NC State and USDA Cucumber Disease Handbook

Cucumber Mosaic Virus

Disease:

Cucumber mosaic.

Pathogen:

Cucumber mosaic virus (CMV).

Description on Host:

CMV causes a mottling of leaves, epinasty of petioles, and stunting of susceptible hosts.

Microscopic Description:

Under the electron microscope the icosahedral particles are 28 nm in diameter.

Source:

P. H. Williams; Plant Pathology Department, University of Wisconsin; 1630 Linden Drive, Madison, WI 53706. Or Dr. Provvidenti; Cornell University, Geneva, NY.

Relative Stability:

Stable with respect to changes in virulence. Crude plant sap used as inoculum is unstable.

Variants:

Numerous strains.

Storage and Retrieval:

Dry infected zucchini squash leaves over calcium carbonate. Store dried leaves in air tight container at 4°C. To retrieve, grind leaves in 0.03 M phosphate buffer pH 7. Swab inoculum over cotyledons of 5-9 day old zucchini ‘Select’ squash dusted with 600 mesh Carborundum. Rinse off excess inoculum with tap water before it dries or within 3-5 minutes of inoculation. Cover with wet newspaper for 24 hr. Place in greenhouse 24-36°C.

Inoculum Increase:

Virus maintained in susceptible zucchini squash plants. To increase, prepare inoculum as in inoculum preparation section. Dust fully expanded cotyledons of 5-9 day old zucchini ‘Select’ squash with 600 mesh Carborundum. Rub the cotyledons with cheese cloth dipped in inoculum. Rinse off excess inoculum with tap water before it dries or within 3-5 minutes of inoculation. Cover with wet newspaper for 24 hr. Place in greenhouse 24-36°C.

Inoculum Preparation:

Collect 16 cm2 of young leaf tissue from zucchini 2-3 weeks after inoculation. Grind in 15 ml 0.03 M phosphate buffer, pH 7.

Quantification:

None.

Inoculum Distribution and Delivery:

When 1st to 4th leaf of cucumber is approximately 3-4 cm in diameter, swab inoculum over one leaf 3-4 cm diameter which had previously been dusted with 600 mesh Carborundum. Dip pad in inoculum before inoculating each plant. Rinse off inoculum before it dries, preferably within 3-5 minutes of inoculation.

Host:

Cucumis sativus L., cucumber.

Source of Resistance:

Numerous common scab- and CMV-resistant cultivars and PI accessions, notably from China.

Differentials – Controls:

Susceptible check Straight Eight. Resistant check Wisconsin SMR 18.

Growth of Host:

Two week old seedlings grown in vermiculite are transplanted to steam sterilized soil in 4″ plastic pots. Soil composed of sand:peat:field soil: field compost:perlite (1:1:1:1:1). Fertilize plants in 4″ pots once/week.

Tissue Age:

Inoculate plants when 1st or 2nd leaf is 3-4 cm in diameter.

Postinoculation Environment:

Rinse off excess inoculum with tap water as soon as possible. Cover plants with wet newspaper for 24 hr. Grown in greenhouse 24-36°C.

Disease Response:

Plants are rated as resistant or susceptible 7-14 days after inoculation. Susceptible plants have mottled yellow-green and green leaves, and may be stunted. They may show epinasty, downward bending of the petioles. Resistant plants show no mottling. If a slight amount of mottling is present, a resistant plant will grow.

Multiple Inoculation:

Previous inoculation with scab, downy mildew, anthracnose, angular leaf spot, bacterial wilt, and powdery mildew.

Saving Host:

Both resistant and susceptible plants can be transplanted to steam sterilized soil.

Paul H. Williams
Mary J. Palmer
Department of Plant Pathology
University of Wisconsin
10-07-82