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Biocontrol of Citrus Canker Disease Caused by Xanthomonas citri subsp. citri Using an Endophytic Bacillus thuringiensis
Plant Pathol. J. 2019;35:486-497
Published online October 1, 2019
© 2019 The Korean Society of Plant Pathology.

Md. Nurul Islam1†, Md. Sarafat Ali1†, Seong-Jin Choi2, Jae-Wook Hyun3, and Kwang-Hyun Baek1*

1Department of Biotechnology, Yeungnam University, Gyeongsan 38541, Korea
2Department of Biotechnology, Catholic University of Daegu, Gyeongsan 38430, Korea
3Citrus Research Station, National Institute of Horticultural and Herbal Science, Rural Development Administration, Seogwipo 63607, Korea
Correspondence to: Phone) +82-53-810-3029, FAX) +82-53-810-4769
E-mail) khbaek@ynu.ac.kr
These authors contributed equally to this work.

Handling Editor : Sang, Mee Kyung
Received March 20, 2019; Revised July 5, 2019; Accepted August 12, 2019.
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
Citrus canker is a devastating disease of citrus caused by Xanthomonas citri subsp. citri (Xcc). A total of 134 endophytic bacteria were isolated from various gymnospermic and angiospermic plants. They were screened for their antagonistic activities against three wild-type and six streptomycin-resistant Xcc strains. TbL-22 and TbL-26, both later identified as Bacillus thuringiensis, inhibited all the wild and resistant Xcc strains. TbL-22 exerted the highest antagonistic activity against XccW3 and XccM6 with inhibition zones of 20.64 ± 0.69 and 19.91 ± 0.87 mm, respectively. Similarly ethyl acetate extract of TbL-22 showed highest inhibition zones 15.31 ± 2.08 and 19.37 ± 3.17 mm against XccW3 and XccM6, respectively. TbL-22 reduced canker incidence on infected leaves by 64.05% relative to positive controls. Scanning electron microscopy revealed that the cell membranes of Xcc treated with ethyl acetate extract of TbL-22 were ruptured, lysed, and swollen. B. thuringiensis TbL-22 can effectively and sustainably controls streptomycin-resistant citrus canker.
Keywords : Bacillus thuringiensis, biocontrol, citrus canker, endophytic bacteria


October 2019, 35 (5)
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