Occurrence of tomato leaf curl Bangladesh virus and associated subviral DNA molecules in papaya in Bangladesh: molecular detection and characterization

Authors: HAMIM, ISLAM - University Of Hawaii; BORTH, WAYNE - University Of Hawaii; MELZER, MICHAEL - University Of Hawaii; Suzuki, Jon; Wall, Marisa; HU, JOHN - University Of Hawaii

Submitted to: Archives of Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/14/2019
Publication Date: 4/4/2019
Citation: Hamim, I., Borth, W.B., Melzer, M.J., Suzuki, J.Y., Wall, M.M., Hu, J.S. 2019. Occurrence of tomato leaf curl Bangladesh virus and associated subviral DNA molecules in papaya in Bangladesh: molecular detection and characterization. Archives of Virology. 164(6):1661-1665. https://doi.org/10.1007/s00705-019-04235-8.
DOI: https://doi.org/10.1007/s00705-019-04235-8

Interpretive Summary: Papaya plants with severe leaf curl symptoms simultaneous with whitefly infestation were recently observed in Bangladesh. Samples from seven papaya growing regions were taken and analyzed by molecular methods for the presence of suspected plant viruses. 43 of the 45 symptomatic plants (96%) were found to be infected with a type of plant virus known as begomovirus. Of these, 29 (67%) tested positive for a type of begomovirus known as Tomato leaf curl Bangladesh virus (TLCBV). Sequence of the entire genome of the papaya-infecting TLCBV indicates a high sequence identity to a TLCBV found in tomato from the same region of Bangladesh. The discovery of ToLCBV in papaya grown in Bangladesh suggest that this virus was either recently introduced into Bangladesh to papaya by whiteflies from tomato, or were already present but simply undetected until now.

Technical Abstract: Severe leaf curl symptoms distinct from those caused by Papaya ringspot virus were observed recently in papaya (Carica papaya) in Bangladesh. These symptoms along with whitefly infestations on affected plants suggested presence of begomovirus infection. A total of 45 symptomatic leaf samples were collected from seven papaya-growing districts in the country and tested by PCR with a degenerate primer set diagnostic for begomovirus. Of these, 43 (96%) tested positive for begomovirus and 29 (67%) of these were positive for Tomato leaf curl Bangladesh virus (ToLCBV). The complete genome sequence of the ToLCBV and its associated Tomato leaf curl beta-satellite (ToLCB) were determined and characterized from a papaya isolate, Gaz:17:Pap. ToLCBV infecting papaya was most closely related to ToLCBV reported from the same region, Gazipur, Bangladesh, causing tomato leaf curl disease of tomato. The ToLCB found in infected papaya had the highest homologies at the nucleotide and amino acid levels to the beta-satellite associated with Tomato leaf curl virus (ToLCV) from tomato in India. The small non-coding satellite sequences associated with ToLCBV infected papaya in Bangladesh clustered with a non-coding DNA satellite sequence identified from papaya in Pakistan and a closely related cluster that contained whitefly-transmitted small DNA satellites from China based on phylogenetic tree analysis. These findings strongly support the association of non-coding DNA satellites with ToLCBV in papaya. The discovery of ToLCBV and its associated beta satellite and small non-coding DNA satellites in papaya in Bangladesh suggest that this virus and its associated satellites were either recently introduced into Bangladesh to papaya by viruliferous whiteflies from tomato, or were present in the region but were simply previously undetected.