Concerted Efforts To Develop Handles For Plant Parasitic Nematode Control

Plant-parasitic nematodes - especially root knot and cyst nematodes - are economically important pests in numerous crops. Chemical soil sterilisation and the use of other unselective pesticides to control plant parasitic nematodes are still a common practice in many European countries and at present no realistic alternatives are available. For the identification of handles to control root knot and cyst nematodes we need to know how they interact with their host. Two main types of endoparasitic nematodes can be distinguished: root-knot and cyst nematodes, both inducing a feeding site in the plant root, but in a different way. To get insight into the molecular mechanisms behind this complex interaction, several strategies to analyse plant gene expression in response to nematode infection have been followed. Random in vivo gus fusions have been particularly successful in identifying plant promoter sequences that are highly activated in nematode feeding sites, with very little expression elsewhere in the plant, but the isolation of the corresponding genes is often not straightforward. Many highly transcribed plant genes have been identified in the feeding sites, but few have been characterised in such detail as to know how important they are for a successful infection. The available data are nevertheless providing interesting tools for novel strategies to engineer nematode resistance into crops. Concomitantly, the signals coming from the nematode that are triggering this plant response or that are important in other steps of the infection process are being characterised. This study has revealed that plant-parasitic nematodes produce many different enzymes to enable them to infect the plant root and to protect themselves against the plant defence response.