Developing rice resources for resilience to climate change and mitigation of carbon emissions

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Climate change associated with global warming poses a threat to our ability to produce sufficient food, energy and water to meet the demands of the growing human population. Human activity is helping to drive the upward trend in global warming by increasing the levels of warming agents such as greenhouse gases in the atmosphere. Episodes of severe weather, such as drought and flooding, increase as global temperatures rise, and this can lead to losses in crop yield. Rice is one of the main staple crops grown in the world and represents a major source of food and livelihood for many people, particularly in the tropics. Every year more than 700,000 million tons of rice straw is produced in the world and much of this is burned in the field in order to make way for the next season's crop. This releases large amounts s of black carbon and tropospheric ozone into the atmosphere with negative consequences for air quality, human health (respiratory illnesses), crop yield and global warming. One of the main aims of the proposed research is to help move rice straw away from being a waste product and toward its widespread utilisation as a valuable resource. Rice straw is primarily composed of lignocellulosic structural cell walls that provide support to the growing plant. Lignocellulose is a strong and resistant fibre composite material composed of a network of structural polysaccharides (polymers of sugars). These polysaccharides are potentially a rich source of sugars that could serve as nutritious animal feed, or be used as feedstock for fermentation to produce biofuels or other valuable chemicals and polymers that can replace those derived from petroleum. Unfortunately, the polysaccharides in lignocellulose are difficult to digest into sugars for animal nutrition or fermentation partly because they are sealed in a highly resistant polyphenol called lignin, and partly because they are partially crystalline, both of which block access to digestive enzymes. In rice straw, this situation is further exacerbated by the presence of large amounts (up to 10% dry weight) of silica, which makes it unpalatable to most animals and also precludes the use of rice straw in biomass furnaces to make electricity as it causes severe slagging of boilers. This project brings together the expertise of five world class laboratories to tackle the complex problem of environmental resilience and carbon footprint in a world staple food crop. We will use cutting edge plant genomic approaches to identify the genetic basis of natural variation in straw digestibility, lignocellulose composition and silica content found in large diversity collections of rice collected in the Philippines and Vietnam. We will employ genome wide association scans in these diversity collections to identify associations in the variation of digestibility, composition and silica content with differences in the sequences of DNA in regions of the genomes of these plants. This will identify molecular markers that can serve as proxies for improved straw quality and allow rapid marker assisted breeding approaches to be used. The same methods will also allow us to identify the genes that have strong influence on these traits in rice. We will also identify regions of the genome influencing the ability of rice crops to deal with drought (a major problem resulting from climate change) and produce molecular markers for improved drought tolerance.Our work will identify existing rice varieties with low silica or highly digestible straw and we will use these to investigate and demonstrate the advantages of using straw with better quality for applications as animal feed and for biofuel production. We will use the results from our research to alert farmers and other stakeholders to the potential benefits of using rice straw in these applications to improve farmer income, local livelihoods and air quality as well as helping mitigate the damaging effects of human activity on global warming.