PHENOTYPIC VARIATION FOR SATURATED FATTY-ACID CONTENT IN SOYBEAN

Concern over high saturates in human diets has prompted the developmen t of soybean [Glycine max (L.) Merr.] lines producing oil with reduced saturated fatty acid concentration. To better understand those factor s that influence phenotypic expression for palmitic and stearic acid c ontent in soybean, thirty soybean lines random for saturated fatty aci d content were grown in eight field environments contrasting for mean temperature during seed-filling. Palmitic and stearic acid content var ied significantly (P<0.01) both among genotypes and across environment s, while genotype x environment interactions were reflected in changes in line variance and ranking for both traits. Therefore selection of a superior genotype for saturated fatty acid composition may not corre late well from one environment to another. In general, early-maturing lines were less sensitive than later-maturing lines in their response to changes in mean daily temperature for palmitic concentration. Howev er, factors in addition to temperature appeared to influence genotype response for stearic acid content. It appears that genetic systems con ditioning palmitic and stearic acids are independent, and that separat e breeding strategies need be adopted to make simultaneous improvement for these two oil traits. In summary, development of soybean lines wi th low or high saturated fatty acid content may be accomplished throug h evaluation and selection in a few environments contrasting for tempe rature.