Plant defence against phytopathogens: Roles of antimicrobial metabolites and breeding strategies for resistance

Abstract Among the various phytopathogenic factors affecting plants in their surroundings, fungal pathogens are the worst because they are responsible for the highest number of disease incidences in plants. Almost 8000 phytopathogenic fungal species are known that adversely affect plant metabolism. Due to infection, plants perceive the stress stimulus employing microbe- or damaged-plant-derived molecules, known as elicitors, produced by pathogen attack. After this perception, plants initiate a defensive response against the pathogen by upregulating the synthesis and accumulation of small antimicrobial compounds. To synthesize these compounds, plant must transform their metabolic activities from growth and reproduction to resistance, adaptation and tolerance. This review critically examines the protective strategies employed by plants in response to fungal infection, with a particular focus on the synthesis and accumulation of antimicrobial compounds, such as secondary metabolites (phenols, terpenoids, and alkaloids), pathogenesis-related (PR) proteins (chitinase and β-1,3-glucanase), defence-related phytohormones and enzymatic and non-enzymatic antioxidants. A comprehensive understanding of these metabolites provides plant breeders with valuable insight to identify and select traits linked with enhanced resistance in crop plants. By integrating and upregulating genes engaged in the biogenesis and accumulation of these metabolites, breeders can develop crop varieties with better resilience against fungal pathogens. Such improvements not only lessen dependence on chemical pesticides but also pave the way towards sustainable and ecologically responsible agricultural practices. Graphical abstract An illustration features a host plant being attacked by pathogens. A cross-section details the plant cell and plant tissue leading to the nucleus, which branches into five defense responses. On the right, several plant breeding techniques are listed.