Pre-selected walnut ( Juglans regia L.) genotypes from the Arslanbob forest: Pomological characterization and identification of promising types

Abstract The Arslanbob walnut forests in Kyrgyzstan represent one of the world’s largest natural walnut ecosystems, currently threatened by climate change and habitat loss. Preserving the genetic diversity within these forests is critical for future breeding and conservation efforts. This study aimed to assess morphological diversity among 28 wild walnut genotypes from the Arslanbob forest, identify superior types for conservation, and provide baseline data for in-situ and ex-situ strategies. A total of 28 mature walnut trees were systematically sampled across different microhabitats. Eight quantitative and several qualitative nut traits were measured. Significant morphological variation was observed for nut weight (4.8–11.1 g), kernel weight (2.17–5.1 g), kernel percentage (33.6–57.7%), and shell thickness (1.9–4.0 mm). Principal Component Analysis revealed two main components explaining 74.4% of total variation, while Hierarchical Cluster Analysis grouped genotypes into three clusters, indicating substantial heterogeneity. Genotypes G15, G16, G17, G18, G19, G22, G23, and G26 were identified as priority candidates for ex-situ conservation due to their superior nut and kernel traits. Overall, the high morphological diversity and presence of elite genotypes demonstrate strong adaptive potential within the Arslanbob walnut population and provide essential material for targeted conservation, breeding, and adaptation studies under climate change.