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Dry Heat and Hot Water Treatments for Disinfesting Cottonseed of Fusarium oxysporum f. sp. vasinfectum

December 2010 , Volume 94 , Number  12
Pages  1,469 - 1,475

Rebecca S. Bennett, Western Integrated Cropping Systems Research Unit, USDA-ARS, 17053 North Shafter Avenue, Shafter, CA 93263; and Patrick D. Colyer, Louisiana Agricultural Experiment Station, Red River Research Station, P.O. Box 8550, Bossier City 71113-8550



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Accepted for publication 30 July 2010.
ABSTRACT

The potential of low- and high-temperature dry heat, and hot water treatments, for disinfesting cottonseed of Fusarium oxysporum f. sp. vasinfectum was investigated. Naturally infected seeds from Louisiana were air-heated at 30, 35, and 40°C for up to 24 weeks. Seed harvested from bolls inoculated with race 4 of F. oxysporum f. sp. vasinfectum were incubated in dry heat at 60, 70, and 80°C for 2 to 14 days, or were immersed in 90°C water from 45 s to 3 min. The effects on seed germination and vigor of hot water treatment and a subset of the high-temperature dry heat treatments were also examined in seeds of a Pima (Gossypium barbadense) and an Upland (G. hirsutum) cultivar. Low- or high-temperature dry heat did not eliminate Fusarium spp. from the seed, although seed infection declined more rapidly with higher incubation temperatures. High-temperature dry heat treatments effective in eliminating fusaria also significantly reduced seed vigor in both the Pima and Upland cultivars. Seed from all times of immersion in hot water were less frequently infected with Fusarium spp. than nontreated seed. Incidence of seed infection did not differ significantly among immersion times ranging from 75 s to 3 min. Immersion in 90°C water did not reduce germination or vigor at exposure times ≤120 s and ≤150 s for seeds of Pima and Upland cotton, respectively. Results from the hot water treatments suggest that thermotherapy may be optimized to provide a tactic to prevent the spread of virulent F. oxysporum f. sp. vasinfectum genotypes into uninfested areas through infected seed.



This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 2010.