Document Type : Original Article- Persian
Authors
1
Department of Biology, CT.C, Islamic Azad University, Tehran, Iran
2
Department of Microbial Biotechnology, Agricultural Biotechnology Research Institute of Iran (ABRII), Agricultural Research, Education and Extension Organization (AREEO), Karaj, Iran
3
Plant Pathology Department, Iranian Research Institute of Plant Protection, Agricultural Research, Education and Extension Organization (AREEO), Karaj, Iran
4
Department of Microbial Biotechnology, Agricultural Biotechnology Research Institute of Iran (ABRII), Agricultural Research, Education and Extension Organization (AREEO), Karaj, Iran Department of Chemical and Biological Technologies, CT.C, Islamic Azad University, Tehran, Iran
Abstract
Despite Capsicum annuum L. being one of the most valuable greenhouse crops, soil-borne diseases, especially root rot caused by Rhizoctonia solani, are significant limitations to its productivity. In this study, the ability of 13 selected actinomycete strains to inhibit the growth of R. solani mycelia in vitro and to control the disease in a greenhouse setup was evaluated in comparison with the chemical fungicide tebuconazole on three commercial bell pepper cultivars (Scarlet, Lomus, and Semer). Results of dual culture assays revealed that all strains significantly suppressed fungal growth, with the highest suppression recorded for strains 603 (80%) and 3513 (70%). In the greenhouse experiments, strain 603 significantly increased the root dry weight and decreased disease severity in the Semer cultivar from 60% in the infected control to less than 30%. In the Scarlet cultivar, the maximum protective index was recorded for strain 3513, while in the Lomus cultivar, both strains outperformed the fungicide treatment. In addition, seedling mortality due to the disease was reduced to zero in plants treated with either bacterial strain. Both strains demonstrated iron-chelating activity and were non-hemolytic. Results of molecular analysis indicated that strain 603 has the potential to induce plant defense responses through upregulation of the GST gene. In conclusion, the results of this study clearly showed that strains 603 and 3513 significantly reduced (p < 0.05) disease severity and disease-induced mortality while improving plant growth parameters, thus establishing their excellent potential as biocontrol agents for the effective management of Rhizoctonia damping-off in bell pepper.
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