Characterization of Phytoplasmas Associated With Almond Diseases in Iran

In recent years, almond witches'-broom disease has been prevalent in almond growing areas in the centre and south of Iran. Furthermore, almond trees showing different symptoms of phytoplasma diseases such as little leaf, leaf rolling, dieback of branches, rosette and yellowing were observed in the central regions of Iran. DNA isolated from symptomatic almond trees was used to amplify 16S rDNA and 16S-23S rDNA intergenic spacer (IS) fragments by nested polymerase chain reaction (PCR) using phytoplasma universal primer pairs (P1/P7, R16F2/R2, PA2F/R and NPA2F/R). Phytoplasmas were detected in symptomatic almonds in two major almond-growing regions, Isfahan and ChaharMahal-O-Bakhtiari. Restriction fragment length polymorphism analyses of nested PCR products using endonuclease enzymes HpaII and TaqI revealed that phytoplasmas associated with infected almonds are genetically different. Sequence analyses of amplified fragments of 16S rDNA and IS region indicated that the almond phytoplasmas in Iran are closely related to 'Candidatus (Ca.) Phytoplasma aurantifolia', 'Ca. Phytoplasma phoenicium', 'Ca. Phytoplasma solani' and 'Ca. Phytoplasma trifolii'. The phytoplasmas related to 'Ca. Phytoplasma aurantifolia' were more prevalent than other phytoplasmas in the central regions of Iran.