Geographic variations in the Fusarium species and toxins associated with maize ear rot in China

Diverse species of the Fusarium genus are usually the primary cause of maize ear rot, which reduces yield and quality, as well as contamination of toxic secondary metabolites. There has been little combined analysis of the diversity of pathogens and toxins in maize kernels in China, and this information is important for disease and mycotoxin control. To address this, a large-scale survey including 1217 samples was performed across China from 2019 to 2021. The most prominent contaminants were B-series fumonisins (FB₁, FB₂, and FB₃), with greater levels of FB₁ were found in southern regions. Trichothecenes and zearalenone were also serious concerns; deoxynivalenol (DON) and nivalenol (NIV) primarily originated from northeast and southwest China, respectively. Fusarium fujikuroi species complex (FFSC) and Fusarium sambucinum species complex (FSAMSC) were the most prevalent species complexes. F. verticillioides dominated in the former complex and widespread in all sampling sites. In FSAMSC, DON-producing F. graminearum and F. boothii were the predominant pathogens in the northeast, whereas all NIV type F. meridionale inhabited in the southwest. The FFSC and FSAMSC strains were pathogenic to maize ear and stalk, with varying severities. The FSAMSC strains also could infect wheat heads, and smaller amounts of toxins were found in FFSC strains inoculated wheat samples without causing any symptoms.