The objective of this study is to clarify the population distribution of Fusarium spp. of maize ear rot in Jilin Province and the inhibitory effect of fungicides on the growth of Fusarium mycelium, and to provide a basis for the targeted control of maize ear rot.

149 samples of maize ear rot collected from 36 cities and counties in Jilin Province in 2020 were isolated and identified by tissue isolation and molecular biology methods. The specific toxin synthesis primers of related genes were synthesized using Fusarium graminearum species complex (FGSC) toxin. The toxigenic chemotypes were detected, and the pathogenicity of some FGSC was determined. The inhibitory effect of 7 fungicides on FGSC was determined by the mycelial growth rate method.

A total of 233 Fusarium strains were isolated, belonging to 4 Fusarium complex species, including 9 Fusarium species, which were F. verticillioides, F. boothii, F. graminearum, F. proliferatum, F. asiaticum, F. chlamydosporum, F. fujikuroi, F. equiseti and F. subglutinans. The isolation frequencies were 33.05%, 26.18%, 25.32%, 12.45%, 0.86%, 0.86%, 0.43%, 0.43% and 0.43%, respectively. The isolate frequency of FGSC was the highest, which was 52.36%, and it was the dominant pathogen of maize ear rot in Jilin Province. The proportions of F. boothii, F. graminearum and F. asiaticum in FGSC were 50.00%, 48.36% and 1.46%, respectively. The phylogenetic tree showed that the interspecific and intraspecific genetic diversity of FGSC was rich. The results of pathogenicity assay showed that 52.73% of FGSC were medium pathogenic strains. F. graminearum isolated from the main maize producing areas in the east had the strongest pathogenicity. Toxigenic chemotype detection showed that F. asiaticum produced nivalenol (NIV) chemotype, F. graminearum and F. boothii produced 15-acetyl-deoxynivalenol (15-AcDON) chemotype. The EC₅₀ of the 7 fungicides for inhibiting the growth of FGSC ranged from 0.02 to 19.45 μg·mL^-1. Fludioxonil (FS), imazalil (FS), flusilazole (EC), tebuconazole (TC) and myclobutanil (EW) had good inhibitory effects on FGSC and the difference was not significant. The EC₅₀ of FGSC was less than 1.20 μg·mL^-1 and EC₉₀ was less than 100 μg·mL^-1. The difference of EC₅₀ between F. graminearum and F. boothii was significant under 30% pyraclostrobin treatment. The EC₅₀ of F. graminearum was 10.24 times higher than that of F. boothii.

The dominant pathogenic Fusarium of maize ear rot in different maize producing areas of Jilin Province is different. F. graminearum and F. boothii are dominant species in the east and west, and F. verticillioides is dominant species in the middle. The interspecific and intraspecific genetic diversity of FGSC is rich. Fludioxonil, imazalil, flusilazole, tebuconazole and myclobutanil have better antifungal effect on FGSC. There is no significant difference in the fungicides susceptibility among FGSC.

The objective of this study is to clarify the relationship between maize aphids damage and the occurrence of maize ear rot and the level of mycotoxin pollution in maize kernels, and to provide a reference for establishing a comprehensive control system of maize ear rot and exploring the effective control technology of main Fusarium toxins.

The 105 aphid-damaged maize ears were collected from 46 cities and counties in Jilin Province in 2021. Pathogenic fungi were isolated and identified using tissue isolation and molecular biology methods for aphids, bracts and kernels. The isolation frequency of different Fusarium species on each sample and the proportion of the same Fusarium number isolated from different sample combinations in aphid-infested samples were calculated. The distribution of pathogens in different regions of Jilin Province and the correlation between the species of Fusarium carried by aphids, bracts and kernels were analyzed. Additionally, ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was employed to determine the presence of Fusarium toxin species and content of maize kernels with and without aphid infestation. The detection rate of fumonisin (FB), deoxynivalenol (DON) and zearalenone (ZEA) in samples exceeding the standard was calculated, and the effect of aphid damage on the toxin secretion of Fusarium in kernels was analyzed.

Aphids, bracts and kernels from 105 ears were tested for the Fusarium, the infection rate of aphids was 57.14%, and that of bracts and kernels was 81.90% and 82.86%, respectively. A total of 1 394 Fusarium strains, including 16 pathogenic Fusarium species, were obtained through single spore isolation and purification. Among them, 8, 13 and 12 Fusarium species were isolated from aphids, bracts and kernels, respectively. The dominant Fusarium species on aphids, bracts and kernels were F. verticillioides and F. proliferatum. Three species including F. andiyazi, F. incarnatum and F. temperatum were detected for the first time on maize kernels in Jilin Province. The results of mycotoxin analysis revealed a higher incidence of positive mycotoxin contamination in aphid-damaged maize ears compared to aphid-undamaged ones. All maize samples exhibiting excessive mycotoxin content were damaged by aphids. The identification of corresponding mycotoxin-producing strains was possible in the majority of cases where mycotoxins were detected in aphid-damaged maize ears.

F. verticillioides and F. proliferatum were the dominant Fusarium species isolated from aphids, bracts and kernels. The main Fusarium species isolated from aphids, bracts and kernels on the same maize ear were the same. Aphid damage significantly increased toxin accumulation levels in maize kernels, and the type of toxin was highly correlated with the detection of Fusarium species.