WILD ALMOND (PRUNUS SCOPARIA), A POTENTIAL SOURCE OF ALMOND WITCHES’ BROOM PHYTOPLASMA IN IRAN

Abstract

Prunus scoparia, a wild almond species, is scattered in vast regions of Iran often close to stone fruit growing areas. P. scoparia witches’ broom (PSWB) disease was observed in several provinces in this country. Graft transmission experiments from affected trees to bitter almond, peach, nectarine and apricot resulted in the appearance of typical phytoplasma symptoms. Total DNA samples from witches’ broom-affected trees reacted positively in PCR assays using phytoplasma-specific P1/P7 and R16F2n/R16R2 primer pairs. Sequence homology, RFLP and phylogenetic analyses showed that the phytoplasma associated with PSWB and transmitted to grafted plants belong to the subgroup B in the 16SrIX (pigeon pea witches’ broom) group. Based on the susceptibility of stone fruits and the presence of potential vector, P. scoparia may serve as a natural reservoir of 'Candidatus Phytoplasma phoenicium' (almond witches’ broom phytoplasma).