First report of a ‘Candidatus Phytoplasma australasia’ associated with crown chocking of arecanut palm in India

Arecanut is an important commercial crop cultivated in many countries of the world. In recent years, crown chocking (“hidimundige”) malady has become a severe problem in major arecanut growing areas especially in plain regions of Karnataka. The symptoms include appearance of dark green dwarfed leaves and witches’ broom. Leaflets fail to unfold properly, become short, fan-like, crinkled and brittle. Affected plants exhibits short intermodal length and tapering of stem at apex region which leads to complete arrest of new leaf and inflorescence production and death of the plants within one or two years from the appearance of the first symptom. Transmission electron microscopy suggested the presence of phytoplasma-like cells in the phloem tissue of symptomatic arecanut. To identify the phytoplasmas both symptomatic and asymptomatic plant samples were subjected to PCR amplification and sequencing of the 16S ribosomal RNA gene. The obtained sequence clusters in phylogenetic analyses confirmed the association with ‘Candidatus Phytoplasma australasia’. The virtual RFLP analysis of the R16F2n/R2 region of the phytoplasma ribosomal gene in iPhyClassifier showed 99.92% identity with phytoplasma strains in subgroup 16SrII-D with similarity coefficient 1.00. This is first report of 16SrII-D phytoplasmas in crown chocking diseased plants of arecanut in India.