Phenotypic Evaluation and Screening of Grape Germplasm in the Dry-Hot Valley of Yuanmou, Yunnan

To address the issues of limited varietal diversity and summer heat-induced fruit quality decline in the dry-hot valleys of Yunnan, this study used 28 table grape accessions conserved at the Yuanmou Comprehensive Experimental Station as experimental materials to systematically evaluate their phenotypic diversity and identify superior accessions suitable for cultivation in this ecoregion. A total of 53 fruit and leaf phenotypic traits were measured and analyzed using correlation analysis, principal component analysis (PCA), and hierarchical clustering analysis (HCA) to characterize trait variation and interrelationships. A comprehensive evaluation model based on PCA scores was constructed to screen elite accessions. The results revealed substantial phenotypic diversity among the tested accessions in both fruit and leaf traits. Cluster weight and brush length showed the most pronounced variation, with coefficients of variation of 47.2% and 46.8%, respectively, while berry width and flesh firmness exhibited notable diversity, with Shannon-Wiener indices of 1.62 and 1.61. Correlation analysis indicated that yield-related traits, such as cluster size and cluster weight, were negatively correlated with soluble solids content (P < 0.05). Based on the PCA-based comprehensive evaluation, five superior accessions including ‘Red Globe’, ‘Langman Hongyan’, ‘Sweet Sapphire’, ‘Huangjinmi’, and ‘Centennial Seedless’, were identified. These accessions are characterized by moderate berry size, desirable flesh firmness, well-balanced sugar-acid composition, and a maturity period concentrated between April to June, indicating their potential for off-season cultivation. The selected accessions exhibited favorable adaptation to the dry-hot valley environment and may serve as candidate materials for variety replacement and crossbreeding programs in this region.