The proliferation of plant-parasitic nematodes as formidable agricultural
pests poses a significant global threat to crop productivity. Despite their diminutive
size, these organisms inflict substantial economic losses, with global damage
surpassing that caused by insect pests. The cryptic nature of nematode infections
renders them particularly insidious, often leading to underestimation and inadequate
management. Beyond their intrinsic harmful effects, plant-parasitic nematodes
exacerbate crop damage by forming synergistic disease complexes with other
pathogenic microorganisms. Nematodes utilize diverse strategies to breach plant host
tissues, with a particular emphasis on the root-knot and cyst-forming nematodes—two
prominent groups that inflict severe agricultural damage. The evolution of plant
defense mechanisms is an intrinsic biological response by which plants counteract
nematode parasitism. Plants deploy receptor molecules against nematode effectors,
facilitating resistance by either preventing nematode penetration or by producing
nematicidal proteins that mitigate nematode pathogenicity. The activation of plant
defense-related genes and the synthesis of defensive hormones are pivotal in enhancing
plant resilience against nematode invasion. However, under certain conditions, these
defensive strategies may inadvertently augment nematode parasitism. Common
symptoms indicative of nematode infestation include tissue necrosis, gall formation,
cyst development, and stunted plant growth. This chapter delves into the current
understanding of plant-nematode interactions, emphasizing the molecular and
physiological mechanisms underpinning plant immune responses to nematode invasion.
Keywords: Effector molecules, Nematode feeding sites, Plant hormones, Plant parasitic nematodes, Secondary metabolites.
