Molecular Identification and In-Vitro Screening of the Isolated Rhizobacteria in Organic Farm Against Rhizoctonia solani Kuhn

this study determined the in vitro effect of isolated rhizobacteria from rice rhizosphere against the rice fungal pathogen Rhizoctonia solani. The antagonistic effects of rhizobacteria against R. solani were assessed using the dual culture technique and scanning electron microscopy for the mode of action and interaction. Among the nine rhizobacteria isolates, seven belong to the genus Bacillus and one belongs to the genus Lysinibacillus, while one isolate, RM-W3-5, and is unknown. The isolated rhizobacteria were identified as B. pumilus, B. megaterium, B. cereus, B. amyloliquefaciens, Bacillus sp., B. rhizosphaerae, B. clausii, and L. macroides. The results from the dual culture method showed that the rhizobacterial isolates reduced the growth of R. solani by between 8.9% and 82.61%. The highest mycelial growth inhibition (MGI) of 82.61% was obtained from R. solani paired with B. pumilus, while the lowest MGI of 8.9% was obtained from B. clausii. The interactions between RM-W3-5 and B. pumilus against R. solani were examined using a scanning electron microscope (SEM) because these two isolates performed well in the dual culture test. Isolate RM-W3-5 paired to R. solani showed the structural alterations such as shrinking, shriveling of the hyphae, and hyphal disintegration. A similar occurrence was observed when R. solani was paired with B. pumilus. The results of the present study suggest that B. pumilus and RM-W3-5 are potential biological control agents against R. solani. However, supplementary analysis has to be done to validate the potential of these rhizobacteria.