Morphological diversity assessment of loquat (Eriobotrya japonica Lindl.) genotypes in the southern region of Caspian Sea

This study investigated the phenotypic diversity in 55 loquat genotypes collected from four regions of the South Caspian Sea, Iran. Descriptive statistics revealed wide variability in key traits, including fruit weight (3–35 g), flesh thickness (2–9 mm), seed number (1–10), total soluble solids (3–17.5 °Brix), and leaf area (19.5–286 cm²). Pearson’s correlation analysis showed several significant associations among fruit and vegetative traits, notably, a strong positive correlation existed between one-year-old and current-year shoot thickness (r=0.733**). Fruit length and diameter were positively correlated with fruit weight, flesh thickness, and flavor index, but negatively correlated with titratable acidity. Factor analysis extracted six principal factors with eigenvalues greater than one, explaining 81% of the total variance. The first factor (38.17%) was mainly associated with fruit yield and quality traits, whereas the second factor (16.94%) reflected leaf and external fruit characteristics. Cluster analysis grouped the genotypes into two main clusters at a linkage distance of 15. Savadkuh–Behshahr genotypes showed stronger vegetative growth, while Juybar–Sari genotypes exhibited superior fruit characteristics. The clustering pattern corresponded well with the geographic origin, indicating the influence of environmental and climatic conditions on phenotypic variation. Overall, the results revealed that fruit- and leaf-related traits are the most discriminative factors among loquat genotypes, providing a valuable basis for selecting elite parents in breeding and regional orchard development programs in northern Iran.