First Report of Maize Ear Rot Caused by <i>Fusarium awaxy</i> in China

Ear rot caused by various fungal pathogens is an important epidemic disease in maize production worldwide, causing significant yield losses and declines in quality. In 2024, a survey was conducted to understand the etiology of ear rot in maize growing areas of China. Symptomatic ears were collected in 589 fields from 16 provinces (Heilongjiang, Jilin, Liaoning, Inner Mongolia, Xinjiang, Gansu, Ningxia, Guangxi, Guizhou, Yunnan, Sichuan, Jiangsu, Anhui, Shandong, Henan and Hebei) and there were usually ten ears from each field. Maize kernels with typical pink and/or white mold were surface sterilized with 5% sodium hypochlorite and 75% ethanol, rinsed in sterile distilled water, and placed on potato dextrose agar (PDA). Suspected Fusarium strains showing cream to salmon colonies on PDA were selected after 3 to 5 days of incubation at 25°C and purified by the single-spore isolation method (Qiu et al., 2020). Morphological and molecular characteristics were used to identify these strains. Consistent with the previous report (Qiu et al., 2025), Fusarium fujikuroi species complex and Fusarium graminearum species complex predominated in Chinese maize samples. However, one strain (C24390) from Heilongjiang province was identified as F. awaxy based on the following results: (I) Colonies on PDA produced dense aerial mycelium and were white to pale violet in color. Macroconidia were mostly 3 septates, moderately curved to straight, and 29.5 ± 8.8 × 3.6 ± 1.1 μm (n = 50). Microconidia were aseptate and 10.7 ± 2.6 × 3.3 ± 0.9 μm (n = 50). (II) Partials of the RNA polymerase second-largest subunit partial genes (RPB2) and translation elongation factor-1α (TEF-1α) were amplified with the primers RPB5F/7CR and EF1/2, respectively (O'Donnell et al., 1998). BLAST searches of the obtained sequences showed 100% homology with several F. awaxy strains from GenBank. DNA sequences of partial TEF-1α and RPB2 were deposited in GenBank as PV798379 and PV798380, respectively. Pairwise DNA alignments against the reference database Fusarioid-ID (https://www.fusarium.org/) revealed the highest similarity, 99.63%, to F. awaxy strain ATCC 38016. (III) The primary metabolite of F. awaxy in rice culture was moniliformin (MON) at the concentration of about 52000 ± 7000 μg/kg (Qiu et al., 2020). (IV) In late April 2025, field pathogenicity tests were conducted in maize cultivation bases of Jiangsu Academy of Agricultural Sciences (32°2′N, 118°52′E) and maize variety Jiangyu877 by injecting 1 mL of conidia suspension (106/ml) through the silk channel of maize ear at the silking stage. Control ears were treated with sterile distilled water. At physiological maturity, white mold was observed in the inoculated ears and was similar to that observed in the sampling field. The inoculated ears were contaminated with high MON levels (5016 ± 372 μg/kg). No symptoms or toxins developed on controls. This pathogen was successfully recovered from the moldy kernels but not from controls. This fungus was first isolated from decayed maize stalks in Brazil (Crous et al., 2019) and recently confirmed to be the pathogen of maize stalk rot in China (Han et al., 2023). To our knowledge, this is the first report about pathogenicity and toxigenicity of F. awaxy in maize ear rot in China and it may be a new risk to food safety and human health.