The selection of superior late‐leafing walnut ( Juglans regia L.) genotypes plays a crucial role in improving the resilience and productivity of walnut orchards. This study was conducted to identify and characterize superior late‐leafing genotypes among 240 seedling‐originated walnut trees. The coefficient of variation ranged from 7.08% (kernel width) to 74.22% (kernel vein). The full leafing date is classified as early (47 genotypes), moderate (104 genotypes), and late (89 genotypes), reflecting varying adaptability to environmental conditions. The majority of genotypes exhibited moderate levels of both male and female flowering, accounting for 112 and 115 genotypes, respectively. In the second phase, 89 late‐leafing genotypes were analyzed in detail, showing kernel length values ranging from 22.61 to 34.04 mm, kernel percentage from 36.23% to 62.26%, and kernel weight from 3.13 to 9.02 g. Correspondingly, nut weight varied between 6.97 and 15.80 g, and shell thickness ranged from 0.76 to 2.01 mm, demonstrating substantial pomological diversity among the evaluated trees. Ultimately, 29 genotypes were identified as superior late‐leafing genotypes based on commercial classification traits. These findings highlight the importance of late‐leafing characteristics as an adaptive mechanism against late spring frosts, offering valuable genetic material for breeding frost‐tolerant and high‐quality walnut cultivars.
Naderi et al. (Fri,) studied this question.