Characterization of plant nematode genes: identifying targets for a transgenic defence

Current control of plant parasitic nematodes often relies on highly toxic a nd environmentally harmful nematicides. As their use becomes increasingly r estricted there is an urgent need to develop crop varieties with resistance to nematodes. The limitations surrounding conventional plant breeding ensu re there isa clear opportunity for transgenic resistance to lessen current dependence on chemical control. The increasing use of molecular biology tec hniques in the field of plant nematology is now providing useful informatio n for the design of novel defences to meet the new needs. Plant responses t o parasitism are being investigated at the molecular level and nematode gen e products that could be targets for a direct anti-nematode defence are bei ng characterized. The potential of an anti-feedant approach to nematode con trol has been demonstrated. It is based on the transgenic expression of pro teinase inhibitors. The rational development of this strategy involves char acterization of nematode proteinase genes and optimization of inhibitors by protein engineering. Durability of the resistance can be enhanced by stack ing transgenes directed at different nematode targets.