Phylogenetic evaluation and haplotype mapping of phytoplasma disease in sesame: insights into leafhopper-mediated disease transmission through molecular investigation

The predominance of leafhopper species like Orosius albicinctus, Hishimonus phycitis, and Amrasca biguttula biguttula indeed poses a significant threat to sesame production in India and globally. This disease is a major challenge for sesame farming, as it can lead to yield reductions of up to 95%. The current study examined phytoplasma and leafhoppers in sesame and analyzed the phylogenetic differences in the phyllody phytoplasma. The identification of both 16Sr group I and group II phytoplasma isolates, along with the discovery of the 16SrI-B group reported for the first time in Tamil Nadu, represents a significant advancement in our understanding of phytoplasma diversity in the region. The utilization of virtual RFLP analysis in sequencing the sesame phyllody phytoplasma highlights the importance of molecular techniques in characterizing the phytoplasma. Leafhoppers in sesame were a co-occurring species complex of O. albicinctus, H. phycitis, and A. bigutulla bigutulla. The leafhoppers were identified using species-specific taxonomical traits, and a mtCOI gene-based genetic study confirmed the species. In disease transmission efficiency studies in the greenhouse, O. albicinctus transmitted phyllody at a rate ranging from 7.8% to 84%, while H. phycitis transmitted phyllody at a rate of 5.2% to 74%. Both of these species showed the highest transmission efficiency in the combination of three insects per plant with five days of acquisition feeding and one day of inoculation feeding. A comprehensive understanding of leafhopper-phytoplasma interactions through molecular studies supports effective monitoring, early detection, and the development of integrated pest management strategies.