Improvement of oil quality in soybean [Glycine max (L.) Merrill] by mutation breeding

Abstract

Low oxidative stability, off-flavor and rancidity are the major drawbacks of soybean oil. Modification of the fatty acid composition of soybean [Glycine max (L.) Merrill] oil can improve its quality and value for processors and acceptability among consumers. Mutation breeding of soybean was therefore initiated with the objective of identifying stable soybean mutants with altered fatty acid composition for improved oxidative stability and nutritional quality. Seeds of soybean cultivar 'MACS 450' were treated with γ-radiation and/or ethyl methane sulfonate (EMS). The harvest of M1 plants was evaluated for fatty acid composition by gas chromatography. Highly significant variation in all the fatty acids except palmitic acid was observed. Treatment of EMS in higher concentrations as well as combined treatment of both the mutagens, i.e., γ-radiation and EMS were effective in increasing the variability for the fatty acid content in soybean oil. The variability was skewed towards high levels of oleic (35-42%) and low levels of linolenic acid (3.77-5.00%). M3 and M4 generations of desirable variants were analyzed for the stability of the mutated trait. Only high oleic variants were stable in M3 and M4 generations. Based on fatty acid values, oxidative stability index (OSI), nutritional quality index (NQI) and ratio of essential fatty acids (ω6/ω 3) were calculated for the control and M2, M3 and M4 generations. The ω6/ω3 ratio in all the high oleic mutants was within the World Health Organization (WHO) recommended value (5-10%). A significant positive correlation between OSI and oleic acid content (P < 0.001) indicated improved oxidative stability of the oil while retaining nutritional quality. These high oleic lines could be utilized further in breeding programs for improvement of soybean oil quality. © 2007 AOCS.