First report of bean yellow mosaic virus infecting nasturtium (tropical majus) in Hawaii

Authors: WANG, DA - University Of Hawaii; OCENAR, JORDIE - Hawaii Department Of Agriculture; HAMIM, ISLAM - University Of Hawaii; BORTH, WAYNE - University Of Hawaii; FUKADA, MACH - Hawaii Department Of Agriculture; MELZER, MICHAEL - University Of Hawaii; Suzuki, Jon; Wall, Marisa; Matsumoto Brower, Tracie; SUN, GUIFAN - China Medical University; KO, MANN - Hawaii Department Of Agriculture; HU, JOHN - University Of Hawaii

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/17/2018
Publication Date: 11/2/2018
Citation: Wang, D., Ocenar, J.R., Hamim, I., Borth, W.B., Fukada, M.T., Melzer, M.J., Suzuki, J.Y., Wall, M.M., Matsumoto Brower, T.K., Sun, G., Ko, M., Hu, J.S. 2018. First report of bean yellow mosaic virus infecting nasturtium (tropical majus) in Hawaii. Plant Disease. 103(1):168. https://doi.org/10.1094/PDIS-06-18-1082-PDN.
DOI: https://doi.org/10.1094/PDIS-06-18-1082-PDN

Interpretive Summary: In February 2018, nasturtium plants exhibiting severe leaf discoloration were observed at the Kula Botanical Gardens on the island of Maui, Hawaii, USA. Garden nasturtium (Tropaeolum majus L.) is an herbaceous annual plant commonly used as a garden ornamental, culinary herb, or medicinal plant. It has become naturalized in many locations and is currently considered an alien invader in New Zealand, Lord Howe Island, and Hawaii. The plant disease symptoms found in nasturtium were shown by molecular analyses to result from infection by a plant virus, the Bean yellow mosaic virus (BYMV). Within a four month span following initial detection of the virus, twenty-four additional nasturtium samples were collected from two different locations on Maui and all tested positive for BYMV infection. BYMV is a plant virus that is spread through the saliva of the garden insect, aphid. BYMV is most notorious for infecting members of the legume or bean family, but otherwise infecting a wide variety of plants. To our knowledge, this is the first report of BYMV infecting nasturtium in Hawaii. Since nasturtium is so widely grown in Hawaii and elsewhere, it may potentially serve as an off-season reservoir of BYMV. Therefore, further study is needed to determine whether BYMV can spread from nasturtium to and negatively impact leguminous or other important agricultural crops.

Technical Abstract: Bean yellow mosaic virus (BYMV) is an aphid-transmitted non-persistent potyvirus with a wide host range. In February 2018, nasturtium plants exhibiting severe chlorotic, mosaic symptoms were observed at the Kula Botanical Gardens on the island of Maui, Hawaii, USA. Garden nasturtium (Tropaeolum majus L.) is an herbaceous annual plant commonly used as a garden ornamental, culinary herb, or medicinal plant. It has become naturalized in many locations and is currently considered an alien invader in New Zealand, Lord Howe Island, and Hawaii. Naturtium leaf samples with severe yellow mosaic, and leaf distortion symptoms as well as leaves from non-symptomatic plants were analyzed by ELISA using potyvirus-specific antibodies and RTPCR using universal, potyvirus-specific nuclear inclusion body (NIb) primers. Symptomatic samples tested positive for potyvirus infection in both tests, while non-symptomatic leaves tested negative. Blastn analysis of the PCR-amplified, 309bp NIb region obtained from these samples indicated a 93% nucleotide sequence identity with the corresponding NIb gene region of a BYMV isolate from Australia. Based on Blastx analysis, this fragment exhibited 93% amino acid identity with the corresponding region of the polyprotein sequence of a BYMV isolate also from Australia. A 257 bp nucleotide subfragment of the NIb region obtained by PCR using BYMV NIb gene-specific primers was 94% identical to the corresponding region of an Australian isolate of BYMV based on Blastn analysis, whereas a 595 bp nucleotide sequence obtained using BYMV coat protein-specific primers was 98% identical at the nucleotide level to the corresponding region of another Australian isolate of BYMV. The 257-bp NIb amplicon exhibited 93% amino acid identity based on Blastx analysis to the corresponding region of the polyprotein sequence from an Australian isolate of BYMV whereas the 595-bp CP amplicon shared 98% amino acid identity to the corresponding region of the BYMV polyprotein sequence from a Japan isolate. All symptomatic samples also tested positive for BYMV by triple-antibody sandwich-ELISA using a BYMV specific antibody. Within a four month span following initial detection of the virus, twenty-four additional nasturtium samples were collected from two different locations on Maui and all tested positive for BYMV infection by RT-PCR and ELISA. To our knowledge, this is the first report of BYMV infecting nasturtium in Hawaii. Since nasturtium is so widely grown in Hawaii and elsewhere it may serve as an off-season reservoir of BYMV in agricultural areas. Therefore, further study is needed to determine whether BYMV can spread from nasturtium via aphids to and negatively impact leguminous crops.