Monitoring Fungicide Resistance: Purposes, Procedures and Progress

AbstractRamularia collo-cygni B. Sutton and J.M. Waller is a major disease in Austrian barley-growing regions. To date, fungicide application is the most effective method to manage the disease; however, fungicide resistance to demethylation and succinate dehydrogenase inhibitors has developed over the last few years. In the growing seasons 2016/2017 and 2017/2018, field trials were carried out to analyze the efficiency of fungicide strategies based on different fungicide classes. Disease development, growth parameters and monitoring of CYP51 and sdh mutations were determined. Fungicide treatments resulted in higher disease control, green leaf area and grain yield. In Austrian R. collo-cygni field populations, the frequency of the mutations CYP51-I325T and CYP51-I328L was low to moderate. Frequency of mutations sdhC-H146R and sdhC-H153R was low. Frequencies of CYP51-I325T and -I328L were similar and increased following DMI application. Frequency of sdhC-H146R was higher compared to sdhC-H153R. The SDHI benzovindiflupyr showed a higher selection rate for sdh mutations compared to bixafen. These sdh mutations were not selected if chlorothalonil was used as mixing partner, leading to a stable composition of sdh resistance alleles over the last two years. Chlorothalonil was proven to be an effective tool for anti-resistance strategies. Currently, SDHIs and DMIs are the backbone of Ramularia leaf spot control in Austria; however, the level of resistance is likely to increase in absence of suitable anti-resistance strategies and following the ban of chlorothalonil.

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Kinetic characterisation and inhibitor sensitivity of Candida albicans and Candida auris recombinant AOX expressed in a self-assembled proteoliposome system

Scientific Reports ◽

10.1038/s41598-021-94320-3 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Alice C. Copsey ◽

Mario R. O. Barsottini ◽

Benjamin May ◽

Fei Xu ◽

Mary S. Albury ◽

...

Keyword(s):

Candida Albicans ◽

Future Development ◽

Therapeutic Target ◽

Fungicide Resistance ◽

Alternative Oxidase ◽

Antifungal Agents ◽

Candida Auris ◽

Novel Treatments ◽

Membrane Bound ◽

Self Assembled

AbstractCandidemia caused by Candida spp. is a serious threat in hospital settings being a major cause of acquired infection and death and a possible contributor to Covid-19 mortality. Candidemia incidence has been rising worldwide following increases in fungicide-resistant pathogens highlighting the need for more effective antifungal agents with novel modes of action. The membrane-bound enzyme alternative oxidase (AOX) promotes fungicide resistance and is absent in humans making it a desirable therapeutic target. However, the lipophilic nature of the AOX substrate (ubiquinol-10) has hindered its kinetic characterisation in physiologically-relevant conditions. Here, we present the purification and expression of recombinant AOXs from C. albicans and C. auris in a self-assembled proteoliposome (PL) system. Kinetic parameters (Km and Vmax) with respect to ubiquinol-10 have been determined. The PL system has also been employed in dose–response assays with novel AOX inhibitors. Such information is critical for the future development of novel treatments for Candidemia.

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Fungicide Resistance Evolving in Ramularia Collo-Cygni Population in Estonia

Microorganisms ◽

10.3390/microorganisms9071514 ◽

2021 ◽

Vol 9 (7) ◽

pp. 1514

Author(s):

Riinu Kiiker ◽

Marite Juurik ◽

Andres Mäe

Keyword(s):

