Phytopathogenic Nematodes

Soil is teeming with life, and rhizosphere soil is even more densely in habited than bulk soil. In terms of biomass, bacteria and fungi are dominant groups, whereas nematodes (roundworms) are the most abundant Metazoans. Bulk soil, soil not directly affected by living plant roots, typically harbours around 2000–4000 nematodes per 100 g, while in the rhizosphere these numbers should be multiplied by a factor 3–5. This difference is not only explained by a higher density of plant parasites, as also bacterivorous and fungivorous nematodes benefit from the local boost of the bacterial and fungal community. Most nematodes feeding on higher plants are obligatory parasites. In this chapter four independent lineages of plant-parasitic nematodes are discussed. Facultative plant parasites often occupy basal positions