EFFECT OF STRATIFICATION FOR PERCENT PROTEIN IN 2 SOYBEAN POPULATIONS

Two populations of soybeans, each having at least 1 parent with high percent seed protein, were studied to determine the effects of selection for percent protein in an early generation (F2 or F3) upon percent seed protein, percent seed oil and seed yield in later generations (F4 and F6). The populations were stratified as follows: from 60 F2 plants in one population the 10 highest, the 10 lowest and 10 intermediate in percent protein were selected; similarly, from 60 F3 lines of the other population the 10 highest, 10 lowest and 10 intermediate in protein were selected. Resulting F4 lines of both populations were grown in replicated yield tests at 2 locations. On the basis of mean percent protein in these tests, the 5 highest lines of the high group, the 5 lowest of the low and 5 intermediate from the intermediate group of each population were identified. Two plant progenies of each selected line were advanced to the F6 generation and grown in replicated yield tests at 2 locations. There was a significant correlation between early generations and subsequent generations for percent protein, indicating that early classification of plants or lines is useful. Although there was a negative correlation between percent protein and seed yield and between percent protein and percent oil, F6 lines with desirable combinations of percent protein, percent oil and seed yield were identified. The majority of these lines could be traced to the intermediate protein stratum established in the early generation.