Molecular Characterization of 16S Ribosomal DNA and Phylogenetic Analysis of Two X-disease Group Phytoplasmas Affecting China-tree (Melia azedarach L.) and Garlic (Allium sativum L.) in Argentina

Two phytoplasmas closely related to the X-disease group were associated with China-tree (Melia azedarach L.) and garlic (Allium sativum L.) decline diseases in Argentina. The present work was aimed at studying their phylogenetic relationship based on molecular characterization of the 16S ribosomal DNA sequences. Phytoplasma DNAs were obtained from naturally infected China-tree and garlic plants from different geographical isolates. The results from analysis of restriction fragment length polymorphisms and nucleotide sequences of the 16S rDNA showed the affiliation of China-tree and garlic decline phytoplasmas to the 16SrIII (X-disease group), subgroups B and J, respectively. Both organisms had high sequence similarities in the 16SrDNA nucleotide sequence with the Chayote witches broom phytoplasma from Brazil. The phylogenetic tree, constructed by parsimony analysis, grouped the Garlic decline, China-tree decline, Chayote witches broom and Clover yellow edge phytoplasmas into a cluster separated from the other phytoplasmas of the X-disease group