Comprehensive evaluation of berry qualities of 101 table grape cultivars cultivated in northern Zhejiang plain based on different methods

Abstract:【Objective】There are various trait differences among different grape germplasms. The assessment of fruit characteristics plays a vital role in the assessment of grape genetic resources. The study aimed to comprehensively evaluate the berry quality traits of the 101 table grapes cultivated in the northern Zhejiang Plain using correlation analysis, cluster analysis and principal component analysis, in order to characterize their representative qualities, and provide technical guidance for the evaluation of grape fruit quality and the screening of excellent germplasm.【Methods】A total of 101 table grape germplasm resources were used as test materials to investigate and analyze the fruit quality traits. In or-der to explore the fruit quality traits, 26 parameters were measured including vetotal organic acidsticity, cohesion, elastic index, chewiness, pericarp puncture strength, total phenols content, flavonoid content, proanthocyanidin, sucrose content, fructose content, glucose content, oxalic acid content, tartaric acid content, malic acid content, citric acid content, total sugar content, total organic acid content, the ratio of total sugar to total organic acid, fruit cracking rate and fruit cracking index. SPSS 27.0 was used to conduct correlation analysis, cluster analysis, and principal component analysis on the above indicators, and to analyze and evaluate the quality of grape fruits through comprehensive scoring ranking.【Results】The 26 quality indicators showed varying degrees of variation, with coefficients of variation ranging from 7.03% to 159.48%. Among all indicators, the proanthocyanidin had the largest variation and the elastic index had the smallest. According to the cluster analysis, the 101 grape germplasm resources were divided into 5 categories when the Euclidean distance was 11.5. The Ⅰ category could be divided into 3 groups when the Euclidean distance was 8.5, the majority were derived from hybridization; the Ⅱ category could be divided into 4 groups when the Euclidean distance was 8.5, the majority were Eurasian population. After eliminating the fruit quality indexes with less variation, 14 traits of the 101 grape germplasm resources were standardized by the principal component analysis and then reduced in dimension. In the principal component analysis, five principal components were extracted with a total cumulative contribution of 82.178%. The contribution rate of the principal component 1 was 26.008%, mainly representing soluble solids, total sugar content, and cohesion, reflecting the quality of fruit sugar content. The contribution rate of the principal component 2 was 19.293%, mainly representing the total phenols and flavonoids, reflecting the fruit nutrients. The contribution rate of the principal component 3 was 14.750%, mainly representing the single fruit cracking rate, fruit cracking index, and sugar-acid ratio, reflecting the resistance to fruit cracking. The contribution rate of the fourth principal component was 13.420%, and the main factors to determine it were the elasticity and cohesion, which reflected the fruit texture. The contribution rate of the principal component 5 was 8.707%, and the main factors to determine it were the total acid and sugar-acid ratio, which reflected the fruit flavor.【Conclusion】In this study, 26 agronomic traits of the 101 grape germplasm resources were analyzed and the resources could be divided into 5 categories based on the diversity analysis, cluster analysis and principal component analysis. Through the comprehensive analysis of the fruit quality, soluble solid, elasticity, cohesion, chewiness, total phenols content, flavonoid content, total sugar content, sugar-acid ratio, fruit cracking rate and fruit cracking index elements were selected as the core indicators for the evaluation of fruit quality traits. Miguang, Pearl Noir, Zhengyan Wuhe, Jingshouzhi, 09-42, Black Beet, 13-653 and 15- 115 were selected as high quality resources by the principal component analysis. It would provide a reference for the evaluation of fresh grape germplasm resources and the selection of new variety in Zhejiang Province.