The application of safe for humans and the environment Polyversum antifungal agent containing living cells of Pythium oligandrum for biotransformation of prochiral ketones.

This report presents the whole-cell biotransformation of benzofuranyl-methyl ketone derivatives with the application of Polyversum antifungal agent containing Pythium oligandrum microorganism. Stereochemistry of the reduction of prochiral substrates was modified by the bioconversion conditions (concentration of reagents, a source of the carbon atom, biotransformation medium). In optimized conditions enantioselective process was noted. Secondary alcohols with excellent enantiomeric purity and high yields were obtained. The enantiomeric excess and conversion degree of 1-(benzofuran-2-yl)ethanol, 1-(7-ethylbenzofuran-2-yl)ethanol and 1-(3,7-dimethylbenzofuran-2-yl)ethanol were 99%/98.1%, 94%/94.4% and 99%/72.6%, respectively. In the presence of P. oligandrum, one of the enantiotopic hydrides of the dihydropyridine ring coenzyme is selectively transferred to a re side of the prochiral carbonyl group to give products with S configuration. This study demonstrates an inexpensive, eco-friendly approach in synthesis of optically pure benzofuran derivatives and can be an interesting alternative to organocatalysis. Furthermore, this method can be used in biotechnology processes due to its good chemical performance and a high degree of product isolation.

Influence of temperature on in vitro zoosporogenesis of Pythium insidiosum.

This study verified the influence of different temperatures on P. insidiosum in vitro zoosporogenesis. P. insidiosum isolates (n = 26) were submitted to zoosporogenesis and incubated at 5°C, 15°C, 20°C and 37°C (1st stage). Grass fragments were evaluated under optical microscopy at 4, 8, and 24 hours of incubation. Afterward, all isolates were incubated at 37°C and assessed at the same periods of time (2nd stage). The development of hyphae, presence of vesicles, zoosporangia and zoospores were checked. Only the presence of short hyphae was observed at 5°C. At 15°C, the hyphae were either under development or elongated and two isolates produced zoospores. When the isolates were submitted to 20°C for 4 hours, the presence of long and mycelial hyphae, vesicles, zoosporangia and zoospores was observed, which also happened at the other periods evaluated. In the second stage, the isolates which were initially at 5°C and 15°C evidenced long developing hyphae with the presence of vesicles, zoosporangia, and zoospores within 4 hours of incubation, and these characteristics were kept at the other evaluated periods. The isolates kept at 37°C showed evident zoosporogenesis in the first 4 hours of evaluation. It was concluded that temperatures of 20°C and 37°C support P. insidiosum zoosporogenesis process. On the other hand, 5°C and 15°C temperatures do not kill the microorganism.

Synthesis and antifungal activity of 2-allylphenol derivatives against fungal plant pathogens.

2-Allylphenol (2-AP) is an effective fungicide against a number of plant pathogens, which can be metabolized and bio-transformed to four chemical compounds by Rhizoctonia cerealis. To determine if its degradation affects antifungal activity, two major metabolites derived from 2-AP including 2-(2-hydroxypropyl) phenol and 2-(3-hydroxypropyl) phenol were synthesized. Inhibition of mycelial growth of several plant pathogens by the metabolites was evaluated, and structures of two metabolites were determined by hydrogen nuclear magnetic resonance (1H NMR). Among these metabolites, only 2-(2-hydroxypropyl) phenol inhibited test pathogens effectively. EC50 values of 2-(2-hydroxypropyl) phenol for inhibition of mycelial growth of R. cerealis, Pythium aphanidermatum, Valsa mali and Botrytis cinerea ranged from 1.0 to 23.5µg/ml, which were lower than the parental fungicide 2-AP that ranged from 8.2 to 48.8µg/ml. Hyphae of R. cerealis and P. aphanidermatum treated with 2-(2-hydroxypropyl) phenol were twisted. Newly developed hyphae were slender, twisted and swollen on the tip, while old hyphae were hollow and ruptured. This is the first report indicating the formation of 2-(2-hydroxypropyl) phenol may have contributed to toxicity of 2-allylphenol in control of plant pathogens.

Molecular and morphological characterization of three new species of Pythium from Iran: P. ershadii, P. pyrioosporum, and P. urmianum.

