Diurnal effects on sporangium and zoospore production by on 'Cunningham's White'.

We evaluated sporangium and zoospore production by three isolates of on 'Cunningham's White' leaves under light and dark conditions at both variable and constant (14 C) temperature. -infected leaves were detached and placed in funnels inside of a 62-L plastic storage container located in a growth chamber. Cool mist was introduced to the container to create a high-humidity environment.

The Effect of Leaf Wetness on Zoospore Infection of 'Cunningham's White' and .

We performed studies using zoospore inoculum combined from nine isolates of and determined the effect of leaf wetness on infection of whole plants of 'Cunningham's White' and . The mean percentage of infected leaves for both host species increased gradually across a dew chamber moisture period of 1 to 6 h, reaching approximately 80% infection by 6 h. We also evaluated the effect of a postinoculation drying period on infectivity of the two host species with zoospore inoculum.

Annotation and analysis of the mitochondrial genome of Coniothyrium glycines, causal agent of red leaf blotch of soybean, reveals an abundance of homing endonucleases.

Coniothyrium glycines, the causal agent of soybean red leaf blotch, is a USDA APHIS-listed Plant Pathogen Select Agent and potential threat to US agriculture. Sequencing of the C. glycines mt genome revealed a circular 98,533-bp molecule with a mean GC content of 29.

Sporangia Production Over Time by Phytophthora ramorum on Rhododendron 'Cunningham's White' After Placement at Different Relative Humidities.

We examined the impact of relative humidity (RH) on Phytophthora ramorum sporangia production on Rhododendron 'Cunningham's White'. When diseased plants were maintained under continuous moisture in a mist tent, sporangia were collected from some plants for 22 weeks. More than 3,000 sporangia/leaf/week were collected over the first 3 weeks but levels declined to <100 sporangia/leaf/week after 7 weeks.

Development of an Inoculation Technique and the Evaluation of Soybean Genotypes for Resistance to Coniothyrium glycines.

Red leaf blotch, caused by Coniothyrium glycines, is a serious disease affecting soybean in several African countries but has not yet appeared in the United States. The fungal pathogen is listed as a Select Agent by the Federal Select Agent Program because of potential consequence to U.S.

Pyracantha 'Mohave' Fruit Infection by Phytophthora ramorum and Transmission of the Pathogen from Infected Fruit to Roots of Viburnum tinus.

Colonization of the fleshy fruit of Cornus florida, C. kousa, Laurus nobilis, Malus hupehensis, and Pyracantha 'Mohave' was observed following inoculation with sporangia of Phytophthora ramorum. However, abundant production of chlamydospores was only observed in the fruit of Pyracantha 'Mohave'.

The effect of temperature on germination of chlamydospores of Phytophthora ramorum.

Mycelium-free chlamydospores of 12 isolates of P. ramorum representing three clonal lineages were produced with a method involving incubation in nonsterile sand at 20 C in darkness for 30 d. Chlamydospores were incubated on selective agar medium at 5, 10, 15, 20, 25 and 30 C and germination assessed after 1, 2, 4, 6 and 8 d incubation.

Isolation of nine Phytophthora capsici pectin methylesterase genes which are differentially expressed in various plant species.

Phytophthora capsici causes damage on many plants species, and secretes various pectin methylesterases during all stages of infection. We identified nine Pme genes (Pcpme 1-9) from a genomic library of highly virulent P. capsici strain SD33 and further analyzed the expression pattern of nine genes on three hosts: pepper, tomato, and cucumber using qRT-PCR during all stages of infection.

Effect of temperature and moisture period on infection of Rhododendron 'Cunningham's White' by Phytophthora ramorum.

We investigated the temperature and moisture conditions that allow Phytophthora ramorum to infect Rhododendron 'Cunningham's White'. Most experiments were performed with a single P. ramorum isolate from the NA1 clonal lineage.

Standardizing the nomenclature for clonal lineages of the sudden oak death pathogen, Phytophthora ramorum.

Phytophthora ramorum, the causal agent of sudden oak death and ramorum blight, is known to exist as three distinct clonal lineages which can only be distinguished by performing molecular marker-based analyses. However, in the recent literature there exists no consensus on naming of these lineages. Here we propose a system for naming clonal lineages of P.

Susceptibility to Phytophthora ramorum and Inoculum Production Potential of Some Common Eastern Forest Understory Plant Species.

Twenty-five plant species (21 genera, 14 families), which comprise a portion of the understory in forests of the Eastern United States, were evaluated for susceptibility to infection by Phytophthora ramorum. The degree to which P. ramorum is able to form sporangia and chlamydospores was also assessed on these hosts.

Molecular Detection of Phytophthora ramorum, the Causal Agent of Sudden Oak Death in California, and Two Additional Species Commonly Recovered from Diseased Plant Material.

ABSTRACT Sudden oak death is a disease currently devastating forest ecosystems in several coastal areas of California. The pathogen causing this is Phy-tophthora ramorum, although species such as P. nemorosa and P.

Real-Time Fluorescent Polymerase Chain Reaction Detection of Phytophthora ramorum and Phytophthora pseudosyringae Using Mitochondrial Gene Regions.

