Molecular detection and identification of a strain related to ‘Candidatus phytoplasma australasia’ in marigold in India

Abstract

Marigold plants with suspected symptoms of phytoplasma infection were collected during field surveys from three different districts of Karnataka where the incidence of these symptoms was ranging from 1 to 11%. The presence of phytoplasmas in the samples showing phyllody and virescence symptoms was confirmed by nested PCR assays using P1/P7 and R16F2n/R16R2 phytoplasma specific primer pairs. The nucleotide sequence identity and phylogenetic analyses of the 16S rRNA gene sequence indicated the presence of a ‘Candidatus Phytoplasma australasia’ -related strain in the diseased marigold samples. The phylogenetic analysis of secA gene sequences of this phytoplasma strain showed its clustering with strains enclosed in the 16SrII-D subgroup, confirming the phytoplasma identification. To the best of our knowledge, this constitutes the first report of 16SrII phytoplasmas associated with marigold phyllody from the Karnataka state. As the most widely cultivated commercial flower of Karnataka, marigold has a significant role in the national and international flower trade. Phyllody and associated symptoms have a direct negative impact on the quality and market value of these flowers.