Preliminary assessment of morphological and pomological characteristics of mature walnut (Juglans regia L.) genotypes in the north of Hamadan Province, Iran

Persian walnut (Juglans regia L.) is one of the most important horticultural crops in the world. It is well known that Iran is one of the primary sources and center of origin for Persian walnut and is rich in walnut germplasm with good diversity. Evaluation and identification of superior walnut genotypes within the rich walnut population of Iran is an important task in the walnut breeding program and further commercial orchard establishment. This research was started in the 2016 growing season in order to explore and evaluate the Persian walnut populations that are grown in the Razan region in the northern part of Hamadan Province in Iran. For this purpose and for the first step a wide and comprehensive survey was done using questionnaires filled in by experienced orchardists in the region as well as the local Department of Horticulture in the Government Agriculture Sector of Hamadan. Eighty-four mature own-rooted walnut tree genotypes were selected according to the extensive survey from the experienced local orchardists and evaluated for phonological and pomological characteristics based on IPGRI and UPOV descriptors. The results showed that nut and kernel weight and kernel percentage varied between 8.55-22.60 g, 4.43-11.56 g, and 40.80-71.02%, respectively. Shell thickness of the studied genotypes is different between 0.34 and 1.30 mm. Moreover, the selected genotypes had a range of kernels color variations between (medium-extra light) and any empty kernel percent was (0%). Also, the genotype HaRaToMa23 was late leafing more than 23 days from the reference standard genotype. Based on the results, high diversity was observed in the studied germplasm.