ARS | Publication request: Variation in rice silica content and its use as an industrial feedstock

Submitted to: Agricultural Experiment Station Publication
Publication Type: Experiment Station
Publication Acceptance Date: June 1, 2011
Publication Date: June 15, 2011
Citation: McClung, A.M., Bryant, R.J., Jackson, A.K., Yan, W., Fjellstrom, R.G. 2011. Variation in rice silica content and its use as an industrial feedstock. Texas Rice Special Section Highlighting Research in 2011. p. XI-XII.

Technical Abstract: Rice can accumulate silicon (Si) from the soil, and although it is not an essential nutrient, it plays an important role in the growth and health of rice plants. Silica is concentrated in the hulls, which are a by-product of the milling process, and in straw which remains in the field after harvest. Some rice hulls are burned to produce steam or electricity, and the silica-rich rice hull ash is usually disposed of in landfills where it remains for years due to its chemical stability. Due to the high silicon concentration, rice hulls and ash can also be used as raw materials in the production of Si-based industrial materials with high economic value. These compounds are used in a wide variety of products including glass, ceramics, cement, pharmaceuticals, cosmetics, detergents, chemical catalysts, and as coatings for electronic and optical materials. This study was conducted to determine the genetic variability present in the USDA world collection of rice for Si content that could be used in the development of new varieties that have dual purpose for use as a food crop and as an agricultural feedstock for high value industrial products. One hundred seventy-four diverse rice accessions were characterized for hull silica concentration in trials conducted at Beaumont, TX, and Stuttgart, AR, and with 164 genome-wide DNA markers. The average silica concentration ranged two-fold among the accessions, with a mean of 200 mg g-1. Most of the accessions from Central America had a higher silica concentration, while those from the Mideast and Eastern Europe had lower silica concentrations compared to accessions from other parts of the world. Accessions from the Tropical japonica subpopulation had some of the highest Si concentrations. This is the same genepool that most of the U.S. long grain rice is developed from, suggesting it is a rich resource for modifying Si in new US rice varieties. Location effects were important, indicating the necessity of having multiple test sites for silica evaluation. Several genetic markers were identified that were linked to Si concentration in the hulls, with five of these having been verified in other studies. This research demonstrates the potential of using genomics to develop rice varieties for use as an industrial feedstock, without competing with its use as a globally important staple food.