基于连锁分析与关联分析的甜瓜果肉厚度QTL定位及相关基因挖掘

Flesh thickness is an important factor affecting the quality of melon. Its QTL/gene discovery and molecular marker development will be the key to the improvement of melon quality. Melon flesh thickness is a complex quantitative trait. This study adopts the strategy of joint linkage analysis and association analysis to the proposed QTL mapping. ①Based on the 148 recombinant inbred lines (RILs) constructed in the previous study, the QTL of the flesh thickness of melon was located by the construction of high density genetic map. ②Association analysis among 170 accessions of melon germplasms will be used to reverify the previous QTLs/loci through a set of high-density single nucleotide polymorphism (SNP) markers. ③High density SNP markers are developed for the reduction of the reverified QTL interval. Furthermore, combined with melon genome information and gene expression analysis, screening of candidate genes underlying melon flesh thickness will be conducted in present project. In addition, we will develop tighter linkaged molecular markers according the allelic variation located in the candidate segment. These results will provide important theoretical basis and technology for melon breeding with flesh thickness and facilitate melon marker-assisted selection.

果肉厚度是影响甜瓜品质的重要因子，其QTL/基因发掘及分子标记开发将是甜瓜品质改良的关键。甜瓜果肉厚度为复杂数量性状，本研究拟采用连锁分析结合关联分析的策略对其进行遗传解析，主要开展以下研究：①利用已有的包含148个家系的重组自交系群体，通过构建高密度遗传图谱，对甜瓜果肉厚度进行QTL定位；②以170份不同果肉厚度甜瓜种质组成的自然群体为材料，开展基于高密度SNP标记的全基因组关联分析，对连锁分析QTL定位结果进行验证；③在验证后的QTL区段内开发高密度分子标记，综合重组自交系群体的进一步定位结果及自然群体候选区段关联分析结果，实现目标区段的收缩和排查，结合甜瓜基因组信息及果实不同发育期表达分析，发掘甜瓜果肉厚度相关基因，并开发相应的分子标记，为甜瓜品质改良提供理论依据和技术支持。

果肉厚度是影响甜瓜品质的重要因子，属于复杂的数量性状，本研究联合关联分析与连锁分析挖掘与甜瓜果肉厚度显著相关的遗传位点。本研究对包含213份种质的自然群体开展了多年表型测定和重测序分析，通过全基因组关联分析检测到55个与果肉厚度显著关联的SNP标记，其中有6个SNPs在3个环境中稳定检测到，2个SNPs在4个环境中稳定检测到。本研究同时对RIL群体及其亲本开展了重测序工作，构建了包含1427个bin标记的遗传图谱，其总遗传距离为1254.34cM，标记间的平均遗传距离为0.88cM。结合RIL群体三年表型数据，检测到9个与甜瓜果肉厚度相关的QTL，分布在第3、6、12号染色体上，其中qFT_6.5在三个环境中稳定检测到，qFT_6.4在4个环境中均可稳定检测到。结合全基因组关联分析与连锁分析结果，在6号染色体上鉴定到一个与甜瓜果肉厚度相关的稳定QTL区段，包含有12个候选基因。本项目鉴定到的QTL/SNPs，将为甜瓜果肉厚度相关基因挖掘与品种改良奠定基础。