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• Several endophytic bacteria were identified as Bacillus species using molecular analysis. • Endophytic bacteria identified have antagonistic activity against Ralstonia solanacearum. • These strains produce VOCs with antibacterial activity. • These VOCs inhibited virulence traits of R. solanacearum in vitro. • VOCs reduced potato wilt incidance caused by R. solanacearum in greenhouse. In this study, we investigated the effects of volatile organic compounds (VOCs) produced by endophytic bacteria belonging to the Bacillus genus on the virulence traits of Ralstonia solanacearum R32, the causal agent of potato bacterial wilt disease. The results of gas chromatography-mass spectrometry analysis showed that strains B. safensis Har267, B. pumilus Fer469, B. zhangzhouensis Kh690, B. aerius Kh867, and B. wiedmannii Ah945 able to produce 10, 4, 18, 6, and 12 VOCs with high quality, respectively. All endophytic bacteria produced VOCs that significantly reduced wilting symptoms in planta , inhibited the cell population of R. solanacearum R32 in vitro, and reduced the cell population both in the shoots and roots of inoculated plants at different levels. The VOCs significantly reduced the attachment of R. solanacearum R32cells to root tissues of potato plants, as well as chemotaxis motility towards root extract. Our results revealed that VOCs could reduce swarming-, swimming-, twitching motility, and biofilm formation by R. solanacearum R32 which are important for pathogenicity. Scanning electron microscopy analysis revealed various morphological abnormalities in the R. solanacearum R32 cells exposed to the VOCs produced by B. safensis Har267 and B. aerius Kh867 strains. Results presented in this study showed that the VOCs produced by endophytic bacteria investigated can reduce bacterial wilt disease. Investigation of the mechanisms of biocontrol activities increases our knowledge to design better methods to control bacterial pathogens. [ABSTRACT FROM AUTHOR]

Brown blotch disease of mushroom caused by Pseudomonas tolaasii , often results of severe damage to mushroom tissues. In this study, the biocontrol mechanisms mediated by endofungal bacteria Pseudomonas sp. De1, Bacillus sp. De3, Pseudomonas sp. Bi1 and Pantoea sp. Ma3 previously isolated from wild growing mushrooms against Pseudomonas tolaasii Pt18 were demonstrated. Our results provide evidence that all bacterial strains can colonize mycelia of Agaricus bisporus. All endogungal bacteria except Pseudomonas sp. Bi1 contained one or more genes encoding antibiotic production. The non-volatile compounds of endofungal bacteria significantly inhibited the biofilm formation by P. tolaasii Pt18. Results showed that all strains except Pantoea sp. Ma3 are capable of detoxify tolaasin, a major virulence factor produced by P. tolaasii Pt18. We also showed that all endofungal bacteria tested were able to significantly decrease the browning symptoms of pretreated-mushroom caps compared to inoculated caps with P. tolaasii alone. AbPPO3 gene expression levels in mycelia and fruiting bodies of A. bisporus significantly increased after P. tolaasii Pt18 inoculation. Our findings indicated that The relative expression level of AbPPO3 gene decreased in the mushroom mycelia and fruiting bodies pretreated with Pantoea sp. Ma3 and Pseudomonas sp. Bi1 strains, and the levels were significantly lower than mushroom tissues treated with P. tolaasii Pt18 alone. Overall, the findings presented in this study revealed the efficacy of the selected endofungal bacteria in biocontrol activity against P. tolaasii and the possible use of these strains as a safe microbial agents in mushroom brown blotch disease management. • The non-volatile compounds of endofungal bacteria significantly inhibited the biofilm formation by P. tolaasii. • Endofungal bacteria belongs to Pseudomonas, Bacillus and Pantoea genus significantly reduced mushroom brown blotch symptoms. • Bacillus and Pseudomonas strains detoxify tolaasin produced by Pseudomonas tolaasii under in vivo conditions. • The relative expression level of AbPPO3 gene decreased in the mushroom tissues pretreated with endofungal bacteria. [ABSTRACT FROM AUTHOR]

The purpose of this research was to explore the control of common bean root rot disease caused by Fusarium solani by the bacterial strain CTA8689 under in vitro and greenhouse conditions. The strain CTA8689 was isolated from common bean root and identified as Achromobacter xylosoxidans using 16S rDNA sequence, morphological and physiological characteristics. The strain CTA8689 suppressed the mycelial growth of F. solani in dual-culture (58.67%) and culture filtrates (41.87%) methods. The volatile compounds (VOCs) produced by CTA8689 inhibited mycelial growth and conidial germination of F. solani by 42.26% and 59.12%, respectively. Also, this strain produced biofilm, lytic enzymes such as chitinase, protease and pectinase, siderophore, IAA and gibberellin, and it was able to phosphate solubilization. Furthermore, the disease severity of common bean root rot was reduced using soil and seed treatment by 83.89% and 87.60%, respectively, 60 days after inoculation. Additionally, the strain improved the plant growth parameters in common bean under greenhouse conditions. The VOCs produced by the strain CTA8689 were analyzed by Gas chromatography-mass spectroscopy (GC-MS). Out of 23 identified VOCs, 1,3-Dimethylbenzene (21.613%), Benzene, 1,3-bis (1,1-dimethylethyl)- (13.823%%), Ethylbenzene (8.636%), Dodecane, 4,6-dimethyl- (8.145%) and Decane (5.905%), were the major bioactive components. The mode of action of the strain CTA8689 on the F. solani was through the production of antifungal compounds (antibiosis) and lytic enzymes, which suppressed mycelial growth and conidial germination of the pathogen in vitro and greenhouse conditions. Overall, our results showed that A. xylosoxidans strain CTA8689 could be a promising biological control agent (BCAs) for common bean root rot. • Strain CTA8689 was isolated from common bean root and against Fusarium solani investigated. • Strain CTA8689 was identified as Achromobacter xylosoxidans. • Strain CTA8689 antagonized the pathogen successfully in vitro and greenhouse conditions. • Strain CTA8689 improved the plant growth parameters in common bean plant. • Strain CTA8689 produced bioactive compounds with antifungal properties. [ABSTRACT FROM AUTHOR]