Abstract Soybean oil hydrogenation alters the linolenic acid molecule to prevent the oil from becoming rancid, however, health reports have indicated trans‐fat caused by hydrogenation, is not generally regarded as safe. Typical soybeans contain approximately 80 g kg −1 to 120 g kg −1 linolenic acid and 240 g kg −1 of oleic acid. In an effort to accommodate the need for high‐quality oil, the United Soybean Board introduced an industry standard for a high oleic acid greater than 750 g kg −1 and linolenic acid less than 30 g kg −1 oil. By combing mutations in the soybean plant at four loci, FAD2‐1A and FAD2‐1B , oleate desaturase genes and FAD3A and FAD3C , linoleate desaturase genes, and seed oil will not require hydrogenation to prevent oxidation and produce high‐quality oil. In 2017 and 2018, a study comparing four near‐isogenic lines across multiple Tennessee locations was performed to identify agronomic traits associated with mutations in FAD3A and FAD3C loci, while holding FAD2‐1A and FAD2‐1B constant in the mutant (high oleic) state. Soybean lines were assessed for yield and oil quality based on mutations at FAD2‐1 and FAD3 loci. Variations of wild‐type and mutant genotypes were compared at FAD3A and FAD3C loci. Analysis using a generalized linear mixed model in SAS 9.4, indicated no yield drag or other negative agronomic traits associated with the high oleic and low linolenic acid genotype. All four mutations of fad2‐1A , fad2‐1B , fad3A , and fad3C were determined as necessary to produce a soybean with the new industry standard (>750 g kg −1 oleic and <30 g kg −1 linolenic acid) in a maturity group‐IV‐Late cultivar for Tennessee growers.
Soybean oil is a major commodity in the US with practical uses for both food and industrial products. A declining market for soybean oil production caused by added restrictions on oil hydrogenation practices, has fueled improvements in oil industry standards. Typical soybean oil contains 8 to 12 g kg-1 of linolenic acid which causes unfavorable odor and rapid rancidity which has been dealt with using hydrogenation in the past. Scientists have identified fatty acid desaturase genes which when mutated, produce oil that does not require hydrogenation. Breeders use single nucleotide polymorphism (SNP) analysis to select for soybean mutations containing FAD2-1A, FAD2-1B, FAD3A, and FAD3C that regulate oleic acid (18:1) and linolenic acid (18:3) respectively. Improved oil quality standards set by the United Soybean Board, necessitate an increase in oleic acid (18:1) to greater than 75 g kg-1 concentration, and a decrease in linolenic acid to less than 3 g kg-1 in soybean oil. In 2016 we performed a multi-location yield study comparing four low linolenic (LL) soybean lines with parents, and high yielding checks in a randomized complete block design (RBD) at two locations. We found that no significant yield drag was associated with low linolenic genotypic lines. In 2017 multi-location studies, testing twelve soybean lines, were tested across eight Tennessee environments. The two studies investigated the effect of planting date, and irrigation on agronomic and seed quality traits of LL lines. A third yield trial was done comparing four lines of double mutant FAD2-1A and FAD2-1B that varied at the FAD3A and FAD3C genes, which was investigated at two Tennessee locations. There was a statistically significant decrease in linolenic acid when tested at α [alpha]=0.05 when both FAD3A and FAD3C mutant alleles are present in soybean lines tested in both 2016 and 2017. The yield of double mutant LL lines were not significantly different when compared to single mutant or double wild-type. Quadruple mutant HOLL lines did not have any yield drag association when compared to both parents and check lines.
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