Dalitso Noble Yabwalo, Plant Science Dept., South Dakota State Univ., South Dakota State University, Brookings, SD and William A. Berzonsky, South Dakota State University, Brookings, SD
Test weight (TW) is one of the integral kernel traits relating to wheat (Triticum aestivum L., 2n = 42, AABBDD genomes) flour yield and determining overall end-use quality. Wheat market grades are dictated by TW, and thus, higher TW genotypes are frequently classified into higher market grades. As a consequence, TW directly impacts economic returns to the grower. Since TW is a measure of weight per unit volume, it is also expected to be influenced by kernel size, shape, density, and packing efficiency (PE), a measure of how much space remains between the kernels when they are fitted to a specific volume. The objectives of this study were to (i) determine kernel traits that affect TW; (ii) determine the genotypic and environmental variances for TW and the traits that affect TW. Winter wheat varieties adapted to the US Northern Plains were sampled from replicated yield trials grown at six different locations in South Dakota. Data was collected on kernel width, length, shape, density, protein content, TW, thousand kernel weight (TKW), and PE. Observed differences in TW were attributed to genotypic and environmental variances and their interaction. A multiple regression analysis of TW and width, length, shape, density, protein content, TW, thousand kernel weight (TKW), and PE indicated that kernel density had the highest positive contribution to TW, followed by PE (p<0.0001). Protein content had a significant negative effect on TW. The relationship between PE and kernel size was negative and significant (p<0.05). This study demonstrated that kernel density can be incorporated in selection indices by breeders to reliably select for TW with a broad sense heritability of 0.75.