Multiyear evaluation of fruit quality diversity, stability, and climatic drivers across a diverse Actinidia germplasm collection

Abstract Understanding the genetic diversity and environmental stability of fruit quality is essential for the selection of elite kiwifruit germplasm and the development of climate-adaptive cultivars. In this study, 47 kiwifruit ( Actinidia spp.) accessions were evaluated over four consecutive years (2021–2024) to characterize fruit-quality diversity and stability and to identify meteorological factors associated with quality variation. 8 quality traits—fruit weight (FW), dry matter (DM), soluble solids content of ripe fruit (SSC_R), sugar, titratable acidity (TA), SSC_R/TA and Sugar/TA ratios, and vitamin C (Vc)—were analyzed using descriptive statistics, correlation, multivariate analysis, and stability coefficients. Associations between quality traits and meteorological factors during key developmental windows were evaluated using Spearman’s rank correlation analysis. The results revealed substantial phenotypic diversity: Vc exhibited the greatest variation (CV = 100.75%), whereas DM was the most stable trait (CV = 8.87%), and a strong predictor of sweetness of ripe fruit ( R 2 = 0.66 with SSC_R). Genetic background significantly influenced trait expression, with A. eriantha hybrids showing exceptionally high levels of Vc, whereas A. rufa hybrids exhibiting small fruit size and low levels of Vc. Multivariate analysis classified the 47 accessions into 4 clades with distinct quality profiles. Stability analysis indicated that environmental variation among years was the primary driver of total phenotypic fluctuation, while certain accessions (e.g., S1, S9, S16, S18, and S43) exhibited both high quality and superior stability. Meteorological conditions during specific developmental windows were significantly associated with several quality traits. DM was positively associated with maximum temperature, diurnal temperature range, and temperature variability (| r | ≈ 0.38–0.41), whereas TA and the sugar–acid ratio were associated with early-season heat accumulation, temperature variability, and preharvest rainfall (| r | ≈ 0.30–0.47). These associations were stage dependent, and no single meteorological factor consistently explained fruit-quality variation. Overall, this study reveals substantial genetic diversity in kiwifruit fruit quality, identifies germplasm combining high quality with cross-year stability, and demonstrates the stage-specific associations of meteorological conditions with key quality traits, providing valuable resources for breeding high-quality, broadly adaptable cultivars and developing climate-adaptive orchard management strategies.