oil, complicating the simultaneous improvement of seed protein and yield. A major protein quantitative trait locus (QTL) on chromosome (Chr) 20 was identified in genome-wide association and bi-parental population mapping studies. The Chr 20 high-protein allele from 'Danbaekkong' was introgressed into an elite maturity group (MG) VII cultivar, Benning. Two groups of near-isogenic lines (NILs) of Benning, with or without the Danbaekkong Chr 20 allele, were developed and yield-tested in two years. The Danbaekkong allele was associated with a significant 33.6 g kg(-1) increase in protein and 14.3 g kg(-1) decrease in oil (P < 0.05). Average yield of NILs with the Danbaekkong allele were lower than those of NILs without the allele and recurrent parent Benning in both years, but were only significantly lower in 2005 (P < 0.05). Due to its high yield performance, one NIL was yield tested against Benning for two additional years. Combined results from 14 environments over four years revealed yield parity between Benning and Benning high protein (HP), and Benning HP possessed 40.0 g kg(-1) more seed protein and 17.3 g kg(-1) less oil than Benning. Despite overall yield drag by the Danbaekkong Chr 20 high-protein allele, we demonstrate that a significant increase in seed protein without associated reduction in yield is possible with breeding and careful progeny selection using this allele.