Wheat genome opens up new possibilites
The draft genome of wheat was recently sequenced by an international consortium of geneticists. The ‘gold standard’ sequence is expected to be created in three more years. In the meantime, Indian scientists are digging up some fascinating genetic traits of the cereal crop.
doi:10.1038/nindia.2014.125 Published online 17 September 2014
Following the release of the draft sequence of the wheat genome by the International Wheat Genome Sequencing Consortium in July this year, Indian scientists are now trying to pinpoint genes that make the cereal heat- and drought-tolerant. They are also looking for genes that will improve the grain to make better flour for chapattis and breads.
Scientists at the Ludhiana-based Punjab Agricultural University (PAU), National Research Centre on Plant Biotechnology (NRCPB) in New Delhi and University of Delhi, South Campus (UDSC) – all involved in the draft sequencing – are looking for genes that confer heat tolerance to wheat.
Kuldeep Singh, Director of PAU’s agricultural biotechnology school and the project leader of the Indian team that sequenced chromosome 2A of the wheat genome says wheat, a staple crop world over, faces continuous challenges from diseases and environmental stresses. “With the sequence now available, these challenges can be targeted in a more efficient and specific way”, Singh told Nature India.
Wheat is a heat sensitive plant, especially during the flowering and seed development stages. Estimates show that a 2°C rise in temperature could reduce wheat productivity by half. Global warming, therefore, poses a serious threat to wheat productivity. The draft genome has yielded a large number of very specific DNA sequences which can be used as ‘tags’ for identification of economically important genes such disease resistance genes, yield enhancing genes, nutritional quality genes and abiotic stress tolerance genes. These genes can be transferred from one wheat variety to another at costs much lower than prevalent, Singh says. India has spent about Rs 35 crore in the wheat genome project.
The PAU team is simultaneously trying to identify new genes that make the plant resistant to rusts and powdery mildew. The team is also looking at how to increase the iron and zinc content in wheat for nutritionally-rich varieties.
Meanwhile, NRCPB scientists are looking for genes for drought tolerance and genes that enhance the bread and chapatti-making quality of wheat. National professor at the centre and member of the sequencing team Nagendra Kumar Singh says they have identified several genomic regions associated with these traits.
“Heat tolerance is one aspect that needs urgent attention. After identification, the genes will need to be functionally validated, for which transgenic varieties will have to be raised,” says Jitendra Paul Khurana of UDSC’s Department of Plant Molecular Biology. The department has developed some protocols for wheat transformation and will compare some families of wheat genes encoding transcription factors and signaling components with other cereal crops. The studies will further basic understanding of the wheat biology, Khurana says.
The wheat genome has been considered a difficult sequencing candidate owing to its very large size – it is about six times the size of human genome. Chromosome 2A alone, on which the Indian scientists worked, is about 2.5 times the size of the whole rice genome. The wheat genome is an amalgamation of three different genomes from three different species, making it more complex.