Activity and cell toxicology of fluazinam on Fusarium graminearum
Luoyu Wu1, Zhiwen Wu1, Feifei Zhao1
1College of Plant Protection, Nanjing Agricultural University, Key Laboratory of Pesticide, Nanjing, Jiangsu Province 210095, China.
Abstract:
Fusarium graminearum is an important plant pathogen and the causal agent of Fusarium head blight (FHB). At present, the principal method of controlling FHB is through fungicides. Fluazinam is an agent with strong broad-spectrum antifungal activity and has been used to control many diseases. However, there are no reported uses of fluazinam for controlling FHB. This study reports the activity and cell toxicology mechanisms of fluazinam on the filamentous fungus F. graminearum and its effect on fungal growth and development. The activity of fluazinam was tested for 95 wild-type field strains of F. graminearum. The EC50 values (the 50% effective concentration) of fluazinam for inhibition of mycelial growth and spore germination ranged from 0.037 μg/ml to 0.179 μg/ml and from 0.039 μg/ml to 0.506 μg/ml, respectively. The fluazinam sensitivity of these strains varied in 4.9 and 13.0 folds, implying that the target of the fungicide remained unchanged. After treatment with 0.3 μg/ml (≈EC90) fluazinam, the production of conidia was reduced, and the cell wall and cell membrane had shrunked; the cell nucleus and septum morphology, cell membrane permeability, and sexual development were not affected. When treated with 0.1 μg/ml (≈EC50) or 0.3 μg/ml fluazinam, the mycelial respiration and deoxynivalenol (DON) synthesis of F. graminearum were decreased. Confocal images showed that the formation of toxisomes was disturbed after fluazinam treatment, suggesting that fluazinam reduces DON synthesis by inhibiting toxisome formation. Infection of wheat coleoptiles revealed that fluazinam had a strong protective activity against F. graminearum. At 250 μg/ml fluazinam the control efficacy of protective treatments reached 100% and controlled strains resistant to carbendazim. These results contribute to the understanding of the mode of action of fluazinam and its application.
Insights
This study reveals fluazinam effectively controls Fusarium graminearum, the cause of Fusarium head blight (FHB). Fluazinam inhibits fungal growth and deoxynivalenol (DON) synthesis by disrupting toxisome formation, offering a new disease management strategy.
Area of Science:
- Plant Pathology
- Mycology
- Fungal Toxicology
Background:
- Fusarium graminearum causes Fusarium head blight (FHB), a significant threat to cereal crops.
- Current FHB management relies heavily on fungicides, necessitating the exploration of novel control agents.
- Fluazinam, a broad-spectrum antifungal, has shown potential but its efficacy against FHB was previously unreported.
Purpose of the Study:
- To investigate the antifungal activity of fluazinam against Fusarium graminearum.
- To elucidate the cellular toxicology mechanisms of fluazinam in F. graminearum.
- To evaluate fluazinam's potential for controlling FHB in wheat.
Main Methods:
- Tested fluazinam activity on 95 wild-type F. graminearum strains, determining EC50 values for mycelial growth and spore germination.
- Analyzed cellular effects of fluazinam, including cell wall, membrane, nucleus, and septum morphology, and conidia production.
- Assessed fluazinam's impact on mycelial respiration, deoxynivalenol (DON) synthesis, and toxisome formation using confocal microscopy.
- Evaluated protective activity against F. graminearum in wheat coleoptile infection assays.
Main Results:
- Fluazinam exhibited potent inhibition of F. graminearum mycelial growth (EC50: 0.037–0.179 μg/ml) and spore germination (EC50: 0.039–0.506 μg/ml).
- Fluazinam treatment reduced conidia production and disrupted toxisome formation, leading to decreased deoxynivalenol (DON) synthesis.
- The fungicide demonstrated strong protective activity in wheat, achieving 100% efficacy at 250 μg/ml and controlling carbendazim-resistant strains.
Conclusions:
- Fluazinam is a highly effective fungicide against Fusarium graminearum, with significant potential for managing Fusarium head blight (FHB).
- The mode of action involves inhibition of fungal growth and DON production through disruption of toxisome formation.
- Fluazinam offers a promising alternative for FHB control, including against fungicide-resistant strains.
