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Fungichromin Production by Streptomyces padanus PMS-702 for Controlling Cucumber Downy Mildew
Plant Pathol. J. 2019;35:341-350
Published online August 1, 2019
© 2019 The Korean Society of Plant Pathology.

Ya-Ting Fan1, Kuang-Ren Chung1* , and Jenn-Wen Huang1,2*

1Department of Plant Pathology, National Chung-Hsing University (NCHU), Taichung 40227, Taiwan
2Innovation and Development Center of Sustainable Agriculture (IDCSA), NCHU Taichung 40227, Taiwan
Correspondence to: Kuang-Ren Chung
Phone) +886-4-2284-0780 ext. 301, FAX) +886-4-2287-7585
E-mail) krchung@nchu.edu.tw
ORCID
https://orcid.org/0000-0002-2640-2951
Jenn-Wen Huang
Phone) +886-4-2284-0780 ext. 351, FAX) +886-4-2287-7585
E-mail) jwhuang@dragon.nchu.edu.tw
https://orcid.org/0000-0003-0798-4332
Received March 18, 2019; Revised April 23, 2019; Accepted May 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
Streptomyces padanus PMS-702 strain produces a polyene macrolide antibiotic fungichromin and displays antagonistic activities against many phytopathogenic fungi. In the present study, experimental formulations were assessed to improve the production of fungichromin, the efficacy of PMS-702 on the suppression of sporangial germination, and the reduction of cucumber downy mildew caused by Pseudoperonospora cubensis. PMS-702 strain cultured in a soybean meal-glucose (SMG) medium led to low levels of fungichromin accumulation and sporangial germination suppression. Increasing medium compositions and adding plant oils (noticeably coconut oil) in SMG significantly increased fungichromin production from 68 to 1,999.6 µg/ml. Microscopic examination reveals that the resultant suspensions significantly reduced sporangial germination and caused cytoplasmic aggregation. Greenhouse trials reveal that the application of PMS-702 cultural suspensions reduced downy mildew severity considerably. The addition of Tween 80 into the synthetic medium while culturing PMS-702 further increased the suppressive efficacy of downy mildew severity, particularly when applied at 24 h before inoculation or co-applied with inoculum. Fungichromin at 50 µg/ml induced phytotoxicity showing minor necrosis surrounded with light yellowish halos on cucumber leaves. The concentration that leads to 90% inhibition (IC90) of sporangial germination was estimated to be around 10 µg/ml. The results provide a strong possibility of using the S. padanus PMS-702 strain as a biocontrol agent to control other plant pathogens.
Keywords : bioformulation, biological control agent, polyene macrolide antibiotic, Pseudoperonospora cubensis, Streptomyces padanus


August 2019, 35 (4)
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