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Detoxification of Fusaric Acid by a Fusaric Acid-Resistant Mutant of Pseudomonas solanacearum and its Application to Biological Control of Fusarium Wilt of Tomato. Hideyoshi Toyoda, Laboratory of Plant Pathology, Department of Agriculture, Kinki University, Higashi-osaka 577, Japan; Hisako Hashimoto(2), Ryutaro Utsumi(3), Hidetaka Kobayashi(4), and Seiji Ouchi(5). (2)(4)(5)Laboratory of Plant Pathology, Department of Agriculture, Kinki University, Higashi-osaka 577, Japan; (3)Laboratory of Biological Chemistry, Kinki University, Higashi-osaka 577, Japan. Phytopathology 78:1307-1311. Accepted for publication 27 April 1988. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/Phyto-78-1307.

Bacteria capable of detoxifying fusaric acid were isolated and tested for their ability to protect tomato plants from the wilting disease caused by Fusarium oxysporum f. sp. lycopersici Race 1. The bacteria used were fusaric acid-resistant mutants derived from an avirulent strain of Pseudomonas solanacearum. The capability of the bacteria to detoxify fusaric acid was assayed by incubating tomato callus cultures in filtrates of bacteria that had been grown in the presence of fusaric acid. Gas chromatography indicated that the detoxification of fusaric acid by the bacteria could be due to changes in the carboxyl group in the position alpha to the nitrogen of the compound. Fusaric acid detoxification was also demonstrated by protection of tomato leaf cuttings that had been treated with bacteria before treatment with fusaric acid. Intact tomato plants were protected from wilt when they were pretreated with fusaric acid-detoxifying bacteria before inoculation with the pathogenic fungus. These results suggest that fusaric acid is important in symptom development of wilting disease of tomato, and our approach shows promise for biocontrol.