Emergence of succinate dehydrogenase inhibitor resistance of Pyrenophora teres in Europe

BACKGROUND Metyltetraprole is a new fungicide with a unique tetrazolinone‐moiety and a similar side chain to a known quinone outside inhibitor (QoI), pyraclostrobin. In this study we describe a unique bioactivity of metyltetraprole on QoI‐resistant strains of Zymoseptoria tritici and Pyrenophora teres . RESULTS Metyltetraprole exhibited potent antifungal activity against Ascomycetes; it was especially effective against Z. tritici and P. teres in seedling pot tests. Metyltetraprole was also effective in field tests with QoI‐resistant mutants. Antifungal activity tests using field strains of Z. tritici and P. teres showed that the performance of metyltetraprole was unaltered by QoI, succinate dehydrogenase inhibitor (SDHI), and sterol 14α‐demethylation inhibitor (DMI) resistance. However, the mitochondrial activity test indicated that the compound inhibits the respiratory chain via complex III. CONCLUSION Metyltetraprole is a novel fungicide that is highly effective against a wide range of fungal diseases, including important cereal diseases. Although metyltetraprole most likely inhibits the respiratory chain via complex III, it remains effective against QoI resistant strains. Therefore, metyltetraprole is considered as a novel fungicidal agent for controlling diseases affecting cereal crops and overcoming pathogen resistance to existing fungicides. © 2018 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Section: Introductionmentioning

confidence: 99%

“…SDHIs are also reported to be under the risk of efficacy loss due to the field isolates which acquired a high level of resistance against this chemical class as a result of a single mutation within the target enzyme (e.g. sdhC ‐H152R in Z. tritici and sdhC ‐G79R in P. teres ) …”

Section: Introductionmentioning

confidence: 99%

Metyltetraprole, a novel putative complex III inhibitor, targets known QoI‐resistant strains of Zymoseptoria tritici and Pyrenophora teres

Suemoto

Matsuzaki

Iwahashi

2019

“…Indeed, the detection of SDHI resistant isolates of Z. tritici obtained from sites in Ireland and the UK [https://cereals.ahdb.org.uk/press/2016/february/12/%20sdhi-fungicide-sensitivity-shift-detected-in-two-uk-septoria-isolates.Aspx (accessed 29 September 2016)] has recently been reported. Furthermore, isolates of Pyrenophora teres (net blotch of barley) resistant to SDHI fungicides have also been detected in several European cereal growing geographies . Cases such as these serve as a constant reminder of the need for continued innovation towards identifying new active chemistries with novel modes of action.…”

Section: Introductionmentioning

confidence: 99%

Biological characterization of fenpicoxamid, a new fungicide with utility in cereals and other crops

Owen¹,

Yao²,

Myung³

et al. 2017

BACKGROUNDThe development of novel highly efficacious fungicides that lack cross‐resistance is extremely desirable. Fenpicoxamid (Inatreq™ active) possesses these characteristics and is a member of a novel picolinamide class of fungicides derived from the antifungal natural product UK‐2A.RESULTSFenpicoxamid strongly inhibited in vitro growth of several ascomycete fungi, including Zymoseptoria tritici (EC50, 0.051 mg L−1). Fenpicoxamid is converted by Z. tritici to UK‐2A, a 15‐fold stronger inhibitor of Z. tritici growth (EC50, 0.0033 mg L−1). Strong fungicidal activity of fenpicoxamid against driver cereal diseases was confirmed in greenhouse tests, where activity on Z. tritici and Puccinia triticina matched that of fluxapyroxad. Due to its novel target site (Qi site of the respiratory cyt bc1 complex) for the cereals market, fenpicoxamid is not cross‐resistant to Z. tritici isolates resistant to strobilurin and/or azole fungicides. Across multiple European field trials Z. tritici was strongly controlled (mean, 82%) by 100 g as ha−1 applications of fenpicoxamid, which demonstrated excellent residual activity.CONCLUSIONSThe novel chemistry and biochemical target site of fenpicoxamid as well as its lack of cross‐resistance and strong efficacy against Z. tritici and other pathogens highlight the importance of fenpicoxamid as a new tool for controlling plant pathogenic fungi. © 2017 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

“…In the case of QoIs, it has been reported that the orthologous amino acid mutations result in similar resistance profiles across different organisms with respect to the strength of resistance; the G143A mutation causes very high level of resistance (the resistance factor RF, [EC 50 of the resistant mutant]/[EC 50 of the wild type], is always greater than 100) to all commercial QoIs in any known cases of more than 20 pathogen species . However, recently some cases of different resistance profiles within the orthologous mutations of different pathogen species were reported in cases of resistance against succinate dehydrogenase inhibitor (SDHI), another important agricultural fungicide class . Considering the unique behavior of metyltetraprole in the G143A mutants of Z. tritici as well as in the F129L mutants of P. teres , its consistency in orthologous mutations in different species should be investigated.…”

Section: Introductionmentioning

confidence: 99%

Antifungal activity of metyltetraprole against the existing QoI‐resistant isolates of various plant pathogenic fungi

Matsuzaki

Kiguchi

Suemoto

et al. 2019

BACKGROUND Metyltetraprole is a novel quinol oxidation site of Complex III inhibitor (QoI) fungicide that inhibits mitochondrial electron transport at the Qo site of the cytochrome bc1 complex. Previous reports have demonstrated that it is also active against the QoI‐resistant (QoI‐R) isolates of Zymoseptoria tritici and Pyrenophora teres with the mutations G143A and F129L in their cytochrome b gene, respectively. Further studies on cross‐resistance between metyltetraprole and existing QoIs were performed using an increased number of isolates of Z. tritici, P. teres, Ramularia collo‐cygni, Pyrenophora tritici‐repentis, and several other plant pathogenic fungi. RESULTS Differences in the EC50 values between the wild‐type and QoI‐R isolates with the mutations G143A or F129L were always smaller for metyltetraprole compared to those for the existing QoIs, and they were never greater than five in terms of resistance factor. The 2‐year field experiments showed that the metyltetraprole treatment did not increase the percentage of QoI‐R isolates likely to harbor the G143A mutation in a Z. tritici population. CONCLUSION The unique behavior of metyltetraprole against the existing QoI‐R isolates was confirmed for all tested pathogen species. Our results provide important information to establish a fungicide resistance management strategy using metyltetraprole in combination or alternation with other fungicides. © 2019 Society of Chemical Industry