Engineering resistance against plant-parasitic nematodes

Plant-parasitic nematodes cause severe damage and economic loss to many crops. Strategies to manage nematode problems are based on application of chemical compounds, use of resistant cultivars and specific agricultural practices. Currently, a number of approaches to engineer resistance against plant-parasitic nematodes also are being developed. Engineered resistance may provide protection against nematodes in cases when conventional means are not effective enough, too expensive or just not available. Hazardous effects on the environment, as observed with all nematicides, may also be avoided. However, environmental effects from extensive use of transgenic plants are not predictable in all aspects. Before engineered resistance will be available in crops, a number of molecular problems in the interaction between the host and the nematode parasite have still to be clarified. Engineered resistance may also raise new problems by indirect effects: it may for example lead to further intensification of agricultural systems, where nematodes are major pests. The extensive use of resistance may also support the rise of resistance-breaking populations. As the development of engineered resistance is expensive, profits presumably can be made only with crops of high economic importance and protection of patents. Patent protection of single genes in cultivars presumably will strongly affect the international seed market.