Phenotypic constraints on crop improvement and the domestication of novel crops

作物驯化和改良要求农民和育种者能够看到新的和重要的特征，并进行选择以增强这些特征。这意味着性状的遗传、生理、形态或生化连锁将对选择有利表型的能力起到深远的作用。对两个相互关联的正面性状的选择将进行得很快(例如，较大的种子和较大的果实)，而选择与负面性状相关的正面性状(较大的植株具有较大的种子，但在风雨中倒下)将产生相互冲突的选择，延迟或阻止性状改进。在气候变化的情况下，培育具有弹性和高产的作物，甚至考虑目前未得到充分利用的作物的潜在价值变得越来越紧迫，这些作物的产量较低，但对气候的适应能力较强。在这个项目中，学生将使用QTL作图来解决性状连锁的遗传基础，并结合分析调查表型性状(包括已知具有农艺价值的性状)的相关结构和协方差，以确定连锁的符号和大小。这将对两个作物祖先(番茄和茄子的祖先)，即发生驯化的地方，以及两个密切相关的从未驯化的作物-野生近亲，即理论上可以驯化但没有发生的地方进行估计。这一系统水平的分配将确定祖先种和从未被驯化的物种在性状整合方面的差异，以检验性状连锁和整合在‘可驯化’中发挥作用的假设。群体遗传学方法将比较候选基因座(驯化基因和周围基因组区域)上四个物种的多样性，并模拟旨在分离负向和正向性状的选择策略的可能结果。这些结果将在农业、气候变化适应能力以及理解物种进化和分化的基本原理方面产生广泛影响。

Crop domestication and improvement requires novel and important traits to be visible to the farmer and breeder and for selection to enhance these. This means that genetic, physiological, morphological or biochemical linkage of traits will play a profound role in ability to select for advantageous phenotypes. Selection on two linked positive traits will proceed quickly (e.g. larger seeds and larger fruits), whereas selection of a positive trait linked to a negative trait (larger plant have bigger seeds but fall over in the wind and rain) will generate conflicting selection, delaying or preventing trait improvement. In a scenario of climate change, it is increasingly urgent to breed resilient and productive crops, and even consider the potential value of currently underutilised crops with lower yield but climate resilience. In this project, the student will use QTL mapping to resolve the genetic basis of trait linkage, combined with analyses investigate the correlational structure and covariance of phenotypic traits (including traits known to be of agronomic value) to determine the sign and magnitude of linkage. This will be estimated for two crop progenitors (the progenitors of tomato and eggplant), i.e. where domestication has occurred, and two closely-related never-domesticated crop-wild relatives, i.e. where domestication could theoretically have taken place but did not. This systems level apporoach will identify differences in trait integration between the progenitors and never-domesticated species to test the hypothesis that trait linkage and integration plays a role in 'domesticability'. Population genetics approaches will compare diversity in the four species at candidate loci (domestication genes and the surrounding genomic region), and to model the possible outcomes of selection strategies aiming at uncoupling negative and positive traits. The results will have broad impact in terms of agriculture, climate change resilience, and understanding the fundamentals of how species evolve and diverge.