Comprehensive Evaluation of Fruit Traits and Altitudinal Adaptability of 189 Wild Camellia oleifera Germplasms in East Guizhou, China

Background: Eastern Tongren City, Guizhou Province, China, possesses abundant wild germplasm resources of Camellia oleifera Abel.; however, there is a lack of systematic evaluation, and the promotion of superior varieties is insufficient. This study aimed to evaluate 21 trait indices of 189 wild C. oleifera accessions from four regions in the Tongren area to clarify their variation characteristics, assess the effects of altitude on trait expression, and identify candidate germplasms with outstanding comprehensive performance. Methods: A total of 21 traits spanning fruit morphology, oil content, fatty acid composition, and bioactive components (tocopherols, squalene, and polyphenols) were measured. Principal Component Analysis (PCA) was employed to construct a comprehensive evaluation score (Zn) for quantitative ranking and screening. Trait differences between a low-altitude group (400–800 m, n = 139) and a high-altitude group (800–1200 m, n = 50) were compared using Welch’s t-test. Results: The germplasms exhibited abundant phenotypic variation, with coefficients of variation (CV) ranging from 5.29% (total unsaturated fatty acids) to 124.42% (beta + gamma-tocopherol). Bioactive components showed the highest variability, while fatty acid composition was relatively stable. Altitude had a significant effect on six of the 21 traits. Seed oil content and kernel oil content were significantly higher in the high-altitude group, with mean differences of 5.92 and 5.74 percentage points, respectively (both p < 0.001). However, oleic acid, total unsaturated fatty acids, fruit morphological traits, and most bioactive components showed no significant altitudinal differences (p > 0.05). The first five principal components explained 65.0% of the total variance. CL40 achieved the highest comprehensive score (Zn = 4.15), followed by MJX2 (Zn = 2.56). Among the top 10 individuals, eight were from the low-altitude group. Conclusions: This study revealed rich phenotypic variations and distinct altitudinal effects among wild C. oleifera germplasms in eastern Guizhou. The superior germplasms identified (such as CL40 and MJX2) can serve as candidate materials for locally adapted variety improvement. This study was primarily based on single-season phenotypic data, and the genetic stability of the selected germplasms should be validated through clonal trials and molecular marker analysis in future research.