Inoculation of Maize Ears with Fusarium graminearum to Study Gibberella Ear Rot

Maize is an important food and fuel crop globally. Ear rots, caused by fungal pathogens, are some of the most detrimental maize diseases, due to reduced grain yield and the production of harmful mycotoxins. Mycotoxins are naturally occurring toxins produced by certain fungal species that can cause acute and chronic health issues in humans and animals that consume mycotoxin-contaminated grain. Pathogens can infect the developing ear through silks, or through wounds in the ears produced by pests. Plants naturally develop genetic resistance to pathogens. The maize genes involved in resistance to the pathogen may be different, depending on whether the ear was infected via silks or wounds. To differentiate between these two forms of resistance, natural infections can be reproduced by injecting inoculum through the silk channel, or by producing wounds using a needle, and introducing inoculum directly onto developing ears. Our protocol describes a technique used to inoculate developing maize ears with Fusarium graminearum, one of the fungal species that causes ear rot. We describe both silk channel and side needle inoculation techniques. Our protocol uses a backpack inoculator for both methods of infection, allowing for high-throughput inoculations, which are necessary for large field experiments. After harvest, the ears are visually rated on a percentage of disease scale. The protocol results in quantitative data that can be used for research on elucidating genetic resistance to fungal pathogens to assist breeding selections, and to understand plant-pathogen interactions of ear rots in maize.