糖和有机酸是决定果实内在品质的两个核心因素。本项目拟采用HPLC技术测定苹果资源成熟果实中糖酸的组分与含量，构建苹果资源果实糖酸品质性状数据库，同时采用简化基因组重测序方法发掘苹果基因组中多态性位点，绘制苹果遗传变异图谱，采用全基因组关联分析（GAWS）方法鉴定出控制苹果果实糖酸合成与积累的遗传位点及不同遗传位点之间的互作效应，并结合区间候选基因关联分析鉴定控制苹果果实糖酸性状的候选基因。通过模式植物番茄和拟南芥的稳定转化，或基于病毒介导的苹果果实瞬时转化等研究对候选基因的功能加以解析。开展染色质免疫共沉淀、Pull-down及酵母杂交等研究，并参照GWAS揭示的基因互作结果，鉴定基因之间的互作，建立决定果实糖酸品质性状形成的遗传调控网络。项目的开展既能系统剖析影响苹果果实糖酸性状形成的分子调控机理，又可获得改良果实糖酸性状的分子元件，具有重要的理论意义和应用价值。

Soluble sugars and organic acids are important components of fruit taste. In this project, soluble sugar and organic acid components in apple mature fruits will be measured using high performance liquid chromatography (HPLC), resulting in an organoleptic fruit database of apple germplasm. The apple germplasm will be genotyped using genotyping-by-sequencing (GBS) approach and a genome-wide high-dense map of apple genetic variation is expected to develop. Genome-wide association mapping study (GWAS) will be performed to identify genetic loci responsible for soluble sugar and organic acid accumulation in apple fruit, and the interactions of different loci will be estimated as well. Region-based association analysis will be performed to identify candidate genes responsible for soluble sugar and organic acid accumulation in apple fruit. Gene functionalities will be evaluated using stable transformation of model plants such as tomato and Arabidopsis, and/or virus-induced gene transient expression system in apple fruit. Subsequently, genetic interaction experiments such as chromatin immunoprecipitation (ChIP) assay, pull-down experiment, and yeast hybridization systems, together with reference gene results of genetic interactions derived from GWAS, will be conduct to identify gene-gene interactions. Finally, we will proceed to construct genetic regulatory networks controlling soluble sugar and organic acid accumulation in apple fruit. This project not only has a theoretical significance in expanding our knowledge of global regulatory mechanisms of soluble sugar and organic acid accumulation in apple fruit, but will also provide molecular tools highly useful for genetic improvement of fruit quality.