Screening and Application of Bacillus Strains Isolated from Nonrhizospheric Rice Soil for the Biocontrol of Rice Blast

Abstract

Rice blast, caused by Magnaporthe oryzae, is one of the most destructive rice diseases worldwide. The aim of this study was to screen bacterial isolates to efficiently prevent the occurrence of rice blast. A total of 232 bacterial isolates were extracted from nonrhizospheric rice soil and were screened for antifungal activity against M. oryzae using a leaf segment assay. Strains S170 and S9 showed significant antagonistic activity against M. oryzae in vitro and in leaf disk assays, and controlled M. oryzae infection under greenhouse conditions. The results showed that strains S170 and S9 could effectively control rice leaf blast and panicle neck blast after five spray treatments in field. This suggested that the bacterial strains S170 and S9 were valuable and promising for the biocontrol of rice disease caused by M. oryzae. Based on 16S rDNA, and gyrA and gyrB gene sequence analyses, S170 and S9 were identified as Bacillus amyloliquefaciens and B. pumilus, respectively. The research also demonstrated that B. amyloliquefaciens S170 and B. pumilus S9 could colonize rice plants to prevent pathogenic infection and evidently suppressed plant disease caused by 11 other plant pathogenic fungi. This is the first study to demonstrate that B. amyloliquefaciens and B. pumilus isolated from nonrhizospheric rice soil are capable of recolonizing internal rice stem tissues.

Characterization of a Bacillus velezensis strain isolated from Bolbostemmatis Rhizoma displaying strong antagonistic activities against a variety of rice pathogens

“…Currently, there have been numerous reports about the antagonistic effects and biocontrol efficacies of B. velezensis strains on M. oryzae, some of which were registered as the bacterial pesticides used in rice production (Chen et al, 2021). From our dual culture tests, B. velezensis BR-01 has an 83.7% relative inhibition rate on M. oryzae, which is comparable to most of other B. velezensis strains on M. oryzae (Sha et al, 2020;Chakraborty et al, 2021). B. velezensis BR-01 also showed antifungal activity against U. virens and F. fujikuroi, with relative inhibition rates 96.6 and 57.9%, respectively.…”

Screening of endophytic fungi as potential antagonistic agents of Pyricularia oryzae and evaluation of their ability in producing hydrolytic enzymes

“…This activity may induce cell wall damage and degradation. Sha et al (2020) reported that P. oryzae P131 cells treated with Bacillus pumilus strain S9 and Bacillus amyloliquefaciens strain S170 had peculiar cell morphology and disruption, indicating that they degrade the cell walls, destroy cell membranes, and damage cellular organelles. In the measurement of chitinase, the standard curve created by NAG was used to determine the reducing sugar concentration of NAG released in colloidal chitinsupplemented medium (Agrawal and Kotasthane 2012).…”

Multi-Omics Techniques for Analysis Antifungal Mechanisms of Lipopeptides Produced by Bacillus velezensis GS-1 against Magnaporthe oryzae In Vitro

“…B. velezensis CE 100 could simultaneously control Phytophthora root rot diseases and enhance growth of Chamaecyparis obtusa seedlings [ 13 ]. Bacillus amyloliquefaciens S170 and B. pumilus S9 isolated from nonrhizospheric rice soil showed significant antagonistic activity against M. oryzae in vitro and in leaf disk assays [ 15 ]. Zhou found Bacillus cereus YN917, obtained from a rice leaf with remarkable antifungal activity against M. oryzae , and exhibited multiple plant growth-promoting and disease prevention traits [ 16 ].…”