YIELD AND COMPOSITION OF SOYBEAN SEED FROM PARENTS WITH DIFFERENT PROTEIN, SIMILAR YIELD

Soybean [Glycine max (L.) Merr.] seed yields often show a negative association with seed protein. The objective of this study was to determine if this association could be minimized by crossing a high and a normal protein line of equal seed yield. An F2 population of 1000 plants was grown. Plants were harvested individually and seed evaluated for oil content using the nuclear magnetic resonance technique. Two bulk populations were developed: one included the 8% having the highest oil and the other the 8% having lowest oil. With the high negative correlation between seed protein and oil, the low oil population was expected to provide lines having high seed protein concentration. The two populations were advanced in bulk through the F6 generation, after which 200 plants were harvested individually from each population and 200 F7 lines grown from each. The F7 lines were harvested individually and seed analyzed for seed protein and oil. The 18 lines having the highest protein and the 18 lines having the highest oil were selected for further evaluation in replicated trials. Lines were evaluated in five environments for seed yield, protein, and oil. The overall mean seed yield of the high protein lines averaged 6% less than the overall mean of the lines selected for high oil; however, when seed yield of the two highest protein lines at each environment were compared with the two highest oil lines, the high protein lines had a 1% advantage in seed yield, an 18% advantage in seed protein, and a 20% reduction in oil. The results demonstrate the potential for developing soybean lines high in seed protein and equal in seed yield to lines having high oil content.