Evaluation of Gram-positive rhizosphere and endophytic bacteria for biological control of fungal rice (Oryzia sativa L.) pathogens

Abstract

Gram-positive bacteria isolated from the rhizosphere and inside the roots of rice were characterized for plant growth promoting (PGP) traits and antifungal activity against some rice plant pathogenic fungi of rice. The results showed the endophytic and rhizosphere isolates had different PGP traits and antifungal activity. Only one rhizosphere isolate and one endophytic isolate showed highly inhibitory effects against the mycelial growth of all fungal rice pathogens tested in this study. The best bacterial isolates, based on multiple PGP traits and inhibitory effects against the mycelial growth of all fungal rice pathogens, were identified. Based on biochemical tests and by comparison of 16S rDNA sequences, the endophytic isolate REN3 and the rhizosphere isolate REN4 were closely related to Bacillus cereus and Bacillus mojavensis respectively. The broad-spectrum antifungal strains, the REN3 and REN4 isolates analyzed here, exert multiple PGP and antagonistic activity and represent an excellent option to be used as either potent bio-promoting or bio-control agents in rice under in vitro conditions. This application may help to minimize dependence on pesticides, which have adverse effects on the environment, finally leading to have sustainable environments. In conclusion, the results of antifungal activity showed rice harbors bacteria with a good potential in biocontrol of rice fungal pathogens.