Zoospores Of Phytophthora Capsici Research Articles

Pseudophomins A–D Produced from Pseudomonas sp. HN8-3 Using an OSMAC Approach and Their Roles in Biocontrol of Phytophthora capsici in Cucumbers

In this study, two new cyclic lipopeptides (CLPs) pseudophomins C (3) and D (4) and two known CLPs pseudophomins A (1) and B (2) were produced and characterized from the bacterial supernatant of Pseudomonas sp. HN8-3 by an OSMAC (one strain-many compounds) approach. OSMAC is a strategy that involves feeding of a single microorganism with divergent substrates to stimulate the production of new secondary metabolites. These pseudophomins were purified and identified via chromatographic methods, droplet collapse assay, genome mining, spectroscopic and spectrometric analyses, and single-crystal X-ray diffraction (XRD). Moreover, bioactivity tests showed that pseudophomins could lyse the zoospores of Phytophthora capsici in vitro, and coapplication of pseudophomins with zoospores of P. capsici further reduced the incidence of P. capsici on cucumber leaves. Collectively, these results indicated that pseudophomins have the potential to be developed as biopesticides for controlling P. capsici in cucumber.

Biosíntesis inducida de fengicina y surfactina en una cepa de Bacillus amyloliquefaciens con actividad oomiceticida sobre zoosporas de Phytophthora capsica

A potential alternative to the use of chemical products with oomyceticidal action for the control of Phytophthora capsici in vegetables is the use of antimicrobial metabolites, biosynthesized in Bacillus species. The objective of this study was to induce the biosynthesis of lipopeptides in Bacillus amyloliquefaciens KX953161.1 by using glutamic acid, iron, cellulose, chitin, or inactive Colletotrichum spp. cells. The in vitro oomyceticidal effect of the bacterial lipopeptides on zoospores of Phytophthora capsici was evaluated. The lipopeptides identified and quantified in the crude extracts by high performance thin layer chromatography (HPTLC) were fengycin and surfactin. The bacterial culture with inactive fungal cells yielded the greatest biosynthesis of lipopeptides, at 1847.02± 11.8 and 2563.45± 18.4 μg/ml of fengycin and surfactin, respectively and the treatments that obtained lower production of these lipopeptides, were those to which iron and cellulose were added with 608.05 ± 22.6 and 903.74± 22.1; 563.31± 11.9 and 936.96± 41.1 μg/ml for fengicin and surfactin, respectively. The lipopeptide extracted showed 100% germination inhibition on zoospores of P. capsici, revealing encystment, malformations in the germ tube and cellular degradation. Lipopeptides have the potential to control P. capsici; however, the biosynthesis of these lipopeptides requires further study to determine their biological mode of action and optimize lipopeptide performance and profile.

Anthraquinones and flavanols isolated from the vegetable herb Rumex abyssinicus inhibit motility of Phytophthora capsici zoospores

Many secondary metabolites derived from Rumex extracts exhibited potent activities against a panel of phytopathogens including those of Phytophthora spp. Phytochemical investigation of Rumex abyssinicus has led to the isolation of nine compounds, including one phenolic acid (1), five anthraquinones (2–6) and three flavanols (7–9). Compounds 1, 4, 6–9 are reported here from R. abyssinicus for the first time. The isolated compounds were evaluated for their inhibitory activity against zoospores of the oomycete phytopathogen Phytophthora capsici. Physcion (3) displayed strongest motility inhibitory activity with a MIC value of 15μgmL−1, and showed lytic activities against zoospores at 500μgmL−1.

Metabolites from the Endophytic Fungus Curvularia sp. M12 Act as Motility Inhibitors against Phytophthora capsici Zoospores.

The endophytic fungus Curvularia sp., strain M12, was isolated from a leaf of the medicinal plant Murraya koenigii and cultured on rice medium followed by chemical screening of the culture extract. Chromatographic analysis led to the isolation of four new compounds, murranofuran A (1), murranolide A (2), murranopyrone (3a), and murranoic acid A (4a), along with six known metabolites, N-(2-hydroxy-6-methoxyphenyl)acetamide (5), curvularin (6), (S)-dehydrocurvularin (7), pyrenolide A (8), modiolide A (9), and 8-hydroxy-6-methoxy-3-methylisocoumarin (10). The structures of the known compounds were confirmed by comparing ESI HR mass spectra, 1H and 13C NMR, and optical rotation data with values reported in the literature. The planar structures of the new compounds were elucidated by extensive analysis of 1D and 2D NMR and mass data. The absolute configurations of the new compounds were established by coupling constant analysis, modified Mosher's method, and CD data. Compound 8 showed a strong motility impairing activity against Phytophthora capsici zoospores at a low concentration (100% at 0.5 μg/mL) in a short time (30 min). Compounds 2, 3a, 6, 7, 9, and 10 exhibited zoospore motility impairment activity at higher concentrations (IC50: 50-100 μg/mL).

