Genetic Diversity of Fatty Acids, Tocols, Squalene, and Phytosterols in Grains of 157 Rice Cultivars Bred in Korea

To understand genetic diversity in nutritional properties, 157 accessions of Korean-bred rice varieties were cultivated in 3 separate fields and harvested brown rice were used for determination of tocopherols (T), tocotrienols (T3), squalene (SQ), campesterol (CA), sitosterol (SI), and stigmasterol (ST) contents as well as fatty acid compositions. The average contents of α-T, γ-T, α-T3, γ-T3, SQ, CA, SI, and ST were 11.9, 1.6, 10.0, 13.9, 35.2, 42.1, 163.5, and 20.0 μg/g, respectively, and total tocols, SQ, and total phytosterols contents ranged 26.8-54.9, 7.9-78.4, and 162.9-320.2 μg/g, respectively. Ecotype of rice significantly affected phytonutrient contents in that japonica-type showed significantly higher α-T and α-T3 contents and α-T/γ-T, α-T3/γ-T3, and T/T3 ratios compared to indicatype varieties. Total T, SQ and ST contents were also higher in japonica-types, while total T3, CA and SI contents were not affected by ecotypes. Linoleic, oleic, and stearic acids were the 3 major fatty acids consisting 36.5, 35.8, and 22.9% of total fatty acids, respectively. Positive correlationships were observed among 3 phytosterols, while oleic acid showed negative correlation with palmitic (r = ‒0.662**) and linoleic (r = ‒0.810**) acids. Partial least squares discriminant analysis (PLS-DA) revealed that phytonutrient profiles may effectively differentiate rice ecotypes, and α-T3/γ-T3, γ-T and α-T3 contents were the key components with highest variable importance in projection (VIP) scores. All these results showed diverse genetic and ecotype-dependent variations in phytonutrients in Korean-bred rice varieties, which can be further used for developing a superior rice variety with higher nutritional value.