Plant cell walls contain important nutrients for insect herbivores. However, access to macro and micronutrients contained within the cell walls are limited by lignin. Therefore, plant lignification may decrease insect fitness and deter host plant feeding. To examine the effect of lignin of western corn rootworm (Diabrotica virgifera vigifera LeConte) fitness, we reared neonate larvae on brown midrib (bm) corn mutants bm1, bm3, and bm5. Each bm mutant targets a specific step in the lignin biosynthetic pathway that results in reduced lignin content and altered lignin composition in roots. Larval weight was increased when reared on low lignin mutants compared to wild-type corn. We paired plant assays with diet assays to test the impact of lignin alone on fitness. Evidence supports a direct anti-nutritive capacity of lignin for western corn rootworm. Altering the rate or location of lignin deposition may reduce herbivore fitness that leads to population reduction over time. Identifying mechanisms by which plants alter lignin deposition in response to environmental cues may help explain variation in herbivore performance and support efforts to improve pest management.
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