© 2009 Plant Management Network.
Detection of Three Whitefly-transmitted Viruses Infecting the Cucurbit Weed Cucumis melo var. dudaim in Florida
Scott Adkins and Craig G. Webster, USDA-ARS, Fort Pierce, FL 34945; Carlye A. Baker and Richard Weaver, Florida Department of Agriculture and Consumer Services-Division of Plant Industry, Gainesville, FL 32608; and Erin N. Rosskopf and William W. Turechek, USDA-ARS, Fort Pierce, FL 34945
Corresponding author: Scott Adkins. email@example.com
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. Online. Plant Health Progress doi:10.1094/PHP-2009-1118-01-BR.
Cucumis melo L. var. dudaim (L.) Naud., commonly known as smellmelon or dudaim melon, is a vining cucurbit weed with mottled or striped fruits that are green when immature (Fig. 1) and yellow or orange at maturity. It is a state noxious weed in California and Arizona and is a problem weed in Texas and Louisiana cotton production (8). C. melo var. dudaim is also found in southern Florida vegetable production areas, where it can survive as a perennial and is known locally as a gherkin.
The importance of cucurbit weeds as virus reservoirs in Florida has recently increased with the appearance of three whitefly-transmitted viruses representing three different viral genera in the state’s cucurbit crops: Squash vein yellowing virus (SqVYV, genus Ipomovirus) (2), Cucurbit leaf crumple virus (CuLCrV, genus Begomovirus) (3), and Cucurbit yellow stunting disorder virus (CYSDV, genus Crinivirus) (5). SqVYV is the cause of a viral watermelon vine decline first reported in Florida (2). Natural SqVYV infections of Momordica charantia (Balsam-apple), a common cucurbit weed, have been recorded throughout the watermelon production areas of south and southwest Florida (1). Experimental SqVYV infection of Melothria pendula (creeping cucumber), another common cucurbit weed in Florida, has also been demonstrated (1).
In May 2008, C. melo var. dudaim plants were observed adjacent to sugarcane and watermelon fields in Hendry County in southwest Florida. Although no symptoms of virus infection were obvious (Fig. 1), samples were collected from four plants due to prior observations of symptomless SqVYV infections of M. charantia (1). Total RNA was extracted from all samples using an RNeasy Plant Mini Kit (Qiagen, Valencia, CA) following the manufacturer’s instructions. A 1,020 bp region of the reverse transcription (RT)-PCR products, amplified from three of the four samples using previously described SqVYV coat protein (CP) gene primers (1), was 99% identical to SqVYV (EU259611). Samples were also tested for CYSDV (using RT-PCR with CP gene primers CYSCPf/CYSCPr) (7), begomoviruses (using PCR with degenerate primers PAR1c496/PAL1v1978) (6), and potyviruses (using commercially available enzyme linked immunosorbent assay; Agdia, Elkhart, IN) and found to be negative.
In October 2008, C. melo var. dudaim plants were again observed in the same general geographic area although chlorosis (yellowing) of lower leaves was now evident in ~50% of the plants (Fig. 2). Seven samples were collected and analyzed for the viruses noted above using the methods indicated. A 1,020 bp region of the SqVYV CP gene RT-PCR products amplified from each of the seven samples was again 99% identical to SqVYV. A 707 bp region of the CYSDV CP gene RT-PCR products amplified from six samples was 99-100% identical to CYSDV sequences in GenBank, indicating double infection of these six samples with SqVYV and CYSDV. An 1,159 bp region of the degenerate begomovirus PCR product amplified from one of these SqVYV and CYSDV infected samples was 96% identical to CuLCrV sequences in GenBank, indicating a triple infection of this sample with SqVYV, CYSDV, and CuLCrV. No evidence of potyvirus infection was found.
A second region of the genomes of all three viruses was cloned and sequenced from the triply infected plant to confirm the original diagnoses. The 699 bp NIa gene sequence, assembled from overlapping RT-PCR products amplified with SqVYV primer pairs I (5’- gtgacaacaac-cgtcgcgggcgc-3’ / 5’-cccctgggagttgtgataataac-3’) and J (5’-gcggcacca-tatgcacatttg-3’ / 5’-ggaaggtccatacctctccttaag-3’), was 99.7% identical to SqVYV. A 175 bp RT-PCR product amplified with primers CYShspF / CYShspR (4) was 98 to 100% identical to CYSDV HSP gene sequences in GenBank. A 533 bp portion of the PCR product amplified with degenerate begomovirus primers AC1048/AV494 (9) was 97% identical to CuLCrV CP gene sequences in GenBank.
To the best of our knowledge this is the first report of SqVYV, CYSDV, or CuLCrV infecting C. melo var. dudaim. Coupled with previous observations of SqVYV and CuLCrV infection of M. charantia (1), our current results are further evidence of the importance of cucurbit weeds as reservoirs for all three recently detected whitefly-transmitted viruses plaguing Florida cucurbit crops, as well as the long-known aphid-transmitted potyviruses. Consequently, cucurbit weed management remains a necessary component of overall management plans for SqVYV, CYSDV, and CuLCrV.
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2. Adkins, S., Webb, S. E., Achor, D., Roberts, P. D., and Baker, C. A. 2007. Identification and characterization of a novel whitefly-transmitted member of the family Potyviridae isolated from cucurbits in Florida. Phytopathology 97:145-154.
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8. 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.
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