Identification of phytoplasmas in stone fruit (Prunus sp.) and persimmon (Diospyros kaki L.) trees exhibiting leaf alterations and witches'-broom in Jordan

During field surveys conducted in 2020 in Jordanian orchards, phytoplasma-like symptoms (leaf yellowing/reddening and rolling, and witches'-broom) were observed in three stone fruit species (peach, European plum, sweet cherry) and persimmon. Molecular analyses identified phytoplasma strains belonging to the species 'Candidatus Phytoplasma solani' (subgroup 16SrXII-A) as largely prevalent in stone fruit and persimmon symptomatic plants. Moreover, 'Ca. Phytoplasma omanense' (16SrXXIX-B) was found in few European plum symptomatic plants. In previous studies, such phytoplasma strains were identified in other important crops (almond, pomegranate, and grapevine) and in several putative insect vectors, suggesting their complex ecology in Jordan. Further studies are needed to in-depth investigate the diffusion of phytoplasma-associated diseases of stone fruits throughout the Country, to clarify their aetiology, and to study their epidemiological pattern(s).