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Ecology and Epidemiology

The Association of Fusarium oxysporum f. sp. betae with Nonprocessed and Processed Sugarbeet Seed. J. D. MacDonald, Graduate Research Assistant, Department of Plant Pathology, University of California, Davis 95616; L. D. Leach, Professor Emeritus, Department of Plant Pathology, University of California, Davis 95616. Phytopathology 66:868-872. Accepted for publication 9 January 1976. DOI: 10.1094/Phyto-66-868.

A blight that is caused by Fusarium oxysporum f. sp. betae in sugarbeet (Beta vulgaris) seed plants occurs in the Willamette Valley of Oregon. Seeds collected from severely diseased plants were infested with the pathogen at a level of 0.45% and 0.23% of the seed from a heavily diseased commercial planting carried the pathogen. Fusarium was eliminated from seed by surface disinfestation in NaOCl or repeated washing with sterile distilled water, which indicated that its presence on sugarbeet seed was as an external contaminant. Commercial processing of sugarbeet seed, in which superficial tissues are milled away and discarded, significantly reduced the percentage of infested seed. Although the pathogen was found on seed, seedlings produced from naturally infested seed planted in pasteurized greenhouse soil were not diseased. Although highly susceptible seed-bearing parents may be severely diseased, the low level of seed-borne inoculum and relatively greater resistance of hybrid cultivars appears to make the transmission of this pathogen less efficient than that of other seed-borne wilt fusaria.