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Enhancing wheat field performance and response to abiotic stress with novel growth-regulatory alleles


The "Green Revolution" dwarfing (Rht) alleles that increase wheat yields under high input conditions are orthologues of the Arabidopsis GAI gene and encode mutant DELLA proteins. DELLAs are repressors of plant growth that are degraded in the presence of gibberellin (GA) whereas the gai/Rht mutants are insensitive to GA. Most UK wheat varieties carry the semi-dwarfing Rht2 (Rht-D1b) allele but variation in height between genotypes suggests that other loci play a role in determining stature. We aim to identify these loci through co-localisation of quantitative stature traits identified in UK wheat germplasm with genes in the GA-DELLA pathway. Based on functional analyses in vitro and performance in the field alleles will be identified for use in wheat breeding. There are reports of Rht mutations affecting the responses of wheat to stress, and a negative correlation between GA content or responsiveness and stress tolerance has been documented. Moreover, our recent work in Arabidopsis implicates the GA-DELLA pathway as a central regulator linking GA, abscisic acid and ethylene in a common stress-related network. It is timely to translate these key discoveries into crop improvement to enhance the tolerance of hexaploid wheat to environmental stresses without compromising productivity. To this end, we will take a knowledge-based approach to compare Arabidopsis and wheat DELLA-mediated stress responses. We will use available genetic stocks to determine whether existing, but relatively untested, Rht alleles affect tolerance to salt, drought and heat stress. Near-isogenic lines will be tested under controlled and field conditions to select alleles that will be taken forward by introgression into elite varieties. The role of other alleles of GA-DELLA genes identified above will also be assessed for effects on tolerance to drought, heat and other abiotic stresses.



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