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Disease Note. Race 2 of Fusarium oxysporum f. sp. apii New to Ontario. R. F. Cerkauskas, Agriculture Canada, Vineland Station, Ontario L0R 2E0. M. R. McDonald, O.M.A.F., Muck Research Station, Kettleby, Ontario L0G 1J0. Plant Dis. 73:859. Accepted for publication 19 June 1989. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0859B. Fusarium yellows of celery (Apium graveolens L. var. dulce (Miller)
Pers.), caused by Fusarium oxysporum Schlect. emend. Snyd. & Hans.
f. sp. apii (Nels. & Sherb.), was observed in four fields in Bradford
Marsh, Ontario, in 1988. Affected plants showed stunting, yellowing,
brown internal discoloration, and necrosis of crown and vascular tissue
(2). Isolations from affected crown tissue using a selective medium
(1) consistently yielded F. oxysporum. Four-week-old plants of
cultivars Golden Plume (yellow type), Florida 683, Surepak, Tall-Utah
(TU) 52-70 HK, TU 52-70 R-Imp., and TU 52-75 (green types)
were transplanted in pasteurized greenhouse soil mix and inoculated
by pouring 25 ml of a spore suspension (5 X 105 spores per milliliter)
around the roots of each plant (one plant per pot, three replicates).
All cultivars showed characteristic symptoms (crown discoloration)
of Fusarium yellows after 6 wk. F. oxysporum was reisolated from
diseased plants. The Ontario isolates are designated as F. o. f. sp.
apii race 2 on the basis of susceptibility of both yellow and green
cultivars. This new race poses a threat to celery production in Ontario. |