Managing tomato bacterial wilt through pathogen suppression and host resistance augmentation using microbial peptide

Abstract

The increasing health and environmental risks associated with synthetic chemical pesticides necessitate the exploration of safer, sustainable alternatives for plant protection. This study investigates a novel biosynthesized antimicrobial peptide (AMP) from Lactiplantibacillus argentoratensis strain IT, identified as the amino acid chain PRKGSVAKDVLPDPVYNSKLVTRLINHLMIDGKRG, for its efficacy in controlling bacterial wilt (BW) disease in tomato (Solanum lycopersicum) caused by Ralstonia solanacearum. Our research demonstrates that foliar application of this AMP at a concentration of 200 ppm significantly reduces disease incidence by 49.3% and disease severity by 45.8%. Scanning electron microscopy revealed severe morphological disruptions in the bacterial cells upon exposure to the AMP. Additionally, the AMP enhanced host resistance by elevating defense enzyme activities, leading to notable improvements in plant morphology, including a 95.5% increase in plant length, a 20.1% increase in biomass, and a 96.69% increase in root length. This bifunctional AMP provides dual protection by exerting direct antimicrobial activity against the pathogen and eliciting plant defense mechanisms. These findings underscore the potential of this biologically sourced AMP as a natural agent for combating plant diseases and promoting growth in tomato crops. To the best of our knowledge, this is the first study to demonstrate the use of a foliar spray application of a biosynthesized microbial peptide as biocontrol agent against R. solanacearum. This interaction not only highlights its biocontrol efficacy but also its role in promoting the growth of Solanum lycopersicum thereby increasing overall agricultural yield.

Keywords: agriculture; bacterial wilt; peptide; phytopathogen; tomato.

Figure 1

Efficacy of foliar spray application on growth promotion of Solanum lycopersicum PKM-1 in presence of Ralstonia solanacearum (RS1: Ralstonia solanacearum, SR1: Supernatant, BR1: Bacteria culture, PR1: Peptide suspension).

Figure 2

(A) Effect of different treatment on chlorophyll content in absence of phytopathogen (B) Effect of different treatment on chlorophyll content in presence of phytopathogen (C) Effect of different treatment on protein and carbohydrate content in leaf (RS1: Ralstonia solanacearum, SR1: Supernatant, BR1: Bacteria culture, PR1: Peptide suspension). *Values represent the mean ± SD (standard deviation) of three independent experiments for each treatment.

Figure 3

Effect of foliar spray on total flavonoid content in leaves of Solanum lycopersicum (RS1, Ralstonia solanacearum; SR1, Supernatant; BR1; Bacteria culture; PR1, Peptide suspension). *Values represent the mean ± SD (standard deviation) of three independent experiments for each treatment.

Figure 4

Estimation of various defense enzymes including (A) Peroxidase Activity (B) Polyphenol Oxidase (C) Superoxide Dismutase (D) Catalase Activity when treated with foliar spray of microbial peptide (PR1 + Rs), culture filtrate of Lactiplantibacillus spp. (SR1 + Rs), cell culture of Lactiplantibacillus spp. (BR1 + Rs) *Rs, Ralstonia solanacearum. *Values represent the mean ± SD (standard deviation) of three independent experiments for each treatment.

Figure 5

The SEM images reveal pore formation and cell membrane damage in Ralstonia solanacearum bacteria after treatment with the microbial peptide, in contrast to the untreated control. The damage is highlighted by arrow indicators.