ABSTRACT A real-time fluorescent polymerase chain reaction (PCR) detection method for the sudden oak death pathogen Phytophthora ramorum was developed based on mitochondrial DNA sequence with an ABI Prism 7700 (TaqMan) Sequence Detection System. Primers and probes were also developed for detecting P. pseudosyringae, a newly described species that causes symptoms similar to P.

Identification of phytophthora isolates to species level using restriction fragment length polymorphism analysis of a polymerase chain reaction-amplified region of mitochondrial DNA.

ABSTRACT Polymerase chain reaction primers spanning the mitochondrially encoded coxI and II genes have been identified that were capable of amplifying target DNA from all 152 isolates of 31 species in the genus Phytophthora that were tested. Digestion of the amplicons with restriction enzymes generated species-specific restriction fragment length polymorphism banding profiles that were effective for isolate classification to a species level. Of the 24 species in which multiple isolates were examined, intraspecific polymorphisms were not observed for 16 species, while 5 species exhibited limited intraspecific polymorphism that could be explained by the addition/loss of a single restriction site.

Survival of Phytophthora ramorum hyphae after exposure to temperature extremes and various humidities.

We examined the effect of short-term exposure to high and low temperatures and a range of relative humidity (RH) on survival of Phytophthora ramorum hyphae. Spore-free hyphal colonies were grown on dialysis squares atop V8 medium. Colonies were transferred to water agar plates positioned at 27.

Recovery of Phytophthora ramorum Following Exposure to Temperature Extremes.

We examined the impact of exposure to high and low temperature extremes on recovery of Phytophthora ramorum both as free chlamydospores and within infected rhododendron tissue over a 7-day period. Chlamydospores held in moistened sand were incubated at 30, 35, 40, 0, -10, and -20°C for up to 7 days. Infected Rhododendron 'Cunningham's White' leaf disks held in sandy loam, loam, or sand at two different soil moisture levels also were subjected to these temperatures for up to 7 days, and to a variable temperature regimen for 12 weeks.

Susceptibility of Some Eastern Forest Species to Phytophthora ramorum.

We tested some common Eastern forest species for their reaction to stem and leaf inoculation with Phytophthora ramorum, the pathogen that causes sudden oak death. Stem lesions were produced on inoculated seedlings of 12 Eastern forest species following 72 to 76 days of incubation in a containment greenhouse cubicle at 20°C. Chestnut oak (Quercus prinus) and white oak (Q.

Growth and sporulation of Phytophthora ramorum in vitro in response to temperature and light.

Phytophthora ramorum, recently found in the US, is causing concern for hardwood forests and the nursery industry. In an effort to identify some of the environmental limitations to growth and sporulation we undertook a laboratory study of four US and three European (EU) isolates. On V8 media, isolates grew when incubated at 2-28 C and produced chlamydospores at 8-28 C.

Analysis of Claviceps africana and C. sorghi from India using AFLPs, EF-1alpha gene intron 4, and beta-tubulin gene intron 3.

Isolates of Claviceps causing ergot on sorghum in India were analysed by AFLP analysis, and by analysis of DNA sequences of the EF-1alpha gene intron 4 and beta-tubulin gene intron 3 region. Of 89 isolates assayed from six states in India, four were determined to be C. sorghi, and the rest C.

Cultural characteristics, morphology, and variation within Claviceps africana and C. sorghi from India.

Sorghum ergot in India is caused by Claviceps africana and C. sorghi. The distributions of these two species in India is not known.

NEP1 orthologs encoding necrosis and ethylene inducing proteins exist as a multigene family in Phytophthora megakarya, causal agent of black pod disease on cacao.

Phvytophthora megakarya is a devastating oomycete pathogen that causes black pod disease in cacao. Phytophthora species produce a protein that has a similar sequence to the necrosis and ethylene inducing protein (Nep1) of Fusarium oxysporum. Multiple copies of NEP1 orthologs (PmegNEP) have been identified in P.

Phylogenetic relationships of Phytophthora ramorum, P. nemorosa, and P. pseudosyringae, three species recovered from areas in California with sudden oak death.

Sudden oak death has been an emerging disease problem in coastal California and has caused significant losses in forest ecosystems in some regions of the state. The causal agent of this disease has been described as Phytophthora ramorum with two other less aggressive species, P. nemorosa and P.

Phylogenetic relationships among Phytophthora species inferred from sequence analysis of mitochondrially encoded cytochrome oxidase I and II genes.

The phylogenetic relationships of 51 isolates representing 27 species of Phytophthora were assessed by sequence alignment of 568 bp of the mitochondrially encoded cytochrome oxidase II gene. A total of 1299 bp of the cytochrome oxidase I gene also were examined for a subset of 13 species. The cox II gene trees constructed by a heuristic search, based on maximum parsimony for a bootstrap 50% majority-rule consensus tree, revealed 18 species grouping into seven clades and nine species unaffiliated with a specific clade.

AFLP Comparisons Among Claviceps africana Isolates from the United States, Mexico, Africa, Australia, India, and Japan.

Eighty-seven isolates of the sorghum ergot pathogen, Claviceps africana, from diverse geographic locations were analyzed using four different amplified fragment length polymorphism (AFLP) primer combinations to determine genetic relationships among isolates. Most isolates showed unique AFLP haplotypes, indicating that substantial genetic variation is present within C. africana populations.