Decosaploid sour black mulberry (Morus nigra L.) in Western Asia: features, domestication history, and unique population genetics

Sour black mulberry (Morus nigra L., BM, 2n = 22x = 308) is a valuable ancient fruit species that has been neglected in the last century. This high polyploidy and long-living perennial tree species' geographical origin, dispersal route, and evolutionary dynamics are mysterious. Our survey conducted in Anatolia and Iran, the regions suggested as the centers of BM's origin, determined exciting features of the BM species, including the lack of autonomous reproduction and landraces. BM accessions of Western Asia (n = 359) were analyzed along with other Morus spp. (Morus alba L., Morus australis Poir., Morus macroura Miq., Morus pendula, and Morus sp.) using 15 simple sequence repeats (SSR) loci. Amazingly, all BM accessions, including the over 250 ancient trees, have been found identical for the SSR loci. This identical genetic structure in all the BM trees is a unique phenomenon among domesticated perennial fruit crop populations and suggestive that either Western Asia is not likely the center of origin for BM or this species lacks diversity globally. Additionally, in this study, common mulberries with different fruit colors (red and purple) misnamed as Morus rubra in the last decades in Western Asia were accurately identified as M. alba, and this group exhibited high genetic diversity (He = 0.69, Ho = 0.79).