Molecular basis of water soaking of strawberry

草莓是一种全球重要的易腐烂水果作物。田间种植的草莓的质量经常受到雨水的严重影响。雨水引起的一个重要紊乱是“浸水”。有症状的果实表面呈浅灰色，呈半透明和潮解状。水浸泡与角质层的微开裂和表皮细胞的花青素渗漏有关。果实采前、采后腐烂的发生率也增加，造成重大的经济损失。因此，草莓生产正从露天转为半保护或完全保护的塑料隧道或温室。基因型对水浸泡的敏感性不同。这种差异的生理、遗传和分子基础尚不清楚。该项目的目的是确定基因型差异易感性的基础。(1)选择一对对水浸泡有不同敏感性的亲本基因型，建立差异基因表达（RNA-seq）、水浸泡、角质层沉积、菌株发育和微裂的发育时间历程。(2)将亲本基因型进行杂交，产生一个f1群体（200个个体），以进行(i)分离f1群体对水浸泡敏感性的表型分析，（ii）遗传连锁图谱的基因分型分析，（iii） QTL分析，以及（iv）在QTL区域两侧开发基于pcr的分子标记，用于标记辅助育种。(3)我们将选择最有希望的候选基因（CGs），并将差异基因表达鉴定的CGs与位于QTL区域的CGs进行比较。这将允许建立第一个耐水浸泡的分子模型。该模型包括鉴定的cg，将通过在独立生长季节使用qRT-PCR进行进一步的表达研究来验证。最后，我们将对亲本基因型中最有希望的cg进行测序，鉴定结构变异，并开发基于pcr的标记物来检测选定的结构变异。结构变化及其与水浸泡的关系将使用f1种群进行验证。这些结果将有助于确定草莓对水浸泡敏感性的遗传和分子基础。此外，如果能找到显著的qtl，就有可能培育出对水浸不敏感的草莓新品种。此外，这些品种可能不太容易发生果实腐烂。这样，露天草莓生产的可持续性将得到提高。

Strawberry is a highly perishable fruit crop species of global importance. The quality of field-grown strawberries is often severely compromised by rain. An important disorder arising from rain is ‘water soaking’. The symptomatic fruit surface has a light greyish color and a translucent and deliquescent appearance. Water soaking is associated with microcracking of the cuticle and anthocyanin leakage from the epidermal cells. The incidence of fruit rots pre- and postharvest is also increased causing significant economic loss. As a result, strawberry production is shifting from open-field, to semi- or fully-protected in plastic tunnels or greenhouses. Genotypes differ in susceptibility to water soaking. The physiological, genetic and molecular bases for such differences are not understood. The objective of the project is to determine the bases of the differential susceptibility of genotypes. (1) We will establish a developmental time course of differential gene expression (RNA-seq), water soaking, cuticle deposition, strain development and microcracking for a pair of parental genotypes selected for their contrasting susceptibilities to water soaking. (2) The parental genotypes will be crossed to produce an F1-population (200 individuals) to perform (i) phenotyping of the segregating F1-population for susceptibility to water soaking, (ii) genotyping for developing genetic linkage maps, (iii) QTL analyses and (iv) develop PCR-based molecular markers flanking the QTL regions for marker-assisted breeding. (3) We will select the most promising candidate genes (CGs) and compare the CGs identified by differential gene expression with those located in the QTL regions. This will allow establishment of a first molecular model for tolerance to water soaking. The model including the identified CGs will be verified by further expression studies using qRT-PCR in independent growing seasons. Finally, we will sequence the most promising CGs in parental genotypes, identify structural variations and develop PCR-based markers for the detection of selected structural variations. The structural variations and their association with water soaking will be verified using the F1-population. These results will help identify the genetic and molecular bases of susceptibility to water soaking in strawberry. Furthermore, provided that significant QTLs are found, new strawberry cultivars that are less susceptible to water soaking may be developed. In addition, these cultivars are likely to be less prone to fruit rots. As a consequence, the sustainability of strawberry production in the open field will be improved.