The Genetic Similarities and the Potential Threat of Candidatus Phytoplasma Australasia Associated with Phyllody Disease of Seasame

Phyllody disease in sesame results from the abnormal conversion of floral organs into leaf-like structures due to phytoplasma infection, often transmitted by insect vectors. This condition significantly impacts yield and seed quality. Ongoing molecular-level investigations in sesame growing in North India aim to identify specific phytoplasmas causing crop losses, providing insights for targeted management strategies. Leaf samples from sesame plants exhibiting Phyllody disease were collected from Varanasi and Mirzapur districts of Uttar Pradesh, India during the survey conducted between month of September to December, 2012-14. Incidence of sesame Phyllody in the farmers at different location was ranged from 30-70 percent indicating its prevalence in Uttar Pradesh. The Phytoplasma infection in sesame plants was confirmed by PCR using universal primers of 16s rRNA (R16F2n/R16R2) and SecY gene (SecYF2 and SecYR1). Amplified 16s rRNA and SecY gene was sequenced and sequence comparisons were made with the available Phytoplasma 16srRNA and SecY gene sequences in NCBI Gen Bank database. The restriction pattern of Phytoplasma samples collected from different fields was identical, which indicates that, the same Phytoplasma is responsible for causing Phyllody disease in different locations. The 16srRNA and SecY gene sequence of Phytoplasma in the current study, shared highest nucleotide identity of 97.9-99.9% and 95.8 to 96.3% with subgroup 16Sr II-D the peanut witches’-broom group. A Comprehensive recombination analysis using RDP4 showed the evidence of inter- recombination in F2nR2 and SecY gene fragment of Phytoplasma infecting sesame. The most of the F2nR2 fragment is descended from Ash yellows-[16SrVIII] and Apple proliferation-[16SrX] group. While for SecY gene, most of the part was descended from Peanut witches’-broom- 16SrII-A (GU004331) and aster yellows 16Sr I-A (GU004345). The genetic similarities and the potential threat of this new Phytoplasma belong to 16Sr II-D subgroup of Peanut witches’ broom’ group infecting to sesame in north India are discussed. This report added one more member of 16Sr IID subgroup from Peanut witches’ broom group in addition to, two Phytoplasma strains belonging Ca. P. asteris (16Sr I group) are responsible for causing sesame Phyllody in India.