The pomological characterization of walnut (Juglans regia L.) to select the superior genotypes - An opportunity for genetic improvement

Persian walnut (Juglans regia L.), the cultivated walnut species for nut production, is one of the main oldest food sources. In the present investigation, a total of 908 walnut seedling originated genotypes were studied to detect the phenotypic variation and to select the superior genotypes based on the fruit traits. Considerable phenotypic variation was found among the genotypes based on the measured traits. The nut diameter ranged from 20.00 to 43.35 mm, while nut length ranged from 22.20 to 47.42 mm. Nut weight ranged from 5.42 to 23.00 g and also it was between 12.00 and 18.00 g in 551 genotypes, while nut weight was very large in 37 genotypes and ranged from 18.14 to 23.00 g. Kernel weight varied from 2.30 to 14.00 g and 568 genotypes had the kernels with the ranges between 6.00 and 10.00 g, while kernel weight in 19 genotypes was very large and ranged from 10.01 to 14.00 g. Kernel percentage ranged from 24.66 to 75.10% that 507 genotypes had more than 50.00% kernel percentage. Based on the ideal values for the main traits in walnut including nut weight, kernel weight, and kernel percentage, 329 genotypes had ideal values for these traits. Thus, they can be cultivated in orchards and/or to be useful as parents for crossing to create proper populations or improve cultivars.