Mass Selection for Increased Seed Protein Concentration of Wheat Based on Seed Density 1

Seed density selection to increase the seed protein concentration of wheat ( Triticum aestivum L.) has not been effective due to the small difference in the dry densities of starch (1.60 Mg m ‐3 ) and protein (1.40 to 1.45 Mg m ‐3 ). In this study, water imbibition wheat seeds for 9 to 10 days at 0 to 3°C was shown to enhance the differential densities of protein and starch. Linear relationships between protein concentration and imbibedensity, and protein concentration and water absorption of wheat seed were demonstrated in samples of three bulk populations and ‘Bennett’ separated in CCl 4‐ hexane solvents ranging in density from 1.16 to 1.28 Mg m ‐3 . An inexpensive and nontoxic solution of sucrose and NaCI was shown to be an effective medium for density separations of seed. Less dense seeds were separated from 52 early generation bulk wheat populations after low temperature seed imbibition using sucrose‐NaCl solutions. The seeds were rinsed, dried, and planted alongside samples of the original populations at Lincoln, NE and Vernon, TX. Analyses of seed after harvest showed that protein concentrations of I0 of the 52 populations were increased by low seed density selection. Increases in protein concentration ranged from 6 to 11 g kg ‐1 and seed weights of the populations were unaffected by selection. A large amount of nongenetic variation in protein concentration of individual seeds appears to limit the effectiveness of seed density selection for increasing protein concentrations of wheat seed.