PLANT HEALTH PROGRESS Vol. 15, No. 1, 2014 Page 29

Plant Health Brief

Detection of Papaya ringspot virus Type W Infecting the Cucurbit Weed Cucumis melo var. dudaim in Florida

Yaowapa Tantiwanich, Plant Pathology Research Group, Plant Protection Research and Development Office, Department of Agriculture, Ministry of Agriculture and Cooperatives, Chatuchuk, Bangkok, 10900, Thailand; Carlye A. Baker, Florida Department of Agriculture and Consumer Services-Division of Plant Industry, Gainesville 32608; and William W. Turechek and Scott Adkins, USDA-ARS, U.S. Horticultural Research Laboratory, Fort Pierce, FL 34945

Accepted for publication 21 January 2014. Published 18 March 2014.

Tantiwanich, Y., Baker, C. A., Turechek, W. W., and Adkins, S. Detection of Papaya ringspot virus type W infecting the cucurbit weed Cucumis melo var. dudaim in Florida. 2014. Plant Health Progress doi:10.1094/PHP-BR-13-0126.

Cucumis melo L. var. dudaim (L.) Naud. is a vining cucurbit weed found in Florida, Louisiana, Texas, Arizona, California, and other areas of the southern United States (2,6). Commonly known as a smellmelon or dudaim melon, and locally in Florida as a gherkin, C. melo var. dudaim has previously been demonstrated to serve as a reservoir for three recently introduced whitefly-transmitted viruses in south Florida vegetable production areas: Squash vein yellowing virus (SqVYV); Cucurbit leaf crumple virus (CuLCrV); and Cucurbit yellow stunting disorder virus (CYSDV) (2).

During a cucurbit survey in May 2013, C. melo var. dudaim plants were observed in a watermelon field in Hendry County in southwest Florida with mosaic, mottling, and deformation of leaves (Fig. 1) typical of symptoms induced by aphid-transmitted potyviruses. Four samples were collected and analyzed using commercially available enzyme linked immunosorbent assays (ELISA; Agdia, Elkhart, IN) for potyviruses and Papaya ringspot virus (PRSV) and found to be positive in both tests. The presence

and appearance of viral inclusion bodies in epidermal strips from symptomatic leaves indicated the presence of PRSV type W (PRSV-W) (5). Total RNA was extracted (RNeasy Plant Mini Kit, Qiagen, Valencia, CA) and tested by reverse transcription-polymerase chain reaction (RT-PCR) to confirm PRSV-W infection using previously described primers and procedures to amplify the 3’ terminal portion of the genome from all four samples (1). RT-PCR products from two samples were cloned (pGEM-T, Promega, Madison, WI), sequenced and submitted to GenBank (KF826911 and KF826912). A 923-nt region of the coat protein gene and 3’ nontranslated region was 94 to 100% identical to PRSV-W sequences in GenBank. No evidence of SqVYV, CuLCrV, or CYSDV infection was found using previously described methods (2).

Numerous watermelon plants with similar symptoms of virus infection (Fig. 2) were collected from this field. A single Melothria pendula (creeping cucumber) plant, another common cucurbit weed in Florida, with mosaic symptoms (Fig. 3) was found adjacent to a nearby watermelon field. Analysis by ELISA, inclusion body morphology, and RT-PCR (as described above) demonstrated that these plants were also infected with PRSV-W.

To the best of our knowledge this is the first report of PRSV-W infecting C. melo var. dudaim in Florida, although common cucurbit weeds including M. pendula and Momordica charantia (Balsam-apple) have been known to serve as reservoirs for aphid-transmitted PRSV-W in Florida for many years (3,4). Together with previous observations of SqVYV, CuLCrV, and CYSDV infection of C. melo var. dudaim (2) and SqVYV and CuLCrV infection of M. charantia (1), our current results provide further evidence of the continued importance of cucurbit weeds as reservoirs for aphid- and whitefly-transmitted viruses that infect Florida cucurbit crops. The finding of only whitefly-transmitted viruses in C. melo var. dudaim in 2008 (2) and only the aphid-transmitted PRSV-W in the current study suggests that the virus species present in this weed host may vary over time. However, due to the presence of at least one commonly occurring cucurbit crop infecting virus during 2008 and 2013, it is important that cucurbit weed management remains an emphasis of cucurbit virus management plans.

FIGURE 1 Mosaic or mottle of leaves of two Cucumis melo var. dudaim plants infected with Papaya ringspot virus type W. In some plants, veins were chlorotic or lighter green than adjacent leaf tissue (A, arrows), whereas in other plants veins and surrounding leaf tissue were darker green than adjacent leaf tissue (B, arrows). Deformation of some leaves (B) on infected plants was also observed.

Corresponding author: Scott Adkins. Email: scott.adkins@ars.usda.gov

http://dx.doi.org/10.1094 / PHP-BR-13-0126 © 2014 The American Phytopathological Society

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LITERATURE CITED

1. Adkins, S., Webb, S. E., Baker, C. A., and Kousik, C. S. 2008. Squash vein yellowing virus detection using nested polymerase chain reaction demonstrates that the cucurbit weed Momordica charantia is a reservoir host. Plant Dis. 92:1119-1123.

2. Adkins, S., Webster, C. G., Baker, C. A., Weaver, R., Rosskopf, E. N., and Turechek, W. W. 2009. Detection of three whitefly-transmitted viruses infecting the cucurbit weed Cucumis melo var. dudaim in Florida. Plant Health Progress doi:10.1094/PHP-2009-1118-01-BR.

3. Adlerz, W. C. 1969. Melothria pendula plants infected with watermelon mosaic virus 1 as a source of inoculum for cucurbits in Collier County, Florida. J. Econ. Entomol. 65:1303-1306.

4. Adlerz, W. C. 1972. Momordica charantia as a source of watermelon mosaic virus 1 for cucurbit crops in Palm Beach County, Florida. Plant Dis. Reptr. 56:563-564.

5. Christie, R. G., and Edwardson, J. R. 1994. Light and electron microscopy of plant virus inclusions. Monograph 9, rev. Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL.

6. Tingle, C. H., Steele, G. L., and Chandler, J. M. 2003. Competition and control of smellmelon (Cucumis melo var. dudaim Naud.) in cotton. Weed Sci. 51:586-591.

FIGURE 3 Mosaic of leaves of Melothria pendula plant infected with Papaya ringspot virus type W .

FIGURE 2 Mosaic and deformation of leaf of representative watermelon plant infected with Papaya ringspot virus type W. Arrows denote veins and surrounding leaf tissue that were darker green than adjacent leaf tissue.