An integrated approach to stabilising HFN in wheat: screens genes & understanding

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The aim of this project is to improve stability of the Hagberg Falling Number (HFN), a major quality trait in wheat. HFN is currently sensitive to a number of environmental conditions that reduce the quality of grain and make it unsuitable for bread-making, resulting in severe financial losses to farmers: last year (2004) only 27% of the UK wheat crop grown for bread-making was of acceptable quality, with an estimated loss to farmers of £100 per acre of wheat grown. UK cultivars vary in their susceptibility to low HFN, partly due to the difficulty of applying conventional phenotypic screens to large populations of breeding selections, but some (eg. Option, Malacca) evidently carry adequate genetic resistance. Recommended List scores for HFN rely on the occurrence of appropriate weather conditions to trigger latent susceptibility or overhead irrigation to provoke pre-harvest sprouting (McVittie J & Draper S (1982) or irrigation of standing plots of winter wheat in order to assess varietal predisposition to pre-harvest sprouting. J. Natn. Inst. Bot. 16: 45-48). A key aim of this project is to furnish new tools and biological insights to enable breeders to identify new lines with stable HFN from the available pool of elite UK germplasm. The fact that existing resistant cultivars do not manifest problems with emergence in field sowings indicates that this aim is compatible with prompt stand establishment. Previous research by the applicants has shown that the two most important causes of high alpha-amylase levels in UK grain are pre-harvest sprouting (PHS) and pre-maturity alpha-amylase (PMA). PHS is the result of premature germination of grain in the ear, promoted in susceptible varieties by wet weather in the period between maturity and harvest. The consequent secretion of alpha-amylases into the starchy endosperm results in the deterioration in grain quality that is measured by the HFN test. PMA is less well defined, but is believed to result from inappropriate production of alpha-amylases by the aleurone layer in the crease region of the endosperm, late in grain development. Within the BBSRC financed objectives of this LINK project we intend to study the biochemical and molecular events in the wheat grain that are responsible for reduction of HFN during both PHS and PMA. Molecular genetic information from model species will be used to provide 'candidate genes' associated with germination potential/ endosperm development. These will be used for testing of function during seed development in relation to PHS/PMA. The characterisation of expression characteristics and genetic variation of candidate genes in existing germplasm, and the development of 'smart screens' and validated genetic markers will provide UK wheat breeders with resources to create improved varieties with more stable HFN. This project will address several components of the BBSRC strategic plan objectives for integrative biology and sustainable agriculture, including 'functional and comparative genomics', 'integrative biology-plant', 'transcriptomics', 'whole organism biology' and 'sustainable agriculture'. It will aim to provide a 'pipeline' for the delivery of information gained from studies in model species to tools for use to enhance breeding germplasm, a key recommendation of the recent BBSRC Crop Science Review.