Molecular Interactions Between Soil-Borne Oomycetes and Plants: Infection Mechanisms, Host Resistance, and Implications for Sustainable Agriculture

Soil-borne oomycetes, such as Phytophthora and Pythium species, are highly destructive pathogens responsible for severe diseases in crops, ornamentals, and natural ecosystems. These pathogens can persist in soil for many years, making them particularly difficult to control. To establish infection, they deploy a diverse arsenal of effector proteins that manipulate host immune responses, disrupt vital cellular functions, and may influence the rhizosphere microbiome to facilitate successful colonization. Phytophthora relies heavily on RxLR effectors to disrupt intracellular immunity, while Pythium species predominantly deploy necrosis-inducing NLPs and cell wall-degrading enzymes, with no confirmed canonical RxLR effectors, suggesting distinct evolutionary strategies. This review aims to explore the detailed mechanisms of plant-pathogen interaction. In recent years, significant progress has been made in understanding the molecular dialogue between pathogens and their hosts, particularly how pathogenic species such as Phytophthora and Pythium manipulate plant immunity through effector secretion, and how plants counteract by activating defense mechanisms at molecular, cellular, and biochemical levels, including changes in hormone signaling, reactive oxygen species (ROS) dynamics, and defense gene expression. The review also outlines emerging disease management strategies and integrative approaches guided by effector biology and microbiome insights.