Association of a ‘Candidatus Phytoplasma aurantifolia’-related strain with apricot showing European stone fruit yellows symptoms in Iran

During 2012–2015 surveys in some orchards in Faraghe (Iran), a number of apricot trees showed symptoms resembling those associated with the phytoplasma disease known as European stone fruit yellows that are severe leaf roll, yellowing and die back. The presence of an infectious agent was confirmed by graft transmission experiments in which all the previously symptomless GF-677 (peach × almond) trees showed phytoplasma-type symptoms. The phytoplasma presence was confirmed by nested PCR assays using DNA extracted from samples from both field collected and graft-inoculated trees. The sequences of four nested PCR products from symptomatic apricot and experimentally graft-inoculated GF-677 trees were 100% identical to each other. RFLP and phylogenetic analyses carried out on these sequences allowed to cluster the strain infecting apricot trees in Iran with the16SrII-C subgroup phytoplasmas. This is the first report of a 16SrII-C phytoplasma associated with leaf roll and yellowing of the leaves in apricot trees.