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Cucurbit Genetics Cooperative Report 23:68-68 (article 22) 2000

A Strain of Watermelon Mosaic Virus from Massachusetts Causes Prominent Symptoms on Squashes and Systematically Infects Cucurbita equadorensis and C. maxima PI 419081-1

R. Provvidenti

Department of Plant Pathology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY 14456

Watermelon mosaic virus (WMV), previously known as WMV-2, commonly occurs in cucurbits and wild legume species growing in the northeastern United States. Generally, the symptoms caused by this virus in cucurbits are less severe than those incited by other cucurbit viruses. However, they may vary with the species and viral strain involved. Symptoms include light and dark green mosaic, green veinbanding, chlorotic spots and some leaf rugosity. Infected plants are slightly stunted and fruits are not distorted, but some colons may be adversely affected (Provvidenti, 1986 and 1993.)

In July, 1999, Dr. Clark W. Nicklow (Ashland, Massachusetts) brought to our attention the occurrence of a widespread viral disease in pumpkins (Cucurbita pepo L) in a four acre field near Hudson, MA. Although plants appeared of quasi normal size, foliar light and dark green mosaic was rather prominent and fruit setting was considerably reduced. On July 14, samples of several infected plants were received directly from Mr. Manouel Ferjulian, the owner of the affected field. the foliar symptoms displayed by infected plants resembled those usually incited by the cucurbit strain of papaya ringspot virus (PRSV-W). However, using differential hosts, including bean plants of Black Turtle 2 (BT-2), and serology, the causal agent was identified as a strain of WMV. This strain henceforth is designated as WMV-MA.

In the greenhouse, BT-2 bean plants infected with WMV-AA were used as sources of inocula to test the following squashes: Cucurbita pepo 'Seneca Zucchini', 'Dark Green Zucchini', 'Butterbar', 'Table Green', and 'Delicata'; Cucurbita maxima: 'Zapalito Rotundo'; and Cucurbita moschata: 'Butternut'. All the plants of these cultivars developed prominent systemic foliar symptoms. Plants C. moschata "Nigerian Local' were systemically resistant, whereas those of C. maxima PI 419081-1 (China) and cucurbita equadorensis were systemically infected. Consequently, this strain of WMV differs from the others that we have found in the Northeast, since it is able to overcome the resistance to WMV in C. eqiuadorensis (Provvidenti et al, 1978) and C. maxima PI 419081-01 (China) (Provvidenti, 1982). However, in these two WMV-resistant species, WMV-Ma causes moderate foliar symptoms and limited plant stunting.

Literature Cited

  1. Provvidenti, 1982. Sources of resistance and tolerance to viruses in accessions of Cucurbita maxima. Cucurbit Genet Coop. Rept. 5:46-47.
  2. Provvidenti, R. 1993. Resistance to viral diseases of cucurbita. In: M.M. Kyle, ed. Resistance to viral diseases of vegetables. Timber Press, Protland, Oregon, pp. 8-43.
  3. Provvident, R., R.W. Robinson and H.M. Munger. 1978. Resistance in feral species to six viruses infecting Cucurbita. Plant Dis. Rep. 62:326-329.
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Page citation: Wehner, T.C., Cucurbit Genetics Cooperative;
Created by T.C. Wehner and T. Ng, 1 June 2005; design by C.T. Glenn;
send questions to T.C. Wehner; last revised on 21 April, 2008