|PEREZ-LOPEZ, EDEL - Auburn State University|
|WANG, JIAWEI - Shandong Institute|
|LUNA-RODRIGUEZ, MAURICIO - University Of Veracruzana|
Submitted to: Annals of Applied Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/25/2017
Publication Date: 8/17/2017
Citation: Perez-Lopez, E., Wei, W., Wang, J., Davis, R.E., Luna-Rodriguez, M., Zhao, Y. 2017. Novel phytoplasma strains of X-disease group unveil genetic markers that distinguish North American and South American geographic lineages within subgroups 16SrIII-J and 16SrIII-U. Annals of Applied Biology. 171:405-416.
Interpretive Summary: Phytoplasmas are tiny bacteria that invade plants’ nutrient-conducting vessels. Infection by such bacteria can lead to severe plant diseases that impact agriculture and natural ecosystems. Phytoplasmas are diverse in terms of their geographic distributions, ranges of plant host, and insect vectors of transmission. While the biological and ecological diversity of phytoplasmas is often correlated with distinctive genetic markers present in evolutionarily conserved genes, such markers are sometimes hidden, leaving important ecological and geographic phytoplasma lineages unrecognized. In the present study, ARS scientists, together with university collaborators, identified new phytoplasma strains in landscaping periwinkle plants growing in Mexico, a North American country. These new phytoplasmas are closely related to the phytoplasmas that were previously only found in South American countries. Through DNA finger printing analysis, the study unveiled reliable genetic markers that can distinguish the North and South American lineages. The findings of this study are important to farmers and extension personnel who are concerned with phytoplasmal disease diagnosis and management. The information is also critical to regulatory agencies for preventing exotic pathogens from being introduced into the U.S.
Technical Abstract: Phytoplasmas in the X-disease group (16SrIII) are highly diverse in terms of geographic distributions, vectorship, and plant host specificity. Such biological and ecological diversity is often correlated with distinctive genetic markers present in evolutionarily conserved genes. Based on restriction fragment length polymorphism (RFLP) markers in the 16S rRNA gene sequences, 29 subgroups have been delineated, with most of them being found in the Americas. However, it has been unknown whether distinct geographic lineages are present within a given subgroup. Prior to this study, phytoplasmas belonging to subgroups 16SrIII-J and 16SrIII-U were reported only in countries located in South America. In the present study, we identified new phytoplasmas strains closely related to the reference strains of the two subgroups in Mexico, a North American country. These newly identified Mexican strains possess unique RFLP, single nucleotide polymorphism (SNP), and fragmental deletion markers in 16S rRNA- and/or ribosomal protein-encoding genes. Since these markers consistently distinguished the Mexican strains from their South American counterparts, they may represent emerging or previously unknown North American geographic lineages of the subgroups 16SrIII-J and 16SrIII-U.