ABSTRACT
Nematodes are a large group of invertebrates living in soil and water. Some feed on higher plants and can cause diseases. Some plant parasitic nematodes cause heavy crop losses. Cereal cyst nematode Heterodera avenae, potato cyst nematode Globodora rostochiensis, and the root-knot nematodes Meloidogyne javanica, M. incognita, and M. arenaria severely affect several cereals and vegetables. Some nematodes cause damage in association, with fungi such as Fusarium, Verticillium, Rhizoctonia, and Phytophthora spp. causing wilt and root rots in several crops. In association with bacterial pathogens such as Clavibacter tritici, the nematode Anguina tritici causes diseases such as spike blight of wheat. Some nematodes such as Xiphinema, Trichodorus, and Paratrichodorus serve as vectors of viruses causing serious diseases in tomato, peach, strawberry, raspberry, grapevine, pea, cowpea, and tobacco. Several nematicides have been developed, and these broad-spectrum nematicides were highly effective in management of nematode-related diseases. However, several effective nematicides have been removed from the marketplace as the result of federal deregulation. Research work has been intensified in developing nematode-resistant plants exploiting single-gene resistance. Cultivars with vertical or horizontal resistance have been developed, with more success with vertical resistance. Several biocontrol agents have been identified, but their practical uses in the field are yet to be demonstrated. All these aspects are described in this chapter.
