Optimizing preharvest sprouting tolerance in malting barley

作为加拿大最重要的经济作物之一，麦芽大麦的生产受到一系列环境胁迫因素的不利影响，例如导致收获前发芽（PHS）的因素，收获前发芽是指收获前母体植物上的谷物发芽。收获前发芽降低了作物等级，使谷物不适合制麦芽，这给生产者带来了很大的经济损失。因此，具有最佳休眠水平的品种，防止田间发芽的风险，同时允许收获后快速发芽，是加拿大啤酒大麦生产商的高需求。已知种子中表现出的休眠水平（PHS耐受性）由通常称为“植物激素”的低丰度植物产生的化合物控制，其中脱落酸（阿坝）和赤霉素（GA）是主要参与者。阿坝促进种子休眠的诱导和维持，GA促进种子萌发。然而，控制种子阿坝水平和响应的分子和遗传因素及其与促进发芽的GA的拮抗相互作用，从而维持最佳休眠在啤酒大麦中知之甚少。本研究的目的是鉴定控制种子阿坝水平和响应的特定阿坝相关遗传元件，并研究阿坝对种子GA水平和响应以及萌发诱导的淀粉降解过程的调控。这项研究的结果将提供分子和遗传工具，可以加速培育具有最佳休眠的啤酒大麦品种，以防止PHS并提高啤酒大麦的产量和质量，从而最大限度地提高加拿大啤酒大麦生产商的经济回报。这项研究还有助于培训作物生物技术和分子育种方面的高素质人员，这对确保加拿大作物产业的竞争地位至关重要。

The production of malting barley, one of the most economically important cereal crops of Canada, is adversely affected by a range of environmental stress factors such as those causing preharvest sprouting (PHS), which refers to the germination of grains on the mother plant before harvest. Preharvest sprouting decreases crop grade and makes the grains unsuitable for malting and this incurs high economic loss to the producers. Therefore, cultivars with optimal level of dormancy that prevents the risk of field sprouting while allowing rapid germination after harvest is in high demand by Canadian malting barley producers. The level of dormancy (PHS tolerance) manifested in seeds is known to be controlled by the low-abundant plant-produced compounds often referred as "plant hormones", of which abscisic acid (ABA) and gibberellin (GA) are the major players. ABA enhances the induction and maintenance of seed dormancy while GA promotes seed germination/sprouting. However, the molecular and genetic factors controlling seed ABA level and response and its antagonistic interaction with the sprouting promoting GA, and thereby the maintenance of optimal dormancy is poorly understood in malting barley. The goals of this research are to identify specific ABA related genetic elements that control seed ABA level and response, and investigate ABA regulation of seed GA levels and response, and starch degradation, a process induced by sprouting. The findings of this research will provide molecular and genetic tools that can accelerate the breeding of malting barley cultivars with optimal dormancy to prevent PHS and enhance the yield and quality of malting barley, which in turn maximizes the economic returns for Canadian malting barley producers. This research also supports the training of highly qualified personnel in crop biotechnology and molecular breeding, which is critical for ensuring the competitive position of Canada's crop industry.