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Efficacy of Seed Treatments on Viability of Fusarium oxysporum f. sp. vasinfectum race 4 in Infected Cotton Seed.
H. DOAN (1), R. M. Davis (2). (1) Univ of California, Davis, CA, U.S.A.; (2) University of California, Davis Department of Plant Pathology, Davis, CA, U.S.A.

Fusarium wilt caused by <i>Fusarium oxysporum </i>f. sp. <i>vasinfectum</i> ( FOV) race 4 is found in an increasing number of fields in California, due at least in part, to seedborne dissemination. The disease can quickly become epidemic as residue from infected plants release numerous propagules into the soil, potentially increasing disease severity in subsequent cotton crops. Detection of the pathogen in seed is possible with race 4-specific primers, but due to the relatively large size of cotton seed and the high plant densities used in cotton production, sampling a seedlot makes seed assays problematic. The aim of this study was to evaluate efficacy of hot water treatments alone or in conjunction with fungicides, potato dextrose broth, bleach, or sodium lauryl sulfate treatments on viability of FOV in infected cotton seeds. To determine the best temperatures and times combination to treat seeds, a series of hot water treatments from 55 to 90 ºC for various lengths of time were evaluated. Seed of all tested varieties remained viable and lost no seedling vigor after immersion in hot water at 60°C for 20 minutes. In the 20 minutes at 60°C hot water bath, seed infection was reduced from 39.2 % to 15.6%. When seed were pre-treated in potato dextrose broth for 1 hour at 23°C (100 rpm) followed by 20 minutes at 60°C hot Topsin® fungicide bath, seed infection was reduced from 39.2 % to 15.6%.

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