Fusarium temperatum shows a hemibiotrophic infection process and differential pathogenicity over different maize breeds from Mexico

The genus Fusarium contains several species that cause diseases, such as drowning and wilting, in cultivable plants. Fusarium temperatum has been included in the Giberella fujikuroi complex and has been reported as a devastating pathogen for maize in Asia, Europe and South America. In Mexico, maize is one of the most important crops, so we consider it of great importance to describe the infection process of F. temperatum on maize plantlets and the susceptibility of several breeds of maize. We use in vivo assays to determine the infectivity of 6 maize breeds from Mexico. The most resistant breed was Pepitilla with less than 10 percent of damage, while Harinoso de 8, Tuxpeño and Tepecintle showed moderate resistance, while Reventador and Zapata 2 showed the most extensive damage. Because of its susceptibility, Zapata 2 was used to follow the infection process of F. temperatum. To follow the fungus in the infected roots we use a transformed strain that expresses GFPs. We found that the fungus directly penetrates the root tissue without forming an appressorium. We were able to establish a hemibiotrophic infection pattern for F. temperatum (biotrophic stage: 5–10 dpi; transition stage: 15 dpi; necrotrophic stage: 20 dpi). Our results described that F. temperatum presents a hemibiotropic infection pattern and suggests the presence of maize breeds in Mexico that have natural resistance to F. temperatum.