Transmission efficiency of a 'Candidatus Phytoplasma australasia'(16SrII-D) related strain associated with sesame phyllody by dodder, grafting and leafhoppers

Severe sesame phyllody (SP) disease exhibiting symptoms of phyllody and witches' broom were recorded in twenty sesame accessions with disease incidence up to 100% in sesame fields from August to December, 2020. The symptomatic samples from all twenty sesame accessions were processed for DNA extraction and nested PCR assays with universal phytoplasma primer pairs (P1/P7 and R16F2n/R16Rn).'Candidatus Phytoplasma australasia' related strain (16SrII-D) was identified. Different transmission assays were employed through grafting (wedge, patch, leaf disc, plug), seed, dodder and insects to assess the efficacy of transmission of sesame phyllody phytoplasma, 16SrII-D strain. The transmission studies revealed that 'Candidatus Phytoplasma australasia' related SP strain was not seed transmitted but efficiently transmitted through dodder (93.33%), wedge grafting (80%) and leaf disc grafting (75%) from infected sesame to healthy sesame and periwinkle plants. Two leafhopper species, Orosius albicinctus and Hishimonus phycitis were found as efficient natural vectors in transmission of 'Candidatus Phytoplasma australasia' related strain from sesame to brinjal and sesame to sesame plants. These methods would be helpful in maintaining the live culture of SP phytoplasma strains in the glasshouse for further characterization studies.These live cultures can also be used for indexing of sesame germplasm accessions for resistance.