Canopy disturbances such as windthrow events have obvious impacts on forest structure and composition aboveground, but changes in soil microbial communities and the consequences of these changes are less understood.We characterized the densities of a soil-borne pathogenic oomycete (Pythium) and a common saprotrophic zygomycete (Mortierella) in nine pairs of forest gaps created by windthrows and...

A new disease causing wilt and death of adult plants of Phaseolus vulgaris was discovered in plastic-house crops of southeast Spain in 2004. The causal agent was shown to be a Pythium species with a unique type of oogonium ornamentation different from any of the described species. Zoospores were not observed, but globose or subglobose hyphal swellings, intercalary or terminal, were frequently f...

The genus Pythium was erected by Pringsheim in 1858 and placed in the family Saprolegniaceae. By the end of 19th century taxonomic details of the genus had been clarified and many new species had been described. The relationship with other Oomycetes was established and the genus was included in a new family, Pythiaceae, by Schroter in 1897. The fungus Pythium belongs to the subdivision Mastigom...

*Globally, exotic invaders threaten biodiversity and ecosystem function. Studies often report that invading plants are less affected by enemies in their invaded vs home ranges, but few studies have investigated the underlying mechanisms. *Here, we investigated the variation in prevalence, species composition and virulence of soil-borne Pythium pathogens associated with the tree Prunus serotina ...

Transgenic ethylene-insensitive tobacco (Tetr) plants spontaneously develop symptoms of wilting and stem necrosis when grown in nonautoclaved soil. Fusarium oxysporum, F. solani, Thielaviopsis basicola, Rhizopus stolonifer, and two Pythium spp. were isolated from these diseased Tetr plants and demonstrated to be causal agents of the disease symptoms. Pathogenicity of the two Pythium isolates an...

A comparison of oomycete diversity in reed stands ( Phragmites australis ) of Lake Constance, Germany, and maize fields close by provided evidence for the occurrence of natural hybridization between Pythium phragmitis , a newly described reed pathogen, and an as-yet unknown Pythium species closely related to P. phragmitis and P. arrhenomanes . Internal transcribed spacer and β -tubulin sequence...

AIMS Four well-described strains of Pseudomonas fluorescens were assessed for their effect on pea growth and their antagonistic activity against large Pythium ultimum inocula. METHODS AND RESULTS The effect of Pseudomonas strains on the indigenous soil microflora, soil enzyme activities and plant growth in the presence and absence of Pythium was assessed. Pythium inoculation reduced the shoot...

The kingdom Stramenopile includes diatoms, brown algae, and oomycetes. Plant pathogenic oomycetes, including Phytophthora, Pythium and downy mildew species, cause devastating diseases on a wide range of host species and have a significant impact on agriculture. Here, we report comparative analyses on the genomes of thirteen straminipilous species, including eleven plant pathogenic oomycetes, to...

Stand problems consistently cause significant production losses and management problems in Arkansas rice fields. Previous research, funded by the Rice Research and Promotion Board, identified the role of environmental factors and soilborne plant pathogens in limiting rice stand establishment, and had the goal of determining the conditions where soilborne pathogens, especially Pythium species, p...

A DNA array containing 172 oligonucleotides complementary to specific diagnostic regions of internal transcribed spacers (ITS) of more than 100 species was developed for identification and detection of Pythium species. All of the species studied, with the exception of Pythium ostracodes, exhibited a positive hybridization reaction with at least one corresponding species-specific oligonucleotide...