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Genotype and Environment Effects on Tocopherol, Tocotrienol, and γ-Oryzanol Contents of Southern U.S. Rice

¹USDA-ARS, Rice Research Unit, 1509 Aggie Drive, Beaumont, TX 77713. Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product to the exclusion of others that may also be suitable. ²Department of Food Science, Louisiana State University, Baton Rouge, LA 70803. ³Corresponding author. E-mail address: cbergman@ag.tamu.edu.

Rice bran contains phytochemicals such as E vitamers (i.e., tocopherols and tocotrienols) and the γoryzanol fraction that reportedly may have positive effects on human health. Brown rice, rice bran, and rice bran extracts are therefore attractive candidates for use in the development of functional foods. The objectives of this project were to quantify the effects of genetics versus environment on the tocopherol, tocotrienol, and γ-oryzanol contents of Southern U.S. rice and to determine associations between the levels of these phytochemicals. Seven rice cultivars grown in four states during two years were studied. Averaged across all samples, the content of α-tocotrienol > γ-tocotrienol > α-tocopherol > gamma;-tocopherol, and the tocopherols and tocotrienols were 27.5 and 72.5% of the total E vitamer content, respectively. Total E vitamer content ranged from 179 to 389 mg/kg and γ-oryzanol from 2,510 to 6,864 mg/kg. A low correlation between total E vitamer and γ-oryzanol contents suggests that to obtain rice bran with high levels of both of these fractions, new cultivars would need to be produced using hybridization and selection. In general, growing environment had a greater effect on E vitamer and γ-oryzanol levels than did genotype. Therefore, rice breeders selecting genotypes with optimized levels of E vitamers and γ-oryzanol will need to grow their breeding material in multiple years and locations.