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Efficacy of Acibenzolar-S-methyl and Its Induced Resistance Mechanism in Controlling Citrus Canker
Sensitivity to copper on mannitol glutamate yeast (MGY) medium and detection of copper resistant genes from the <i>Xanthomonas citri</i> subsp. <i>citri</i> strains. (A) Growth of copper resistant strain Xcc1023, copper tolerant strains Xcc1954 and Xcc1808 on MGY medium supplemented with different concentrations of copper. (B) PCR amplification of copper resistance gene fragments of <i>copL</i> (356 bp), <i>copA</i> (870 bp) and <i>copB</i> (531 bp) from <i>Xanthomonas citri</i> subsp. <i>citri</i> strains. Lane M: 1 kb DNA ladder. lanes 1 and 2, copper resistant strain Xcc1004 and Xcc1023. lanes 3, 4 and 5, copper tolerant strains Xcc1942, Xcc1954 and Xcc1808.
Sensitivity to copper on mannitol glutamate yeast (MGY) medium and detection of copper resistant genes from the Xanthomonas citri subsp. citri strains. (A) Growth of copper resistant strain Xcc1023, copper tolerant strains Xcc1954 and Xcc1808 on MGY medium supplemented with different concentrations of copper. (B) PCR amplification of copper resistance gene fragments of copL (356 bp), copA (870 bp) and copB (531 bp) from Xanthomonas citri subsp. citri strains. Lane M: 1 kb DNA ladder. lanes 1 and 2, copper resistant strain Xcc1004 and Xcc1023. lanes 3, 4 and 5, copper tolerant strains Xcc1942, Xcc1954 and Xcc1808.

Author:Ching-Yi Lin* and Hui-Ju Lin

Abstract:

     Citrus canker caused by Xanthomonas citri subsp. citri (Xcc) is one of the most economically important bacterial disease in the international citrus industry. The copper-based bactericides were widely use to or control citrus canker. However, frequent applications of copper-based bactericides induce the development of bacterial strains either resistant or tolerant to copper. In this study, Xcc strains were collected from citrus orchards in Yunlin and Chiayi of Taiwan and used to assess the sensitivity to copper on a solid medium. The tests identified two copper resistant strains and 46 copper tolerant strains. Copper resistance in plant pathogenic bacteria contributes to a failure to control plant bacterial diseases by copper bactericides. In view of this, it is necessary to develop alternative control methods for sustainable agricultural practices. In this study, the individual and combined effects of acibenzolar-S-methyl (ASM) and 4-4 bordeaux mixture (Bor) were investigated in a greenhouse to control citrus canker disease. Three treatments were conducted on potted lemon (Citrus limon) seedlings: soil drench with 5 mg a.i. ASM, foliar spray with Bor, and a combination of the above two treatments (ASM + Bor). The lemon seedlings were inoculated with Xcc 3 d post treatments. The results showed that the disease severities of ASM, Bor and ASM + Bor were 19.14%, 15.0%, and 15.4%, respectively, which were significantly different from the untreated control (39.96%). For the defence-related enzyme activity assay, progressive increases in peroxidase and catalase activities were found in lemon seedlings treated with ASM alone. Our results suggested that ASM was effective in reducing canker disease severity, mainly through enhancing the activities of peroxidase and catalase in planta.

Key words:Acibenzolar-S-methyl, Citrus, Citrus canker

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Journal of
Taiwan Agricultural Research
Vol. 72, No.3 (2023) ISSN: 2790-086X Vol. 72, No.3 (2023)
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