Optimizing preharvest sprouting tolerance in malting barley

作为加拿大经济上最重要的谷类作物之一，麦芽的生产受到一系列环境胁迫因素的不利影响，例如引起收获前发芽（PHS）的环境胁迫因素，PHS指的是收获前谷物在母体植物上的发芽。收获前发芽降低了作物等级，使粮食不适合麦芽酿造，给生产者造成了巨大的经济损失。因此，具有最佳休眠水平的品种，既可以防止田间发芽的风险，又可以在收获后快速发芽，这是加拿大麦芽生产商的高需求品种。众所周知，种子的休眠水平（PHS耐受性）是由低丰度的植物产生的化合物控制的，通常被称为“植物激素”，其中脱落酸（ABA）和赤霉素（GA）是主要的参与者。ABA增强了种子休眠的诱导和维持，而GA促进了种子萌发/发芽。然而，控制种子ABA水平和反应的分子和遗传因素及其与发芽促进GA的拮抗相互作用，从而维持麦芽最佳休眠的机制尚不清楚。本研究的目的是确定控制种子ABA水平和响应的ABA相关基因，并研究ABA对种子GA水平和响应的调控，以及发芽诱导的淀粉降解过程。本研究结果将为加速培育休眠最佳的麦芽品种提供分子和遗传工具，以防止小PHS，提高麦芽产量和质量，从而使加拿大麦芽生产者的经济回报最大化。这项研究还支持培养作物生物技术和分子育种方面的高素质人才，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.