Association of Pigeon pea witches' broom phytoplasma (16Sr IX) infecting Phlox drummondii in India.
During a survey at the Indian Agricultural Research Institute Campus in New Delhi, India, from 2010 to 2011, symptoms including extensive yellowing and stunting, proliferation of shoots, little leaves and reduced size of flowers were observed in approximately 17% of plants of Phlox drummondii. BLAST analysis of the partial 16S rDNA sequence of the P. drummondii phytoplasma revealed the highest sequence identity (99%) with that of phytoplasma members of group 16SrIX, 'Candidatus Phytoplasma phoenicium', the former Pigeon pea witches' broom group. Phylogenetic analysis confirmed the closest phylogenetic relationship of the P. drummondii phytoplasma 16S rDNA sequence with those of the 16SrIX phytoplasma group. Phytoplasmas of group 16SrI 'Candidatus Phytoplasma asteris' subgroup M (16SrI-M) have been previously associated with P. drummondii in Lithuania. This is thought to be the first world report of the association of the 16SrIX group with a phytoplasma disease on P. drummondii.