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ARS Home » Southeast Area » Charleston, South Carolina » Vegetable Research » Research » Publications at this Location » Publication #372720
Research Project: Biological, Genetic and Genomic Based Disease Management for Vegetable Crops

Location: Vegetable Research

Title: Identifying races of Fusarium oxysporum f. sp. niveum in South Carolina recovered from watermelon seedlings, plants, and field soil

Author
item KEINATH, ANTHONY - Clemson University
item DUBOSE, VIRGINIA - Clemson University
item Katawczik, Melanie
item Wechter, William - Pat

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/16/2020
Publication Date: 8/26/2020
Citation: Keinath, A.P., Dubose, V.B., Katawczik, M.L., Wechter, W.P. 2020. Identifying races of Fusarium oxysporum f. sp. niveum in South Carolina recovered from watermelon seedlings, plants, and field soil. Plant Disease. 104:2481-2488. https://doi.org/10.1094/PDIS-11-19-2385-RE.
DOI: https://doi.org/10.1094/PDIS-11-19-2385-RE

Interpretive Summary: Fusarium wilt of watermelon is the most serious disease of watermelon in South Carolina and other southeastern U. S. states. Isolates of the pathogen collected from field-grown plants, greenhouse-grown seedlings, and field soil between 1999 and 2018 were inoculated onto three differential watermelon cultivars to identify races. Of 197 isolates obtained from plants, 12% were non-pathogenic, 2% were race 0, 23% were race 1, and 64% were race 2. Race-specific molecular markers were 66% successful at confirming pathogen races compared to standard plant inoculation-based race identification. Because a majority of the F. oxysporum f. sp. niveum isolates from South Carolina was race 2, integrated management practices should be used until commercial cultivars with resistance to race 2 are available.

Technical Abstract: Fusarium wilt of watermelon (Citrullus lanatus), caused by the soilborne fungus Fusarium oxysporum f. sp. niveum, is the most serious disease of watermelon in South Carolina and other southeastern U. S. states. Isolates of F. oxysporum collected from field-grown plants, greenhouse-grown seedlings, and field soil between 1999 and 2018 were inoculated onto three differential watermelon cultivars to identify races. Of 197 isolates obtained from plants, 12% were non-pathogenic, 2% were race 0, 23% were race 1, and 64% were race 2. One collection of isolates from greenhouse seedlings was exclusively race 1 and the other was exclusively race 2. Seventeen of 81 soil isolates were pathogenic: five were race 1 and 12 were race 2. Reactions of C. amarus PI 296341-FR, Carolina Strongback, and SP-6, cultigens with resistance to race 2, did not differ significantly among five highly virulent race 2 isolates and a standard race 2 isolate, indicating a lack of a race 3 phenotype. Forma specialis-specific primers matched phenotypic race identification for 74% of the isolates. Race-specific primers based on a secreted-in-xylem elicitor present in race 0 and 1 isolates matched phenotypic race identification for 66% of the isolates. Because a majority of the F. oxysporum f. sp. niveum isolates from South Carolina was race 2, integrated management practices should be used until commercial cultivars with resistance to race 2 are available.