Wednesday, November 7, 2007
261-12

Screening of Rice Cultivars for Grain Arsenic Concentration and Speciation.

Tushara Raghvan, Molecular and Environmental Plant Science, Texas A&M University, 370 Olsen Blvd, College Station, TX 77840- 2474, Wengui Yan, USDA-ARS, Dale Bumpers National Rice Research Center, 2890 Hwy 130 East, PO Box 1090, Stuttgart, AR 72160, Hesham A. Agrama, Rice Research and Extension Center, University of Arkansas, 2890 Hwy 130 E., Stuttgart, AR 72160, William D. James, Elemental Analysis Laboratory, Texas A&M University, College Station, TX 77840-3144, Terry J. Gentry, Soil & Crop Sciences, Texas A&M University, 370 Olsen Blvd, College Station, TX 77843-2474, and Richard H. Loeppert, Soil and crop Science, Texas A&M University, 370 Olsen Blvd, College Station, TX 77843-2474.

Recently, there has been growing interest in the concentration and speciation of arsenic in rice grain because of concerns with food quality and interest in minimizing any potential risk from dietary exposure.  Our objective was to screen a range of rice varieties from the USDA world collection for tolerance to soil arsenic and their relative arsenic concentration and speciation in rice grain.  Based on known or suspected susceptibility of rice to arsenic in soil, associated with the physiological disease symptom called straighthead, thirty-seven indica and japonica cultivars were chosen and grown in a replicated trial at Stuttgart, AR using native soil and test plots amended with very high levels of As (i.e., MSMA).  Total arsenic concentration in milled rice grain was determined by ICP-MS following digestion by HNO3/H2O2.  Arsenic species were quantified by HPLC-ICP-MS following extraction with 1M TFA.  With the MSMA-amended soil, the As concentration in grain was 2-6 times higher compared to that with the native soil.  A few cultivars had especially low concentrations of grain arsenic from the native soil as well as the MSMA-amended soil.  Cultivar susceptibility to the straighthead disease symptom, as induced by high As in soil, was not related to total grain-arsenic content.  The dominant species of grain arsenic were DMA and As (III), but these were found at different relative levels in different cultivars.  These results demonstrate the potential for selection of rice cultivars that have lower grain arsenic concentrations and lower ratios of inorganic to organic arsenic.

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