Disease Control ◽

High Resistance ◽

Fungicide Resistance ◽

Spring Barley ◽

Point Mutations ◽

Ramularia Leaf Spot ◽

Entire Collection ◽

Dmi Fungicides ◽

Fungicide Target ◽

Succinate Dehydrogenase Inhibitors

Ramularia leaf spot caused by the fungus Ramularia collo-cygni, has recently become widespread in Estonian barley fields. Currently, disease control in barley fields relies on SDHI and DMI fungicides, which might be threatened by R. collo-cygni isolates that are well-adapted to fungicide pressure. In a two-year study, 353 R. collo-cygni isolates were collected from spring barley fields in Estonia. A total of 153 R. collo-cygni isolates were examined for sensitivity to azoles (DMIs; prothioconazole-desthio, epoxiconazole, mefentrifluconazole) and succinate dehydrogenase inhibitors (SDHIs; boscalid, fluxapyroxad). Epoxiconazole was the least effective and a new fungicide mefentrifluconazole was the most effective DMI. Among SDHIs, fluxapyroxad was more effective than boscalid. Also, single R. collo-cygni isolates with high resistance to tested fungicides occurred, which could affect fungicide control of the pathogen. The entire collection of R. collo-cygni was analysed for mutations in fungicide target proteins. Six mutations were identified in CYP51 gene, the most dominant being I381T, I384T, and S459C. Also, numerous point mutations in the SdhC gene were present. The mutation G143A in strobilurin target protein CytB dominates in over 80% of the R. collo-cygni population, confirming the low efficacy of strobilurin fungicides in barley disease control.

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Combination of Suspension Array and Mycelial Growth Assay for Detecting Multiple-Fungicide Resistance in Botrytis cinerea in Hebei Province in China

Plant Disease ◽

10.1094/pdis-07-18-1269-re ◽

2019 ◽

Vol 103 (6) ◽

pp. 1213-1219

Author(s):

Zehua Su ◽

Xin Zhang ◽

Jianjiang Zhao ◽

Wenqiao Wang ◽

Lei Shang ◽

...

Keyword(s):

Botrytis Cinerea ◽

High Throughput ◽

Fungicide Resistance ◽

Mycelial Growth ◽

Accurate Method ◽

Hebei Province ◽

Combination Method ◽

Major Type ◽

Suspension Array ◽

Growth Assay

To provide a high-throughput, efficient, and accurate method to monitor multiple-fungicide resistance of Botrytis cinerea in the field, we used the suspension array, sequencing, and mycelial growth assay in our research. Discriminating-dose bioassays for detecting carbendazim, diethofencarb, boscalid, and iprodione resistance (CarR, DieR, BosR, and IprR, respectively) were used to analyze 257 isolates collected from Hebei Province in China during 2016 and 2017. High resistance frequencies to carbendazim (100%), diethofencarb (92.08%), and iprodione (86.59%) were detected. BosR isolates accounted for 11.67% of the total. In addition, 103 isolates were randomly selected for phenotype and genotype detection. The high-throughput suspension array was utilized to detect eight genotypes simultaneously, including BenA-E198, BenA-198A, SdhB-H272, SdhB-272Y, BcOS1-I365, BcOS1-365S, erg27-F412, and erg27-412S, which were associated with resistance toward carbendazim or diethofencarb, boscalid, iprodione, and fenhexamid (FenR), respectively. Most of the benzimidazole-resistant isolates (81.55%) possessed the E198V mutation in the BenA gene. Ninety-three isolates with dual resistance to carbendazim and diethofencarb showed the E198V/K mutation. All BosR isolates carried the H272R mutation in the SdhB gene. The I365S and Q369P+N373S (66.99%) mutations in the BcOS1 gene were more frequently observed. No mutation was detected in the erg27 gene in Hebei isolates. There were 13 resistance profile phenotypes. Phenotypes with triple resistance were the most common (83.50%), and CarRDieRBosSIprRFenS was the major type. CarR isolates that carried E198V/K/A were all highly resistant (HR) and only one F200Y mutant was moderately resistant (MR) to carbendazim. Isolates that possessed E198V/K were MR or HR to diethofencarb. BosR isolates that possessed H272R mutation were lowly resistant (LR). IprR isolates were all LR or MR. The distribution of half maximal effective concentrations of CarR isolates with E198V/K mutations and IprR isolates with Q369P+N373S mutations significantly increased from 2016 to 2017. Combined with our observations, a combination method of the high-throughput suspension array and the mycelial growth assay was suggested to accurately monitor multiple resistance of B. cinerea in the field.

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