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Screening and Evaluation of the Potential Bacterial Antagonists for Controlling the Bacterial Soft Rot of Chinese Cabbage
Effects of the inoculation with the different concentrations [colony-forming unit (CFU) mL<sup>-1</sup>] of <i>Pectobacterium</i> <i>carotovorum</i> subsp. <i>carotovorum</i> Pcc10602 on (A) the growth of the Chinese cabbage and (B) the disease severity of bacterial soft rot. Disease severity (%) = Σ(disease index × numbers of leaf tissue for this index)/(5 × total numbers of leaf tissue) × 100%. DAI: Day after inoculation.
Effects of the inoculation with the different concentrations [colony-forming unit (CFU) mL-1] of Pectobacterium carotovorum subsp. carotovorum Pcc10602 on (A) the growth of the Chinese cabbage and (B) the disease severity of bacterial soft rot. Disease severity (%) = Σ(disease index × numbers of leaf tissue for this index)/(5 × total numbers of leaf tissue) × 100%. DAI: Day after inoculation.

Author:Chun-Wei Chen*, Yu-Yao Fu, Chia-Hsin Tsai and Tsung-Chun Lin

Abstract:

The bacterial soft rot caused by Pectobacterium carotovorum subsp. carotovorum (Pcc) is one of the destructive diseases of Chinese cabbage in Taiwan. The purpose of this study was to screen and evaluate the potential antagonists for control of this disease. The six Bacillus spp. isolates, AC35, BAC15, NA0301, HTT-11, HTT-61, and HTT-62, showed superior antagonistic ability against Pcc strain Pcc10602. Thus, the effect on controlling this disease was evaluated on leaf tissue of Chinese cabbage by using puncture and spray method. The results showed that the disease severity of Pcc10602 inoculated-only were 100% at the 5th day after inoculation (DAI 5) by using two different methods. In addition, Bacillus amyloliquefaciens isolates BAC15, HTT-61, and HTT-62 significantly reduced the disease severity to 52.4%, 57.1%, and 57.1% at DAI 5 by using puncture method, respectively. In the greenhouse test, the B. amyloliquefaciens HTT-62 was applied to Chinese cabbage with using different methods (cotton-cover method and spray method). After 1 day, Pcc10602 was subsequently applied by the same method. The results revealed that the disease severity of the control treatment was 97.9% and 74.5% at DAI 12 by two different methods, respectively, while the disease severity of the treatment with HTT-62 was only 47.5% and 30.2%, respectively. Therefore, it is speculated that B. amyloliquefaciens HTT-62 can delay the occurrence of soft rot and reduce disease severity on cabbage in any way one day before inoculation. This study revealed that B. amyloliquefaciens HTT-62 is a potential antagonist to control the bacterial soft rot of Chinese cabbage.

Key words:Chinese cabbage, Bacterial soft rot, Biocontrol, Bacillus

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