Alveolarides: Antifungal Peptides from Microascus alveolaris Active against Phytopathogenic Fungi.

Three novel cyclodepsipeptides, alveolarides A (1), B (2), and C (3), each possessing the rare 2,3-dihydroxy-4-methyltetradecanoic acid unit and a β-phenylalanine amino acid residue, along with the known peptide scopularide were isolated and identified from the culture broth of Microascus alveolaris strain PF1466. The pure compounds were evaluated for biological activity, and alveolaride A (1) provided strong in vitro activity against the plant pathogens Pyricularia oryzae, Zymoseptoria tritici, and Ustilago maydis. Moderate activity of alveolaride A was observed under in planta conditions against Z.

Characterization of the mechanism of action of the fungicide fenpicoxamid and its metabolite UK-2A.

Background: Fenpicoxamid is a new fungicide for control of Zymoseptoria tritici, and is a derivative of the natural product UK-2A. Its mode of action and target site interactions have been investigated.

Results: UK-2A strongly inhibited cytochrome c reductase, whereas fenpicoxamid was much less active, consistent with UK-2A being the fungicidally active species generated from fenpicoxamid by metabolism.

MALDI-MS Imaging Analysis of Fungicide Residue Distributions on Wheat Leaf Surfaces.

Improved retention and distribution of agrochemicals on plant surfaces is an important attribute in the biological activity of pesticide. Although retention of agrochemicals on plants after spray application can be quantified using traditional analytical techniques including LC or GC, the spatial distribution of agrochemicals on the plants surfaces has received little attention. Matrix assisted laser desorption/ionization (MALDI) imaging technology has been widely used to determine the distribution of proteins, peptides and metabolites in different tissue sections, but its application to environmental research has been limited.

Transmission of the G143A QoI-resistance point mutation through anastomosis in Magnaporthe grisea.

Background: Soon after the introduction of Qo inhibitor fungicides in 1996, the point mutation leading to the amino acid exchange glycine to alanine at the 143 position of the mitochondrial cytochrome b gene was identified as the main cause of resistance. The present study describes the role of anastomosis in the transmission of the G143A mutation in Magnaporthe grisea.

Results: Two M.

Phoslactomycins from Streptomyces sp. MLA1839 and their biological activities.

Phoslactomycins H (1) and I (2), two new members of the phoslactomycin class of chemistry, were isolated from Streptomyces sp. MLA1839 on the basis of their antifungal activities. Their structures were elucidated using extensive NMR spectroscopy and mass spectrometry.

Mitochondrial genome sequences and molecular evolution of the Irish potato famine pathogen, Phytophthora infestans.

The mitochondrial genomes of haplotypes of the Irish potato famine pathogen, Phytophthora infestans, were sequenced. The genome sizes were 37,922, 39,870 and 39,840 bp for the type Ia, IIa and IIb mitochondrial DNA (mtDNA) haplotypes, respectively. The mitochondrial genome size for the type Ib haplotype, previously sequenced by others, was 37,957 bp.

A Two-Phase Resistance Response of Venturia inaequalis Populations to the QoI Fungicides Kresoxim-Methyl and Trifloxystrobin.

The class of fungicides acting as respiration inhibitors by binding to the Qo center of cyto-chrome b (QoIs) are in wide use for the management of apple scab caused by Venturia inaequalis. In order to assess responses of V. inaequalis populations to treatments with QoIs, sensitivities of isolates were determined for germinating conidia or for mycelial colonies developing from germinating conidia.

Characterization of Colletotrichum graminicola Isolates Resistant to Strobilurin-Related QoI Fungicides.

Isolates of Colletotrichum graminicola were collected from annual bluegrass or bent grass turf in Japan and the United States, and their sensitivities to QoI fungicides (QoIs) as well as their cytochrome b sequences were characterized. Five isolates sampled from turf treated repeatedly with azoxystrobin were highly QoI resistant under both in vivo and in vitro test conditions. The nucleotide sequences of a large cytochrome b gene segment involving the binding site of QoIs were fully homologous for all resistant isolates and contained the G143A target site mutation known to confer QoI resistance in other pathogens.

Impact of alternative respiration and target-site mutations on responses of germinating conidia of Magnaporthe grisea to Qo-inhibiting fungicides.

Qo-inhibiting fungicides act as respiration inhibitors by binding to the Qo center of cytochrome b. Sensitivities of fungi to Qo inhibitors can be influenced by the induction of alternative respiration or by mutational changes of the cytochrome b target site. Previous studies on both mechanisms in Magnaporthe grisea (Hebert) Barr were focused on the mycelial stage of the pathogen.

Characterization of spontaneous mutants of Magnaporthe grisea expressing stable resistance to the Qo-inhibiting fungicide azoxystrobin.

The class of Qo-inhibiting fungicides (QoIs) act as respiration inhibitors by binding to the Qo center of cytochrome b. The longevity of these fungicides has been challenged by the selection of fungal sub-populations resisting high doses of QoI fungicides, with a G143A amino acid exchange in the cytochrome b target site identified as the most common cause of resistance. In contrast, the mechanism of alternative respiration, as another mechanism of fungal QoI resistance, has thus far not been affiliated with practical resistance.

Disruption of the alternative oxidase gene in Magnaporthe grisea and its impact on host infection.

Plants and numerous fungi including Magnaporthe grisea protect mitochondria from interference by respiration inhibitors by expressing alternative oxidase, the enzymatic core of alternative respiration. The alternative oxidase gene AOXMg of M. grisea was disrupted.