Three new species of Pythium: P. ershadii, P. pyrioosporum, and P. urmianum from soils of various regions in Iran are described and illustrated. These species are morphologically distinct from all other known species. Pythium ershadii is morphologically characterized by pyriform ornamented oogonia and rarely production of pyriform oospores. Pythium pyrioosporum differs from other species of the genus by the production of pyriform oospores and smooth walled oogonia, oospores with a tapering elongation toward a hypogynous antheridium and intercalary hypogynous antheridia. Pythium urmianum is distinguished by the presence of intercalary hypogynous antheridia, smooth walled oogonia formed laterally on hyphae or on short side branches and peanut-shaped oospores. Phylogenetic relationships of these new taxa with other Pythium species were investigated using internal transcribed spacers rDNA and partial coxI sequence data. The three species reside in clade E1 and are separated from closely related species.

Chlorophyll fluorescence imaging as a tool to monitor the progress of a root pathogen in a perennial plant.

MAIN CONCLUSION: The chlorophyll fluorescence parameter ΦNO is an excellent metric for the non-destructive monitoring of disease progression, measured over a broad range of light intensities. The suitability of the slow induction chlorophyll fluorescence parameters ΦPSII, ΦNPQ, and ΦNO to monitor in vivo disease progression in a host-root pathogen pathosystem was evaluated and compared to the established method of monitoring disease by measuring Fv/Fm. Using the infection of ginseng plants (Panax quinquefolius L.) with Pythium irregulare Buisman as a model, light response curves were used to establish the optimal irradiance for the resolution of differences between fluorescence parameters ΦPSII, ΦNPQ and ΦNO. As infection progressed only changes in ΦNO remained consistent with increased irradiance, and increased as infection progressed. Furthermore, ΦNO showed a high sensitivity for distinguishing increased disease load. In contrast, the magnitude in change of ΦPSII and ΦNPQ were sensitive to irradiance levels. The magnitude of increase in ΦNO per unit disease score was equivalent to the corresponding decline in Fv/Fm values. Thus ΦNO is as sensitive as Fv/Fm in monitoring biotic stress. The ability to measure ΦNO under a wide range of light intensities, including natural light, potentially without the need for dark adaptation, means that it can be used in the development of a general protocol for non-invasive, in vivo monitoring of plant health, from the laboratory to the field scale.

Pythium cederbergense sp. nov. and related taxa from Pythium clade G associated with the South African indigenous plant Aspalathus linearis (rooibos).

The genus Pythium consists of more than 120 species and is subdivided into 11 phylogenetic clades (A-K) based on internal transcribed spacer (ITS) region sequence data. Pythium clade G contains only seven known species, with most not being well described. Our study characterized 12 Pythium isolates from Aspalathus linearis (rooibos) that fit into clade G. Phylogenetic analyses of the ITS region and a combined phylogeny of four gene regions (ITS, ß-tubulin, COX1 and COX2 [cytochrome c oxidase subunits I, II]) identified five clade G subclades. The rooibos isolates formed two groups, Pythium Rooibos I (RB I) and II (RB II), that clustered into two separate clades within subclade 1. The nine Pythium RB I isolates formed a distinct clade from P. iwayamai and is described here as a new species, Pythium cederbergense sp. nov. The three Pythium RB II isolates had P. canariense and P. violae as their closest relatives and were genetically diverse, suggesting the presence of several new species or a species complex that cannot be resolved with the current data, thus precluding a species description of this group. Morphological analyses showed that P. cederbergense and Pythium RB II were indistinguishable from each other but distinct from known clade G species. Clade G studies are being hampered by imprecise morphological descriptions of P. violae, P. canariense and P. iwayamai and each species being represented by only one isolate. The P. cederbergense and Pythium RB II isolates all were nonpathogenic toward rooibos, lupin and oats seedlings. One oligonucleotide was developed for each of P. cederbergense and Pythium RB II, which was able to differentiate the isolates with DNA macro-array analyses.

Pythium polare, a new heterothallic oomycete causing brown discolouration of Sanionia uncinata in the Arctic and Antarctic.

