Characterization of natural walnut (juglans regia) population in aksaray and selection of superior walnut genotypes

The walnut population in the Central District of Aksaray Province, comprising approximately 2 500 trees, was investigated in 2019. A total of 78 trees were examined to characterize the population and to identify superior genotypes in terms of yield, disease resistance, nut and kernel quality, and kernel color. The characterization was carried out using UPOV descriptors. Mean values of 10.81 g in nut weight, 5.15 g in kernel weight, 1.51 mm in shell thickness, and 47.68% in kernel percentage were determined in the population. In terms of nut weight distribution, 17% of trees ranged between 13.56–15.43 g, 13% between 11.69–13.55 g, 42% between 9.82–11.68 g, and 17% between 7.95–9.81 g. Regarding ease of kernel removal, 6.41% of genotypes were classified as very easy, 53.85% as easy, and 32.05% as moderate. Variation in nut shape was limited. Kernel color was mainly medium (47.44%) and light (38.46%). Kernel plumpness was primarily observed at moderate (44.87%) and plump (37.18%) levels. Furthermore, 76.9% of the genotypes bore fruit on annual shoots, 19.2% on lateral branches, and 3.9% on clusters. Based on the Weight Ranked Method and additional selection criteria, eight superior genotypes were chosen. In these, fruit dimensions (E, L, H) and roundness index (R) were 32.57–39.67 mm, 31.05–36.44 mm, 36.00–43.70 mm, and 0.76–0.90, respectively. Nut weights ranged from 12.13–15.43 g, kernel weights from 5.65–7.68 g, shell thickness from 1.38–2.03 mm, and kernel ratio from 45.11%–50.25%.