GEM Germplasm – Unlocking Maize Diversity for Improving Host Plant Resistance against West Corn Rootworm and Other Biotic Stresses

The Western corn rootworm (WCR) is a serious pest of maize in the U.S. and of growing importance in Europe. Soil insecticides, the use of transgenic maize hybrids producing a Bt toxin, and the rotation of maize with other crops are successfully used to manage WCR populations. However, the occurrence of WCR populations resistant to insecticides and adapted to cultural practices raises the question of how sustainable transgenic control measures against WCR are. In addition, monogenic resistances, like the Bt resistance, might be overcome by the target pest within a short time as amply documented in the literature. It seems, therefore, to make sense to invest in improving the multigenic host plant resistance in corn and to investigate its genetic basis. Secondary infections with Fusarium verticillioides, F. proliferatum, and F. subglutinans occur after European corn borer (ECB) larvae feeding, causing ear rots and contamination with fumonisin, a mycotoxin associated with severe animal and human health disorders. The tolerance of maize germplasm adapted to the Midwest against the ECB larvae was gradually improved over a 60 year period of continuous selection. However, improvements regarding WCR and Fusarium resistance over this time period are small. A major roadblock towards WCR and Fusarium host plant resistant maize genotypes is the apparent lack of genetic variation for these traits in the Midwestern maize pools. This lack of diversity is in stark contrast to the diversity available for improving other quantitative and agronomically important traits, like grain yield, early maturity, or grain composition and emphasizes the need for broadening the genetic basis of the Midwestern maize pools using exotic maize germplasm. The underlying hypotheses of this pre-breeding project are: