Physical resistance: a different perspective on maize ear rot resistance

Maize ear rot, caused by multiple pathogens, is one of the most common fungal diseases of maize. It can not only seriously cause yield losses, but also contaminate grains with mycotoxins and threaten both human and animal health. Resistance to maize ear rot is mainly composed of physical resistance and biochemical resistance. For decades, researchers have conducted extensive studies on resistance genes and molecular resistance mechanisms and have made some progress on biochemical resistance. However, very little research has been carried out on physical resistance. Currently, the general research approach for maize ear rot is invasive inoculation, which artificially breaks the physical resistance. Hence, this method is unable to screen for the physical resistance of plants. Here, we point out that maize ears are usually invaded by multiple pathogens simultaneously under natural conditions. The biochemical defense pathways induced by different pathogens are diverse, leading to extremely complex resistance mechanisms that severely restrict the detection of resistance candidate genes and resistance breeding. By contrast, the physical resistance of plants can provide broad-spectrum resistance by preventing the invasion of multiple pathogens. Therefore, refocusing on the physical barriers against pathogen invasion may be an important direction for future research on maize ear rot.