Multilocus Gene Characterisation of a Phytoplasma Associated With Pigeon Pea in Andhra Pradesh, India

ABSTRACT An investigation was carried out to identify and characterise the phytoplasma strains associated with pigeon pea ( Cajanus cajan , common names include red gram) showing symptoms of phyllody, stunting and little leaf in Andhra Pradesh, a major pigeon pea‐growing state in southern India. A survey was conducted in the kharif (monsoon; June to October) season of 2023. Phytoplasma detection was confirmed in 10 samples through nested PCR amplification of the 16S rRNA gene using primer sets P1/P7 and R16F2n/R16R2, yielding ~1.8 kb and ~1.25 kb amplicons, respectively. The results of phytoplasma identification in the symptomatic samples were further substantiated by using the rp gene, resulting in a ~1.39‐ kb amplicon using the primer pair rp(II)F/rp(I)R1A. BLAST and phylogenetic analysis of the 16S rRNA and rp genes revealed that the phytoplasma associated with pigeon pea belonged to the ‘ Candidatus Phytoplasma australasiaticum’ (16SrII) group. To confirm phytoplasma classification at the subgroup level, virtual RFLP analysis was performed, which classified the pigeon pea isolates under the 16SrII‐D subgroup. Symptomatic weeds were collected from in and around infected pigeon pea fields. Two weed species, Cleome viscosa and Celosia argentea , tested positive for phytoplasmas using the same primer set of 16S rRNA and rp genes. The study concluded that the phytoplasmas associated with pigeon pea phyllody, stunting and little leaf symptoms in Andhra Pradesh, India, belong to ‘ Ca . Phytoplasma australasiaticum’ (16SrII‐D subgroup) and identified symptomatic weeds as alternative hosts, highlighting their potential role in disease epidemiology.