Exploiting natural variation in susceptibility of Arabidopsis thaliana to Meloidogyne incognita to breed broad-spectrum resistance to root-knot nematodes

The root knot nematode Meloidogyne incognita is able to parasitize hundreds of plant species and is a major threat in nearly all vegetable-growing regions in the world. Current resistance is based on major dominant resistance (R) genes, which are frequently overcome by the occurrence of resistance-breaking races of M. incognita. Allelic variation in genetic loci associated with susceptibility to plant-parasitic nematodes within a single plant species has thus far not been used to breed durable broad-spectrum resistance in crops. We investigated the susceptibility of 350 different ecotypes of A. thaliana for the root-knot nematode M. incognita. A nine-fold difference in susceptibility to M. incognita was found between the most and the least susceptible ecotypes. This quantitative variation can be caused by polymorphic levels of gene transcripts, and by allelic variation within transcripts of essential susceptibility genes. We conducted a genome wide association mapping study to determine loci that contribute to susceptibility of A. thaliana to M. incognita. Genes underlying these loci were investigated with T-DNA insertion mutation analysis to confirm their effect on nematode susceptibility of A. thaliana. Our data indicate that allelic variation can be used to breed for broad-spectrum nematode resistance.