azoxystrobin and pyrimorph

Chili pepper (Capsicum annum L.) is an important economic crop that is severely destroyed by the filamentous oomycete Phytophthora capsici. Little is known about this pathogen in key chili pepper farms in Punjab province, Pakistan. We investigated the genetic diversity of P. capsici strains using standard taxonomic and molecular tools, and characterized their colony growth patterns as well as their disease severity on chili pepper plants under the greenhouse conditions. Phylogenetic analysis based on ribosomal DNA (rDNA), β-tubulin and translation elongation factor 1α loci revealed divergent evolution in the population structure of P. capsici isolates. The mean oospore diameter of mating type A1 isolates was greater than that of mating type A2 isolates. We provide first evidence of an uneven distribution of highly virulent mating type A1 and A2 of P. capsici that are insensitive to mefenoxam, pyrimorph, dimethomorph, and azoxystrobin fungicides, and represent a risk factor that could ease outpacing the current P. capsici management strategies.

Topics: Acrylamides; Alanine; Capsicum; Cluster Analysis; DNA, Ribosomal; Drug Resistance; Evolution, Molecular; Fungicides, Industrial; Genes, Mating Type, Fungal; Genetic Variation; Morpholines; Pakistan; Peptide Chain Elongation, Translational; Phenotype; Phylogeny; Phytophthora; Plant Diseases; Plant Roots; Pyrimidines; Risk Factors; Sporangia; Strobilurins; Temperature; Tubulin; Virulence

The antifungal activity of the novel fungicide pyrimorph, (E)-3-[(2-chloropyridine-4-y1)-3-(4-tert-butylpheny1)acryloyl]morpholin, against Phytophthora capsici was investigated in vitro. Pyrimorph inhibited different stages in the life cycle of P. capsici including mycelial growth, sporangium production, zoospore release, and cystospore germination with EC(50) values of 1.84, 0.17, 4.92, and 0.09 microg mL(-1), respectively. The effect of pyrimorph on mycelial growth was reduced by the addition of different concentrations of ATP, which suggested that the action mechanism of pyrimorph was connected with impairment of the energy generation system. Meanwhile, pyrimorph exhibited certain inhibition on metabolic approaches of Embden-Meyerhof-Parnas (EMP), tricarboxylic acid cycle (TCA), and hexosemonophosphate (HMP) by measuring the oxygen consumption of pyrimorph combining with three representative inhibitors to the metabolic approaches. The results indicated that pyrimorph could inhibit the approach of HMP significantly. Morphological and ultrastructural studies showed that pyrimorph caused excessive septation and swelling of hyphae, distortion and disruption of most vacuoles, thickening and development a multilayer cell wall, and accumulation of dense bodies. These results suggested pyrimorph exhibited multiple modes of action including impairment of the energy generation system and effect on cell wall biosynthesis directly or indirectly.

Topics: Acrylamides; Adenosine Triphosphate; Fungicides, Industrial; Microscopy, Electron, Scanning; Microscopy, Electron, Transmission; Morpholines; Phytophthora