Resources of Juglans regia in Uzbekistan: a Valuable Step along the Silk Road

Central Asia where walnut was grown since Oligocene was recognized as a center of its origin and distribution. Now in Uzbekistan, J. regia stands occupy three areas geographically isolated from each other by more than 250 km: Western Tien-Shan, Nurata and Hissar. Survey expeditions were performed mainly in natural thickets, half-wild plantations and single tree in "dehkan" gardens. Morphological descriptors, biochemical and genetic markers were used to evaluate the biodiversity of walnut for conservation and developmental use. Trees from 20-30 years up to over-matured (300-500 years old) were considered. A variety in nuts was recorded: as to weight (5 up to 25 g) and other morphological and biochemical attributes. Lipid in kernels contain PUFA for more of 80%. Vitamin E was also extracted in the range 0.1-1.5 mg/g of kernel. Using 14 SSR primers, DNA fragments of different size were obtained with variable number of alleles in the walnut trees sampled. Spatial genetic structure analysis divided the Uzbek trees into three groups that partially corresponded to the growing area of trees. Studies in progress preliminary indicated that the genetic structure of Uzbek walnut partially overlapped to trees from outside the country. The ancestors of Uzbek trees could share the origin with the nearby forests, now belonging to other countries, but in the past together identified as Turkestan, and focal point of the Silk Roads for East-West trade and migrations.