Phenotypic Characterization, Phenotypic Variation, and Phenotype–Environment Associations of Hovenia acerba Germplasm in Fujian, China: Its Multipurpose Utilization

Hovenia acerba is a high-value multipurpose tree with edible, medicinal, and timber applications. However, systematic investigations of phenotypic variation, phenotypic diversity, and phenotype–environment associations for H. acerba germplasm in Fujian Province remain limited, which impedes targeted breeding and efficient resource exploitation. In this study, 25 quantitative morphological traits were assessed across 31 H. acerba accessions originating from 11 Fujian provenances. Multiple analytical pipelines were implemented, including analysis of variance, temporal repeatability estimation, correlation analysis, principal component analysis (PCA), cluster analysis, and climate–trait correlation analysis. Abundant phenotypic variation and considerable phenotypic diversity were detected. Infructescence-related traits exhibited the largest variation (mean coefficient of variation = 0.42), while fruit-associated traits had the highest mean repeatability (temporal repeatability = 0.52), demonstrating strong multi-year phenotypic temporal consistency. Observed phenotypic correlations suggest a putative trade-off between vegetative and reproductive growth. Primary peduncle length was strongly associated with yield performance, and tree height emerged as a promising candidate trait for potential early-stage seedling-based selection. PCA condensed the 25 traits into five principal components that collectively explained 73.94% of the total phenotypic variation. Six candidate evaluation indices were identified within this germplasm panel, and accessions were grouped into five phenotype-based clusters that were not congruent with their geographic provenances. Exploratory correlation analyses revealed that annual precipitation was positively associated with yield-related traits, while elevated spring high temperature (March to April) was negatively associated with infructescence-related phenotypes. Eight phenotypically superior candidate accessions were preliminarily selected for edible peduncle or dual-purpose cultivation for both fruit and timber outputs. This study fills regional research gaps and provides a reliable phenotypic dataset and preliminary candidate germplasm to support the conservation, characterization, and directional breeding of H. acerba germplasm.