Evaluation of Trichoderma spp., Pseudomonas fluorescens and Bacillus subtilis for biological control of Ralstonia wilt of tomato

Abstract

Background: Ralstonia spp. is a major pathogenic microbe for tomato, which invades the roots of diverse plant hosts and colonizes xylem vessels causing wilt, especially in tropical, subtropical and warm-temperate regions. Ralstonia spp. produces several virulence factors helping it to invade the plant’s natural defense mechanism. Native isolates of Trichoderma spp., Pseudomonas fluorescens and Bacillus subtilis can be used as biocontrol agents to control the bacterial wilt and combined application of these beneficial microbes can give better results. Methods: Bacterial wilt infection in the field was identified by field experts and the infected plant part was used to isolate Ralstonia spp. in CPG media and was positively identified. Subsequently, the efficacy of the biocontrol agents was tested and documented using agar well diffusion technique and digital microscopy. 2ml of the microbial concentrate (109 cells/ml) was mixed in one liter of water and was applied in the plant root at the rate of 100 ml per plant as a treatment method. Results: It was observed that the isolated Trichoderma spp. AA2 and Pseudomonas fluorescens PFS were most potent in inhibiting the growth of Ralstonia spp., showing ZOI 20.67 mm and 22.33 mm, respectively. Digital microscopy showed distinct inhibitory effect on the growth and survival of Ralstonia spp. The results from the field data indicated that Trichoderma spp. and Pseudomonas fluorescens alone were able to prevent 92% and 96% of the infection and combination of both were more effective, preventing 97% of infection. Chemical control methods prevented 94% of infection. Bacillus subtilis could only prevent 84 % of the infection. Conclusions: Antagonistic effect against Ralstonia spp. shown by native isolates of Trichoderma spp. and P. fluorescens manifested the promising potential as biocontrol agents. Combined application gave better results. Results shown by Bacillus subtilis were not significant.

Combined Effects of Biological and Chemical Treatment on Rice Seed Physiological and Sanitary Quality

“…and P. fluorescens, or the three microorganisms combined was more effective against the pathogen Ralstonia spp. than inoculation with a single microorganism or chemical control (Yendyo, Ramesh, & Pandey, 2018). Similar effects are expected for coinoculation of seeds.…”

Biocontrol of tomato bacterial wilt by the new strain Bacillus velezensis FJAT-46737 and its lipopeptides

“…The identification of safe, effective and alternative methods for controlling plant pathogen diseases is becoming increasingly important for improving the output and quality of agricultural products. Furthermore, biological control using antagonistic microorganisms including bacteria, yeasts, and filamentous fungi, represent a safe, effective and sustainable alternative method for fighting plant pathogens compared with chemical bactericides [4][5][6]. Members of the genus Bacillus have been used as effective biocontrol agents to reduce damages caused by bacterial wilt, and their derived products account for approximately half of the commercially available biopesticides [7].…”

Isolation and molecular identification of Rhizoctonia solani and Fusarium solani isolated from cucumber (Cucumis sativus L.) and their control feasibility by Pseudomonas fluorescens and Bacillus subtilis

“…Different measures for controlling of plant pathogens have been developed such as the use of resistant varieties (Borrelli et al 2018), plant extracts (Han et al 2018), chemical control (Karim et al 2018), and biological control (Yendyo et al 2017). Overuse of the chemicals can cause environmental problems, negatively affecting human health and increasing the pest resistance to pathogens.…”