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 (10 9 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.

In vitro evaluation of the inhibitory capacity of three Trichoderma isolates on Ralstonia solanacearum

“…The in-depth analysis of the data presented, when compared to those of other authors, reveals that the results obtained in this research are consistent with previous studies conducted by Alvarez (20), Yendyo (21) and Goszczynska (22). These studies have demonstrated that Trichoderma genus isolates possess a significant antibiotic effect due to the production of thermostatic metabolites.…”

Microbes assisted management of bacterial wilt of brinjal in pesticide contaminated soil

“…Identified OPDB isolates were further observed having compatibility with MBCA and within MBCA (Pf versus Th) . The compatibility of Pf and This widely reported by several workers( Yendo et al 2018 ;Yang et al 2005 ) , revealing their dual functional ability, growth promotion and effectiveness against a variety of plant diseases Yang et al (2005). examining the role of strain DSP3 ( Alcaligenes faecalis treated at 10 8 cells/g) in the degradation of chlorpyriphos and 3,5,6-trichloro-2-pyridinol (TCP) under different culture and soil conditions, showed higher rate of pesticide degradation over untreated soil.…”

Biocontrol of Tomato Bacterial Wilt by Foliar Spray Application of a Novel Strain of Endophytic <i>Bacillus</i> sp.

“…Since bacterial wilt is a soil-borne disease, the majority of studies have focused on the use of antagonistic microorganisms dwelling in root-associated zones, including the rhizosphere and endosphere (inside roots), for the protection of plant roots from pathogen attack (Eljounaidi et al, 2016;Mamphogoro et al, 2020). Accordingly, a variety of antagonistic microorganisms, such as Pseudomonas spp., Bacillus spp., Streptomyces spp., non-pathogenic Ralstonia spp., and Trichoderma spp., have recently been identified from the Article ME20078 rhizospheres or interior of roots as effective biocontrol agents against bacterial wilt (Chandrasekaran et al, 2016;Farahat et al, 2016;Cao et al, 2018;Marian et al, 2018;Yendyo et al, 2017;Ling et al, 2020). It is widely accepted that root colonization by introduced biocontrol agents (BCAs) is an essential prerequisite for the successful biocontrol of soil-borne diseases (Sachdev and Singh, 2018).…”

“…Since bacterial wilt occurs continuously during warm weather seasons, it is important to maintain a sufficient population of BCAs in order to protect plants during the warmer months, from early summer to early fall. Therefore, many researchers have repeated drench applications of BCAs to roots at regular intervals after transplantation to ensure consistent colonization (Nguyen and Ranamukhaarachchi, 2010;Ramesh and Phadke, 2012;Yendyo et al, 2017). However, the "booster" drench application of a sufficient volume of a BCA inoculum to protect the entirety of the roots is technically difficult, laborintensive, and costly.…”