- Vegetables: cucurbits
- Education and Training: on-farm/ranch research
- Pest Management: general pest management
Surveys were conducted during 2004-2006 in Illinois to determine occurrence and distribution of viruses in pumpkin, squash, and gourd fields. CMV, PRSV, SqMV, TRSV, ToRSV, WMV, ZYMV, and unknown potyvirus(es) were detected as single and mixed infections. WMV was detected in more samples and SqMV was detected in samples from more counties than any other virus. ToRSV and TRSV were detected for the first time in Illinois in 2004 and 2005, respectively. Unknown potyvirus(es) are yet to be identified. General symptoms caused by viruses were mosaic and deformation of leaves and color-breaking and deformation of fruits.
Cucurbits are valuable crop in Illinois and other parts of the North Central region. There are approximately 20,000 acres of pumpkin and about 8,000 acres of other cucurbits (e.g., cucumber, gourd, melons, and squash) in Illinois (1). Diseases caused by viruses are serious threats to cucurbit industry in Illinois and other parts of the North Central region. Among the 32-reported viruses causing diseases on cucurbits (17), only five viruses including Cucumber mosaic virus (CMV), Watermelon mosaic virus (WMV), Papaya ringspot virus (PRSV), Squash mosaic virus (SqMV), and Zucchini yellow mosaic virus (ZYMV) (15), have been have been reported in Illinois. No previous study had been conducted to identify the viruses present in pumpkin and squash fields from all over the state of Illinois.
Different cucurbit viruses have been reported from different regions of the US. CMV (genus Cucumovirus, family Bromoviridae), has been reported from all over the US in squashes and watermelons (3,8,9,12,14). PRSV-W (3,10,12,14), WMV (3,8,10,12), and ZYMV (3,9,10,11,14) of the genus Potyvirus (family Potyviridae) have also been reported in squashes, pumpkins, and other cucurbit crops from many regions in the US. SqMV (genus Comovirus, family Comoviridae) has been detected in South Carolina and Texas (8,12). Tobacco ringspot virus (TRSV) and Tomato ringspot virus (ToRSV), in the genus Nepovirus of the family Comoviridae, have been reported in cucurbits in South Carolina, Texas, and Wisconsin (8,12,13), and in the northeastern US (17), respectively. Squash leaf curl virus (SLCV; genus Begomovirus, family Geminiviridae) has been reported on cucurbits from Arizona, California, and Texas (2,10).
Virus symptoms on cucurbits vary from mild mosaic or veinbanding to severe systemic mosaic and malformation of leaves and plant stunting (3). WMV can cause severe stunting and leaf distortion (8) and PRSV and ZYMV can induce severe leaf mosaic, plant stunting, and malformation of foliage with blisters and shoestring (3) on cucurbits. CMV, PRSV, SqMV, TRSV, and WMV infection in squash can induce systemic mottling with leaf malformation (16). In squash and pumpkins, SLCV induces leaf curl and mosaic symptoms (2). Virus infections in cucurbits produced unmarketable fruit due to deformation, color change, and cracking in fruits (12) depending on the stage of fruit development at infection (11,15).
The virus diseases in cucurbits can be caused by a single or mixed infection of two or more viruses that are capable of producing similar symptoms (3,12). CMV, PRSV, SLCV, WMV, and ZYMV can infect most cucurbit species and have low host specificity, whereas SqMV is found only on Cucurbita pepo and does not infect cucumber, melons or watermelons (2, 8,15). CMV has a wide host range and can infect more than 800 plant species (17).
Weed hosts are important sources of inoculum for CMV, PRSV, SqMV, WMV, and ZYMV on cucurbits (10,17). Transmission of cucurbit viruses in the fields is mostly by insect vectors. Bemicia tabaci transmit SLCV (2,10) whereas CMV, PRSV, WMV, and ZYMV are vectored by aphids in a non-persistent manner (10,11,16). SqMV is transmitted by seed, western striped cucumber beetle [Acalymma trivittatum (Mannerheim)], and spotted cucumber beetle [Diabrotica undecimpunctata howardi Barber] (10,17). The viruses ToRSV and TRSV are reported to be mostly transmitted by dagger nematode Xiphinema americanum (17). Most cucurbit viruses are also mechanically transmitted (17).
