Two imide substances from a soil-isolated Streptomyces atratus strain provide effective biocontrol activity against grapevine downy mildew |
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Authors: | Chunhao Liang Chaoqun Zang Mark I McDermott Kuihua Zhao Shuyi Yu |
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Institution: | 1. College of Plant Protection, Shenyang Agricultural University, Shenyang, People’s Republic of China;2. Institute of Plant Protection, Liaoning Academy of Agricultural Sciences, Shenyang, People’s Republic of China;3. Institute of Plant Protection, Liaoning Academy of Agricultural Sciences, Shenyang, People’s Republic of China;4. Department of Molecular and Cellular Medicine, Texas A&5. M Health Science Center, College Station, TX, USA |
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Abstract: | Grapevine downy mildew (Plasmopara viticola) is a devastating disease of grapevine. In this study, 151 actinomycete isolates were obtained and tested for antagonistic activity against P. viticola. The assay suggested that 28 isolates displayed antagonistic effects to varying degrees. The greatest reduction in disease severity was observed with isolate PY-1, which reduced disease severity by 92.13% in the detached leaf assay, and by 83% in a field assay. It was identified as Streptomyces atratus using the 16S rDNA sequence analysis. To elucidate the antagonistic mechanism of PY-1 against P. viticola, scanning electron microscopy showed that major damage to the pathogens sporangia and sporangiophores was observed after treatment for PY-1. Furthermore, PY-1 showed antagonistic activity against other pathogens, including: Botrytis cinerea, Colletotrichum orbiculare, Fusarium oxysporum, Phytophthora capsici and Phytophthora infestans. Two imide compounds were purified from the fermentation liquid using silica gel chromatography and high-performance liquid chromatography and identified as 5-acetoxycycloheximide and cycloheximide using nuclear magnetic resonance. Both compounds showed significant antagonistic activity against P. viticola, determining a reduction in disease severity by 65% and 84%, respectively. In conclusion, 5-acetoxycycloheximide and cycloheximide were identified for the first time in a new S. atratus strain able to effectively control grapevine downy mildew. |
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Keywords: | Antimicrobial spectrum biological control cycloheximide 5-acetoxycycloheximide Plasmopara viticola Streptomyces atratus |
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