Drought-tolerant genes mapped in Indian variety
scientists from the University of Hyderabad have mapped the drought-tolerant genes in the indica sub-species of rice. "Though such work has been done earlier for japonica rice, it was irrelevant for India where most rice varieties belong to the indica sub-species," says Ajay Parida, programme director, biotechnology with Chennai-based M S Swaminathan Research Foundation. The study will help identify the drought-tolerant genes in different Indian rice species and drastically reduce the effort to produce drought-resistant varieties.
India loses as much as 15 per cent of rice yield to drought and water stress. Drought is the major constraint to rice production on at least 17 of the 43 million hectare (ha) where rice is grown. In addition, it also affects production on about 4 million ha in areas dependent on surface irrigation. "Rice is the staple food for two-thirds of Indians and drought is the major threat to India's food security," says Robert S Zeigler, director general of the Manila-based International Rice Research Institute.
The mapping was done using what is called the rapid genomic approach to identify the required genes. Under this process, 5,814 Expressed Sequence Tags (est) corresponding to water-stress characteristics were identified from the genome sequence. The scientists subsequently looked only for genes with these ests. "This was possible since the complete genome sequence of rice is available and we just needed to recognise the trait-specific genes as drought tolerance in this case," says Arjula R Reddy, who headed the team of scientists at the university's department of plant sciences.
The ests were then thoroughly analysed and 589 genes involved in drought tolerance were identified. "Such exact information on gene's response to drought will help us develop a drought-resistant variety in less time using less cumbersome methods," says Dow Johnson, a rice breeder at the Allahabad Agricultural Institute.
The mapping has been done for Nagina-22, a popular upland drought-resistant variety. The whole process has been done in silico (using computer simulations) and functional assay or practical identification on the seedlings is underway, says Reddy.
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