Medicinal plant extracts and protein kinase C inhibitor suppress zoosporogenesis and impair motility of Phytophthora capsici zoospores

Ansary M.W.R., Haque E., West H.M., Rahman M.M., Akanda A.M., Wang Y., Islam M. T. (2016): Medicinal plant extracts and protein kinase C inhibitor suppress zoosporogenesis and impair motility of Phytophthora capsici zoospores. Plant Protect. Sci., 52: 113–122. The effects of water and acetone extracts from 100 medicinal plants growing in Bangladesh, along with a selective inhibitor of protein kinase C (PKC), chelerythrine chloride, were tested on zoosporogenesis (release of zoospores from the sporangia) and motility of Phytophthora capsici zoospores. Among 10 active crude acetone extracts, those from Psidium guajava and Nigella sativa (100 μg/ml) suppressed zoosporogenesis relative to the control (100% zoospore release) to 60 and 40% released, respectively and inhibited motility of 100% of the zoospores within 60 min of treat ment. Chelerythrine chloride also suppressed zoosporogenesis (30% released) at 0.1 μg/ml and inhibited motility of 100% zoospores at 0.2 μg/ml within 60 minutes. Among water extracts of 100 medicinal plants, 56 impaired motility of zoospores in a dose- and time-dependent manner. Diluted (20-fold) water extracts of 10 plants including Ocinum gratissimum, Terminalia bohera , and Duranta plumeri inhibited motility and subsequently caused lysis of zoospores.

Gageopeptins A and B, new inhibitors of zoospore motility of the phytopathogen Phytophthora capsici from a marine-derived bacterium Bacillus sp. 109GGC020.

The motility of zoospores is critical in the disease cycles of the peronosporomycetes that cause devastating diseases in plants, fishes, vertebrates, and microbes. In the course of screening for secondary metabolites regulating the motility of zoospores of Phytophthora capsici, we discovered two new inhibitors from the ethyl acetate extract of the fermentation broth of a marine-derived strain Bacillus sp. 109GGC020. The structures of these novel metabolites were elucidated as new cyclic lipopeptides and named gageopeptins A (1) and B (2) by spectroscopic analyses including high resolution MS and extensive 1D and 2D NMR. The stereoconfigurations of 1 and 2 were assigned based on the chemical derivatization studies and reviews of the literature data. Although compounds 1 and 2 impaired the motility of zoospores of P. capsici in dose- and time-dependent manners, compound 1 (IC50 = 1 μg/ml) was an approximately 400-fold stronger motility inhibitor than 2 (IC50 = 400 μg/ml). Interestingly, the zoospores halted by compound 1 were subsequently lysed at higher concentrations (IC50 = 50 μg/ml). Compounds 1 and 2 were also tested against some bacteria and fungi by broth dilution assay, and exhibited moderate antibacterial and good antifungal activities.

Benefits of photo-Fenton at low concentrations for solar disinfection of distilled water. A case study: Phytophthora capsici

Water phytopathogens may be a big issue in irrigation water. Huge efforts for controlling this problem have changed along the time, from traditional culturing to the use of chemical and biological methods like fungicides and antagonist microorganisms. Moreover, techniques to enhance water quality are still under investigation especially due to the increasing pressure over human intensive agriculture activities. Advanced oxidation processes (AOPs) have been demonstrated to be highly efficient on the removal of hazardous chemical compounds as well as microorganisms contained in water. This work reports on the capacity of photo-Fenton to remove Phytophthora capsici zoospores in distilled water at small scale (250mL solar bottle reactor) under natural solar radiation. Photo-Fenton process efficiency was evaluated using two different iron sources, ferrous sulphate (Fe2+) and ferric nitrate (Fe3+), which led to different zoospores inactivation kinetics. The highest inactivation rate was measured with 5mg/L of Fe3+ (89.5μM) and 10mg/L of H2O2 (294μM), which required 2.5kJ/L of solar UV-dose (only 60min of solar exposure). Different results observed between both iron salts may be due to the nature of zoospores cell wall and the different role played by the iron speciation in cells. In addition, the separated effects of H2O2, Fe2+ and Fe3+ over P. capsici spores under natural solar radiation and in the dark were also evaluated. For all solar processes evaluated, we observed the following order of inactivation of P. capsici zoospores: Fe3+–H2O2/solar>H2O2/solar>Fe2+–H2O2/solar≥Fe3+/solar>Fe2+/solar>solar photo-inactivation.

