Activity of Demethylation Inhibitor Fungicide Metconazole on Chinese Fusarium graminearum Species Complex and Its Application in Carbendazim-Resistance Management of Fusarium Head Blight in Wheat

Abstract

Fusarium graminearum species complex (FGSC), causing Fusarium head blight (FHB) of wheat, has species-specific geographical distributions in wheat-growing regions. In recent years, benzimidazole resistance of FHB pathogens has been largely widespread in China. Although the demethylation inhibitor fungicide metconazole has been used for FHB control in some countries, no information about metconazole sensitivity of Chinese FHB pathogen populations and efficacy of metconazole in FHB control in China is available. In this study, the sensitivity of FGSC to metconazole was measured with 32 carbendazim-sensitive strains and 35 carbendazim-resistant strains based on mycelial growth. The 50% effective concentration values of 67 strains were normally distributed and ranged from 0.0209 to 0.0838 μg ml−1, with a mean of 0.0481 ± 0.0134 μg ml−1. No significant difference in metconazole sensitivity was observed between carbendazim-sensitive and -resistant populations. An interactive effect of metconazole and phenamacril, a novel cyanoacrilate fungicide approved in China against Fusarium spp., in inhibiting mycelial growth showed an additive interaction at different ratios. Furthermore, field trials to evaluate the effect of metconazole and metconazole + phenamacril treatments in FHB control, deoxynivalenol (DON) production, and grain yields were performed. Compared with the fungicides carbendazim and phenamacril currently used in China, metconazole exhibits a better efficacy for FHB control, DON production, and grain yields, and dramatically reduces use dosages of chemical compounds in the field. The mixture of metconazole and phenamacril at ratios of 2:3 and 1:2 showed the greatest efficacy for FHB control, DON production, and grain yields among all the fungicide treatments but its use dosages were higher in comparison with metconazole alone. In addition, FHB control, grain yields, and DON levels were significantly correlated with each other, showing that visual disease indices can be used as an indicator of grain yields and DON contamination. Meanwhile, the frequency of carbendazim-resistant alleles in F. graminearum populations was dramatically reduced after metconazole and phenamacril alone and the mixture of metconazole and phenamacril applications, indicating that metconazole and a mixture of metconazole and phenamacril can be used for carbendazim resistance management of FHB in wheat. Overall, the findings of this study provide important data for resistance management of FHB and reducing DON contamination in wheat grains.

Baseline sensitivity of Fusarium graminearum from wheat fields in Henan, China, to metconazole and analysis of cross resistance with carbendazim and phenamacril

“…The results showed that the range of EC 50 values to metconazole for the 119 F. graminearum isolates recovered from Henan wheat fields were 0.0103 to 0.0775 μg/ml with an average EC 50 value of 0.0293 ± 0.0114 μg/ml. In previous studies, similar results were detected in the Jiangsu F. graminearum population to metconazole with EC 50 values ranging from 0.0209 to 0.0838 μg/ml and an average of 0.0481 ± 0.0134 μg/ml (Duan et al, 2019). The mean EC 50 value of the Brazilian F. graminearum population from wheat fields was 0.037 μg/ml (Spolti et al, 2012), and the EC 50 value of 80% of 101 F. graminearum isolates recovered from wheat fields in Japan was lower than 0.1 μg/ ml (Tateishi et al, 2010).…”

“…As resistance in the FGSC population is seen to increase to fungicides belonging to benzimidazoles and cyanoacrylates, it is recommended to include the use of metconazole in control programmes against FHB. The DMI fungicide metconazole has high activity against F. graminearum (Duan et al, ). In the current study conducted during 2016 and 2017, the susceptibility of the Henan F. graminearum population that had no previous exposure to metconazole was determined by inhibiting mycelial growth.…”

“…Metconazole, belonging to the triazole fungicides, is an inhibitor of C-14α demethylase in ergosterol biosynthesis and is called the demethylation inhibitor (DMI) fungicide. It has high activity against F. graminearum, Zymoseptoria tritici and many other plant pathogens (Doukas, Markoglou, Vontas, & Ziogas, 2012;Duan et al, 2019;Kumazawa, Ito, Saishoji, & Chuman, 2000;Taher et al, 2014). Until now, the inhibition of mycelial growth of F. graminearum by metconazole has been reported often in Japan and Brazil (Spolti, Jorge, & Ponte, 2012;Tateishi et al, 2010).…”

Impact of Five Succinate Dehydrogenase Inhibitors on DON Biosynthesis of Fusarium asiaticum, Causing Fusarium Head Blight in Wheat

“…However, phenamacril has a high resistance risk in FGSC [10]. Previous studies have reported a strong correlation between FHB control efficacy and DON contamination [32,37,38,39]. Therefore, it is necessary to find novel fungicides for controlling FHB and DON contamination caused by FGSC.…”

Fusarium Toxins in Chinese Wheat since the 1980s

“…Several studies have proved that tebuconazole alone at varied concentrations or in combination with other fungicides was effective in inhibiting FHB and DON, and the drug showed optimal performance at the early anthesis stage or later anthesis stage [147,148,149,150]. The sensitivities of FHB pathogens to metconazole and the efficacy of this fungicide in FHB and DON control in China were reported in a recent study; metconazole exhibited better efficacy than phenamacril and carbendazim [151]. Propiconazole also had a certain role in toxin management [148], but it was reported that this fungicide may have the opposite effect on toxin control at low doses.…”