Crop Protection against Botrytis cinerea by Rhizhosphere Biological Control Agent Bacillus velezensis XT1

Abstract

<jats:p>This study aims to evaluate the use of Bacillus velezensis strain XT1 as a plant growth-promoting rhizobacterium (PGPR) and biocontrol agent against B. cinerea in tomato and strawberry plants. Foliar and radicular applications of strain XT1 increased plant total biomass as compared to the control and B. cinerea-infected plants, with root applications being, on the whole, the most effective mode of treatment. Applications of the bacterium were found to reduce infection parameters such as disease incidence and severity by 50% and 60%, respectively. We analyzed stress parameters and phytohormone content in order to evaluate the capacity of XT1 to activate the defense system through phytohormonal regulation. Overall, the application of XT1 reduced oxidative damage, while the H2O2 and malondialdehyde (MDA) content was lower in XT1-treated and B. cinerea-infected plants as compared to non-XT1-treated plants. Moreover, treatment with XT1 induced callose deposition, thus boosting the response to pathogenic infection. The results of this study suggest that the signaling and activation pathways involved in defense mechanisms are mediated by jasmonic acid (JA) and ethylene hormones, which are induced by preventive treatment with XT1. The study also highlights the potential of preventive applications of strain XT1 to activate defense mechanisms in strawberry and tomato plants through hormone regulation.</jats:p>

Insight into the Microbiological Control Strategies against Botrytis cinerea Using Systemic Plant Resistance Activation

“…Similarly, the inoculation of B. velezensis in pepper roots is capable of causing hydrogen peroxide accumulation and superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) activity in leaves [69]. On the other hand, the JA/ET pathway reduced disease incidence and severity by 50% and 60% in tomato and strawberry leaves, respectively, due to the reduction in oxidative damage and the induction of callose deposition by B. velezensis root inoculation [70], as well as by B. cereus in A. thaliana roots [65,99]. This systemic resistance can be activated by the recognition of bacterial lipopeptides, such as surfactins and fengycins, which are recognized in bean and tomato plants when B. subtilis is applied radicularly, systemically increasing lipoxygenase (LOX) and lipid hydroperoxidase (LHP) activity against the necrotrophic pathogen [66].…”

From Strain Characterization to Field Authorization: Highlights on Bacillus velezensis Strain B25 Beneficial Properties for Plants and Its Activities on Phytopathogenic Fungi

“…Independently of their potential to colonize rhizosphere (which has not been evaluated in this study), strain B25 expressed a higher resistance to UV-C exposure, which could be seen as an advantage for application on aerial plant parts, giving it a better chance to survive in this particular case of use. This might open the way to foliar treatments against foliar pathogens such as the ones tested in this study or against the ubiquitous pathogen Botrytis cinerea against which some strains of B. velezensis have already shown a certain biocontrol efficiency [ 39 , 40 ]. In fact, this higher resistance might be due to the physiological state of the strain, as it has already been highlighted that the dormant spore forms of Bacillus are 5 to 50 times more resistant to UV radiation compared to the corresponding growing cells [ 41 ].…”

Beneficial Microorganisms to Control the Gray Mold of Grapevine: From Screening to Mechanisms

“…The 16S rRNA gene sequences of S3 exhibited 100% similarity to B. velezensis , while the strain S6 showed 98.5% similarity to E. cloacae. B. velezensis and E. cloacae have been frequently reported as plant growth promoting bacteria and/or biocontrol agents [ 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 ]. The fact that many Bacilus species have very close phenotypic and physiological properties as well as 16S rRNAs gene sequences makes their classification very difficult [ 51 ].…”