ASSOCIATION OF SEED SIZE WITH GENOTYPIC VARIATION IN THE CHEMICAL-CONSTITUENTS OF SOYBEANS

Ten soybean genotypes grown in 1992 with seed size ranging from 7.6 to 30.3 g/100 seeds and maturity group V or VI were selected and tested for oil and protein content and for fatty acid composition. In these g ermplasm, protein varied from 39.5 to 50.2%, oil, 16.3 to 21.6%, and p rotein plus oil, 59.7 to 67.5%. Percentages of individual fatty acids relative to total fatty acids varied as follows: palmitic, 11.0 to 12. 8; stearic, 3.2 to 4.7; oleic, 17.6 to 24.2; linoleic, 51.1 to 56.3 an d linolenic, 6.9 to 10.0. Seed size showed no significant correlations with individual saturated fatty acids, protein or oil content. Howeve r, significant correlations were found between seed size and individua l unsaturated fatty acids: positive with oleic, and negative with lino leic and linolenic. Oil and protein content were negatively correlated with each other. Among the major fatty acids, only the unsaturated we re significantly correlated with each other: negative between oleic an d linoleic or linolenic, and positive between linoleic and linolenic. A subsequent study with soybeans grown in 1993 generally confirmed the se findings. Variation in relative percentages of unsaturated fatty ac ids and r values for most pairs of relationships were even higher than those obtained from the 1992 crop.