Genetic and haplotype analysis of phytoplasma disease on sesame and insights into transmission biology and leafhopper interactions

The predominance of leafhopper species such as Orosius albicinctus, Hishimonus phycitis and Amrasca biguttula biguttula poses a significant threat to sesame production in India and globally. Phytoplasma disease, caused by Candidatus Phyto plasma species, has become a major challenge for sesame farming, with the potential to reduce yields by up to 95 %. First documented in Myanmar, this disease has since spread to various regions worldwide, affecting sesame crops across Asia, Africa and North America. The current study examined the relationship between phytoplasma and leafhoppers in sesame as well as the phylogenetic differences in phyllody phytoplasma. Previous research identified phytoplasma subgroups 16SrI-B and II-C in eastern Uttar Pradesh, Bihar and Delhi, India. Notably, this study discovered the 16SrI-B subgroup in Tamil Nadu for the first time, marking significant progress in understanding phytoplasma diversity in the region. The use of virtual RFLP analysis in sequencing sesame phyllody phytoplasma highlights the importance of molecular techniques in characterizing these phytoplasma. The leafhoppers species complex, including O. albicinctus, H. phycitis and A. bigutulla bigutulla was identified using species-specific taxonomical traits and a mtCOI gene-based genetic study confirmed their identities. In greenhouse studies on disease transmission efficiency, O. albicinctus transmitted phyllody at rates ranging from 7.8 % to 84 %, while H. phycitis transmitted it at rates of 5.2 % to 74 %. Both species exhibited the highest transmission efficiency when three insects were placed on a single plant for 5 days of acquisition feeding, followed by one day of inoculation tection and the development of integrated pest management strategies.