Analysis and comprehensive evaluation of fruit quality of 39 sweet cherry accessions in Shanxi region

【Objective】Germplasm resources, serving as the material basis of agricultural production, are directly intertwined with the manifestation and enhancement of fruit quality. The sweet cherry, as a superior introduced fruit tree variety, has not yet been fully recognized and exploited in China. A comprehensive and in- depth exploration of sweet cherry germplasm resources holds tremendous significance for the exploitation of sweet cherry resources and the sustainable development of the industry within China. This study made a comprehensive assessment of the phenotypic traits of 39 sweet cherry fruits in the Shanxi region, with an intention of furnishing a reference foundation for the quality appraisal of sweet cherry fruits and the selection of superior germplasm. Moreover, the study aims to offer technical and theoretical sustenance for the sustainable development of the sweet cherry industry in Shanxi. 【Methods】39 sweet cherry samples were used for this study and 25 phenotypic traits were identified for the investigation. The quantitative traits encompassed single fruit mass, flesh recovery, fruit longitudinal diameter, fruit lateral diameter, fruit transverse diameter, fruit stalk length, stone mass, stone trans-verse diameter, stone longitudinal diameter, soluble solids content, vitamin C content, protein content, total soluble sugar content, reducing sugar content, total acid content, pericarp puncture strength, pulp firmness, fruit shape index, and solid-acid ratio. The qualitative traits comprised fruit shape, fruit apex shape, exocarp color, degree of coloration, flesh color, and fruit flavor. Subsequently, diversity analysis, correlation analysis, and cluster analysis were successively conducted on these phenotypic traits. Finally, a comprehensive evaluation was carried out through principal component analysis based on these phenotypic characteristics.【Results】The 39 sweet cherry samples possessed rich genetic diversity. The genetic diversity indices of the 19 quantitative traits ranged from 1.68 to 2.08. Among them, the genetic diversity indices of single fruit mass, fruit transverse diameter, fruit stalk length, stone longitudinal diameter, stone transverse diameter and fruit shape index were greater than 2, belonging to highly variable traits, and the genetic diversity indices of the remaining traits were between 1 and 2. The range of genetic diversity indices of 6 qualitative traits was 1.032 9-1.497 2. According to the results of diversity analysis, it was found that the fruit size among different cherry varieties was significantly different, and most of the qualitative traits had rich genetic diversity. The variation coefficient of the 19 quantitative traits ranged from 1.05% to 71.01%. The coefficient of variation of fruit hardness and vitamin C content exceeded 50%, indicating a large degree of dispersion of the phenotypic traits among sweet cherry species. Correlation analysis showed that the relationships among various phenotypic traits of different germplasms were close and complex. Cluster analysis divided the 39 sweet cherries into three groups. GroupⅠ include cherries with high solid-acid ratio and good fruit flavor; Group Ⅱ were characterized with large single fruit mass, large fruit size, and high pericarp and fruit hardness; and Group Ⅲ were featured by high nutrient content. This was similar to the results of the other classification methods reported by predecessors, but there were also some differences. Principal component analysis screened out 7 principal components, whose eigenvalues were all greater than 1, and the cumulative contribution rate reached 80.329%. The first principal component was mainly related to fruit size; the second principal component was mainly related to fruit nutritional value and marketability; the third principal component was mainly related to fruit shape; the fourth and fifth principal components were related to fruit taste, and the indicators such as single fruit mass, fruit transverse diameter and fruit lateral diameter related to fruit size had the greatest impact on phenotypic diversity. The comprehensive evaluation results of sweet cherry phenotypic traits showed that Tieton had the highest comprehensive score (3.82).【Conclusion】Through the integration of diverse evaluation methodologies, sweet cherry varieties in Shanxi such as Tieton, Santina, Heizhenzhu, Fuchen, and Крупноплодная manifested outstanding comprehensive performances, in contrast to LY 1, 1-72, and C-1, which exhibited relatively inferior qualities. Simultaneously, twelve crucial indices for the appraisal of sweet cherry phenotypic traits, namely fruit vertical diameter, fruit transverse diameter, fruit lateral diameter, pericarp color, flesh color, single fruit mass, stone mass, solid-acid ratio, flesh hardness, soluble solid content, protein content, and total soluble sugar content, were identified. These served as valuable references for the subsequent quality analysis, evaluation of sweet cherry germplasm, and variety breeding endeavors.