Quantitative trait loci mapping of western corn rootworm (Coleoptera: Chrysomelidae) host plant resistance in two populations of doubled haploid lines in maize (Zea mays L.)

Authors: BOHN, MARTIN - University Of Illinois; MARROQUIN, JUAN - University Of Illinois; Flint-Garcia, Sherry; Dashiell, Kenton; WILMOT, DAVID - Agreliant Genetics, Llc; Hibbard, Bruce

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/11/2017
Publication Date: 2/9/2018
Publication URL: http://handle.nal.usda.gov/10113/5922792
Citation: Bohn, M.O., Marroquin, J.J., Flint Garcia, S.A., Dashiell, K.E., Wilmot, D.B., Hibbard, B.E. 2018. Quantitative trait loci mapping of western corn rootworm (Coleoptera: Chrysomelidae) host plant resistance in two populations of doubled haploid lines in maize (Zea mays L.). Journal of Economic Entomology. 111(1):435-444. https://doi.org/10.1093/jee/tox310.

Interpretive Summary: The western corn rootworm is the most serious insect pest of corn in the United States and parts of Europe. Over the last 70 years, more than 12,000 maize lines have been screened for their level of resistance to western corn rootworm larval feeding, but fewer than 1% of this germplasm was selected for breeding programs. The lines that were selected were characterized by large root systems and superior root regrowth after root damage caused by western corn rootworm larvae. However, no hybrids claiming native (i.e., host-plant) resistance are currently commercially available. We investigated the genetic basis of western corn rootworm resistance in maize materials with improved levels of resistance using current gene mapping approaches. Two mapping populations were created and crossed to a standard inbred line to make hybrids. These populations were evaluated for their level of resistance in three or four different environments. For each hybrid, an average root damage score was estimated and used for genetic analysis. We found several regions of the maize genome that contributed to western corn rootworm resistance spanning all maize chromosomes except chromosomes 2 and 4. Our findings confirm the complex genetic structure of maize resistance to western corn rootworm larval feeding. Nevertheless, it was interesting that three of the genome regions we identified also carried genes involved in the synthesis of ascorbate (vitamin C and an antioxidant) a key compound we postulate is involved in rootworm resistance. If the genetic regions we have associated with resistance can be moved into elite maize lines, improved native resistance can be made available to growers.

Technical Abstract: Over the last 70 years, more than 12,000 maize accessions have been screened for their level of resistance to western corn rootworm, Diabrotica virgifera virgifera LeConte, larval feeding. Less than 1% of this germplasm was selected for initiating recurrent selection or other breeding programs. Selected genotypes were mostly characterized by large root systems and superior root regrowth after root damage caused by western corn rootworm larvae. However, no hybrids claiming native (i.e., host-plant) resistance to western corn rootworm larval feeding are currently commercially available. We investigated the genetic basis of western corn rootworm resistance in maize materials with improved levels of resistance using linkage disequilibrium mapping approaches. Two populations of topcrossed doubled haploid maize lines (DHLs) derived from crosses between resistant and susceptible maize lines were evaluated for their level of resistance in three to four different environments. For each DHL topcross an average root damage score was estimated and used for QTL analysis. We found genomic regions contributing to western corn rootworm resistance on all maize chromosomes, except for chromosomes 2 and 4. Models fitting all QTL simultaneously explained about 30% of the phenotypic variance for root damage scores in both mapping populations. Our findings confirm the complex genetic structure of host plant resistance against western corn rootworm larval feeding in maize. Interestingly, three of these QTL regions also carry genes involved in ascorbate biosynthesis, a key compound we hypothesize is involved in the expression of western corn rootworm resistance.