Water potential affects Coniothyrium minitans growth, germination and parasitism of Sclerotinia sclerotiorum sclerotia.

Water availability is an important environmental factor which has major effects on fungal activity. The effects of osmotic (KCl amended agar) and matric Polyethylene glycol ((PEG) 8000 amended agar) potentials over the range -0.1 to -5.

Both leaf properties and microbe-microbe interactions influence within-species variation in bacterial population diversity and structure in the lettuce (Lactuca Species) phyllosphere.

Morphological and chemical differences between plant genera influence phyllosphere microbial populations, but the factors driving within-species variation in phyllosphere populations are poorly understood. Twenty-six lettuce accessions were used to investigate factors controlling within-species variation in phyllosphere bacterial populations. Morphological and physiochemical characteristics of the plants were compared, and bacterial community structure and diversity were investigated using terminal restriction fragment length polymorphism (T-RFLP) profiling and 16S rRNA gene clone libraries.

Forecasting sclerotinia disease on lettuce: toward developing a prediction model for carpogenic germination of sclerotia.

ABSTRACT The feasibility of developing a forecasting system for carpogenic germination of Sclerotinia sclerotiorum sclerotia was investigated in the laboratory by determining key relationships among temperature, soil water potential, and carpogenic germination for sclerotia of two S. sclerotiorum isolates. Germination of multiple burials of sclerotia to produce apothecia also was assessed in the field with concurrent recording of environmental data to examine patterns of germination under different fluctuating conditions.

Forecasting Sclerotinia Disease on Lettuce: A Predictive Model for Carpogenic Germination of Sclerotinia sclerotiorum Sclerotia.

ABSTRACT A predictive model for production of apothecia by carpogenic germination of sclerotia is presented for Sclerotinia sclerotiorum. The model is based on the assumption that a conditioning phase must be completed before a subsequent germination phase can occur. Experiments involving transfer of sclerotia from one temperature regime to another allowed temperature-dependent rates to be derived for conditioning and germination for two S.

Disruption of the Coniothyrium minitans PIF1 DNA helicase gene impairs growth and capacity for sclerotial mycoparasitism.

A non-mycoparasitic restriction enzyme-mediated DNA integration (REMI) mutant of Coniothyrium minitans (R2427) contains two tandem plasmid copies integrated towards the 3' end of an ORF. The predicted polypeptide (845 aa) exhibits high similarity with DNA-helicase proteins from other filamentous fungi and yeasts that play a role in mitochondrial DNA maintenance and repair. Disruption of the C.

Analysis of cDNA transcripts from Coniothyrium minitans reveals a diverse array of genes involved in key processes during sclerotial mycoparasitism.

Coniothyrium minitans colonises and destroys the sclerotia of Sclerotinia sclerotiorum in nature exhibiting ecologically obligate mycoparasitism as its spores remain dormant in soil and only grow actively in the presence of the sclerotia. Molecular mechanisms underlying sclerotial mycoparasitism are poorly defined. We identified 251 unisequences representing genes preferentially expressed by C.

Differences in microbial activity and microbial populations of peat associated with suppression of damping-off disease caused by Pythium sylvaticum.

The microbiological characteristics associated with disease-suppressive peats are unclear. We used a bioassay for Pythium sylvaticum-induced damping-off of cress seedlings to identify conducive and suppressive peats. Microbial activity in unconditioned peats was negatively correlated with the counts of P.

Mycorrhization helper bacteria: a case of specificity for altering ectomycorrhiza architecture but not ectomycorrhiza formation.

Mycorrhization helper bacteria (MHB), isolated from phylogenetically distinct ectomycorrhizal symbioses involving Lactarius rufus, Laccaria bicolor or Suillus luteus, were tested for fungus specificity to enhance L. rufus-Pinus sylvestris or L. bicolor-P.

Importance of mycorrhization helper bacteria cell density and metabolite localization for the Pinus sylvestris-Lactarius rufus symbiosis.

Mycorrhization helper bacteria, Paenibacillus sp. EJP73 and Burkholderia sp. EJP67, were used to study the importance of bacterial inoculum dose and bacterial derived soluble and volatile metabolites localization for enhancing mycorrhiza formation in the Pinus sylvestris-Lactarius rufus symbiosis, using a laboratory based microcosm.

