Intrinsic Natural Resistance of Various Plant Pathogens to Ipflufenoquin, a New DHODH (Dihydroorotate Dehydrogenase)-inhibiting Fungicide, in Relation to Unaltered Amino Acid Sequence of the Target Site.

In recent years, increasingly stringent pesticide regulations have made the development of new chemistries challenging. Under these regulations, the new fungicide ipflufenoquin (FRAC Code 52) was first released in Japan. Its mode of action is new; it inhibits dihydroorotate dehydrogenase (DHODH), a key enzyme in the biosynthesis of pyrimidine-based nucleotides.

Interspecificity of Scab Fungus Isolated from Wild Syrian Pear ().

Scab on pear is caused by two pathogens, on European pear and on Asian pear. Five races of and seven races of have been reported thus far and pathological specialization occurs in both species. Among them, the five race isolates of were previously found from wild Syrian pear.

Sensitivity to fungicides in isolates of Colletotrichum gloeosporioides and C. acutatum species complexes and efficacy against anthracnose diseases.

Colletotrichum species cause diseases on many plants and are among the 'top 10' fungal plant pathogens. Species of the C. gloeosporioides and C.

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

Scab, caused by , is among the most serious diseases of Asian pears and control of this disease largely relies on sterol demethylation inhibitor (DMI) fungicides. However, pear growers have complained about field performance of DMIs since the mid-2000s. In this study, to evaluate pathogen sensitivity, mycelial growth tests and inoculation tests were conducted using DMI-amended culture medium and fungicide-sprayed potted pear trees, respectively.

Inherent tolerance of Colletotrichum gloeosporioides to fludioxonil.

Colletotrichum spp. cause devastating diseases in agricultural crops, including fruit crops. They can differ in host plant and plant organ specificity and even in fungicide sensitivity.

Cross-resistance to the new fungicide mefentrifluconazole in DMI-resistant fungal pathogens.

In the European Union (EU), regulation of sterol demethylation inhibiting (DMI) fungicides is tightened due to their suspected endocrine disrupting properties. However, the new DMI fungicide mefentrifluconazole was reported to have high fungicidal activity with minimal adverse side effects. In addition, some evidence suggests inconsistent cross resistance between mefentrifluconazole and other azoles.

Pathogenic Specialization of , Causal Agent of Asian Pear Scab, and Resistance of Pear Cultivars Kinchaku and Xiangli.

Scab caused by is one of the most serious diseases of Asian pears, including Japanese pear ( var. ) and Chinese pears ( and ). Breeding scab-resistant pear cultivars is essential to minimize fungicide use and development of fungicide resistance.

Whole Genome Sequence Resource of the Asian Pear Scab Pathogen .

, the cause of scab disease of Asian pears, is a host-specific, biotrophic fungus. It is restricted to Asia and is regarded as a quarantine threat outside this region. European pear displays nonhost resistance (NHR) to and Asian pears are nonhosts of (the cause of European pear scab disease).

Systemic resistance inducer acibenzolar-S-methyl (ASM) and its microencapsulated formulations: their long-lasting control efficacy against cucumber diseases and mitigation of phytotoxicity.

Background: The development of fungicide resistance by pathogens is a major limiting factor for the control of plant diseases. To combat resistance development, the use of broad-spectrum but nonfungitoxic resistance inducers such as acibenzolar-S-methyl (ASM) is a promising approach because the orchestrated mechanisms underlying systemic acquired resistance induced by ASM are less likely to be overcome easily by pathogens. However, phytotoxicity is the main limiting factor of ASM.

Proposal for a unified nomenclature for target-site mutations associated with resistance to fungicides.

Evolved resistance to fungicides is a major problem limiting our ability to control agricultural, medical and veterinary pathogens and is frequently associated with substitutions in the amino acid sequence of the target protein. The convention for describing amino acid substitutions is to cite the wild-type amino acid, the codon number and the new amino acid, using the one-letter amino acid code. It has frequently been observed that orthologous amino acid mutations have been selected in different species by fungicides from the same mode of action class, but the amino acids have different numbers.

Efficacy of SDHI fungicides, including benzovindiflupyr, against Colletotrichum species.

Background: Colletotrichum species cause anthracnose diseases on many plants and crops. A new generation of succinate dehydrogenase inhibitors (SDHIs) was developed recently. The inhibitory activity of the five SDHI fungicides against Colletotrichum species was determined in this study.

Genetic analysis and molecular characterisation of laboratory and field mutants of Botryotinia fuckeliana (Botrytis cinerea) resistant to QoI fungicides.

Background: QoI fungicides, inhibitors of mitochondrial respiration, are considered to be at high risk of resistance development. In several phytopathogenic fungi, resistance is caused by mutations (most frequently G143A) in the mitochondrial cytochrome b (cytb) gene. The genetic and molecular basis of QoI resistance were investigated in laboratory and field mutants of Botryotinia fuckeliana (de Bary) Whetz.

Cytological evaluation of the effect of azoxystrobin and alternative oxidase inhibitors in Botrytis cinerea.

Azoxystrobin (AZ), a strobilurin-derived fungicide, is known to inhibit mitochondrial respiration in fungi by blocking the electron transport chain in the inner mitochondrial membrane. Germination was strongly inhibited when Botrytis cinerea spore suspension was treated with AZ and the alternative oxidase (AOX) inhibitors, salicylhydroxamic acid (SHAM) and n-propyl gallate. However, chemical death indicators trypan blue and propidium iodide showed that those spores were still alive.

Lack of cross-resistance to a novel succinate dehydrogenase inhibitor, fluopyram, in highly boscalid-resistant isolates of Corynespora cassiicola and Podosphaera xanthii.

Background: Recently in Japan, isolates resistant to boscalid, a succinate dehydrogenase inhibitor (SDHI), have been detected in Corynespora cassiicola (Burk. & Curt.) Wei and Podosphaera xanthii (Castaggne) Braun & Shishkoff, the pathogens causing Corynespora leaf spot and powdery mildew disease on cucumber, respectively.

Site-directed mutagenesis of the cytochrome b gene and development of diagnostic methods for identifying QoI resistance of rice blast fungus.

Background: It is possible that a single nucleotide polymorphism (SNP) (G143A mutation) in the cytochrome b gene could confer resistance to quinone outside inhibiting (QoI) fungicides (strobilurins) in rice blast fungus because this mutation caused a high level of resistance to fungicides such as azoxystrobin in Pyricularia grisea Sacc. and other fungal plant pathogens. The aim of this study was to survey Magnaporthe oryzae B Couch sp.

Acibenzolar-s-methyl-induced resistance to Japanese pear scab is associated with potentiation of multiple defense responses.

ABSTRACT This study reports the mode of action of acibenzolar-S-methyl (ASM) against Japanese pear scab, caused by Venturia nashicola. Pretreatment of potted Japanese pear trees with ASM reduced scab symptoms and potentiated several lines of plant defense response. This included transcripts encoding polygalacturonase-inhibiting protein (PGIP) that were highly and transiently promoted after scab inoculation of plants pretreated with ASM, suggesting a possible role for defenses involved in direct interaction with the pathogen.

Fungicide Sensitivity and Phylogenetic Relationship of Anthracnose Fungi Isolated from Various Fruit Crops in Japan.

Anthracnose diseases of fruit crops are mainly caused by Colletotrichum gloeosporioides and C. acutatum. In these Colletotrichum species, intra- and interspecific variation in fungicide sensitivity has been reported; however, the relationship between fungicide sensitivity and molecular phylogeny has not been analyzed.