Host-pathogen interaction in bacterial leaf blight of rice: Mechanisms of infection, colonisation and symptom development

Abstract

Bacterial leaf blight (BLB) is a major constraint to rice production worldwide due to its rapid spread and the high genetic variability of its causal agent, Xanthomonas oryzae pv. oryzae. The pathogen primarily enters rice plants through natural openings such as hydathodes or through wounds, subsequently colonising the xylem vessels and spreading systemically within the vascular system, leading to characteristic disease symptoms. The ability of the bacterium to infect the host depends on several virulence factors, including biofilm formation, exopolysaccharide production, quorum sensing and the secretion of effector proteins into the host. These proteins, known as transcription activator-like (TAL) effectors, play a crucial role in pathogenesis by modulating host gene expression to facilitate infection. Rice plants counter BLB through multiple defence mechanisms, including the formation of structural barriers, production of antimicrobial compounds andmodulation of gene expression. Some rice cultivars exhibit greater resistance to BLB than others, which is largely determined by genetic factors. This review examines the defence strategies of rice and provides key insights into host-pathogen interactions that inform the development of durable resistance and improved disease management strategies. Understanding these interactions provides a foundation for integrating molecular breeding with sustainable agricultural practices to mitigate yield losses caused by BLB.