Use of REMI and Agrobacterium-mediated transformation to identify pathogenicity mutants of the biocontrol fungus, Coniothyrium minitans.

Restriction enzyme mediated integration (REMI) and Agrobacterium-mediated transformation (ATMT) were used to transform protoplasts or germinated conidia of the mycoparasite Coniothyrium minitans to hygromycin resistance. Using REMI, up to 32 transformants mug DNA(-1) were obtained, while 37.8 transformants 5 x 10(5) germlings(-1) were obtained using ATMT.

Production, survival and efficacy of Coniothyrium minitans conidia produced in shaken liquid culture.

Coniothyrium minitans is a fungal biocontrol agent of the plant pathogen Sclerotinia sclerotiorum. Growth and sporulation of 21 strains of C. minitans were examined on potato dextrose agar (PDA) and compared with that in potato dextrose broth (PDB) in shaken culture after 12 days at 20 degrees C, to identify strains with potential for inoculum production in liquid culture.

Use of Coniothyrium minitans transformed with the hygromycin B resistance gene to study survival and infection of Sclerotinia sclerotiorum sclerotia in soil.

A Coniothyrium minitans strain (T3) co-transformed with the genes for beta-glucuronidase (uidA) and hygromycin phosphotransferase (hph), the latter providing resistance to the antibiotic hygromycin B, was used to investigate the survival and infection of sclerotia of Sclerotinia sclerotiorum by C. minitans over time in four different soils. Infection of sclerotia was rapid in all cases, with the behaviour of transformant T3 and wild type parent A69 being similar.

Spatial and temporal analysis of the microbial community in slow sand filters used for treating horticultural irrigation water.

An experimental slow sand filter (SSF) was constructed to study the spatial and temporal structure of a bacterial community suppressive to an oomycete plant pathogen, Phytophthora cryptogea. Passage of water through the mature sand column resulted in complete removal of zoospores of the plant pathogen. To monitor global changes in the microbial community, bacterial and fungal numbers were estimated on selective media, direct viable counts of fungal spores were made, and the ATP content was measured.

Production of macrosphelide A by the mycoparasite Coniothyrium minitans.

Coniothyrium minitans, a mycoparasite of sclerotia of Sclerotinia sclerotiorum and Sclerotium cepivorum, produced four closely related metabolites inhibitory to fungal growth. The major metabolite, identified as macrosphelide A, had IG(50) values (the concentration of metabolite to inhibit growth by 50%) of 46.6 and 2.

Molecular characterization of Legionella populations present within slow sand filters used for fungal plant pathogen suppression in horticultural crops.

The total bacterial community of an experimental slow sand filter (SSF) was analyzed by denaturing gradient gel electrophoresis (DGGE) of partial 16S rRNA gene PCR products. One dominant band had sequence homology to Legionella species, indicating that these bacteria were a large component of the SSF bacterial community. Populations within experimental and commercial SSF units were studied by using Legionella-specific PCR primers, and products were studied by DGGE and quantitative PCR analyses.

Transfer of plasmid pBC16 between Bacillus thuringiensis strains in non-susceptible larvae.

Plasmid transfer was investigated in larvae of insects of the orders Coleoptera, Diptera, and Lepidoptera. The effects of introducing Bacillus thuringiensis strains in live non-susceptible larvae, and in the presence of added insecticidal toxins to kill the larvae, were examined. Plasmid transfer was not detected as the strains passed through non-susceptible live larvae, but was detected when the larvae were toxin-killed.

Characterisation of bacteria from Pinus sylvestris-Suillus luteus mycorrhizas and their effects on root-fungus interactions and plant growth.

Bacteria from Pinus sylvestris-Suillus luteus mycorrhizas were isolated, characterised, and their effects on P. sylvestris-S. luteus interactions and plant growth investigated in vitro.

Bacteria associated with Pinus sylvestris-Lactarius rufus ectomycorrhizas and their effects on mycorrhiza formation in vitro.

•  The structure and functioning of mycorrhizosphere bacterial communities from the soil organic fermentation horizon (FH) of a Pinus sylvestris stand was investigated. •  Bacteria were isolated from P. sylvestris-Lactarius rufus mycorrhizas, and their effect on ectomycorrhiza formation, localization within the mycorrhizosphere, and phenotypic and genotypic characteristics determined.