Mungbean (Vigna radiata) and cowpea (Vigna unguiculata) are economically important legumes widely cultivated in China. Phytoplasmas are phloem-limited plant-pathogenic bacteria transmitted by the phloem-sucking insect vectors (e. g., leafhoppers, planthoppers, and psyllids) (Kumari et al. 2019; Wang et al. 2024). In October 2025, typical phytoplasma-like symptoms of phyllody, witches’ broom, small leaves, wrinkling were observed on mungbean and cowpea plants at the harvesting stage in Wuming district, Nanning city, Guangxi, China, with a disease incidence of less than 10%, which may represent a potential, yet unconfirmed, risk to local mungbean and cowpea cultivation. To determine the causal agent, total DNA was extracted from symptomatic and healthy leaf midribs (2 symptomatic, 1 healthy sample per crop from the same field plot) using the CTAB method. The 16S rRNA and tuf genes were amplified via nested PCR with primer pairs P1/P7 and R16F2n/R16R2 (Gundersen and Lee 1996) or fTuf1/rTuf1 (Schneider and Gibb 1997), respectively. Approximately 1800 bp and 1250 bp (for 16S rRNA) or 1000 bp (for tuf) fragments were amplified from symptomatic mungbean and cowpea samples, but no amplicons from healthy controls. The PCR products were purified, cloned into a TA vector, and transformed into Escherichia coli cells for sequencing. The 16S rRNA gene sequences from mungbean and cowpea were both 1806 bp in length and identical to each other. Representative sequences were deposited in NCBI GenBank under accession numbers PX597226 (Mungbean phyllody phytoplasma GX-NN-01) and PX597227 (Cowpea phyllody phytoplasma clone GX-NN-01). BLASTN analysis of 16S rRNA sequences revealed a 99.94% identity (1,805/1,806 nt) with Candidatus Phytoplasma australasiaticum strain CrWB-Hnsy1 (16SrII-A subgroup, GenBank accession no. EU650181), a provisional species in the 16SrII group, from Crotalaria pallida in Hainan, China. Further, virtual RFLP analysis of the P1/P7-amplified 16S rRNA gene sequences were performed using the online iPhyClassifier tool (Zhao et al. 2009), further confirming the classification of the isolated phytoplasmas into the 16SrII-A subgroup (Peanut WB group). Additionally, a neighbor-joining phylogenetic tree constructed using MEGA 11 (Bootstrap value 1,000) confirmed that the phytoplasmas from mungbean and cowpea clustered within the 16SrII group. To our knowledge, this is the first report of 16SrII group-related phytoplasmas infecting mungbean and cowpea in Guangxi, China. This finding highlights a new threat to local legume cultivation and provides a foundation for further studies on the dissemination of phytoplasma diseases in legumes.
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