Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 9/14/2007
Publication Date: 10/26/2007
Citation: Baze, K.D., Fish, W.W., Bruton, B.D. 2007. The development and application of a plant bioassay to elucidate toxic principles directed at watermelon by Fusarium Oxysporum f. sp. niveum [abstract]. Oklahoma Research Day, October 26, 2007, Edmond, Oklahoma. Paper No. 06.01.16. Interpretive Summary:
Technical Abstract: Formae speciales of Fusarium oxysporum cause wilt and death of numerous agronomic crops worldwide. The objective of this research was to develop a bioassay for Fusarium toxins directed toward watermelon. Watermelon seedlings were grown to the two leaf stage; the roots were washed and trimmed. Two seedlings were placed in a 7 mL polypropylene vial containing the appropriate medium. Four plants were utilized for each treatment and controls. Constant light was provided 15 cm above the plants at a temperature of 20 to 25 C. Plants were evaluated and photographed daily over a period of 4 to 7 days. Cotyledons, leaves, stems, and roots were individually assigned a rating from 1 (healthy) to 5 (dead) to quantify plant response. A dose response experiment employing the bioassay was performed with fusaric acid, a mycotoxin believed to be associated with some Fusarium wilts. Rates of seedling wilt and/or death were observed to be proportional to concentration of fusaric acid. Two highly pathogenic isolates of F. oxysporum f. sp. niveum were grown in shake flask culture. The combined results from fusaric acid analyses and bioassay of the mycelia/spore-free media demonstrated that one of the races produced fusaric acid as a primary toxin while the other produced a different toxic principle(s). Using this bioassay procedure, toxins can be identified based on rate and severity of specific plant responses.