Morphological and molecular basis of host specificity in fungal pathogens - an overview

Host specificity in fungal pathogens is a critical factor influencing disease incidence, spread and management in agricultural and natural ecosystems. This specificity denotes the selective ability of a fungal pathogen to infect certain plant species while avoiding others. This emerges from a complex interaction of morphological adaptations and molecular signalling pathways that regulate host-pathogen compatibility. Structures like appressoria, haustoria and penetration pegs assist in host recognition and tissue invasion morphologically, often adapted to the specific host surface characteristics. At the molecular level, host specificity is influenced by the secretion of effector proteins, recognition by host resistance (R) genes and modulation of the host defense responses. Advances in genomics, transcriptomics and proteomics have revealed the dynamic role of avirulence genes, small RNAs and genome plasticity in host range. These interactions are further refined by co-evolutionary pressure and epigenetic regulation. Understanding the morphological and molecular basis of host specificity provides insights into pathogen evolution and host adaptation, enabling targeted breeding for resistance and the development of precise disease management strategies, which are essential for sustaining crop health and food security in the face of evolving fungal threats. • Host-specific infection structures (appressoria, haustoria, penetration pegs) adapted to plant surface traits. • Effectors, Avr genes, small RNAs and genome plasticity shape compatibility. • Dynamic interplay of pathogen effectors and host R genes influenced by epigenetics. • Omics insights aid resistant crop breeding and targeted disease management.