Speaker: Steven Whitham, Professor in the Department of Plant Pathology, Entomology and Microbiology at Iowa State University 

Title: Effects of elevated atmospheric CO2 on interactions between pathogens and crops

Abstract: Rising atmospheric CO₂ influences many aspects of plant physiology and biology including interactions with pathogens, which may reshape disease pressure in agriculture. At the present time, predicting how elevated CO₂ (eCO₂) influences any particular crop–pathogen interaction remains challenging. We investigated how eCO₂ (550 parts per million) modulates immunity and disease outcomes in soybean and maize for bacterial, viral, fungal, and oomycete pathogens with diverse lifestyles. In both soybean (C3) and maize (C4), eCO₂ enhanced activation of early immune signaling and reduced susceptibility to bacterial pathogens Pseudomonas syringae pv. glycinea and Clavibacter nebraskensis, respectively, consistent with stronger pattern-triggered immunity. In contrast, eCO₂ increased susceptibility to bean pod mottle virus and soybean mosaic virus in soybean and sugarcane mosaic virus in maize, indicating diminished in antiviral defense. We observed different effects on fungal pathogens with more severe symptoms of sudden death syndrome caused by Fusarium virguliforme in soybean, less disease on maize plants infected with Exserohilum turcicum and Colletotrichum graminicola, and no effect on Puccinia sorghi in maize. Responses of soybean and maize to the oomycete root pathogen, Pythium sylvaticum, were comparable under ambient and elevated CO₂. Together, these results indicate that eCO₂ alone can have similar effects on basal immune signaling in both C3 and C4 crops while driving divergent, pathosystem-specific disease outcomes. While much attention is given to abiotic factors such as temperature, water availability, and relative humidity, this work underscores the need to integrate atmospheric CO₂ into mechanistic and predictive frameworks for crop immunity under future climates

Host: Dior Kelley, GDCB associate professor