Development of hormone based genomic tools to accelerate wheat breeding for enhanced preharvest sprouting tolerance

小麦是加拿大最重要的经济作物之一，然而，它的生产不断受到各种胁迫因素的挑战，如收获前发芽（PHS），这是指收获前母体植物上的谷物发芽。小灵通降低了粮食产量，严重限制了最终使用质量，给生产者造成了巨大的经济损失。鉴于小灵通的发病率预计会随着气候变化引起的降水和温度的季节性变化而增加，对小灵通的耐受性是加拿大小麦生产者所寻求的一个非常理想的性状。调控小灵通耐受性的许多遗传和环境因素主要由脱落酸（ABA）和赤霉素（GA）介导，它们是植物产生的化合物，在极低浓度下影响生长和发育过程，通常被称为“植物激素”。ABA和GA对小灵通具有拮抗作用；ABA增强小灵通耐受性，GA增强小灵通潜能。然而，温度等环境因素如何调节成熟过程中籽粒ABA/GA水平的平衡和敏感性，从而影响小麦对小灵通的耐受性，目前尚不清楚。小麦基因型之间小灵通耐受性的差异也可能由与小灵通控制有关的关键基因的基因组序列和/或表达水平的差异引起。本研究的目的是确定调控成熟小麦籽粒ABA/GA平衡变化的特定分子元件、ABA相关基因序列的小灵通相关变异，以及其他控制小灵通的关键遗传因子的温度调控。本研究结果将为培育耐小灵通小麦品种提供有力的基因组工具；从而提高小麦的产量和质量，以及加拿大小麦生产者的农业收入。此外，这项研究涉及培养作物生物技术和分子育种领域的高素质人才，这对加拿大作物工业的竞争力至关重要。

Wheat is one of the most economically important crops of Canada, however, its production is challenged constantly by a variety of stress factors such as preharvest sprouting (PHS), which refers to the germination of grains on the mother plant prior to harvest. PHS lowers grain yield and severely limits end-use quality, causing substantial economic loss to the producers. Given that the incidence of PHS is expected to increase with climate change induced seasonal shifts in precipitation and temperature, tolerance to PHS is a highly desirable trait sought by Canadian wheat producers. Many of the genetic and environmental factors that regulate PHS tolerance are mediated mainly by abscisic acid (ABA) and gibberellins (GA), which are among the plant produced compounds that influence growth and developmental processes at very low concentrations, usually coined as "plant hormones". ABA and GA play antagonistic roles in controlling PHS; ABA enhances PHS tolerance while GA promotes PHS potential. However, how environmental factors such as temperature regulate the balance of grain ABA/GA levels and sensitivity during maturation, and thereby PHS tolerance is poorly understood in wheat. Difference in PHS tolerance between wheat genotypes can also be induced by variations in the genomic sequences and/or expression levels of key genes implicated in the control of PHS. The goals of this research are to identify specific molecular elements that regulate temperature-induced changes in ABA/GA balance in maturing wheat grains, identify PHS associated variations in the sequences of ABA related genes, and investigate temperature regulation of other key PHS controlling genetic factors. The findings of this research will provide powerful genomic tools that can facilitate the breeding of wheat cultivars with adequate PHS tolerance; thereby improving wheat yield and quality, and farm income for Canadian wheat producers. Further, this research involves the training of highly qualified personnel in the area of crop biotechnology and molecular breeding, which is critical to the competitiveness of Canada's crop industry.