Microbial Metabolites in Agriculture: Promises and Limitations

This review analyses the growing field of microbial metabolites in agriculture, moving beyond the widespread narratives to evaluate the scientific foundations, efficacy claims, and ecological implications of their widespread application. This article discusses the widespread benefits of using microbial metabolites in agriculture to enhance plant physiology, biochemistry, and defense. The biocontrol agents protect crops through direct and indirect mechanisms, including direct antagonism, resource competition, and niche exclusion at root infection sites. Furthermore, they also activate innate plant immunity via Induced Systemic Resistance (ISR) and Systemic Acquired Resistance (SAR). By recognizing Pathogen-Associated Molecular Patterns (PAMPs), these metabolites trigger defense hormones such as salicylic acid, jasmonic acid, and ethylene and also prompt the synthesis of defense proteins. While live microbes are sensitive to environmental shifts, the benefits of isolating their pure metabolites and formulating biopesticides help standardize doses and offer extended shelf lives. While microbial metabolites offer a “green” alternative to synthetic agrochemicals, the current research landscape is often characterized by reductionist “single-strain, single-metabolite” approaches and a significant lack of comprehensive environmental impact studies. Here, we have also discussed progress in metabolite discovery through omics technologies, re-evaluated the often-overstated efficacy of these compounds in plant growth and defense, and assessed the ecological consequences, including soil microbiome disruption and associated risks such as horizontal gene transfer. We propose a framework for (i) efficacy validation across environments, (ii) ecological risk assessment endpoints, and (iii) regulatory monitoring priorities and ethically guided precision agricultural solutions to fully harness the potential of microbial metabolites for a sustainable future.