Genome Mining and Evaluation of the Biocontrol Potential of Pseudomonas fluorescens BRZ63, a New Endophyte of Oilseed Rape (Brassica napus L.) against Fungal Pathogens

Abstract

Endophytic bacteria hold tremendous potential for use as biocontrol agents. Our study aimed to investigate the biocontrol activity of Pseudomonas fluorescens BRZ63, a new endophyte of oilseed rape (Brassica napus L.) against Rhizoctonia solani W70, Colletotrichum dematium K, Sclerotinia sclerotiorum K2291, and Fusarium avenaceum. In addition, features crucial for biocontrol, plant growth promotion, and colonization were assessed and linked with the genome sequences. The in vitro tests showed that BRZ63 significantly inhibited the mycelium growth of all tested pathogens and stimulated germination and growth of oilseed rape seedlings treated with fungal pathogens. The BRZ63 strain can benefit plants by producing biosurfactants, siderophores, indole-3-acetic acid (IAA), 1-aminocyclopropane-1-carboxylate (ACC) deaminase, and ammonia as well as phosphate solubilization. The abilities of exopolysaccharide production, autoaggregation, and biofilm formation additionally underline its potential to plant colonization and hence biocontrol. The effective colonization properties of the BRZ63 strain were confirmed by microscopy observations of EGFP-expressing cells colonizing the root surface and epidermal cells of Arabidopsis thaliana Col-0. Genome mining identified many genes related to the biocontrol process, such as transporters, siderophores, and other secondary metabolites. All analyses revealed that the BRZ63 strain is an excellent endophytic candidate for biocontrol of various plant pathogens and plant growth promotion.

Analysis of the Genome of the Heavy Metal Resistant and Hydrocarbon-Degrading Rhizospheric Pseudomonas qingdaonensis ZCR6 Strain and Assessment of Its Plant-Growth-Promoting Traits

“…To enhance the bioavailability of hydrocarbons, microorganisms produce biosurfactants [ 107 , 108 ]. The biosurfactants produced by bacteria can also contribute to inhibiting the growth of phytopathogens, help colonize plant tissues and improve bacterial motility [ 109 ]. In this study, the ZCR6 strain produced a surface-active compound, which showed a positive result for the oil-spreading test and exhibited emulsification activities against p -xylene (E24 = 71.43% ± 1.43), diesel oil (E24 = 14.71% ± 0.29) and n -hexadecane (E24 = 25.71% ± 0.57) ( Table 1 ).…”

Biostimulants Managed Fungal Phytopathogens and Enhanced Activity of Beneficial Microorganisms in Rhizosphere of Scorzonera (Scorzonera hispanica L.)

“…The species Pseudomonas fluorescens, P. putida, P. cepacia, and P. chlororaphis showed high antagonistic activity against polyphagous fungi [84,85]. Pseudomonas fluorescens BRZ63 inhibited mycelium growth of Rhizoctonia solani, Colletotrichum dematium, Sclerotinia sclerotiorum, and Fusarium avenaceum [86].…”

Metabolism of Aldoximes and Nitriles in Plant-Associated Bacteria and Its Potential in Plant-Bacteria Interactions

“…The interaction of plant-growth-promoting bacteria with the host plant is complex. The beneficial effects are associated with the bacterial ability to produce IAA, nutrients (ammonia, phosphate), surfactants, siderophores, or enzymes that attack the cell wall polysaccharides in fungal pathogens [ 51 ]. Other mechanisms strengthen the plant cell wall, prevent an excessive production of the plant hormone ethylene [ 51 ], or change the distribution of the plant hormone abscisic acid [ 52 ].…”

“…It supports germination and growth, triggers plant resistance mechanisms, and also has nematocidal activity [ 60 ]. However, IAA only has plant-promoting effects within a restricted range of concentrations [ 51 ]. The regulation of IAA production in bacteria is also sensitive to environmental factors [ 10 ].…”

“…The endophyte P. fluorescens BRZ63 showed biocontrol activity against some fungal pathogens ( Rhizoctonia , Sclerotinia , Colletotrichum , and Fusarium ) in Brassica napus (oilseed rape). The bacterium improved plant fitness by a complex mechanism that also included the production of significant concentrations of IAA (0.06 mg/mL) [ 51 ]. Another strain of P. fluorescens protected the host plant ( Medicago trunculata , a legume) against the fungus Botrytis cinerea at lower IAA concentrations (0.022 mg/mL).…”