Partners in Crime: Elucidating the Molecular Underpinnings of Nematode–Pathogen Disease Complexes

Plant-parasitic nematodes (PPNs) are a serious threat to global food security, with estimated annual losses exceeding $173 billion. Beyond their direct damage, interactions between PPNs and other phytopathogens can lead to synergistic relationships, referred to as disease complexes, which result in more severe symptoms than either pathogen alone. Disease complexes have been documented across diverse PPN species with distinct lifestyles, including migratory ectoparasites, migratory endoparasites, and sedentary endoparasites, and have been shown to involve partners spanning viruses, bacteria, oomycetes, and fungi. In this review, we discuss specific aspects of PPN life cycles that may facilitate disease complex formation. Nematode-induced wounding may provide entry points or release exudate signals that promote secondary pathogen infection. Nutrient-rich feeding sites established by endoparasitic nematodes may support proliferation of secondary parasites. Furthermore, certain PPN families can vector pathogens such as viruses directly into the plant via their stylet or by carrying bacteria on the cuticle surface. Finally, PPNs can suppress or evade host immune responses, thereby increasing plant susceptibility to other microbial pathogens. Elucidating the molecular mechanisms underlying these interactions will improve our understanding of disease complexes associated with PPN infection and may inform the development of novel management strategies to mitigate their impact on agricultural systems. [Figure: see text] The author(s) have dedicated the work to the public domain under the Creative Commons CC0 “No Rights Reserved” license by waiving all of his or her rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law, 2026.