Cucurbit Genetics Cooperative Report 8:76-77 (Article 29) 1985

Lack of Resistance to Zucchini Yellow Mosaic Virus in Accessions of Cucurbita maxima

Provvidenti, R.

New York State Agricultural Experiment Station, Cornell University, Geneva, NY 14456

R. Alconero

USDA Northeast Regional Plant Introduction Station, Geneva, NY 14456

Zucchini yellow mosaic virus (ZYMV) is one of the most destructive pathogens infecting cucurbits, and although of recent identification (1981), it is known to be present in 15 countries on five continents (1, 2, 3, 5). Epidemics have occurred in Europe, the Middle East, and in the United States and particularly devastated were melon (Cucumis melo) and summer squash (Cucurbita pepo) (1,5, 6). Efforts to find sources of resistance in accessions of C. pepo have been unsuccessful, however, C. ecuadorensis and an accession of C. moschata are resistant (1, 5).

The search for additional sources of resistance or tolerance to ZYMV in other Cucurbita species has continued, and this report deals with the evaluation of the C. maxima collection available at the USDA Northeast Regional Plant Introduction Station, Geneva, New York. This collection comprises 418 accessions, of which 386 bear the Plant Introduction numbers (P.I.), and 32 the Geneva State numbers (G). These accessions were originally collected in 35 countries on six continents, and they are listed in the Northeast Regional Plant Introduction Station Serial Publications N° 24 (1975) and N° 24C (1983).

In screening for resistance to ZYMV, ten plants of each accession were mechanically inoculated at the first leaf stage with each of the two known strains of the virus present in the United States: ZYMV-CT and ZYMV-FL (5). Plants which failed to develop symptoms after the first inoculation were reinoculated with the pertinent strain. All tests were conducted in an insect-free greenhouse maintained at 25-30 C.

None of the 418 accessions tested was resistant or tolerant to either strain of ZYMV. All plants develop a persistent and rather prominent mosaic, foliar distortion and severe stunting.

Considering the number of lines involved, their origin and diversity, the lack of resistance or tolerance in C. maxima is disappointing. However, some accessions of this species were demonstrated to be resistant or tolerant to other cucurbit viruses (4).

Literature Cited

1. Lecoq, H., M. Pitrat, and M. Clement. 1981. Identification et
   caracterisation d'un potyvirus provoquant la maladie du rabougrissement
   jaune du melon. Agronomie 1:827-834.
2. Lecoq, H., V. Lisa, and G. Dellavalle. 1983. Serological identity of
   muskmelon yellow stunt and zucchini yellow mosaic viruses. Plant
   Disease 67:824-825.
3. Lisa, V., G. Boccardo, G. D'Agostiono, G. Dellavalle, and M. D'Aquino. 1981. Characterization of a potyvirus that causes zucchini yellow mosaic. Phytopathology 71:667-672.
4. Provvidenti, R. 1982. Sources of resistance or tolerance to viruses in accessions of Cucurbita maxima. Cucurbit Genetics Coop. 5:46-47.
5. Provvidenti, R., D. Gonsalves, and H. S. Humaydan. 1984. Occurrence of zucchini yellow mosaic virus in cucurbits from Connecticut, New York, Florida, and California Plant Disease 68:443-446.
6. Provvidenti, R., H. M. Munger, and A. O. Paulus. 1984. Epidemics of zucchini yellow mosaic virus and other cucurbit viruses in Egypt in the spring of 1983 Cucurbit Genetics Coop. 7:78-79.