ABSTRACT

Tomato (Solanum lycopersicum L.) is among the most extensively grown vegetables globally, but its yield is significantly under attack by early blight caused by Alternaria solani, which could contribute to more than 80% loss of yield under ideal conditions. Routine management is based primarily on chemical fungicides like mancozeb and chlorothalonil, but their excessive use has led to fungicide resistance, environmental issues, and health hazards. This underscores the imperative demand for sustainable and environmentally friendly substitutes. Pseudomonas fluorescens, a plant growth-promoting rhizobacterium (PGPR), is also a potential biocontrol agent owing to its multi- faceted systems, such as antibiosis by production of secondary metabolites (2,4- diacetylphloroglucinol, pyoluteorin, phenazines), siderophore-mediated iron sequestration, nutrient and niche competition, and induction of systemic resistance in tomato plants. Field, greenhouse, and laboratory tests have all consistently shown that it can inhibit the growth of hyphae, conidial germination, disease severity, and improve plant vigor and yield. Powder and liquid forms of commercial formulations are already available and have proven to be effective in farmer demonstrations in various parts of India and other nations. In addition, integration of P. fluorescens with Trichoderma spp., neem extracts, organic amendments, and reduced fungicide regimens further enhanced disease suppression and lowered chemical inputs. Its application in Integrated Pest Management (IPM) systems highlights its ability to decrease fungicide application by 50%, improve ecological resilience, and facilitate residue-free tomato production. This review integrates available evidence regarding the biocontrol potential of P. fluorescens against tomato early blight and highlights its potential as part of sustainable agricultural tactics in the future.

Keywords: Antifungal metabolites; Siderophore production; Bioformulations; Integrated pest management; 2,4 diacetylphloroglucinol.