Discovery and biological profile of pyridachlometyl.

Pyridachlometyl is a novel tubulin dynamics modulator fungicide developed by Sumitomo as a new agent designed to tackle fungicide resistance. Pyridachlometyl is being developed as a first-in-class molecule with an anti-tubulin mode of action, the chemical structure of which is characterized by a unique tetrasubstituted pyridazine ring. The first commercial product 'Fuseki flowable' received initial registration in 2023 in Japan. The concepts of the discovery project, optimization of chemical structures, and biological profiles are reviewed herein. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Physiological effects of mandestrobin.

Mandestrobin is a novel and potent fungicide with a methoxyacetamide structure, and inhibits complex III on the mitochondrial respiratory chain of fungi. It is widely accepted that some fungicides, including QOIs and SDHIs, have additional physiological effects on treated plants. In this study, we evaluated the physiological effects of mandestrobin both in the field and the laboratory. Mandestrobin treatment increased the yield of Brassica napus by an average of 6.3% in the field under disease-free conditions. Mandestrobin treatment delayed chlorophyll degradation and the senescence of B. napus leaf discs, and excised Arabidopsis thaliana leaves in darkness. Analyses of transcriptome and gene ontology enrichment of mandestrobin-upregulated genes showed that chlorophyll degradation genes and jasmonate-related genes were downregulated while salicylate-related genes were upregulated by mandestrobin treatment. A possible mechanism by which mandestrobin triggered the physiological effects observed in the field and the laboratory was discussed.

Antifungal activity of metyltetraprole against the existing QoI-resistant isolates of various plant pathogenic fungi: Metyltetraprole against QoI-R isolates.

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.

Discovery of metyltetraprole: Identification of tetrazolinone pharmacophore to overcome QoI resistance.

Quinone outside inhibitors (QoIs) are one of the major agricultural fungicide groups used worldwide. However, the development of resistance by different pathogenic species associated with specific mutation at the target gene site is becoming a critical issue for the sustainable use of QoIs. The authors aimed to design a novel QoI molecule to overcome the aforementioned issue. A rational approach to avoid steric hindrance between the QoI molecule and the mutated target site was successfully employed. The resulting compound, metyltetraprole, is characterized by 3-substituted central ring with a tetrazolinone moiety, the key structure to retain potent activity against QoI-resistant mutants. Metyltetraprole is a promising new fungicide under commercial development, and its development in this study has paved the way to overcoming resistance to QoI fungicides.

Identification and molecular mapping of a wheat gene for resistance to an unadapted isolate of Colletotrichum cereale.

To elucidate genetic mechanisms of host species specificity between graminicolous anthracnose fungi and gramineous plants, infection assays were performed with a Sorghum isolate (Colletotrichum sublineolum), a Digitaria isolate (C. hanaui), a Polypogon isolate (C. cereale), and an Avena isolate (C. cereale). They were specifically virulent on the plants from which they were isolated. When 72 wheat lines were inoculated with an unadapted isolate from Asia Minor bluegrass (Cgp29), however, some exceptional cultivars were recognized. Although most cultivars were resistant to Cgp29, 'Hope' was susceptible. In F2 populations derived from crosses between three resistant cultivars-'Norin 4' (N4), 'Chinese Spring' (CS), and 'Shin-chunaga' (Sch)-and the susceptible Hope, resistant and susceptible seedlings segregated in a 3:1 ratio, suggesting that a major gene is involved in the resistance of each cultivar to Cgp29. In F2 populations derived from crosses between the three resistant cultivars, all seedlings were resistant, suggesting that these three cultivars carry the same gene. This resistance gene was designated as "resistance to Colletotrichum cereale 1" (Rcc1). Analysis with the CS-Hope chromosome substitution lines and molecular mapping revealed that Rcc1 was located on the long arm of chromosome 5A. Cytologically, Rcc1 was mainly associated with hypersensitive reaction. These results suggest that major genes similar to those controlling cultivar specificity are involved in the resistance of wheat against the unadapted isolate of C. cereale.