Disease suppression by the cyclic lipopeptides iturin A and surfactin from Bacillus spp. against Fusarium wilt of lettuce
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Iturin A and surfactin are antimicrobial cyclic lipopeptides secreted by antagonistic Bacillus strains, and both elicit defence gene expression in host plants. We previously showed that a soil amendment with either of the purified lipopeptides confers suppression against Fusarium yellows of tatsoi (Brassica rapa) caused by the soil-borne pathogen Fusarium oxysporum and that excess amounts of iturin A or surfactin do not confer suppression. Here, we evaluated the impacts of purified iturin A or surfactin against Fusarium wilt of lettuce (Lactuca sativa). As a soil amendment, iturin A and surfactin each conferred suppression of Fusarium wilt of lettuce on diverse lettuce cultivars similar to the results for tatsoi. However, higher concentrations of iturin A (1.88 mg/l of soil or higher) but not of surfactin (up to 7.5 mg/l of soil) negated the suppression. Growth of Fusarium in liquid cultures was suppressed by iturin A but not surfactin.
KeywordsLipopeptide Lettuce Fusarium Iturin A Surfactin Bacillus
We are grateful to Dr. Russell A. Scott for helpful discussions. We thank Dr. Masashi Fujinaga of the Nagano Vegetable and Ornamental Crops Experiment Station for providing Fusarium oxysporum f. sp. lactucae race 2 F9501. This study was funded by Japan Society for the Promotion of Science (KAKENHI 16K07628).
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Human and animal rights statement
This article does not contain any studies with human participants or animals performed by any of the authors.
Conflict of interest
The authors declare that they have no conflict of interest.
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