Serological relationship among three phytoplasma strains belonging to the group 16SrII in Iran

Phytoplasmas are among the most important plant pathogens belonging to the class Mollicutes. In this study the serological relatedness of three 16SrII- related phytoplasmas including lime witches’ broom (LWB; 16SrII-B), alfalfa witches’ broom (AlfWB, 16SrII-C) and cucumber phyllody (CuPh; 16SrII-D) phytoplasmas was examined. A recombinant antibody raised against the Immunodominant membrane protein of the LWB phytoplasma was used in indirect ELISA. Results showed that the produced antiserum reacted with the LWB and AlfWB phytoplasma infected samples, although with lower absorption rate with the later. Under the same conditions, the mean OD obtained from periwinkle extracts infected with CuPh phytoplasma was not significantly different from that of healthy periwinkle. With the antiserum raised against AlfWB phytoplasma, however, the OD value obtained with AlfWB phytoplasma was higher than that obtained with LWB phytoplasma samples. These data suggest that LWB and AlfWB phytoplasmas but not CuPh phytoplasma are serologically related, although not identical. In this study we compared the results of ELISA test and western blot analysis. The serological variation was also compared with Imp and DnaD sequence variability. AS serological distinction is an important criterion for description of new phytoplasma species within a 16S rRNA group, results of this study argues that phytoplasmas of 16SrII-D (CuPh phytoplasma) and II-B (LWB phytoplasma) could be accommodated within two species. However, further evidences are needed to support this argument.