Pythium polare sp. nov. is a new heterothallic oomycete species isolated from fresh water and moss from various locations in both the Arctic and Antarctic. This water mould is able to infect stems and leaves of Sanionia moss (Sanionia uncinata). Pythium polare causes brown discolouration in in vitro inoculation tests at 5 °C after 5 weeks of inoculation. It is characterized by globose sporangia with various lengths of discharge tubes releasing zoospores and aplerotic oospores with usually one to five antheridia. The sexual structures are only produced in a dual culture of antheridial and oogonial isolates. Phylogenetic analysis, based on ITS sequencing, places all isolated strains of P. polare in a unique new clade, hence it is considered a novel species. Pythium canariense and Pythium violae are the most closely related species of P. polare based both on morphology and the phylogenetic analysis.

Microbial-induced carbon competition in the spermosphere leads to pathogen and disease suppression in a municipal biosolids compost.

The aim of this study was to understand whether competition for fatty acids in plant seed exudates by compost-derived seed-colonizing microbial communities could explain the suppression of plant infections initiated by sporangia of Pythium ultimum. The germination behavior of P. ultimum sporangia in response to cucumber seeds was measured to determine the impact of seed-colonizing microbes on pathogen suppression. Seed-colonizing microbial communities from municipal biosolids compost utilized cucumber seed exudates and linoleic acid in vitro, reducing the respective stimulatory activity of these elicitors to P. ultimum sporangial germination. However, when sporangia were observed directly in the spermosphere of seeds sown in the compost medium, levels of germination and sporangial emptying did not differ from the responses in sand. The percentage of aborted germ tubes was greater after incubating sporangia in compost medium for 12-h than the level of germ tube abortion when sporangia were incubated in sand. Abortion did not occur if previously germinated sporangia were supplemented with cucumber seed exudate. Furthermore, removal of cucumber seed exudate after various stages of germ tube emergence resulted in an increase in aborted germ tubes over time. Adding increasing levels of glucose directly to the compost medium alleviated germ tube abortion in the spermosphere and also eliminated disease suppression. These data fail to support a role for linoleic acid competition in Pythium seedling disease suppression but provide evidence for general carbon competition mediated by seed-colonizing microbial communities as a mechanism for the suppression of Pythium seed infections in municipal biosolids compost.

Larval Bradysia impatiens (Diptera: Sciaridae) potential for vectoring Pythium root rot pathogens.

A series of laboratory experiments were conducted to investigate the capacity of Bradysia impatiens (Johannsen) larvae to ingest propagules from two strains each of Pythium aphanidermatum (Edson) Fitzp. and P. ultimum Trow and transmit the pathogens to healthy geranium seedlings on a filter-paper substrate in petri dishes. The capacity of fungus gnat larvae to transmit P. aphanidermatum to seedlings rooted in a commercial peat-based potting mix and germination of Pythium oospores and hyphal swellings before and after passage through the guts of larval fungus gnats were also examined. Assays revealed that Pythium spp. transmission by larval fungus gnats varied greatly with the assay substrate and also with the number and nature of ingested propagules. Transmission was highest (65%) in the petri dish assays testing larvae fed P. aphanidermatum K-13, a strain that produced abundant oospores. Transmission of strain K-13 was much lower (<6%) in plug cells with potting mix. Larvae were less efficient at vectoring P. ultimum strain PSN-1, which produced few oospores, and no transmission was observed with two non-oospore-producing strains: P. aphanidermatum Pa58 and P. ultimum P4. Passage of P. aphanidermatum K-13 through larval guts significantly increased oospore germination. However, decreased germination of hyphal swellings was observed following larval gut passage for strains of P. ultimum. These results expand previous studies suggesting that larval fungus gnats may vector Pythium spp.

Two new species of Pythium, P. senticosum and P. takayamanum,isolated from cool-temperate forest soil in Japan.

Pythium senticosum and P. takayamanum spp. nov. were isolated from cool-temperate forest soil in Japan. P. senticosum can grow at 5 C and is fast growing at 25 C with a radial growth of 22.2 mm 24 h(-1). The species is morphologically characterized by ovoid to ellipsoid sporangia with apical papilla, ornamented oogonia with acute conical spines, and antheridia with broad attachment to oogonia. P. takayamanum is very different and can grow at 35 C. This species is morphologically characterized by its wavy antheridial stalks and ellipsoidal oogonia with constricted areas. Phylogenetic analyses of the ITS rDNA region and the partial COX2 gene showed that the two species are genetically distinct from each other and from their closest relatives. P. senticosum is closely related to P. dimorphum and P. undulatum whereas P. takayamanum is closely related to P. rhizosaccharum and P. parvum.