Masters Theses

Date of Award

8-2018

Degree Type

Thesis

Degree Name

Master of Science

Major

Plant Sciences

Major Professor

Vincent R. Pantalone

Committee Members

Hem Singh Bhandari, Feng Chen, Carl E. Sams, Virginia R. Sykes

Abstract

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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