Identification of Quantitative Trait Loci for Lipid Metabolism in Rice Seeds

Plant seed oil is important for human dietary consumption and industrial application. The oil trait is controlled by quantitative trait loci (QTLs), but no QTLs for fatty acid composition are known in rice, the monocot model plant. QTL analysis was performed using F2 and F2: 3 progeny from a cross of an indica variety and a japonica variety. Gas chromatography- mass spectrometry (GC-MS) analysis revealed significant differences between parental lines in fatty acid composition of brown rice oil, and 29 associated QTLs in F2 and/ or F2: 3 populations were identified throughout the rice genome, except chromosomes 9 and 10. Eight QTLs were repeatedly identified in both populations across different environments. Five loci pleiotropically controlled different traits, contributing to complex interactions of oil with fatty acids and between fatty acids. Nine rice orthologs of Arabidopsis genes encoding key enzymes in lipid metabolism co-localized with 11 mapped QTLs. A strong QTL for oleic (18: 1) and linoleic (18: 2) acid were associated with a rice ortholog of a gene encoding acyl-CoA: diacylglycerol acyltransferase (DGAT), and another for palmitic acid (16: 0) mapped similarly to the acylACP thioesterase (FatB) gene ortholog. Our approach rapidly and efficiently identified candidate genes for mapped QTLs controlling fatty acid composition and oil concentration, providing information for improving rice grain quality by marker assisted selection.