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Accumulation of Elsinochrome Phytotoxin does not Correlate with Fungal Virulence among Elsinoë fawcettii Isolates in Florida

Authors

  • Li-Yuan Wang,

    1. Authors’ addresses: 1Citrus Research and Education Center, Institute of Food and Agricultural Sciences (IFAS), University of Florida, 700 Experiment Station Rd., Lake Alfred, FL 33850, USA; 2Department of Plant Protection, Chiayi Experiment Station, Taiwan Agricultural Research Institute, 2 Min-Cheng Road, Chiayi 60014, Taiwan; 3Department of Biotechnology, Transworld Institute Technology, Douliu, 640 Taiwan (correspondence to Kuang-Ren Chung. E-mail: krchung@ufl.edu)
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  • 1,2 Huey-Jiunn Bau,

    1. Authors’ addresses: 1Citrus Research and Education Center, Institute of Food and Agricultural Sciences (IFAS), University of Florida, 700 Experiment Station Rd., Lake Alfred, FL 33850, USA; 2Department of Plant Protection, Chiayi Experiment Station, Taiwan Agricultural Research Institute, 2 Min-Cheng Road, Chiayi 60014, Taiwan; 3Department of Biotechnology, Transworld Institute Technology, Douliu, 640 Taiwan (correspondence to Kuang-Ren Chung. E-mail: krchung@ufl.edu)
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  • and 3 Kuang-Ren Chung 1

    1. Authors’ addresses: 1Citrus Research and Education Center, Institute of Food and Agricultural Sciences (IFAS), University of Florida, 700 Experiment Station Rd., Lake Alfred, FL 33850, USA; 2Department of Plant Protection, Chiayi Experiment Station, Taiwan Agricultural Research Institute, 2 Min-Cheng Road, Chiayi 60014, Taiwan; 3Department of Biotechnology, Transworld Institute Technology, Douliu, 640 Taiwan (correspondence to Kuang-Ren Chung. E-mail: krchung@ufl.edu)
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Abstract

Citrus scab caused by Elsinoë fawcettii is cosmopolitan in humid citrus-growing areas. We have previously demonstrated that production of non-host selective elsinochrome phytotoxin is a prerequisite for fungal full virulence and lesion formation. In this study we evaluated 71 field-collected isolates from Florida for pathogenicity and toxin production and found most of the isolates to be pathogenic to rough lemon, grapefruit and sour orange and able to produce elsinochromes in axenic culture. Elsinochromes were recovered, for the first time, from leaf lesions infected by 21 isolates, including four isolates that did not produce any measurable toxin in culture. There was no direct correspondence between the level of elsinochrome production in culture and virulence among the isolates. However, Elsinoë isolates failed to produce elsinochromes in culture and in planta were non-pathogenic to citrus hosts tested. Several isolates were non-pathogenic or only moderately virulent to the citrus hosts tested even though they could produce elsinochromes in culture, a phenotype not previously described in Florida.

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