Genetic diversity and yield stability for increased resilience against climate change in the UK

通过增加多样性来提高作物对气候变化的适应能力是有重大机遇的。在英国，天气模式可能会变得更加多变；干旱、洪水和短期高温压力的频率增加(11)。这些变化将使英国农业高度脆弱，气温突然变化，而不是平均气温上升，可能对农业生产力产生重大影响(11；24)。英国最重要的经济作物是小麦。作物发育与温度之间的相互作用是复杂的，但已证明最脆弱的时期是开花(如6)。极端天气事件的强度和持续时间影响籽粒灌浆期，减产与最大温度应力直接相关(2)。这些突如其来的极端事件与全球气温的平均变化截然不同；逐渐增加使人们能够选择改善遗传适应环境的特征(16)，而突发事件被认为在很大程度上超出了细胞功能的门槛。物种多样性高的植物群落在(1)资源利用(22)和(2)生物量生产的稳定性(10)方面对环境变化有更大的适应能力。在将这些生态学原理应用于耕地系统时，可以通过利用不同基因类型之间的互补性来增加作物多样性，从而降低作物歉收的风险。在开花期，这一脆弱的生长阶段的延长将增加一些个体通过在极端事件之前或之后开花来逃脱极端事件的机会。在冬小麦中，控制出穗和开花的遗传机制根据它们之间的环境互作而被分类。28-56天的冷处理(春化)会诱导耳朵出芽。控制春化需求的基因包括VRN-A1、VRN-B1、VRN-D1和VRN-B3(14；15)。品种也可以根据日光(光周期)要求进行分类。在面包小麦中，这种差异很大程度上是由PPD-D1和PPD-B1(17)控制的，这两个显性等位基因通过光周期不敏感来实现早穗出苗。这些基因对大环境适应有深远的影响，但第三组基因，早熟本身(EPS)，可以独立于特定的环境信号调节发育速度(19)。春化和光周期基因赋予环境适应能力；但EPS效应有助于更微妙地操纵生活史以实现区域适应。全基因组基因分型和数量性状基因座(QTL)分析的出现使得许多重要的EPS效应得以在西欧的精英种质中分离出来；现在可以解释很大比例的穗出苗的遗传变异(8)。EPS基因描述了平均开花时间点，但基因型的差异可能来自：(1)第一次开花时间；(2)单穗内开花持续时间；(3)分蘖持续时间；(4)开花高峰期。进一步的遗传效应包括结实时的绝对温度耐受性。这项拟议的研究旨在检验这样一个假设：更大的基因异质性提高了作物在不断增加的气候胁迫下的韧性。选择开花的单一性状进行概念验证。这项拟议的研究将开发新的抽穗期遗传标记。英国EPS QTL的近等位基因和两个CCP，一个是EPS基因的异质性，另一个具有广泛的遗传背景，将从遗传和生理上进行剖析。不同的基因型对特定的定时热胁迫事件的表现将决定开花多样性对作物抗逆性的贡献。

There are major opportunities to increase crop resilience to climate change by increasing diversity. In the UK, weather patterns are likely to become more variable; with increased frequency of droughts, floods and short spells of high temperature stress (11). These changes will render UK agriculture highly vulnerable, with sudden temperature changes, rather than the mean rise, likely to have major effects on agricultural productivity (11; 24). The most economically important crop in the UK is wheat. The interaction between crop development and temperature is complex, but it has been demonstrated that the most vulnerable stage is at flowering (anthesis) (e.g. 6). The intensity and the duration of an extreme weather event affects the period of grain filling and yield reduction is directly linked to maximum temperature stress (2). These sudden, extreme events are distinct from the mean changes in global temperature; gradual increase enables selection of characteristics that improve genetic adaptation to an environment (16) whereas sudden events are considered to be largely beyond the threshold of cellular function. Plant communities with high species diversity have a greater resilience to environmental variations, in terms of (i) resource use (22); and (ii) the stability of biomass production (10). In applying these ecological principles to arable systems, the risk of crop failure can be reduced by increasing crop diversity by harnessing the complementation between different genotypes. At anthesis, an extension of this vulnerable growth stage will increase the chance that a number of individuals will escape the extreme event by flowering before, or after it. In winter wheat, the genetic mechanisms controlling ear emergence and anthesis are categorised according to their environmental interaction. Twenty eight to 56 days of cold treatment (vernalization) induces ear emergence. Genes shown to control vernalization requirement include Vrn-A1, Vrn-B1, Vrn-D1, and Vrn-B3 (14; 15). Varieties can also be categorised according to daylight (photoperiod) requirement. In bread wheat this difference is largely controlled by Ppd-D1 and Ppd-B1 (17), dominant alleles which confer early ear emergence through photoperiod insensitivity. These genes have profound effects on mega-environment adaptation but a third set, earliness per se (eps) genes, can mediate developmental rate independent of specific environmental signals (19). The vernalization and photoperiod genes confer environmental adaptation; but the eps effects facilitate more subtle manipulation of the life cycle for regional adaptation. The advent of whole genome genotyping and Quantitative Trait Locus (QTL) analysis has allowed the identification a number of important eps effects segregating in Western European elite germplasm; a large proportion of the genetic variation in ear emergence can now be accounted for (8). The eps genes describe the mean flowering time point, but variation in genotype can result from: (1) Time of first anthesis; (2) Duration of anthesis within a single ear; (3) Duration across tillers; and (4) Time of day for peak anthesis. Further genotypic effects involve absolute temperature tolerance at seed set. This proposed research aims to test the hypothesis that: greater genotypic heterogeneity increases crop resilience under increasing climatic stress. The single character of flowering has been selected to test the proof of concept. The proposed research will develop new genetic markers for heading date. NILs for the UK eps QTLs and two CCPs, one heterogeneous for eps genes alone, and the other with a wide genetic background, will be dissected genetically and physiologically. The performance of the different genotypes to specific timed heat stress events will determine the contribution of flowering diversity to crop resilience.