Identification and molecular characterization of a begomovirus associated with yellow vein leaf curl disease of Kalmegh (Andrographis paniculata)

Kalmegh (Andrographis paniculata) is an important medicinal plant growing in the Southeast Asia. Recent initiatives have been undertaken by various agencies to promote its cultivation. Symptoms such as leaf curling, yellowing of vein and clearing were observed on Kalmegh plants in Bhubaneshwar, Odisha. To identify the causal virus, DNA extracted using the CTAB method and subjected to PCR amplification using primers targeting the coat protein gene, DNA-A and the associated betasatellite. The coat protein gene, DNA-A component and betasatellite were successfully amplified, cloned and sequenced. The sizes of the begomovirus DNA-A and betasatellite components were approximately 2.7 kb and 1.4 kb respectively. The nucleotide sequence shared highest identity (89 %) with Andrographis yellow vein leaf curl virus (AYVLCV) isolate- 64 (KM359406). The associated betasatellite showed 95 % sequence similarity with AYVLC betasatellite (KC9672282, KM359409). The analysis identified three key structural elements: the satellite conserved region (SCR), an adenine (A)-rich region and the open reading frame (ORF) ßC1. The present investigation characterizes the leaf curl virus and the associated satellite DNA molecule, which will pave the way for further research for reliable diagnosis, epidemiology and durable management strategies.