Dissecting the control of continuous cropping in strawberry using genetic mapping and gene-editing

种植者对能够在整个生长季节连续种植的长生草莓品种越来越感兴趣。然而，在果实质量和种子产量方面，常生代和传统的“短日照”品种之间存在显著的权衡。在某种程度上，这可能是由于长生不育的特性是从一个野生草莓品种中发现的单个个体逐渐渗入的，现在才开始渗透到“精英”基因库中。我们的工作表明，与之前的报道相反，万代是一种复杂的性状，需要基因组的多个区域来预测该性状的表达。需要进一步的研究来探索哪些等位基因组合需要在整个季节中保持永育系的一致表现，以及它们产生无性繁殖的跑子的能力。由于这些性状的遗传结构复杂，需要对现有标记进行额外的验证和开发新的标记，以准确地选择具有均匀种植和足够的跑穗产量的基因型。这些标记还将加速通过长结实基因型与短日优良型杂交选育出果实品质优良的长结实品种。本博士项目的目的是了解草莓持久性状的遗传基础，并开发可靠的标记，以选择最佳的持久习惯。基于我们从大量种质收集的基因型数据，我们将开发一个作图群体，对控制常育性状的三个位点进行精细作图。将进行详细的表型分析，探讨不同等位基因组合对整个生长季节开花、结果和果实产量的影响。为了更详细地了解八倍体草莓的恒育性状及其环境调控，该学生将参与CRISPR-Cas9基因编辑品系的培育，并在可控气候条件下分析最有希望的品系。了解常熟草莓花形成的关键分子过程将有助于高产品系的选择和繁殖过程的优化，这反过来将为种植者提供具有更高产量潜力和更均匀性能的植物材料。

Growers are increasingly interested in everbearing strawberry cultivars that enable continuous cropping throughout the growing season. However, significant trade-offs exist in fruit quality and runner production between everbearers and traditional 'short day' varieties. This may, in part, be due to the fact that the everbearing trait was introgressed from a single individual identified in a wild species of strawberry and is only now starting to permeate into the 'elite' gene pool. Our work has shown that, in contrast to earlier reports, everbearing is a complex trait, with multiple regions of the genome required to predict expression of the trait. Further studies are needed to explore which allele combinations are needed for uniform performance of everbearing lines throughout the season and for their ability to produce runners for vegetative propagation. Because of the complex genetics architecture of these traits, additional validation of existing markers and the development of new markers are needed to accurately select genotypes with uniform cropping and adequate runner production. These markers would also speed up the breeding of everbearing cultivars with improved fruit quality through crosses between everbearing genotypes and elite short-day types.The aim of this PhD project is to understand the genetic basis of everbearing trait in strawberries and to develop reliable markers for the selection of optimised everbearing habit. Based on our genotypic data from across a large germplasm collection, a mapping population will be developed for fine mapping of the three loci controlling the everbearing trait. Detailed phenotypic analysis will be carried out to explore the effect of different allele combinations on flowering, fruiting and runner production throughout the growing season. To understand the everbearing trait and its environmental regulation in more detail in octoploid strawberry, this studentship will participate in generating CRISPR-Cas9 gene-edited lines and analyse the most promising lines in controlled climatic conditions. Understanding the key molecular processes that underpin floral initiation in everbearing strawberries will facilitate the selection of high yielding lines and optimisation of the propagation processes, which in turn will deliver plant material to growers that has a higher yield potential and more uniform performance.