Identification and Characterization of Carbendazim-Resistant Isolates of Gibberella zeae

Abstract

Sensitivity of Gibberella zeae to carbendazim was determined by measuring mycelial growth in fungicide-amended media. Among 1,529 isolates tested, 31 isolates showed a high level of resistance (HR) to carbendazim (fungicide concentration that results in 50% inhibition of mycelial growth [EC50] of 10.35 to 30.26 mg a.i. liter–1) and 10 isolates were moderately resistant (MR) (EC50 of 4.50 to 7.28 mg a.i. liter–1). The remaining 1,488 isolates were sensitive to carbendazim and were unable to grow on potato dextrose agar amended with carbendazim at 2 mg a.i. liter–1. Analysis of DNA sequences of the β2-tubulin (Tub2) gene showed that all 10 MR isolates had a point mutation at codon 198 causing a replacement of glutamic acid by glutamine. At the codon position 167, the amino acid phenylalanine was replaced by tyrosine in 28 of 31 HR isolates. The remaining three HR isolates had a point mutation at codon 200 which converted phenylalanine to tyrosine. Based on these point mutations in the Tub2 gene, allele-specific polymerase chain reaction primers were developed for rapid detection of the point mutations. The rapid molecular method will be a valuable tool for the monitoring of carbendazim resistance in G. zeae. Additionally, deletion of the β1-tubulin gene (Tub1) in the HR isolate GJ33 resulted in increased resistance to carbendazim. These results indicate that Tub1 plays a role in the sensitivity of G. zeae to carbendazim.

α1-Tubulin FaTuA1 plays crucial roles in vegetative growth and conidiation in Fusarium asiaticum

“…Several studies have been conducted to explore the functions of b-tubulins in this pathogen. The resistance to MBC fungicides is caused by point mutations in the b2-tubulin [19,20]. Deletion of the b2-tubulin resulted in reduced conidiation, vegetative growth and pathogenicity, but increased sensitivity to carbendazim [19,21].…”

A single-nucleotide-polymorphism-based genotyping assay for simultaneous detection of different carbendazim-resistant genotypes in the Fusarium graminearum species complex

“…So far, five resistant genotypes of FGSC have been characterized. Based on the previous reports (more than 10,000 isolates tested) in China (Duan et al, 2014; Liu et al, 2010; Liu et al, 2014), F167Y was predominant (>80%), followed by E198Q and F200Y. These three genotypes covered 99.99% tested resistant isolates.…”

“…Several studies report that F167Y was the most common resistant genotype (Chen et al, 2009; Liu et al, 2010). In this study, we also found F167Y to be the predominant resistant genotype in both Jiangsu and Anhui Province followed by E198Q and F200Y.…”

“…MBC-resistant isolates of the FGSC were detected for the first time in 1992 in the Zhejiang Province, while subsequently resistant populations were observed in neighboring provinces in the lower reaches of the Yangtze River including Jiangsu, Shanghai and Anhui, resulting in a decline in the efficiency of control of FHB by MBC (Chen et al, 2007; Liu et al, 2010). Rotational application of several fungicides is an effective way for management of resistant populations and to extend the lifespan of the fungicides.…”

“…Based on the SNPs, several molecular techniques have been developed for rapid detection of MBC-resistant isolates. Liu et al (2010) developed three pairs of allele-specific PCR (ASPCR) primers to detect the resistant isolates harboring F167Y, E198Q and F200Y mutations respectively. PIRA-PCR and cycleave PCR approaches were developed for the specific detection of the F167Y genotype (Hou et al, 2011; Luo et al, 2009).…”