The researchers did not find the gene for resistance, but they identified regions of the genome that appear to contribute to resistance, using QTL mapping. Looking at the genes in those regions, they found that ascorbate biosynthesis is common. One mechanism explaining western corn rootworm resistance might be the manufacture of ascorbate in plants. The ascorbate synthesis pathway produces free radicals that injure feeding insects.
Their analysis turned up another set of genes that may be involved in resistance, although a little more complex. When western corn rootworm larvae are feeding on roots, some corn plants release a compound into the soil that calls nematodes to attack the larvae. The second set of genes appears to be related to the manufacture of compounds that attract those nematodes.
For more details about this research, read the University of Illinois College of ACES News.