Tocopherol content of soybean lines with reduced linolenate in the seed oil

Soybean [Glycine max (L.) Merr.] oil is an important source of the tocopherols (vitamin E) used as a dietary supplement and as an antioxidant in foods. Previous research studies have indicated that genotypes with lower linolenate than that of conventional soybean genotypes have less tocopherols and that the relative amounts of alpha- and gamma-tocopherol may change as linolenate content is reduced by genetic modification. Those studies have utilized a limited number of genotypes with diverse genetic backgrounds and with greater linolenate content than that of currently available genotypes. The purpose of our study was to evaluate the tocopherol content of 20 lines with reduced linolenate of about 10 g kg(-1) and 20 lines with normal linolenate of about 70 g kg(-1) derived from each of three single-cross populations segregating for the trait. The lines were grown in replicated tests at Isabela, PR, and at two locations near Ames, IA, during 2002. The mean total tocopherol content of the lines with reduced linolenate was 6.0% less than for the normal-linolenate lines averaged across populations and environments. There was significant variation for total tocopherol among the lines of each type in each population, and some reduced-linolenate lines were not significantly different from normal-linolenate lines for the trait. Lower total tocopherol in reduced-linolenate lines was due to a proportionate decrease in alpha, gamma, and delta tocopherol, and the mean percentages of the three tocopherols in the total tocopherol were not significantly different in the reduced- and normal-linolenate lines. It should be possible to develop cultivars with about 10 g kg(-1) linolenate that have an acceptable content of total tocopherol and with the same proportions of alpha, gamma, and delta tocopherol as conventional soybean cultivars.