Morphological Diversity among Walnut Genotypes of in Azadshar, Iran

Introduction: Persian walnut (Juglans regia L.), a monoecious tree with a long history of cultivation in Middle East and Europe, is currently one of the major nut crops in Iran. Since Iran is known to be one of walnut origins, a high genetic diversity can be found in this area. Almost all traditional commercial walnut orchards in Iran propagated by seed, therefore these orchards are rich in genetic resources. Morphological studies on the basis of pomological traits can be used for assessment of genetic variability in fruit trees, as well as for selection superior genotypes. Some researchers studied walnut genetic diversity in several areas of Iran but not in Azadshahr region, an area located in north and north-eastern of Iran with high walnut production. As walnut is highly diverse due to open-pollination system and seed propagation, we intend to study genetic diversity of Azadshar walnut genotypes by using morphological and pomological traits. Materials and Methods: This research was conducted in Azadshare, Golestan province, Iran in 2012. Considering walnut orchards distribution, distance and height above sea level, four areas, namely Vamenan, Kashidar, Roodbar and Sidabad, with the distance of 15 Km apart were selected. Based on tree density and distribution, 15 to 40 trees in each area were labeled, and 102 walnut genotypes were generally evaluated. In each genotype, 30 morphological characteristics related to fruit, leaf and tree-growing habit were studied by using IPGRI walnut descriptor with a few modifications. Data analysis was performed by SPSS 16 software. Correlation coefficient of quantitative and qualitative characteristics was performed by using Pearson and Spearman methods, respectively. Cluster analysis was also performed by Ward method. Results and Discussion: The results of anatomical characteristics analysis showed that genotypes of this area have high diversity in some pomological traits such as kernel percentage, nut weight, kernel color, easy separation of kernel. Based on the results, genotypes Ka17 and Va31 had the highest average of nut weight (19.79 gr). Va31 genotype had the heaviest kernel (9.4 gr). SID1 genotype had the highest kernel percentage (60.34%). Moreover, e genotypes ROOD4 and Va34 were typified by easy removal of kernel halves (very easy) and fruit flavor desirability (desirable). 26.47% of the genotypes showed very easy separation of kernel from shell. Correlation analysis showed that there was significant correlat