Mass Selection by Specific Gravity for Protein and Oil in Soybean Populations1

Abstract

The effects of two cycles of mass selection by specific gravity were investigated in two hybrid soybean populations (Glycine max (L.) Merrill). Effects were measured on chemical composition and on six agronomic attributes. Selection was employed for high (Hi) and low (Lo) specific gravity within each population. A solution of glycerol and water was used to establish the desired specific gravity. Cycle 1 stratified the original populations into groups differing in chemical composition. Hi populations had a higher mean protein and lower mean oil content than the control populations. Lo populations were above average in oil and below average in protein content. Protein increased in the Hi populations and ranged from 0.3 to 1.2% and the decrease in protein in the Lo populations ranged from 0.6 to 1.5%. The increase in oil in the Lo populations ranged from 0.1 to 1.0% and thedecrease in oil in the Hi populations ranged from 0.0 to 0.9%.The effects of continued selection (cycle 2) varied among and within populations. In general, selections in cycle 1 were more effective than in cycle 2 for protein and oil.Specific gravity measures relative density; therefore, density of the seed was determined using a Bechman gaspycnometer. Average heritability for seed density was 69%. High seed density was associated with high protein, low oil and late maturity.