Cucumber Mosaic Virus
Cucumber mosaic virus (CMV).
Description on Host:
CMV causes a mottling of leaves, epinasty of petioles, and stunting of susceptible hosts.
Under the electron microscope the icosahedral particles are 28 nm in diameter.
P. H. Williams; Plant Pathology Department, University of Wisconsin; 1630 Linden Drive, Madison, WI 53706. Or Dr. Provvidenti; Cornell University, Geneva, NY.
Stable with respect to changes in virulence. Crude plant sap used as inoculum is unstable.
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.
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.
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.
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.
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.
Inoculate plants when 1st or 2nd leaf is 3-4 cm in diameter.
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.
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.
Previous inoculation with scab, downy mildew, anthracnose, angular leaf spot, bacterial wilt, and powdery mildew.
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