Phenological and pomological characterization of Persian walnut to select promising trees

Abstract

Iran has significant Persian walnut (Juglans regia L.) trees, most of which are seedling-grown. Due to the extensive variability of biological material, the result of cross-pollination and generative propagation prevailed about by natural dissemination or anthropogenic, Neiriz region in Iran has rich phenotypic diversity in walnut germplasm. Thus, morphological diversity of 540 walnut accessions from this region was studied and trees with promising fruits characteristics were identified. There was high variability for the measured phenological and pomological characteristics. The variance analysis detected significant differences among the studied accessions for most of characters. The coefficient of variation varied from 9.02 (nut diameter) to 104.20 % (first female flowering date). Among the accessions studied, the ranges of 3.60–20.28 g for nut weight, 1.32–10 g for kernel weight and 17.44–83.88 % for kernel percentage were observed. Positive and negative correlations were detected among different phenotypic traits. The first three factors explained 34.95 % of the total variability among the studied accessions. The accessions studied were clustered into several groups by a bi-plot and cluster analysis. The best accessions were no. 573, 506, 374, 399, 527, 101, 150, 95, 91 and 472, which had thinner shell, heavier kernel, light kernel, more lateral fruitfulness and late flowering. The most promising trees will be used to the benefit of conservation research, breeding and cultivation. Moreover, based on the observed structures of variation, it is concluded that the magnitude of morphological variation in the material studied is high and the implications of the results for plant breeding programs are discussed.