Biochemical Diversity and Genetic Variability among Walnut (Juglans regia L.) Genotypes from Jammu and Kashmir, India

Abstract

Walnut (Juglans regia L.) is cultivated primarily for its edible kernel, which serves as a valuable source of energy, essential fatty acids, proteins, carbohydrates, minerals, and bioactive compounds. Considerable variation in walnut kernel composition has been reported globally, influenced by genotype and growing environment. The present study evaluated the biochemical and nutritional composition of twenty-one walnut (Juglans regia L.) genotypes collected from diverse agro-climatic regions of Baramulla, Jammu and Kashmir, India. The investigation aimed to quantify genetic variability, heritability, and genetic advance for key kernel quality traits such as moisture, protein, ash, carbohydrate, oil, fatty acids, and flavonoid content. Moisture content ranged from 2.19 % to 3.25 %, whereas kernel oil content exhibited the greatest variability (50.39 %–70.55 %), with linoleic acid predominating (44.65 %–62.49 %). Protein content varied between 17.12 % and 20.88 %, and carbohydrate content between 8.48 % and 24.43 %. Ash content ranged from 1.12 % to 2.21 %, while total flavonoid content varied from 5.43 to 26.66 mg g⁻¹ QE. High heritability and expected genetic gain for oil, ash, carbohydrate, and flavonoid content highlight their suitability for selection-based improvement. Principal component analysis indicated that oil, linoleic acid, and flavonoid content contributed most to total variability among genotypes. The results demonstrate substantial biochemical diversity that can be utilized to develop nutritionally rich, industrially valuable walnut cultivars and support the sustainable production of high-quality genotypes in temperate regions, particularly Jammu and Kashmir.