Fusarium Wilt (Fusarium oxysporum f. sp. cucumerinum)
Fusarium wilt of cucumber, cucumber wilt, foot-rot of cucumber.
Fusarium oxysporum (Schlect.) Snyd. and Hans. f. sp. cucumerinum Owen.
On potato dextrose agar (PKA white mycelium, purple pigment usually develops with age.
Macroconidia are crescent shaped, multiseptate, fine, and well pointed; Microconidia are single celled and oval; Conidiophore are very short bearing microconidia in false heads; Chlamydospores are the resting structures having thick cell wall.
American Type Culture Collection; 12301 Parklawn Drive; Rockville, MD 20852. Races 1 through 3 available. P. H. Williams; Plant Pathology Department; University of Wisconsin; 1630 Linden Drive; Madison, WI 53706. Race 2.
Three races reported. Probably loses pathogenicity after periodic transfer on PDA.
Storage and Retrieval:
Store in sterile soil at 4°C for several years. Store on PDA or PDA under sterile mineral oil for 3 months. For retrieval aseptically remove soil or mycelium, place on PDA, and incubate at 24°C.
Place a piece of mycelium in 50 ml of potato dextrose broth (PDB) in a 125 ml Erlenmeyer flask. Shake on a rotary shaker 26-30°C for 3-6 days.
Comminute fungus and PDB in Waring blender at low speed for 30 sec. 2 times. Centrifuge at 3,000 rpm for 10 min. to wash the spores. Discard supernatant. Resuspend pellet in distilled water.
Count spores with a hemacytometer. Check percent germination of spore suspension on water agar after 24 hours.
Inoculum Distribution and Delivery:
Fill metal pan (50 x 29 x 11 cm) with silica sand. Weigh sand. Need 105 spores per gram sand. Calculate ml of concentrated inoculum needed per pan. Mix inoculum with deionized water to 1,500 ml volume. Add to sand. Mix thoroughly in a large mixing pan. Return sand to metal pan. Make 8 1.5 cm furrows. Plant 20 seeds per row. Row 5 contains resistant and susceptible checks.
Cucumis sativus L., cucumber.
Source of Resistance:
Wisconsin SMR 18.
Susceptible check Straight Eight. Resistant check Wisconsin SMR 18.
Line Race 1 2 3 MSU 8519 S R R MSU 441034 (Chipper) S S R PI 390265 R S R
R=resistant, S=susceptible (include cucumber cultivar Ashley to check pathogenicity of race 3).
Reference for races:
Armstrong, G. M., J. K. Armstrong, and D. Netzer. 1978. Pathogenic races of the cucumber-wilt Fusarium. Plant Dis. Reporter. 62:824-828.
Growth of Host:
See inoculum distribution and delivery section. Water with tap water or fertilizer daily. Photoperiod 12 hr. light, 12 hr. dark.
Seeds are sown in infested sand. See inoculum distribution and delivery section.
Place pans in Wisconsin temperature tanks. Sand temperature 28°C. No light first 2 days to prevent drying.
Plants are rated on a scale from 0 to 9 three weeks after inoculation.
0 = no symptoms
1 = hypocotyl browning, no wilt, no stunting
3 = cotyledon lesion, no wilt, no stunting
5 = slight wilt, stunted
7 = severe wilt, stunted
9 = dead
Plants rated 0 are classified as resistant, 1 or 3 as intermediate, 5, 7, or 9 as susceptible.
No information. Experiments planned.
Using this method resistant and possibly intermediate plants can be transplanted to steam sterilized soil.
Paul H. Williams
Mary J. Palmer
Department of Plant Pathology
University of Wisconsin