Differences in stability of seed-associated microbial assemblages in response to invasion by phytopathogenic microorganisms.

Seeds are involved in the vertical transmission of microorganisms from one plant generation to another and consequently act as reservoirs for the plant microbiota. However, little is known about the structure of seed-associated microbial assemblages and the regulators of assemblage structure. In this work, we have assessed the response of seed-associated microbial assemblages of Raphanus sativus to invading phytopathogenic agents, the bacterial strain Xanthomonas campestris pv.

The Arabidopsis thaliana-Alternaria brassicicola pathosystem: A model interaction for investigating seed transmission of necrotrophic fungi.

Background: Seed transmission constitutes a major component of the parasitic cycle for several fungal pathogens. However, very little is known concerning fungal or plant genetic factors that impact seed transmission and mechanisms underlying this key biological trait have yet to be clarified. Such lack of available data could be probably explained by the absence of suitable model pathosystem to study plant-fungus interactions during the plant reproductive phase.

Cell wall integrity and high osmolarity glycerol pathways are required for adaptation of Alternaria brassicicola to cell wall stress caused by brassicaceous indolic phytoalexins.

Camalexin, the characteristic phytoalexin of Arabidopsis thaliana, inhibits growth of the fungal necrotroph Alternaria brassicicola. This plant metabolite probably exerts its antifungal toxicity by causing cell membrane damage. Here we observed that activation of a cellular response to this damage requires cell wall integrity (CWI) and the high osmolarity glycerol (HOG) pathways.

The group III two-component histidine kinase of filamentous fungi is involved in the fungicidal activity of the bacterial polyketide ambruticin.

We have shown that the plant pathogen Alternaria brassicicola exhibited very high susceptibility to ambruticin VS4 and to a lesser extent to the phenylpyrrole fungicide fludioxonil. These compounds are both derived from natural bacterial metabolites with antifungal properties and are thought to exert their toxicity by interfering with osmoregulation in filamentous fungi. Disruption of the osmosensor group III histidine kinase gene AbNIK1 (for A.

Characterization of mutations in the two-component histidine kinase gene AbNIK1 from Alternaria brassicicola that confer high dicarboximide and phenylpyrrole resistance.

Highly iprodione- and fludioxonil-resistant field and laboratory isolates of A. brassicicola were found to be either moderately sensitive or tolerant to osmotic stress. AbNIK1, a two-component histidine kinase gene, was isolated from a fungicide-sensitive strain.

Conventional and Real-Time PCR-Based Assay for Detecting Pathogenic Alternaria brassicae in Cruciferous Seed.

Alternaria brassicae is an important seedborne pathogenic fungus responsible for the black spot disease of crucifers. Sanitary control of commercial seed is necessary to limit the spread of this pathogen. Current detection methods, based on culture and morphological identification of the fungus, are time consuming, laborious, and not always reliable.