First multigene characterization of phytoplasmas associated with brinjal little leaf disease in Sri Lanka.

Eggplant is an important vegetable crop, however, its production in Sri Lanka is lower compared to other Asian countries mainly due to the presence of several biotic and abiotic stresses among which little leaf disease is one of the most important. In the last years symptoms of this disease were observed in several brinjals growing areas of the country. Sampling from symptomatic plants followed by molecular identification analyses aimed to verify the presence of phytoplasmas allows to obtain the expected length PCR amplicons from the symptomatic plants and not from those asymptomatic. The RFLP analysis of amplicons obtained for the 16S rRNA gene showed patterns identical with those of phytoplasmas in group 16SrVI; the phylogenetic analysis confirms that the phytoplasma strain has above 99% identity to the ‘Candidatus Phytoplasma trifolii’ and to a number of sequences of phytoplasmas belonging to subgroup 16SrVI-D. Virtual RFLP analyses enclose the detected phytoplasma in the 16SrVI-D subgroup. The phytoplasma detected was further characterized on secA and leuS genes showing 99% to 100% identity to ‘Ca. P. trifolii’ strains from brinjal and other plant host species mainly growing in India. This first identification of 16SrVI-D phytoplasmas in brinjal in Sri Lanka indicates that the geographical distribution of this phytoplasma is wider than previously reported. Considering the spread, broad host range and capability of transmission through insect vectors, weeds and seeds in brinjal, further studies are necessary to clarify the epidemiology of the disease in Sri Lanka for planning appropriate management approaches to avoid its further spreading.