Diversity assessment and selection of superior Persian walnut (Juglans regia L.) trees of seedling origin from North-Western Himalayan region

Abstract

North-Western Himalayan region of Jammu and Kashmir has significant Persian walnut (Juglans regia L.) trees, most of which are of seedling origin. The region have rich morphological, phenological, and carpological walnut diversity because of the large variability of native walnut, resulting from cross-pollination and seedling propagation. We studied 84 walnut accessions from this region to assess this diversity and identified trees with superior fruit traits. Studying the growth, leaf, phenological, inflorescence, and fruit characteristics show high variability. Nut weight (NW) ranged from 10.04 to 22.66 g, whereas kernel weight (KW) varied from 4.75 to 14.00 g. In this study, we recorded kernel percentage in a broader range from 30.64% to 61.78%, and shell thickness (ST) from 0.98 to 2.83 mm. The principal component analysis revealed that traits related to KW, kernel percentage, ST, NW, nut length (NL), kernel length (KL), and kernel width (KW) accounted for a large proportion of phenotypic variability. Cluster analysis divided accessions into four cluster groups. We identified three promising genotypes, such as JWSP-06, JWSG-43, and JWSD-59, after considering the important traits in a selection index. These promising genotypes will be used to the benefit of conservation research, cultivation, and breeding. Based on the observed differentiation of variation, it is concluded that the magnitude of phenotypic variation in the population under study is high, and the implication of the results will play a vital role in future walnut breeding programmes.