Characterizing genetic & soil induced variation in arsenic uptake translocation & metabolism in rice to mitigate arsenic contamination in Asia.

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Widespread arsenic contamination of paddy fields in South East Asia has led to elevated rice grain levels of this carcinogenic element. In arsenic affected regions, dietary exposure from arsenic from rice is above World Health Organization limits. Our scoping studies where we grew a range of cultivars on one soil type and, also, where we have looked at variation in arsenic tolerance in mapping populations, have shown that there is considerable genetic variation in arsenic uptake, metabolism and export to the grain. We propose to conduct field trials to determine which currently grown local cultivars are most suitable for arsenic contaminated soils. These cultivars may be used in future low-arsenic breeding programs. We will also study the genetics of arsenic accumulation and speciation by conducting both quantitative trait loci (QTL) analysis on mapping populations and association genetic mapping using a collection of diverse rice cultivars. This will locate the genes responsible for the traits, and provide a list of candidate genes based on position on the genome. Gene expression studies, including the Affymetrix whole genome array, will be used to identify strong candidate genes within these lists, and when combined with the study of available mutants we may even prove the identity of the genes responsible. The project will also ascertain the soil factors that determine the bioavailability of arsenic in soils polluted from irrigation water or via mine waste to determine if different strategies are required for these contrastingly contaminated soils in order to deliver grain low in arsenic.