Maintaining rice reproduction under high temperature stress:- identifying mechanisms and germplasm to increase crop resilience.

点击翻译按钮获取中文摘要

Rice is the principal crop in China, comprising 36.9% of the world rice crop. Estimates suggest yield increases of 50% are needed by 2050 to ensure food security. The areas used to cultivate rice and timings of planting are driven by climatic conditions. Rice is cultivated across China; nevertheless the frequency of cropping and the areas where high yields can be realised are limited by temperature. Global climate warming negatively affects mean rice yield, but also variance in yield, leading to increased frequencies of low yields. Additionally, increased mean temperature negatively impacts on the length of vegetative growth and reproductive growth periods.Flower development is critical for plant breeding and seed production, and thus directly impacts on yield. Pollen formation is highly sensitive to temperature stress; high temperature stress during flowering therefore poses a serious threat to current and long-term crop yields. This is particularly the case since flowering and seed set typically occur during a single, transient stage of plant development, which unlike vegetative associated-stress, cannot be rescued if conditions subsequently improve. High temperatures reduce the number of flowering branches and therefore the number of flowers per plant, however abnormalities in pollen formation result in male sterility and thus failure of seed set. There is thus the potential for devastating yield losses if resilience to reproductive temperature stress is not developed, particularly given the rises in global temperature and the increased volatility of climatic conditions. Nevertheless there is considerable genetic variability in tolerance to high temperature between species and genotypes. Understanding how plants cope with heat stress during reproductive development offers the potential to identify genetic traits that can be manipulated and utilised to improve temperature tolerance in crops. This project will address these issues by developing germplasm with enhanced resilience to temperature stress. The programme will also provide detailed understanding of the molecular and cytological changes occurring during reproduction under heat stress, and the mechanisms conferring resilience to high temperatures. Developing such resilience will allow expansion of the areas used for rice cultivation, but also the timing and frequency of rice planting. This will lead to higher rice yields, but also to more resilient yields regardless of environmental fluctuations and global climate changes. Environmentally controlled male fertility also has major applications for developing materials for hybrid breeding. Knowledge and germplasm obtained from this project will therefore have direct application in hybrid rice breeding programmes for increased yield.The programme will use Natural Variation to identify loci conferring resistance to reproductive heat stress for breeding programmes for crop improvement, and to characterise these traits. Two populations will be screened, i) a "Diversity Panel" comprising 800 global representative rice lines derived from diverse locations and environments, identified from the 3000 Genome Rice Project and, ii) a population of indica/japonica chromosomal segment substitution lines, which has known diversity in fertility responses to environment. This material will be phenotyped in field and glasshouse conditions for altered fertility and floral architecture as a consequence of heat stress. GWAS and Introgression marker analysis will be used to identify the loci responsible. Molecular tools and transgenic lines will be used to dissect the mechanisms behind these traits. This will be supported by detailed microscopic and expression analysis. In addition transcriptomic approaches will be used to characterise the molecular changes occurring during plant reproduction under heat stress, specific emphasis will be paid to tapetum function and Programmed Cell Death (PCD) during pollen development.