Quantitative trait loci for brown rice color, phenolics, flavonoid contents, and antioxidant capacity in rice grain

Abstract

Phytochemicals such as phenolics and flavonoids, which are present in rice grains, are associated with reduced risk of developing chronic diseases such as cardiovascular disease, type 2 diabetes, and certain cancers. The phenolic and flavonoid compounds in rice grains also contribute to the antioxidant activity. Biofortification of rice grain by conventional breeding is one way to improve nutritional quality to combat nutritional deficiency. For improvement of the phenolics, flavonoids, and antioxidant capacity, we must understand the genetic bases of the related traits. In the present study, mapping of quantitative trait locus (QTL) for five color parameters, phenolics, flavonoids, and antioxidant capacity was completed using a composite interval mapping approach using a doubled haploid (DH) population. Correlation analysis showed that the five color parameters lightness (L*), redness (a*), yellowness (b*), chroma (C), and hue angle (H°) were intercorrelated. The phenolic content was positively correlated with the flavonoid content and antioxidant capacity (P < 0.001), whereas the flavonoid content had no relationship with antioxidant capacity, but it was positively correlated with color parameters L* and H° (P< 0.05). A total of 21 putative QTL were detected for the eight traits with at least one QTL and as many as four QTL for different traits. Three QTL at the same interval of GA285 and CT580 on chromosome 2 were significant for color parameters L *, b*, and C; the latter two traits also shared another QTL region on chromosome 8. Two QTL on chromosome 2, qPH-2 and qFL-2-1, flanked by CT87 and G1234, were identified for phenolic and flavonoid content with large additive effects, explaining 16.91 and 12.71%, respectively, of the total phenotypic variation. Three QTL located at the same interval of G379A and CT360 on chromosome 7 were detected for color parameters a * and H°, and antioxidant capacity, which might be allelic to the Rd gene that is responsible for the production of the pigment in brown rice. The results of the present study may provide new opportunities for rice breeders with potential markers to improve nutritional quality by marker-assisted selection approach. © 2009 AACC International, Inc.