Plant growth-promoting endophytes from Stevia rebaudiana identified to possess bio-control potential against maize sheath blight pathogen Rhizoctonia solani.

The phytopathogenic fungus Rhizoctonia solani distributed worldwide is one of the most serious fungal pathogens causing a wide range of plant diseases. Therefore, the present study was conducted to select endophytes from Stevia rebaudiana with biocontrol potential against Rhizoctonia solani causing sheath blight disease in maize. Out of 22 distinct bacterial endophytes from Stevia rebaudiana leaves, three bacteria showed growth inhibition of R. solani varying from 61-86% singly or in combinations. Scanning electron microscopy showed stripping of fungal hyphae leading to accumulation of debris in the presence of the antagonistic bacterial endophytes. The isolates were identified as Ochrobactrum ciceri SR₁EB_1,Achromobacter spanius SR₁EB₁₁ and Bacillus licheniformis SR₂EB₅ based on 16S rRNA gene sequencing. The strains were also tested positive for phosphate and zinc solubilization; production of auxins and ammonia; and hydrolysis of cellulose and starch. These bacterial strains exhibited disease control ranging from 66-83%, and also increased the vigour index, root length, shoot length and dry weight up to 273%, 64%, 40% and 47%, respectively, over the uninoculated control in maize grown under greenhouse conditions. The treatment OcSR₁EB₁+ AsSR₁EB₁₁+ BlSR₂EB₅ showed 2.75, 0.56, and 2.83% N, P and K content, respectively, which was the highest among all the treatments. Ochrobactrum ciceri as an endophyte from Stevia rebaudiana is reported here for the first time. The results indicated that Ochrobactrum ciceri SR₁EB_1,Achromobacter spanius SR₁EB₁₁ and Bacillus licheniformis SR₂EB₅ hold the potential to be used as biocontrol agents in controlling the sheath blight disease in maize. [ABSTRACT FROM AUTHOR]