Multilocus genes based characterization of phytoplasma strains associated with Mexican and French marigold species in India

During the winters of 2018 to 2020, witches’ broom, phyllody, flat stem, little leaf, yellowing and stunting symptoms were recorded in Mexican and French marigold fields in four states of India. The average recorded disease incidence ranged from 3 to 30% in different states. The ~1.2 kb product of 16S rRNA gene was amplified in symptomatic marigold samples using universal phytoplasma-specific nested primer pairs. Sequence comparison, phylogenetic and virtual RFLP analysis of 16S rRNA gene sequences identified the phytoplasmas in marigold samples as enclosed in the 16SrII-C subgroup for the strains from Delhi and in the 16SrI-B subgroup for the strains from Tripura, Uttar Pradesh and Maharashtra. Phytoplasma presence was further confirmed amplifying four genes ( secA , rp , secY and tuf ) in the symptomatic marigold species from all the surveyed places. Moreover, six weed species growing in marigold fields resulted positive for phytoplasmas. Phyllanthus niruri (Delhi) was tested positive for 16SrII-C subgroup phytoplasma, however, Ageratum conyzoides, Acmella calva and Ludwigia perennis (Tripura), Cannabis sativa (Uttar Pradesh) and Parthenium hysterophorus (Maharashtra) were tested positive with 16SrI-B subgroup related phytoplasma strains. Four leafhopper species were also detected positive for 16SrI-B subgroup collected from marigold fields at Tripura, Uttar Pradesh and Maharashtra and were identified as putative vectors for identified marigold phytoplasma strains. The report of association of 16SrII-C subgroup phytoplasma in Mexican marigold and P. niruri and 16SrI-B subgroup phytoplasma in L. perennis and A. calva are new reports in world.