BIOLOGICAL AND MOLECULAR CHARACTERIZATION OF A PHYTOPLASMA ASSOCIATED WITH GREENHOUSE CUCUMBER PHYLLODY IN FARS PROVINCE

Greenhouse cucumber phyllody (GCP) is an economically important disease in Iran. Agent of GCP from Larestan (Fars province) was transmitted from greenhouse cucumber to periwinkle and eggplant using dodder inoculation. Agents of phyllody of greenhouse cucumber, petunia, rapeseed, and phytoplasmas associated with Macrosteles levis and Psammottetix striatus leafhoppers, all maintained and propagated in periwinkle, were graft transmitted to young periwinkle plants of the same age for symptomatological differentiation. On the basis of disease symptoms in periwinkle, GCP phytoplasma was not differentiated from Petunia phyllody (PP) phytoplasma but was differentiable from the other phytoplasma strains used in this study. Restriction fragment length polymorphism (RFLP) analysis of P1/P7 primed PCR products showed that GCP phytoplasma is not differentiable from PP phytoplasma but different from phytoplasmas associated with rapeseed phyllody and those found in the leafhoppers. Sequence homology and phylogenetic analyses of 1800 bp of rRNA operon identified GCP phytoplasma as a member of peanut witche's broom phytoplasma group(16SrII). On the basis of the same molecular analyses GCP phytoplasma was differentiable from the Fars and Yazd alfalfa witche's broom phytoplasmas and the phytoplasma associated with lime witche's broom disease, the three economically important phytoplasma diseases in Iran, all from peanut witche's broom phytoplasma group. Greenhouse cucumber is reported for the first time as a new natural host for the peanut witche's broom phytoplasma group.