Natural host-plant resistances
The first plant-nematode interaction for which a gene-for-gene relation was formally proven is the interaction between the avrH1 gene of G. rostochiensis and the H1 resistance gene of potato (Jansen et al. 1991). Right now, substantial effort is put in the precise chromosomal localization and the cloning of both the avrH1 (Rouppe van der Voort et al. 1994) and the H1 gene. Potato cyst nematodes are obligatory sexual and, as a consequence, clonal multiplication is impossible. The DNA content of a cyst is about 10 ng, and analysis of the genetic constitution of single cysts is the only way to create a detailed genetic map. The relatively novel AFLP technique is invaluable is this respect since it is fast, reliable and sensitive.
For its host plant Solanum spp. the quantity of tissue is not a limiting factor and within a few months the existing potato map could be saturated with a several hundreds of genetic markers that were shown to be present in other genetic potato backgrounds as well (Van Eck et al. 1995, Rouppe van der Voort et al. 1997). A this moment, we are fine-mapping the nematode-resistance genes H1 (against G. rostochiensis, pathotypes Ro1 and Ro4) and Gpa2 (against a number of Globodera pallida populations).
Artificial host-plant resistances
In a number of cases unfortunately no natural resistance genes against plant-parastic nematodes are available. Presumably this gap can be bridged by the creation of artificial host-plant resistance. If we could express a specific monoclonal antibody in a plant that blocks a pathogenicity factor crucial for the development of the pathogen, this would in principle result in a resistant host plant. It is unlikely that the pathogen can modify this pathogenicity factor without the loss of its function. Plants are good factories for the production of functional (fractions of) antibodies (Van Engelen et al. 1994).
Targeting to various cell compartments was shown to be feasible (Schouten et al. 1996, 1997) and, in the meantime, potato plants are endowed with antibodies directed against salivary proteins (see picture on the left). Efficient inhibition of these proteins will presumably hamper the penetration of the roots of a host plant.
- Van Eck et al. 1995. Mol. Breed. 1: 397-410
- Jansen et al. 1991. Fund. Appl. Nematol. 15: 463-466
- Rouppe van der Voort et al. 1997. Mol. Gen. Gen. 255: 438-447
- Rouppe van der Voort et al. 1994. In: Advances in Molecular Plant Nematology (Ed. F. Lamberti et al.) Plenum Press, New York, pp 57-63.
- Schouten et al. 1996. Plant Mol. Biol. 30: 781-793
- Schouten et al. 1997. FEBS Letters 415: 235-241
- Van Engelen et al. 1994. Plant Mol. Biol. 26: 1701-1710