Tracing Superior Late-Leafing Genotypes of Persian Walnut for Managing Late-Spring Frost in Walnut Orchards

Evaluating genetic diversity in walnut (Juglans regia L.) populations is a rapid approach used by breeding programs to distinguish superior genotypes. The present study was conducted on the population of Hamedan Province, one richest and most genetically diverse regions Iran, during 2018–2019. After initial screening, 47 genotypes were selected for further evaluation pomological phenological traits based International Plant Genetic Resources Institute (IPGRI) descriptors. Nut kernel weights among ranged from 7.15 21.05 g 3.0 10.8 g, respectively. Principal component analysis (PCA) categorized into three distinct groups. Whereas cluster (CA) revealed similarities dissimilarities identifying four major clusters. Spearman correlation showed positive (p < 0.01) between nut weight (NWT), size, (KW), while negative shell thickness (STH) packing tissue (PTT) with percentage (KP) observed. Lastly, 10 (TAL8, TAL9, TAL10, TAL14, TAL19, TAL22, TB2, TB4, TB6, RDGH5) considered superior. Superior late-leafing (25–40 days after standard) displayed lateral bearing (LB) habit heavy nuts (12.52–16.82 g) kernels (6.53–8.15 g), thin shells (1.06–1.25 mm), lightly colored kernels.