SP4: Combined Effects of Stem Borers and Abiotic Stresses on Maize Commercial Hybrids

Insect herbivores consistently exploit host plants that have been weakened by environmental stress; however, the exact mechanisms driving these interactions in field environments remain elusive. SP4 focuses on agricultural entomology and chemical ecology, quantifying how drought and nitrogen deficiency alter maize susceptibility to the African and European stem borers. In particular, SP4 investigates both early and late defense mechanisms in plants, including the emission of volatile organic compounds (VOCs).

Project description

This subproject (SP4) investigates the combined effects of abiotic (drought, nitrogen deficiency) and biotic (stem borer infestation) stressors on the growth, defense mechanisms, and yield of commercial maize hybrids.

Maize cultivation worldwide is being constrained by the increasingly frequent co-occurrence of environmental stressors and pest pressure, yet the mechanistic understanding of their interactions, particularly under field conditions, remains incomplete. The project aims to elucidate how these stressors interact at multiple biological levels (physiological, transcriptional, metabolic) in maize, and how these changes affect the development of herbivores, their behaviour, and the recruitment of natural enemies. Field and greenhouse experiments will be conducted in both temperate (Germany) and tropical (Kenya) climate zones, using commercial hybrids.

From a phytocentric perspective, the research investigates how combined stress conditions modulate the structural integrity of the plant, central and specialised metabolite profiles, phytohormonal signalling, and herbivore-induced emissions of plant volatile compounds. Particular attention is paid to early interactions between insects and plants, including plant responses to oviposition and the feeding activity of early-instar larvae.

Two pieces of split maize stem with discolouration are placed on a wooden surface next to a folding ruler showing measurements in centimetres, illustrating Ecophysiology studies for MultiStress Research.

From an entomocentric perspective, the study examines how stress-induced changes in the plant’s phenotype influence the performance of stem borers, their oviposition preferences, and their parasitoid attraction. The project is based on the hypothesis that abiotic stress alters host suitability and the composition of the volatile blend in a genotype-dependent manner, thereby affecting trophic interactions and the effectiveness of indirect defense mechanisms. Another important component is the development of a mechanistic, process-based crop-insect interaction model. This model will integrate experimental data to simulate maize growth, the development of stem borers, and yield under variable stress conditions. The model builds on existing platforms and aims to bridge statistical and physiological modelling approaches to predict genotype-specific responses. Overall, SP4 aims to close critical knowledge gaps in multitrophic plant-insect-environment interactions by linking detailed empirical observations with novel modelling strategies.