Walnut Genetic Diversity Investigation Using Phenological and Morphological Characteristics and ISSR Markers

There is little information about the genetic resources of Persian walnut (Juglans regia L.), an important edible and one of the most important plants in pomology and economy in Iran. Germplasm identification and conservation are important and fundamental issues in breeding programs. Six regions in BoyerAhmad and Dena Counties were chosen, and 82 walnut genotypes were selected randomly. Annual growth period was short in Setangun and Ganjegun Regions (190-200 days), but in other investigated regions was long and more than 230 days. Maximum fruit and kernel weights were 63.44 and 8.35 g, respectively. The number of observed alleles ranged from seven (ISSR7A) to 14 (ISSR3A) for primers, and the Number of effective alleles (Ne) in the primers used was between 1.19 to 1.45. The highest Ne alleles belonged to the ISSR1A primer (1.445). Walnut genotypes showed the highest genetic diversity based on the information derived from ISSR1A and ISSR2A with PIC index of 0.44 and 0.41, respectively. The Neichr('39')s gene diversity ranged from 0.13 to 0.24, and the Shannonchr('39')s index was from 0.23 to 0.44. In general, increase in the altitude and decrease in the temperature delayed phenological characteristics.Suitable genetic diversity was found among the genotypes, based on the morphological and phenological characteristics and the ISSR markers. Overall, the results are useful in walnut breeding and conservation programs, and by choosing late leafing and flowering genotypes from Setangun and Ganjegun Regions, it would be possible to reduce the risks of late spring frost.