Biological Characteristics and Molecular Mechanisms of Fludioxonil Resistance in Fusarium graminearum in China

Abstract

Fusarium graminearum is the primary causal agent of Fusarium head blight (FHB) of wheat. The phenylpyrrole fungicide fludioxonil is not currently registered for the management of FHB in China. The current study assessed the fludioxonil sensitivity of a total of 53 F. graminearum isolates collected from the six most important wheat-growing provinces of China during 2018 and 2019. The baseline fludioxonil sensitivity distribution indicated that all of the isolates were sensitive, exhibiting a unimodal cure with a mean effective concentration for 50% inhibition value of 0.13 ± 0.12 μg/ml (standard deviation). Five fludioxonil-resistant mutants were subsequently induced by exposure to fludioxonil under laboratory conditions. Ten successive rounds of subculture in the absence of the selection pressure indicated that the mutation was stably inherited. However, the fludioxonil-resistant mutants were found to have reduced pathogenicity, higher glycerol accumulation, and higher osmotic sensitivity than the parental wild-type isolates, indicating that there was a fitness cost associated with fludioxonil resistance. In addition, the study also found a positive cross resistance between fludioxonil, procymidone, and iprodione, but not with other fungicides such as boscalid, carbendazim, tebuconazole, and fluazinam. Sequence analysis of four candidate target genes (FgOs1, FgOs2, FgOs4, and FgOs5) revealed that the HBXT2R mutant contained two point mutations that resulted in amino acid changes at K223T and K415R in its FgOs1 protein, and one point mutation at residue 520 of its FgOs5 protein that resulted in a premature stop codon. Similarly, the three other mutants contained point mutations that resulted in changes at the K192R, K293R, and K411R residues of the FgOs5 protein but none in the FgOs2 and FgOs4 genes. However, it is important to point out that the FgOs2 and FgOs4 expression of all the fludioxonil-resistant mutants was significantly (P < 0.05) downregulated compared with the sensitive isolates (except for the SQ1-2 isolate). It was also found that one of the resistant mutants did not have changes in any of the sequenced target genes, indicating that an alternative mechanism could also lead to fludioxonil resistance.

Exploring Potential Mechanisms of Fludioxonil Resistance in Fusarium oxysporum f. sp. melonis

“…The fungal cultures were incubated at 24 °C with a 12 h light/dark photoperiod, and preserved on potato dextrose agar (PDA) medium at 4 °C. Mycelial samples were prepared using the protocol of a previous study [ 18 ].…”

“…Fludioxonil, a phenylpyrrole fungicide, has been shown to have broad-spectrum activity against a wide range of fungal pathogens, and has been used to control many diseases in the field [ 13 , 14 , 15 , 16 , 17 , 18 ]. Previous studies have suggested that the mode action of fludioxonil is to inhibit fungal growth by overstimulating the high osmolarity glycerol (HOG) stress response signal transduction pathway, which causes the hyphae to swell and burst [ 19 ].…”

The Endoplasmic Reticulum Cargo Receptor FgErv14 Regulates DON Production, Growth and Virulence in Fusarium graminearum

“…In addition, F. graminearum produces a kind of trichothecene mycotoxin named deoxynivalenol (DON), which is toxic to humans and livestock by binding to the ribosome to inhibit the protein synthesis of eukaryotic organisms [ 6 , 7 ]. However, the effective control of FHB remains challenging, with management relying mainly on fungicides, which have many unwanted effects [ 8 , 9 ]. Therefore, understanding the underlying mechanisms responsible for the virulence in F. graminearum may facilitate the development of novel strategies and effective means for FHB control.…”

Toxicity of procymidone to Bombyx mori based on physiological and transcriptomic analysis

“…As low toxic fungicide, procymidone was widely used in the prevention and treatment of fungal diseases such as sclerotinia and gray mode in agriculture. Procymidone is often used on many crops in China including tomato (Cai et al, 2020; H. Li, et al, 2020; T. T. Li et al, 2020), wheat (Zhou et al, 2020), and mulberry tree (Wei et al, 2016) due to its wide spectrum and high efficiency. A number of studies have shown that procymidone had toxicity to organisms (Abe et al, 2018; Lai et al, 2021; Tarui et al, 2018; Tomigahara et al; 2018, Y. Wu et al, 2018, A. Wu et al, 2021).…”