Molecular characterization of a new phytoplasma associated with Helianthus annuus phyllody in Iran

Sunflower is an important oil crop in Iran. During two years surveys, sunflower phyllody was observed in fields of Yazd, Fars and Esfahan provinces. Affected plants showed proliferation of abnormal shoots and heads along the stem, virescence and phyllody of the main flowers. Total DNA extracted from fresh sunflower tissues allow to obtain amplification of phytoplasma 16S ribosomal DNA from eight symptomatic plants but not from samples collected from the symptomless ones. Eight P1/P7 DNA fragments amplified from phyllody-affected sunflower plants were separately cloned and sequenced. The obtained 16S rDNA sequences shared 100% identity with each other and an Abarkooh sunflower phyllody (ASP) strain was deposited in the GenBank. Sequence comparison by BLAST analysis showed the highest sequence identity with phytoplasmas in group 16SrII (‘Candidatus Phytoplasma aurantifolia’). Phylogenetic analysis confirmed that the ASP phytoplasma clusters with phytoplasmas enclosed in ribosomal group 16SrII and is therefore a ‘Ca. P. aurantifolia’-related strain. Analysis carried out using the iPhyClassifier showed that the RFLP pattern of ASP phytoplasma was different from all described 16SrII subgroups, having the major similarity coefficient (0.63) with subgroup 16SrII-D. Therefore, considering the RFLP divergences this phytoplasma could be assigned to a new subgroup designed 16SrII-W.