Abstract
Cucumber is a common vegetable all over the world; however, its production is seriously affected by cucumber downy mildew caused by Pseudoperonospora cubensis. Endophytes have great potential to control such fungal diseases. The aim of the study was to isolate, screen and identify endophytic bacteria, which show antagonistic activity to downy mildew, in cucumbers. Here, surface sterilized leaves were used for endophytic bacteria isolation. All the isolates were further screened for the antagonistic activities against P. cubensis by leaf discs assay, separate leaves assay and sporangia releasing inhibition assay. The control efficacies of the endophytic bacteria (screened above) were finally evaluated through field tests. In this study, a total of 81 endophytic bacteria were isolated from cucumber leaves sampled at blossoming and fruiting stages, respectively, among which, six (strains CE1, CE8, CE9, Y1, Y2 and Y22) were tested for their strong antagonistic activity in vitro. In the field test, strain CE8, identified as belonging to Bacillus sp. based on 16S rDNA phylogenetic analysis, showed a strong control efficacy of 42.1 %, a value almost two times as high as that using 69 % metalaxyl-mancozeb WG, a widely used antifungal chemical in China. Based on the results above, CE8 was finally screened out for its great potential in cucumber downy mildew control, implicating a powerful value of the strain in the production practice.
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Acknowledgments
This work was supported by the National Natural Science Foundation of China (No. 31170035) and the Natural Science Foundation of Shandong (No. ZR2010CQ042). We thank Mr. Yunfu Wang for providing cucumber plants and Dr. Wenqiao Wang and Runjie Meng (Institute of Plant Protection, Hebei Academy of Agricultural and Forestry Sciences, Baoding, China) for their technical assistance. We also thank Ms Lauren Stirling (Chinese Academy of Agricultural Sciences) and Dr. Kai Ding (Department of Civil and Environmental Engineering, Villanova University, USA) for their assistance in the correction of the manuscript.
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Sun, ZB., Yuan, XF., Zhang, H. et al. Isolation, screening and identification of antagonistic downy mildew endophytic bacteria from cucumber. Eur J Plant Pathol 137, 847–857 (2013). https://doi.org/10.1007/s10658-013-0293-5
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DOI: https://doi.org/10.1007/s10658-013-0293-5