Analyzing infection dynamics between Pythium and maize grown in two container types under greenhouse conditions

• Joseph Romano, Plant Science, University of Delaware

• Qi Mu, Plant and Soil Sciences, University of Delaware

Pythium is a member of the fungus-like group of oomycete pathogens. The organism causes Pythium Root Rot (PRR), a soilborne disease which gives rise to seedling damping-off and root necrosis, leading to major yield losses in maize and other susceptible crops. In this experiment, we evaluated the suitability of different growing containers with the goal of selecting the most ideal one to study plant-pathogen interactions under greenhouse conditions. Maize plants inoculated with Pythium were grown in standard 4-inch square pots and 2.5 x 10-inch cone containers to assess container dimension related growth differences. Treatments were composed of three groups: a control, inoculation with aggressive Pythium graminicola, and inoculation with milder Pythium dissotocum. Two inbred maize varieties—susceptible B73 and moderately resistant WIL900—were included across all treatments to assess potential genotype-specific responses. Disease severity was evaluated through seedling emergence timing, survival rates, shoot and root biomass and length measurements, and root quality grading based on infection level. Imaging of both shoots and root systems was conducted, with raw root images processed for additional feature extraction via a root phenotyping software. In addition to macroscopic imaging, roots were examined microscopically to assess refined structural features and infection symptoms. Findings indicate that container type significantly influences plant-pathogen interactions, resulting in distinct differences in root and shoot phenotypes, as well as trait variation across different treatments. Disease severity also differed between maize genotypes, highlighting genotype-driven responses to infection. These results demonstrate that container type can significantly impact disease spread and plant development, underscoring the importance of standardized growth conditions for reliable phenotyping. Through the creation of a benchmark protocol based on ideal growing methods, additional genotypes can then be screened to breed for PRR resistance in maize.