Phenotypic constraints on crop improvement and the domestication of novel crops

作物驯化和改良需要农民和育种者能够看到新的和重要的性状，并通过选择来增强这些性状。这意味着性状的遗传、生理、形态或生化联系将在选择有利表型的能力中发挥深远的作用。两个相互关联的积极性状的选择将迅速进行（例如，更大的种子和更大的果实），而与消极性状（更大的植物有更大的种子，但在风雨中倒下）相关的积极性状的选择将产生冲突的选择，延迟或阻止性状的改进。在气候变化的情况下，培育具有抗灾力和生产力的作物变得越来越紧迫，甚至需要考虑目前未充分利用的产量较低但具有气候抗灾力的作物的潜在价值。在本项目中，学生将利用QTL定位解决性状连锁的遗传基础，并结合分析研究表型性状（包括已知农艺性状）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）进行估计，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亲属，即理论上可能发生驯化但没有发生驯化的地方。这种系统水平的方法将识别祖先和未驯化物种之间性状整合的差异，以检验性状联系和整合在“可驯化性”中起作用的假设。群体遗传学方法将比较四个物种在候选位点（驯化基因和周围基因组区域）上的多样性，并对旨在解耦负性状和正性状的选择策略的可能结果进行建模。研究结果将对农业、气候变化适应能力以及了解物种进化和分化的基本原理产生广泛影响。

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.