Unveiling subgroups of 16SrIII phytoplasmas affecting Trillium sp. and Melothria pendula in Brazil and Canada

Melothria pendula and Trillium spp. are important weed species in Brazil and Canada. M. pendula plants showing symptoms of chlorosis, little leaf and leaf malformation and T. grandiflorum and T. erectum exhibiting virescence were tested for phytoplasma presence by nested PCR with primers that amplify the 16S rRNA, ribosomal protein, and secA genes, and subjected to RFLP and sequencing analyses. A phytoplasma of group 16SrIII was identified from M. pendula and classified as a new variant of subgroup 16SrIII-U. The 16SrIII phytoplasmas, first reported in T. grandiflorum and T. erectum in Ontario in 2016 were classified as members of the subgroup 16SrIII-F. Besides, one strain from each Trillium species examined, corresponded to a new variant of subgroup 16SrIII-F (for T. grandiflorum) and a new variant of subgroup 16SrIII-J (for T. erectum). Results refer to the first report of a phytoplasma affecting M. pendula, and the identification of new variants of 16SrIII phytoplasma subgroups in Melothria and Trillium species, which may pose a threat for the spread of 16SrIII phytoplasmas to other plant species grown nearby.