Relationship between seed mass and linolenic acid in progeny of crosses between cultivated and wild soybean

Soybean [Glycine max (L.) Merr.] oil from current commercial cultivars typically contains ca. 8% linolenic acid (18:3). Applications of plant biotechnology have enabled plant breeders to develop germplasm having as low as 2.0% 18:3. Oils that are naturally low in 18:3 exhibited improved flavor characteristics and greater oxidative stability in high-temperature frying applications compared to hydrogenated soybean oil. As an extension of that research, efforts are underway to characterize genes in soybean that govern expression of higher than normal 18:3 concentration. Such oils may be of interest to the oleochemicals industry for various nonfood applications. Relatively high 18:3 in seed oil is a characteristic trait of the ancestor of modern soybean cultivars, Glycine soja (Sieb. and Zucc.). Accessions of this species have rarely been utilized in soybean improvement, and thus represent a virtually untapped genetic resource for genes governing 18:3 synthesis. We have hybridized cultivated soybean with wild soybean plant introductions. F_3:4 seed from the resultant G. max × G. soja populations exhibited a wide segregation pattern for 18:3 and seed mass. A strong negative association was found between 18:3 concentration and seed mass. Oil concentration was positively correlated with seed mass. Evaluation of glycerolipid composition revealed that high 18:3 was not associated with an altered proportion of phospholipid and triacylglycerol among lines segregating for seed mass. Thus, smaller seed mass may be a convenient trait to distinguish future soybean cultivars with highly polyunsaturated oils from other cultivars in production.