Tree Genetics and Molecular Breeding 2025, Vol.15, No.5, 176-184 http://genbreedpublisher.com/index.php/tgmb 180 6 Case Study: Breeding Progress for Fruit Quality in Vitis vinifera 6.1 Breeding objectives: aroma, anthocyanin accumulation, and seedlessness The improvement of grape fruit quality mainly focuses on aroma, anthocyanin content and seedlessness. Aroma substances (such as monoterpenoids and other volatile compounds) directly determine the flavor of grapes and wine and are also the factors that consumers care about the most. Anthocyanins are the main pigments in fruits. They not only affect the color of fruits and wine but also have antioxidant and health-promoting effects. Seedlessness is an important trait of table grapes and some wine grapes, as it meets the market's demand for convenience in consumption. In recent years, climate change has affected the sugar-acid ratio and balance of fruits, and the breeding goals have gradually expanded to acidity regulation and stress resistance to ensure fruit quality (Yamada and Sato, 2016; Gascuel et al., 2017; Bigard et al., 2018; Bigard et al., 2020; García-Abadillo et al., 2024). 6.2 Methods: integration of classical hybridization with molecular tools Traditional hybrid breeding has made progress in quality improvement through sexual hybridization and phenotypic selection of superior varieties. However, due to the long life cycle and complex genetic traits of grapes, relying solely on traditional methods is not very efficient. In recent years, tools such as molecular marker-assisted selection (MAS), genome-wide association study (GWAS), QTL mapping and gene editing (such as CRISPR/Cas9) have been widely applied. These technologies can accelerate the localization and utilization of genes related to target traits and improve the efficiency of selection and breeding. For instance, the early screening of traits such as seedlessness, fruit size and anthocyanin synthesis by using molecular markers has significantly shortened the breeding cycle. Meanwhile, genomic sequencing and high-throughput phenotypic analysis also provide support for genetic analysis and precise improvement of complex traits (Figure 2) (Tello et al., 2019; Butiuc-Keul and Coste, 2023; Rao, 2023; García-Abadillo et al., 2024; Rahman et al., 2024; Xie et al., 2025). Figure 2 Progression of agricultural breeding methods (Adopted from Rahman et al., 2024) Image caption: The process of crossbreeding takes a significant amount of time, often 8-10 years, to improve desirable characteristics or features in a particular species, such as disease tolerance or resistance. Mutation breeding uses chemical or physical irradiation to develop unique genetic variants in the genome over 6-7 years. Tissue culture improves crop attributes in 4-6 years by exogenously transforming genes into commercially relevant elite cultivars. Genome editing: precisely updating the target gene or regulatory sequence or modifying elite kinds’ DNA and/or RNA bases in 2-3 years to improve a specified characteristic (Adopted from Rahman et al., 2024)
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