'Candidatus Phytoplasma platensis', a novel taxon associated with daisy (Bellis perennis) virescence and related diseases in South America

Bellis perennis virescence (BellVir) phytoplasma affects ornamental daisies in Argentina. It has been previously classified within the X-disease group, subgroup III-J, which is one of the most important and widely distributed in South America, affecting diverse plant hosts. In this study, we compared 16S rRNA, ribosomal proteins rpIV and rps3, secA and immunodominant proteins imp and idpA genes of BellVir phytoplasma with previously described Candidatus Phytoplasma species. The 16S rRNA gene of strain BellVir shared less than 97.5% with all previously described Ca. Phytoplasma taxa except for Ca. Phytoplasma pruni. According to the recommended rules for the description of novel taxa within Ca. Phytoplasma, it should be considered as Ca. P. pruni-related strain. However, multilocus analysis showed further molecular diversity that distinguished BellVir phytoplasma from Ca. Phytoplasma pruni. Besides, BellVir phytoplasma and 16SrIII-J related strains have a geographical distribution restricted to South America, where Ca. P.pruni has not been detected. Two insect vectors have been reported to transmit 16SrIII-J phytoplasmas, which have not been found to transmit Ca. Phytoplasma pruni. Having a wide host range, they have not been detected in Prunus persica. Therefore, based on multilocus sequence analyses, specific vector transmission and geographical distribution, we propose the recognition of the novel phytoplasma species Ca. Phytoplasma platensis, within the X-disease clade, with Bellis perennis virescence phytoplasma as the reference strain.