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Role of Blossoms in Watermelon Seed Infestation by Acidovorax avenae subsp. citrulli

May 2003 , Volume 93 , Number  5
Pages  528 - 534

R. R. Walcott , R. D. Gitaitis , and A. C. Castro

First and third authors: Department of Plant Pathology, University of Georgia, Athens 30602; and second author: Department of Plant Pathology, The University of Georgia, Coastal Plain Experiment Station, Tifton 31793

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Accepted for publication 16 December 2002.

The role of watermelon blossom inoculation in seed infestation by Acidovorax avenae subsp. citrulli was investigated. Approximately 98% (84/87) of fruit developed from blossoms inoculated with 1 × 107 or 1 × 109 CFU of A. avenae subsp. citrulli per blossom were asymptomatic. Using immunomagnetic separation and the polymerase chain reaction, A. avenae subsp. citrulli was detected in 44% of the seed lots assayed, despite the lack of fruit symptoms. Furthermore, viable colonies were recovered from 31% of the seed lots. Of these lots, 27% also yielded seedlings expressing bacterial fruit blotch symptoms when planted under conditions of 30°C and 90% relative humidity. A. avenae subsp. citrulli was detected and recovered from the pulp of 33 and 19%, respectively, of symptomless fruit whose blossoms were inoculated with A. avenae subsp. citrulli. The ability to penetrate watermelon flowers was not unique to A. avenae subsp. citrulli, because blossoms inoculated with Pantoea ananatis also resulted in infested seed and pulp. The data indicate that watermelon blossoms are a potential site of ingress for fruit and seed infestation by A. avenae subsp. citrulli.

Additional keywords: Citrullus lanatus, Pseudomonas pseudoalcaligenes subsp. citrulli, stigma.

© 2003 The American Phytopathological Society