Submitted to: Experiment Station Bulletins
Publication Type: Experiment Station
Publication Acceptance Date: June 5, 2009
Publication Date: June 5, 2009
Citation: Chen, M. 2009. The Rice Quality Program of the USDA-ARS Rice Research Unit. Experiment Station Bulletins. Texas Rice. Vol. IV. p. 7. Available: http://beaumont.tamu.edu/elibrary_default.htm Technical Abstract: Since the establishment of the USDA-ARS Rice Quality Laboratory in the 1950s, we have committed to provide service to the Federal and State breeding programs by evaluating U.S. breeding lines to ensure that all future U.S. varieties have quality traits acceptable to the industry. In addition, we have also been conducting research to better understand cooking and processing traits of importance to the rice industry, and to develop new and rapid screening methods for these traits utilizing new analytical and molecular-genetic technologies. We also have been investigating the health beneficial compounds in rice and determining factors affecting the storage stability of whole grain. Cooked rice texture and rice processing properties are strongly associated with the amylose content. Recent studies conducted in the Rice Research Unit, which were collaborative efforts among scientists Bob Fjellstrom, Shannon Pinson, Christine Bergman, and Ming Chen, and were partially funded by the Rice Foundation, have established the correlations of Waxy gene sequence variations with the amylose content and rice processing properties. The Waxy gene is the gene that synthesizes the enzyme called granule bound starch synthase, which in turn is responsible for the synthesis of one of the rice starch components, amylose. The results from these research studies provided a powerful tool for the rice breeders by enabling them to select breeding materials for the desired amylose-content quality using a molecular-genetics tool, the molecular marker, without the influence of environment. The environment is known to affect the amylose content. We are currently developing quick and easy molecular-marker protocols that can be easily implemented in molecular breeding programs. The increased public interest in the health-benefits of phytonutrients has led us to investigate the phytonutrients in whole grain rice and rice bran. The bran layer of whole grain rice contains both lipophilic and hydrophilic phytonutrients which are unique in comparison with fruits and vegetables, which contain primarily hydrophilic phytonutrients. These phytonutrients of rice and these other sources are antioxidants and are known to promote health and to protect against diseases such as cancer, diabetes and cardiovascular disease. The lipophilic phytonutrients of rice include various forms of vitamin E and a group of antioxidant compounds called oryzanols. The genetic diversity in the concentrations of these compounds in US rice and in diverse international germplasm was investigated by us. Ranges greater than two-fold for the vitamin-E and oryzanol concentrations were found. We are currently studying the hydrophilic phytonutrients in the whole grain rice and in bran to identify what types of hydrophilic phytonutrients (i.e. phenolics, flavonoids) rice has and what the genetic diversity of these compounds is in a selected set of international germplasm. The awareness of the health benefits of consuming whole grain has led to the 2005 USDA dietary guideline of recommending that half of the grain group consumed should be in the form of a whole-grain product. Brown rice is whole grain and its sales have been steadily increasing in recent years. However, brown rice has a short shelf life (three to six months) because of the hydrolytic and oxidative deterioration of bran oil. This deterioration is partially due to the process of de-hulling the paddy, or rough, rice when producing brown rice, in which there is a disruption of the outer bran layer, in turn promoting the contact of lipase enzymes with the lipids. We are currently developing a quick assay to determine the lipase activity to use in evaluating the genetic diversity in lipase activity of a representative set of international germplasm. The objective is to identify rice accessions having low lipase activity that can then be used to bring this trait into US cultivars with the purpose of improving the storage stability of brown rice through the use of breeding techniques.