Improving malt barley agronomics via allelic selection of senescence and flowering time controlling genes
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Malt barley (Hordeum vulgare L.) is a high-profit crop for farmers; yet, its production raises challenges that need to be addressed. The standards for grain quality in malt barley are stringent, and the rejection of non-qualified grains by maltsters is the leading cause of revenue loss for malt barley producers. Rejection is mainly due to high grain protein content and low kernel plumpness which both cause significant problems in the malting process. While proper growing practices can improve malt quality, the industry requires genotypes that have more stable malt quality. Therefore, understanding the molecular mechanisms associated with grain quality can be applied to improve selection of superior malt varieties. A considerable volume of literature has suggested that regulation of whole-plant senescence and flowering processes in cereals have direct influences on grain yield and quality parameters. The central question in this dissertation examined whether malt barley agronomic and end use quality can be improved by the selection of varying alleles for genes associated with plant development. With this purpose, two whole-plant senescence-regulating NAM, ATAF and CUC (NAC) transcription factors, HvNAM1 and HvNAM2, and a flowering-time controlling Glycine-Rich RNA Binding Protein (HvGR-RBP1) were studied. Molecular markers for selection of alleles from varieties 'Karl' (with consistently low grain protein) and 'Lewis' were developed, and an advanced-generation malt barley breeding population was genotyped. Statistical analysis of growth parameters from this population showed that selection of HvNAM1 'Karl', HvNAM2 'Karl' and HvGR-RBP1 'Lewis' alleles ensures a longer grain filling period in malt barley. Plants with prolonged grain filling also exhibited increased kernel plumpness and test weight. Additionally, selection of 'Karl' alleles for both NAC genes decreased grain protein content ensuring grain quality for malting. The improvement of grain characteristics correlated with improved malt phenotypes, for example a ~2% increase in malt extract, and improvement in other malt characteristics such as beta-glucan content and alpha-amylase activity was observed. Overall, these data show that molecular genetics and allelic selection for genes controlling plant development is promising for advancing malt quality. Research performed here has a direct potential for improving the profits for malt barley producers.