Three mutant lines of soybean [Glycine max (L.) Merrill] were identified that had three‐ to six‐fold increases in stearic acid content in the seed oil compared with their parents. Our objective was to determine the inheritance of high stearic acid in the three mutants. Reciprocal crosses were made between each mutant and its parent and among the three mutants. Fatty acid analysis of the seed oil of the parents and the F1, F2, and F3 generations indicated that high stearic acid in the mutants was controlled by a single locus. The Fas allele for low stearic acid in each parent was partially dominant to the allele for high stearic acid in the mutant derived from it. Crosses among the mutants indicated that each possessed a different allele at the same locus. The allele fasa, in the mutant A6, and fas6, in the mutant FA41545, were not dominant to each other. Both fasa and fasb were completely dominant to thefas allele in the mutant A81‐606085. None of the segregates from the mutant ✕ mutant crosses had a stearic acid content outside the range of the parents. Maternal and cytoplasmic effects were not important in the control of stearic acid content in these mutants.

Linolenic acid is the unstable component of soybean [Glycine max (L.) Merr.] oil responsible for undesirable odors and flavors commonly associated with poor oil quality. The objective of this study was to determine the inheritance of fatty acid composition in A5, a soybean mutant with the lowest linolenic acid percentage of any genotype that has been evaluated for the character. Reciprocal crosses were made between A5 and two soybean cultivars, Weber and Pella. The parents were significantly different for all fatty acids, except palmitic acid in A5 and Pella. The F1 seeds, F2 seeds from F1 plants, and seeds from replicated tests of F2‐derived lines were evaluated for the percentage of palmitic, stearic, oleic, iinoleic, and linolenic acids. The F1 seeds from reciprocal crosses differed significantly for oleic, linoleic, and linolenic acids in both crosses, and for palmitic acid in the Weber cross, which indicated a maternal effect on composition for these fatty acids. Cytoplasmic inheritance of fatty acid composition was not observed, based on the lack of reciprocal cross differences for fatty acid composition in the analysis of F2 seeds from F1 plants. The composition of the F2‐derived lines exhibited a continuous distribution typical of a quantitative character for each of the fatty acids in both crosses. There were 14% of the F2‐derived lines in the Pella cross and 10% in the Weber cross that had a linolenic acid percentage as low as A5. Heritability estimates on a plot basis averaged across crosses from the analysis of F2‐derived lines were 33% for palmitic, 5% for stearic, 54% for oleic, 59% for linoleic, and 58% for linolenic acid. The results indicated that fatty acid composition should be considered a quantitative character in crosses that involve A5 as a parent.

The fatty acid composition of developing soybean (Glycine max [L.] Merrill) seeds was evaluated in the mutant line, A6, and its parent, FA8077. Seeds of both lines were harvested at 2‐day intervals from 15 to 39 days after flowering (DAF) and at 4‐day intervals from 39 DAF until maturity. Significant differences between the two lines were observed for stearic and oleic acid percentages at 19 DAF. The maximum difference between the lines was at 25 DAF, when A6 had 45.4% and FA8077 had 4.1% stearic acid. The increase in stearic acid percentage in A6 was accompanied by a decrease in oleic acid to 16.8% at 25 DAF, compared with 53.7% oleic acid for FA8077. The two lines did not differ in development of palmitic, linoleic and linolenic acids. The protein and oil content of mature seeds were similar for the two lines.

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