Nematodes: an overlooked tiny engineer of plant health.

The rhizobiome is a critical determinant of plant health, generally attributed to diverse bacteria and fungi. However, the contribution of soil-dwelling animals to plant health has been greatly underestimated and deserves further investigation. Nematodes, as co-evolved partners of plants, may be significantly enhancing plant health due to their predominant role as plant allies rather than plant enemies in the rhizosphere. Plant-parasitic nematodes cause root damage that facilitates opportunistic pathogen colonization. However, the damaged root cells also develop a community of beneficial microbiota and attract antagonists that strengthen plant defense responses. While bacterivorous nematodes cannot suppress plant disease directly by consuming bacterial pathogens, they could have a larger impact on plant protection by bringing antagonistic bacteria into contact with plant pathogens, thereby inhibiting pathogen growth. Nematodes are a crucial component of rhizosphere biodiversity, affecting plant health as the most abundant and functionally diverse soil animals. Plant-parasitic nematodes are generally considered harmful, which may overlook their potential benefits to plants when coexisting with free-living nematodes in soil. We provide new insights into nematodes as vital plant partners. Plant root damage by plant-parasitic nematodes creates opportunities for pathogens and beneficial microbiota to colonize the rhizosphere. Free-living nematodes coordinate microbiota to suppress plant diseases, but they are susceptible to mortality from plant pathogens, potentially favoring pathogen release in the root zone. We conclude that the nematode's role in regulating plant pathogens represents a missing link, constraining our ability to predict and control soil-borne diseases in healthy plants. [ABSTRACT FROM AUTHOR]