Genetic regulation of linolenic acid concentration in wild soybean Glycine soja accessions

Abstract

Soybean [Glycine max (L.) Merr.] oil from current commercial cultivars typically contains ca. 8% linolenic acid. Inheritance studies have shown that linolenic acid concentration in soybean seed is determined by at least two genes which govern activity of the predominant ω‐6 and ω‐3 desaturases. Selection of germplasm exhibiting homozygous recessive alleles that encode these desaturases has enabled development of soybeans having less than 3.0% linolenic acid. However, accessions of the wild ancestor of modern soybean cultivars, Glycine soja (Sieb. and Zucc.), have oils containing twice the highest linolenic acid concentration found in normal G. max cultivars. Although little is known about inheritance of linolenic acid in wild soybean, it would appear that additional or alternative forms of genes may govern its synthesis. To test this hypothesis, cultivated soybean germplasm was hybridized with wild soybean genotypes having significant differences in linolenic acid concentration. Seed of F3 progeny from these G. max x G. soja populations exhibited distinct segregation patterns for relative estimates of ω‐6 and ω‐3 desaturase activity. Frequency class distribution analyses of the segregation patterns, and linear relations between median ω‐6 or ω‐3 desaturation estimates and corresponding linolenic acid concentration among allelic classes from these populations suggested the high‐linolenic acid trait in wild soybean genotypes was determined by a set of desaturase alleles that were different from corresponding alleles in G. max. Introgression of these alternative alleles in G. max germplasm opens a new avenue of research on the genitic regulation of linolenic acid, and may lead to the production of highly polyunsaturated soybean oils for various industrial applications.

Genetic relationship between lipid content and linolenic acid concentration in soybean seeds

“…and Zucc. ), the direct wild ancestor of cultivated soybean, contains lipids with almost twice the linolenic acid concentration than that of cultivated soybean (Pantalone et al 1997a), while the lipid content of wild soybean seeds is lower than that of soybean cultivars. We also confirmed these relationships and carried out genetic analysis of the lipid content and linolenic acid concentration to identify the relationship between these traits and to improve the lipid quantity and quality of soybean seeds.…”

“…Linolenic acid is considered unstable and responsible for the development of off-flavors because it is easily oxidized compared to other unsaturated fatty acids (Frankel et al 1980). In the oil industry, the oxidative stability of edible oil is improved by hydrogenating soybean oil to reduce linolenic acid levels (Pantalone et al 1997a); however, transisomer fatty acids are produced during hydrogenation, which are believed to increase the risk of heart disease. Consequently, a major breeding aim for soybean oil has been to reduce the amount of linolenic acid in soybean oil.…”

Identification of Environmentally Stable Wild Soybean Genotypes with High Alpha‐Linolenic Acid Concentration

“…The higher ALA concentration in wild soybeans is likely due to the difference in desaturase alleles related to ALA biosynthesis between cultivated and wild soybean (Pantalone et al, 1997). The higher ALA concentration in wild soybeans is likely due to the difference in desaturase alleles related to ALA biosynthesis between cultivated and wild soybean (Pantalone et al, 1997).…”

“…In contrast, wild soybeans have almost twice the ALA concentration and have a much lower ratio (4:1) between omega-6 and omega-3 fatty acid in oil than in cultivated soybeans (Asekova et al, 2014). The trait of high ALA concentration in wild soybean was controlled by a different set of desaturate alleles compared with corresponding alleles in cultivated soybean (Pantalone et al, 1997). Recent research revealed that wild soybean had different quantitative trait loci (QTLs) controlling ALA than QTLs in cultivated soybeans .…”

Soybean

“…The wild species is fully sexually compatible with soybean, allowing gene transfer for enhanced polyunsaturated fatty acids to be realized. Pantalone et al (1997a) made interspecific hybridizations between N87-2120-3 (G. max) x PI342434 (G. soja) and PI424031 (G. soja), identifying a wide range in o-6 desaturation and o-3 desaturation among progeny, suggestive that the wild species carries alternative forms of Fad and Fan alleles. The recombination of alternative desaturases with G. max alleles acted in an additive genetic manner, producing higher 18:3 concentration in the oil (Pantalone et al 1997b;Rebetzke et al 1997).…”