Juglans regia Phenotype or Genotype. Juglans regia

We evaluated the spatial genetic structure and genetic diversity of 2,929 J. regia samples from 150 walnut populations using 14 SSR loci. Our study revealed that regions with the highest genetic diversity included southern Asia, western Asia, western Europe, and China, as illustrated using a Geostatistical IDW interpolation of HO, HE, PPL, NA, and RS in ArcGIS. Ecological Niche Model (ENM) showed that Persian walnut had a high probability of association with central Asian and eastern Asian habitats. Population genetic structure, phylogeny, and PCA identified three genetic groups corresponding to three geographic sources. Turkish and Georgian populations served as a bridge between Asian populations and Europe populations. We suggest that Persian walnut evolved in central Asian mountain ranges ~65Mya and dispersed across Eurasia during climate shifts (~65 to 3Mya). The population contracted into multiple refugia during the Last Glacial Maximum. The current distribution of walnut across Eurasia was shaped by the cumulative effects of contraction/ expansion from different refugia and human exploitation after LGM.