Molecular characterization and infectivity analysis of a bipartite begomovirus associated with cotton leaf curl Multan betasatellite naturally infecting Rumex nepalensis in northern India

Rumex nepalensis (Nepal Dock) is an Indian traditional medicinal herb of the Western Himalayas. During a survey in 2013, typical begomovirus-like symptoms were observed on naturally grown R. nepalensis in the Bandla region of Palampur, Himachal Pradesh, India. PCR-based detection identified a bipartite begomovirus and a betasatellite in all the symptomatic plant samples. Complete sequence characterization established their identity as tomato leaf curl Palampur virus (ToLCPalV) and cotton leaf curl Multan betasatellite (CLCuMuB), respectively. Infectious clones of the virus and betasatellite were agro-infiltrated on both natural (R. nepalensis) as well as experimental (Nicotiana benthamiana) hosts. At 25 days post infiltration (dpi), N. benthamiana developed typical virus symptoms in DNA-A + DNA-B and DNA-A + DNA-B + CLCuMuB-infiltrated plants, whereas the plants infiltrated with DNA-A alone did not show any diseased phenotype. However, in combination with CLCuMuB, mild symptoms were observed. Agro-infiltrated R. nepalensis plants did not show visible symptoms in any of the above combinations. PCR and Southern blot analysis confirmed the replication and systemic spread of ToLCPalV and CLCuMuB in both R. nepalensis and N. benthamiana infiltrated plants. The present report shows R. nepalensis as a new natural host of the bipartite ToLCPalV associated with CLCuMuB. It also demonstrates the efficient trans-replication compatibility of CLCuMuB by a bipartite ToLCPalV in both of its natural and experimental hosts.