Yield and growth characteristics of a high oil-protein soybean with enhanced diacylglycerol acyltransferase

Introduction of the VgDGAT1A gene in soybean [Glycine max (L.) Merr.] genotypes increased both protein and oil content and resulted in earlier maturation compared with commonly cultivated soybean genotypes (i.e., Jack). However, the effect of VgDGAT1A gene on the length of the vegetative, reproductive, and the overall growth period of soybean has not been thoroughly evaluated. A randomized complete block design consisting of two transgenic soybean genotypes with VgD1-1 and VgD1-2 highly active acyl-CoA: diacylglycerol acyltransferase (DGAT) from ironweed [Vernonia galamensis (Cass) Less.] and nontransgenic control (Jack) was evaluated in field studies in 2015 and 2016 in Lexington, Kentucky. Levels of sucrose accumulation and seed weight were calculated for the three genotypes. Soybean grain yield, seed weight, and seed number were similar among all genotypes in both years. Modified genotypes reached the R7 (beginning of physiological maturity) stage earlier, and the rate of dry weight accumulation in individual seeds ranged between 2.8 to 4.4 mg seed(-1) day(-1) and was not different in comparison with the control (range: 3.4-4.7 mg seed(-1) day(-1)). While days to reach R7 was shorter in VgD, there were no differences among genotypes for pod weight (PW), seed weight (SW), pod sucrose (PS), or seed sucrose (SS) concentrations. Linear plateau and cubic models were the best fit for seed weight for both years. These results indicated that despite earlier maturation in VgD genotypes, seed growth, and final soybean yield were similar among VgD and Jack.