‘Candidatus Phytoplasma asteris’ is associated with citrus “huanglongbing” disease in Mexico

“Huanglongbing” is one of the most devastating citrus diseases worldwide. ‘Candidatus Liberibacter’ and ‘Candidatus Phytoplasma’ species are commonly associated with the disease, although phytoplasmas were only found in citrus showing “huanglongbing”-like symptoms in Brazil and China. In Mexico samples were evaluated ‘Ca. L. asiaticus’ and ‘Ca. Phytoplasma’ presence by PCR assays. Fifty-four out of 86 citrus plants were positive for ‘Ca. L. asiaticus’, 20 were positive for ‘Ca. Phytoplasma’ and 7 were found as hosts of mixed infections with both prokaryotes. RFLP analyses of the 16S rDNA sequences enabled to identify two of the phytoplasma strains as members ‘Candidatus Phytoplasma asteris’ subgroups 16SrI-B and 16SrI-S. Moreover partial ‘Ca. L. asiaticus’ sequences were identical to those of strains from countries affected by “huanglongbing” disease. These results confirm the association of ‘Ca. Phytoplasma’ with “huanglongbing” in citrus in Mexico, and its occurrence in mixed infections with ‘Ca. L. asiaticus’.