Identification of ‘Candidatus Phytoplasma asteris’ causing sesame phyllody disease and its natural weed host in Jammu, India

Abstract

During May–June 2016, little leaf and phyllody symptoms were observed on 8% of sesame crop in Chakbhalwal and Kotbhalwal regions of Jammu, India. Phytoplasma suspected witches’ broom symptoms on Cannabis sativa subsp. sativa was also observed in and around sesame fields with the incidence varied from 5 to 12% in different fields. Total genomic DNA from both symptomatic sesame and Cannabis plants were subjected to nested PCR assays using two sets of universal phytoplasma specific primers P1/P7 followed by R16F2n/R16R2 and 3Far/3Rev to amplify the 16S rDNA fragments. First round PCR amplification with primer pair P1/P7 did not yield expected 1.8 kb products of 16S rRNA gene region from any of the symptomatic test samples. However, DNA specific fragments of approximately 1.2 and 1.3 kb were amplified from sesame and C. sativa sub sp. sativa by using R16F2n/R16R2 and 3Far/3Rev primer pairs, respectively. BLASTn comparison and phylogenetic analysis of 16SrDNA phytoplasma sequences of sesame and cannabis phytoplasma strains revealed the association of ‘C. Phytoplasma asteris’ (16Sr I group) with symptomatic samples. The virtual RFLP analysis of the 16Sr DNA sequence of sesame and cannabis further identified as phytoplasma strains of 16SrI-B subgroup.