Relationship of Resistance to Benzimidazole Fungicides with Mutation of β-Tubulin Gene in Venturia nashicola

Abstract

Pear scab caused by Venturia nashicola has been reported as an important disease of pear resulting in lowering the quality of pear fruits. In this study, it was conducted to investigate the relationship between resistance of V. nashicola and mutation of β-tubulin gene and the fungicide resistance in field isolate group in benzimidazole fungicides. Responce of V. nashicola to carbendazim could be classified into 3 groups as sensitive that does not grow at all on PDA amended with 0.16 μg/ml of carbendazim, low resistance that could not grow in 4.0 μg/ml medium, and high resistance that can grow even at 100 μg/ml. Thirty isolates of V. nashicola collected from 3 regions as Wonju, Naju, and Okcheon were highly resistant to carbendazim. Analysis of the nucleotide sequence of β-tubulin gene of V. nashicola showed that there was no difference in the nucleotide sequence between the sensitive and the lowresistant isolate, but GAG at codon 198 (glutamic acid) was replaced with GCG (alanine) in the highresistant isolate. Among 10 isolates obtained from the Okcheon, 5 isolates showed the substitution of glycine for glutamic acid, which were resistant to carbendazim, but more sensitive to the mixture of carbendazim and diethofencarb than others. Through these results, all isolates of V. nashicola isolated in pear orchard were found to be resistant to benzimidazoles. Also, mutants E198A and E198G at β-tubulin were found to be important mechanisms of V. nashicola resistance against benzimidazole fungicides.

DMI-Fungicide Resistance in Venturia nashicola, the Causal Agent of Asian Pear Scab—How Reliable Are Mycelial Growth Tests in Culture?

“…If conventional culture methods are not appropriate to monitor fungicide resistance, molecular-based methods might be useful as alternatives for a slow-growing and poor-sporulating fungus like Venturia in particular. The mechanism of MBC resistance was well characterized in V. nashicola [ 10 , 57 ] and various molecular methods such as PCR-RFLP (restriction fragment length polymorphism) analysis and ASPCR (allele-specific PCR) have been developed for the diagnosis of resistance [ 10 ]. However, mechanisms of the DMI resistance are not well known yet.…”

Genetic Diversity of the Pear Scab Fungus Venturia nashicola in Korea

“…In a previous study, Kwak et al. (2017) reported that mutation of E198A may indicate whether the isolates are resistant to benzimidazole fungicides [26]. It is already known that benzimidazole fungicides bind to fungal TUB2 and inhibit microtubule formation [30,31].…”

“…The partial TUB2 sequence was amplified with primer Btub14F (5′-AACCAAATTGGTGCTGCCTTCTG-3′) and BtubR (5′-TGGAGGACATCTTAAGACCACG-3′) as described by Kwak et al. [26]. The partial TEF-1α sequence was amplified with primer VNEFI-f (5′-ACTTGATCTACAAGTGCGGTG-3′) and VNEFI-r (5′-AGGAGTCTCACTTCCAGAG-3′) as described by Zhao et al.…”

Monitoring of Benzimidazole Resistance in Botrytis cinerea Isolates from Strawberry in Korea and Development of Detection Method for Benzimidazole Resistance

“…Benzimidazole fungicides, also known as methyl benzimidazole carbamates, interfere with the formation of the α, β-dimer by binding to the β-tubulin subunit during the microtubule biosynthesis process in fungi ( Davidse and Flach, 1977 ). However, if mutations occur in specific nucleotide sequences of the TUB2 gene, which encodes the β-tubulin protein, benzimidazole fungicides fail to bind to their target, leading to resistance to the fungicidal effects ( Kwak et al, 2017 ; Leroux et al, 2002 ; Yarden and Katan, 1993 ). Specifically, the benzimidazole resistance in B. cinerea has been attributed primarily to a mutation at the 198th codon of the β-tubulin ( Bardas et al, 2008 ).…”