Investigating the Potential of Streptomyces spp. in Suppression of Rhizoctonia solani (AG1-IA) Causing Rice Sheath Blight Disease in Northern Iran

A study was conducted in the Guilan Province of Iran, using a variety of Actinomycetes species isolated from the rice fields, with the intention of identifying useful biocontrol agents to lessen rice sheath blight disease. The antagonistic effects against the rice pathogen agent were also assessed both in vitro and in vivo. The antifungal abilities of more than 30 Actinomycetes isolates against the Rhizoctonia solani Kühn (AG1-IA) were used. The biocontrol abilities of the most active isolates were studied in a greenhouse. The size of the inhibition zone against pathogen development and the most potent antagonist Actinomycetes isolates were determined based on the dual culture screening test findings. The ability to create hydrolytic enzymes including amylase, chitinase, protease, and lipase were shown by hydrolytic enzyme assays on the putative antagonists. Antifungal activities of Streptomyces isolates against fungus mycelia were also studied using SEM since, compared to the control grown mycelia and mycelia adjacent to the inhibition zone in the plate, tests revealed an unusual and deformed structure; in our opinion, the chitinase secreted can destroy fungal mycelium. Chloroform test showed that its antifungal effect persists upon exposure to chloroform. All possible isolates belonged to the Streptomyces species, according to the 16S rDNA molecular analysis of the majority of active isolates. Comparing isolates, G had the highest impact in reducing sheath blight disease. The Iranian strain of the Streptomyces has antifungal capabilities, highlighting its potential as a viable biocontrol agent to be used in an Integrated Disease Management (IDM) program to control the rice sheath blight disease. © 2022 by the authors.