First report of zucchini tigre mosaic virus infecting bitter melon (momordica charantia) in Hawaii

Authors: WANG, D. - University Of Hawaii; BOLUK, G. - University Of Hawaii; QUINTO, E.A. - University Of Hawaii; HAMIN, I. - University Of Hawaii; BORTH, W.B. - University Of Hawaii; MELZER, M.J. - University Of Hawaii; GREEN, J. - University Of Hawaii; Suzuki, Jon; Wall, Marisa; Matsumoto Brower, Tracie; SUN, G.F. - China Medical University; HU, J. - University Of Hawaii

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/25/2019
Publication Date: 5/1/2019
Citation: Wang, D., Boluk, G., Quinto, E., Hamin, I., Borth, W., Melzer, M., Green, J., Suzuki, J.Y., Wall, M.M., Matsumoto Brower, T.K., Sun, G., Hu, J. 2019. First report of zucchini tigre mosaic virus infecting bitter melon (momordica charantia) in Hawaii. Plant Disease. 103(5). https://doi.org/10.1094/PDIS-08-18-1391-PDN.
DOI: https://doi.org/10.1094/PDIS-08-18-1391-PDN

Interpretive Summary: Bitter melon is an important vegetable and medicinal crop used in Asia and tropical Africa. In 2018, bitter melon plants exhibiting severe chlorotic mosaic symptoms were observed on Oahu, HI. Symptomatic samples were found positive for potyvirus infection. The specific potyvirus present was identified as zucchini tigre mosaic virus (ZTMV) using molecular genetics. The virus isolate shared 94% nucleotide sequence identity with a ZTMV isolate from Guadeloupe and it shared 96% amino acid identity with a polyprotein of a ZTMV isolate from France. This is the first report of ZTMV infecting bitter melon plants in Hawaii. Further studies are needed to determine whether ZTMV can infect commercially important papaya crops via aphid transmission.

Technical Abstract: Bitter melon (Momordica charantia L.) is an important vegetable crop and is also used for traditional treatment of diabetes in Asia, and as a remedy for other diseases in tropical Africa. Zucchini tigre mosaic virus (ZTMV) was first reported as a divergent strain of papaya ringspot virus (PRSV) in zucchini from Guadeloupe, French West Indies, in 1982. ZTMV is closely related to PRSV; and was originally considered to be papaya ringspot virus T strain (PRSV-T) until 2014. However, biological, serological, and molecular biology studies suggested that it is a distinct species in the genus Potyvirus. In February 2018, bitter melon plants exhibiting severe chlorotic mosaic symptoms were observed in the Manoa Community Garden on Oahu, HI (21°18'56.2' N, 157°48'22.7' W). Sixteen samples with severe symptoms of yellow mosaic and leaf distortion were collected, plus three leaves from non-symptomatic plants. The leaves were tested with potyvirus-specific ELISA (Agdia, Elkhart, IN) and potyvirus-specific RT-PCR with potyvirus nuclear inclusion body (NIb) primers NIb2F and NIb3R. All symptomatic samples were found positive for potyvirus infection in both tests, whereas all three non-symptomatic leaves tested negative. To identify the specific potyvirus present, 366-bp amplicons (GeneBank accession-MH477835) of the NIb region generated by RT-PCR were sequenced using the above potyvirus-specific primers. BLASTn analysis of the sequences showed that this virus isolate shared 93% nucleotide sequence identity with a ZTMV isolate from Guadeloupe (KC345605) and BLASTx determined it shared 92% amino acid identity with a polyprotein of a ZTMV isolate from France (YP_008992091). We used an additional set of PCR primers to further characterize the isolate: ZTMV gene NIb-specific primers ZTMFP (5´-TTTACAGTAAGAACATGATTTGCC-3´) and ZTMRP (5´-CACTGTTCCCTTTAAATTTCT-3´) that were designed from the sequence generated by the above potyvirus-specific primers. BLASTn analysis of the 234-bp NIb amplicon (GenBank accession-MH477836) shared 94% nucleotide sequence identity with the isolates from Guadeloupe and BLASTx analysis showed the NIb amplicon shared 96% amino acid identity with a polyprotein of the ZTMV isolate from France (AGY36218). To our knowledge, this is the first report of ZTMV infecting bitter melon plants in Hawaii. Further studies on the distribution of ZTMV-infected bitter melon and identification of other ZTMV-infected plants in the Hawaiian Islands are also needed. For example, it is important for the papaya industry in Hawaii to know whether ZTMV can infect papaya plants via aphid transmission.