Research Progress in Genetic Characteristics and Loci Mapping for Grape Berry Quality Traits

Berry quality is a core objective of grapevine breeding. Most related traits are quantitative characteristics controlled by multiple genes, which are susceptible to the combined effects of genetic background and environmental factors. Deciphering the genetic basis of these traits is of great significance for molecular design breeding of grapes. This study systematically reviews the genetic characteristics of grape berry quality traits (e.g., berry size, texture, sugar and acid content, color, seedlessness, and aroma) and summarizes the research progress over the past three decades in identifying QTLs/candidate genes for quality traits using linkage analysis in bi-parental segregating populations and association analysis in natural populations. Grape berry size, shape and texture are typical polygenic quantitative traits with high broad-sense heritability; traits such as berry color, seedlessness and muscat flavor exhibit dual genetic characteristics of both qualitative and quantitative traits, which are regulated by major genes combined with minor genes. In addition, the phenotypic expression of most quality traits is significantly affected by environmental factors such as cultivation practices, light and temperature. In terms of linkage analysis, a total of approximately 386 QTLs associated with grape berry quality traits were mapped using about 60 hybrid populations dominated by F₁ generations, among which the number of QTLs related to sugar and acid content was the largest. Major QTLs for seedlessness, berry size, texture and other traits were identified on linkage group 18, and a major QTL for muscat aroma was detected on linkage group 5. Meanwhile, key candidate genes such as VviAGL11, DXS and MYBA1/2 were excavated, and their core regulatory roles in seedlessness, muscat aroma and berry color were clarified. For association analysis, candidate gene association analysis confirmed that the sequence polymorphisms of gene clusters such as VvMybA and genes including DXS were significantly associated with fruit color, muscat aroma and other traits, and some genes exhibited pleiotropy. Genome-wide association analysis has identified a large number of single nucleotide polymorphism (SNP) loci and structural variations (SVs) related to berry quality traits, among which SVs contribute more to the genetic regulation of some traits than SNPs. At present, the application of molecular markers in grape quality breeding is still limited to traits controlled by major genes such as berry color, seedlessness and muscat aroma, and marker-assisted selection has not been practically applied to complex quantitative traits such as berry size and texture. Currently, the gene mapping of grape berry quality traits is still faced with challenges such as insufficient mapping accuracy, difficulties in multi-omics data integration, complexity in deciphering multi-gene interaction networks, and poor stability of molecular markers. In the future, relying on super pan-genome and high-throughput phenotyping platforms, combined with technologies such as deep learning and gene editing, it is necessary to strengthen research on gene-environment interactions, improve the accuracy of QTL mapping and the efficiency of gene function analysis, and construct an efficient molecular breeding technology system, so as to provide theoretical support and technical guarantee for the cultivation of high-quality grape varieties. This paper aims to offer a comprehensive literature reference and theoretical foundation for subsequent molecular design breeding of premium grape cultivars.