Detection of the viruses is done by utilizing enzyme linked immunosorbent assay (ELISA) procedures. Healthy plant is used as negative control (14). Double antibody sandwich enzyme linked immunosorbent assay (DAS-ELISA) method is used to test plant tissues for presence of several cucurbit viruses (3,12,14) SLCV antiserum has been used to detect SLCV in cucurbits (2). Detection of ToRSV and TRSV by reverse-transcriptase polymerase chain reaction (RT-PCR) is done by amplify conserved coat protein region of the viral RNA (6). A degenerate oligonucleotide primer, that amplifies 1.6 – 2.1 Kb fragment, has been reported as a general potyvirus primer in detection of potyvirus by RT-PCR (5).
Although this research was scheduled for 2005 and 2006, because of the importance of the overall results, some of the results related to studies in 2004 are also reported here.
1. Babadoost, M., and Islam, S.Z. 2003. Fungicide seed treatment effects on seedling damping-off of pumpkin caused by Phytophthora capsici. Plant Dis. 87: 63-68.
2. Cohen, S., Duffus, J.E., Larsen, R.C., Liu, H.Y., and Flock, R.A. 1983. Purification, serology and vector relationships of Squash leaf curl virus, a whitefly-transmitted geminivirus. Phytopathology 73: 1669-1673.
3. Davis, R.F., and Muzuki, M.K. 1987. Detection of cucurbit viruses in New Jersey. Plant Dis. 71: 40-44.
4. Freitag, J.H. 1956. Beetle transmission, host range, and properties of Squash mosaic virus. Phytopathology 46: 73-81.
5. Gibbs, A., and Mackenzie, A. 1997. A primer pair for amplifying part of the genome of all potyvirids by RT-PCR. J. Gen. Virol. 63: 9-16.
6. Hughes, P.L., and Scott, S.W. 2003. First report of Tomato ringspot virus in Butterfly Bush (Buddleia davidii). Plant Dis. 87: 102.
7. Jossey, S., and Babadoost, M. 2006. First Report of Tobacco ringspot virus in Pumpkin (Cucurbita pepo) in Illinois. Plant Dis. 90: 1361.
8. McLean, D.M., and Meyer, H.M. 1961. A survey of cucurbit viruses in the lower Rio Grande Valley of Texas: Preliminary report. Plant Dis. Rep. 45: 137-139.
9. McLeod, P.J., Scott, H.A., and Morelock, T.E. 1986. Zucchini yellow mosaic virus: a new severe cucurbit disease. Arkansas Farm Res. 35: 2.
10. Nameth, S.T., Dodds, J.A., Paulus, A.O., and Laemmlen, F.F. 1986. Cucurbit viruses of California: An ever changing problem. Plant Dis. 70: 8-11.
11. Provvidenti, R., Gonsalves, D., and Humaydan, H.S. 1984. Occurrence of Zucchini yellow mosaic virus in cucurbit for Connecticut, New York, Florida, and California. Plant Dis. 68: 443-446.
12. Sammons, B., Barnett, O.W., Davis, R.F., and Mizuki, M.K. 1989. A survey of viruses infecting yellow summer squash in South Carolina. Plant Dis. 73: 401-404.
13. Sinclair J.B. and Walker J.C. 1956. A survey of ring spot on cucumber in Wisconsin. Plant Dis. Rep. 40: 19-20.
14. Ullman, D.E., Cho, J.J., and German, T.L. 1991. Occurrence and distribution of cucurbit viruses in the Hawaiian Islands. Plant Dis. 75: 367-370.
15. Walters, S.A., Kindhart, J.D., Hobbs, H.A., and Eastburn, D.M. 2003. Viruses associated with cucurbit production in southern Illinois. HortScience 38: 65-66.
16. Webb, R.E. 1971. Watermelon mosaic virus 1 and 2 in squash on the Atlantic seaboard. Plant Dis. Rep. 55: 132-135.
17. Zitter, T.A., Hopkins, D.L., and Thomas, C.E. 1996. Compendium of Cucurbit Diseases. APS Press, St. Paul, MN.
The over-all goal of this two-year project was to identify viruses associated with cucurbit crops mainly pumpkin and squash in Illinois. The specific objectives were: 1) to determine the occurrence and distribution of viral diseases in pumpkin and squash in Illinois using serological detection methods; 2) to determine symptoms associated with each virus; 3) to test the “Koch’s Postulates” for all the viruses identified in pumpkin and squash; and 4) to use molecular diagnostic methods to confirm the identification of viruses detected for the first time in Illinois.