Inoculation of Maize Roots with Globisporangium ultimum var. ultimum to Study Pythium Root Rot.

Maize is a globally important field crop for food and fuel production. Yield can be affected early in the growing season by oomycete and fungal pathogens that cause root rot or prevent seed germination. The diseases caused by these pathogens are referred to as seedling blights, root rots, or damping off. Pythium root rot is one of the most significant of these diseases. The disease is caused by multiple species of the oomycete genera Globisporangium and Pythium and results in significant yield losses due to reduced seed germination and reduced vigor of surviving seedlings. In this protocol, we mimic the natural infection process by mixing the inoculum into the potting media in which seeds are planted. Then, we flood the seeds daily for several days in large plastic totes to induce flooding conditions. Disease severity is assessed using stand counts and measuring root mass and length. This protocol allows researchers to investigate quantitative differences in disease symptoms, isolate aggressiveness, as well as levels of host resistance. This protocol was developed for the pathogen Globisporangium ultimum var. ultimum, but it can be adapted for other species.