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.
Highlights
In recent years, the yield and the quality of many crops and medicinal plants, as well as vegetables and fruits have decreased because of plant diseases caused by soil-borne pathogens, including fungi
Fungal pathogens are responsible for a range of serious plant diseases, such as Fusarium wilt, highly destructive to tomatoes [1]; phytophthora blight, the most destructive disease caused by the infection of oomycete pathogen Phytophthora capsici [2]; Rhizoctonia diseases of many crops, cotton, and lettuce [3]; or Sclerotinia stem rot (SSR), reducing the yield of rapeseed [4], a major source of vegetable oil for human consumption and biodiesel production [5]
The antagonism test results showed that the BRZ63 strain reduced and inhibited the mycelium growth of all plant pathogens used in this study (Figure 1a, Figure S1)
Summary
The yield and the quality of many crops and medicinal plants, as well as vegetables and fruits have decreased because of plant diseases caused by soil-borne pathogens, including fungi. Fungal pathogens are responsible for a range of serious plant diseases, such as Fusarium wilt, highly destructive to tomatoes [1]; phytophthora blight, the most destructive disease caused by the infection of oomycete pathogen Phytophthora capsici [2]; Rhizoctonia diseases of many crops, cotton, and lettuce [3]; or Sclerotinia stem rot (SSR), reducing the yield of rapeseed [4], a major source of vegetable oil for human consumption and biodiesel production [5]. Among different methods used for controlling soil-borne pathogens, chemical control based on synthetic products dominates. Given the intimate contact with plants, these microorganisms hold tremendous potential for use as biocontrol agents [12]
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