Mint (Mentha arvensis) is an aromatic and medicinal herb belonging to the family Lamiaceae which is commercially grown in India. During a field survey in Deen Dayal Upadhaya Gorakhpur University, Gorakhpur, Uttar Pradesh, India, in January 2026, we found mint plants with typical phytoplasma symptoms growing outdoors (Figure 1). These plants had characteristic little leaf symptoms, including shortened internodes and stunted growth. The plants were approximately 2–3 months’ old at the time of sampling, and had been sourced locally. Disease prevalence ranged from 3% to 5%. Three diseased and two asymptomatic mint plants were collected and the CTAB method (Ahrens and Seemuller 1992) was used to harvest DNA from leaf midrib tissues. The 16S rRNA gene was amplified initially using a nested PCR technique with universal phytoplasma primer pairs P1/P7 and R16F2n/R2 (Lee et al. 1998) and the sec A gene was amplified using secfor1/secArev3 and secAfor2/secArev3 primer pairs in semi-nested PCR (Hodgetts et al. 2008). PCR amplicons of both 16S rRNA (c. 1.25 kb) and sec A (c. 450 bp) genes were obtained from all diseased plants but not asymptomatic plants. PCR products from one representative sample (MLL-01) were sequenced directly in both directions using the respective amplification primers without prior cloning (Barcode Biosciences, India). The sequences were assembled and deposited in GenBank under Accession Nos. PZ052713 (16S rRNA) and PZ133386 (secA). A BLASTn search showed > 99% nucleotide identity of the 16SrRNA gene with multiple strains of ‘Ca. P. asteris’, including 99.1% identity to the reference strain of ‘Ca. P. asteris’ belonging to 16SrI subgroup B (M30790). Further confirmation was obtained through secA gene analysis, which also supported the association of 16SrI-B phytoplasma with mint little leaf disease in India. Phylogenetic analysis using the maximum likelihood method based on partial 16S rRNA gene and secA gene sequences of the mint little leaf-associated phytoplasma along with selected phytoplasma strains from GenBank showed that isolate MLL 01 clustered closely with ‘Ca. P. asteris’ strains within the 16SrI-B subgroup (Figures 2 and 3). Mentha piperita was previously reported to be infected with ‘Ca. P. solani’ (stolbur) phytoplasma in Serbia (Mitrović et al. 2016). ‘Ca. P. asteris’ (16SrI group; aster yellows phytoplasma) is one of the most widely distributed phytoplasmas in India, infecting diverse species, including economically important crops, ornamentals and weeds. In India, it has been associated with diseases in plants such as sesame (Sesamum indicum), brinjal (Solanum melongena), periwinkle (Catharanthus roseus), and sugarcane (Saccharum officinarum). Several reports have also documented its occurrence in northern regions of India, including Uttar Pradesh and adjoining states, indicating its widespread distribution in similar agro-climatic zones. The present finding further expands the host range of ‘Ca. P. asteris’ to Mentha arvensis in India. To our knowledge, this is the first report of phytoplasma disease caused by ‘Ca. P. asteris’ (16SrI-B) on mint (Mentha arvensis) worldwide.
Mall et al. (Wed,) studied this question.