고추역병 생물적방제 근권세균의 선발 및 근권정착 능력 연구

하남성지역의 고추역병 발병포장 건전한 고추뿌리와 근권토양에서 세균 507균주를 분리하였는데, 그중에서 고추역병균에 길항효과가 우수한 G28-6, G28-5, I7-6과 H14-1균주를 선발하였다. In vitro에서 선발된 균주들은 고추역병균의 균사생장, 유주자낭과 유주자 형성, 그리고 피낭포자의 발아를 현저하게 억제하였고, Pot시험에서 선발된 균주 모두 70% 이상의 방제효과를 나타냈고, 포트시험에서 방제효과가 우수하였던 G28-6균주는 고추역병 자연발생 비닐하우스에서 79.4%의 방제가를 보여 공시된 화학농약 80% Mancozeb 보다 훨씬 높은 방제효과를 보였다. 뿐만 아니라 선발된 4균주 모두 in vitro에서 우수한 근권정착능력을 보였다. 고추역병 방제에 우수한 길항세균으로 선발된 G28-6균주의 16S rRNA gene 염기서열분석과 그의 형태적, 생리적 특성들을 Bergey's manual of Systematic Bacteriology를 기준으로 비교하여 Pseudomonas aurantiaca로 동정하였다. Four promising biocontrol agents against Phytophthora capsici were selected from 507 bacterial isolates collected from rhizosphere soils and roots of pepper plants. In vitro experiment, these four biocontrol agents inhibited mycelial growth, germination of cystospores, and formation of zoosporangia and zoospores of Phytophthora capsici. In the pot experiment, the four biocontrol agents showed control efficiency higher than 70%. In greenhouse experiment, the isolates G28-6 gave the control value of 79.4%. These four biocontrol agents successfully colonized in the population density beyond 105 cfu/g on roots of pepper in vitro. The isolates G28-6 was identified as Pseudomonas aurantiaca, based on its cultural, morphological, and biochemical characterization and 16S rRNA gene sequence analysis.

Effect of high-power monochromatic (pulsed UV laser) and low-power broadband UV radiation on Phytophthora spp. in irrigation water

Cysts or zoospores of Phytophthora capsici, P. citrophthora and P. nicotianae were suspended in distilled water or in recycled irrigation water collected from commercial nurseries. Propagules, suspended in shallow layers of still water in 60 mm-diameter plastic Petri dishes with lids off, were exposed to various UV doses emitted from either an excimer laser or a mercury vapor lamp. The laser emitted a monochromatic (248 nm, 5 eV/pulse), pulsed UV beam with an intensity of 1 to 2 mJ/cm2/pulse with 20-ns pulse durations and a high peak power of 50 to 100 kW/cm2/pulse. The UV lamp was from a commercial water purifier that emitted broadband (continuous) UV radiation at an intensity of ∼8 mW/cm2. Survival was assessed by culturing aliquots of the treated or non-treated suspensions onto corn meal agar amended with ampicillin (250 ppm) and rifampin (10 ppm), and then counting numbers of developing colonies. The UV dose (as energy per unit area) required to kill propagules was smaller when they were suspended in distilled water than when suspended in recycled nursery water. The reduced kill effectiveness in recycled water appears to be related to UV-absorbing soluble chemicals. Cysts and zoospores were equally susceptible to UV, although the high-peak power pulsed-UV laser source with ultra-short exposure times appeared to have greater kill effectiveness than the conventional Hg-vapor UV lamp. Phytophthora capsici and P. nicotianae isolates were somewhat less sensitive to UV than isolates of P. citrophthora obtained from various hosts and geographical regions. Furthermore, hyphae of Phytophthora spp. were less susceptible to UV than were cysts or zoospores.

Combinatorially selected defense peptides protect plant roots from pathogen infection.

Agricultural productivity and sustainability are continually challenged by emerging and indigenous pathogens. Currently, many pathogens can be combatted only with biocides or environmentally dangerous fumigants. Here, we report a rapid and pathogen-specific strategy to reduce infection by organisms that target plant roots. Combinatorially selected defense peptides, previously shown to effect premature encystment of Phytophthora capsici zoospores, were fused to maize cytokinin oxidase/dehydrogenase as a display scaffold. When expressed in tomato roots, the peptide-scaffold constructs were secreted and accumulated to sufficient concentrations in the rhizosphere to induce zoospore encystment and thereby deter taxis to the root surface. Pathogen infection was significantly inhibited in roots expressing bioactive peptides fused to the maize cytokinin oxidase/dehydrogenase scaffold. This peptide-delivery technology is broadly applicable for rapid development of plant defense attributes against plant pathogens.

Influence of Sub- Versus Top-irrigation and Surfactants in a Recirculating System on Disease Incidence Caused by Phytophthora spp. in Potted Pepper Plants

Zoospores of Phytophthora capsici spread from inoculated source plants to healthy potted pepper plants located on separate ebb-and-flow benches when the recycled nutrient solution originated from a common reservoir. Amending the recirculating nutrient solution with a surfactant, which selectively kills zoospores, resulted in 100% control of the spread of the pathogen in an ebb-and-flow and a top-irrigated cultural system. Without a surfactant in the recirculating nutrient solution, all plants in an ebb-and-flow cultural system died within 6 weeks. In contrast, all plants in a top-irrigated cultural system died within 2 weeks after inoculation of source plants. These results suggest that the use of recycled irrigation water in an ebb-and-flow cultural system is less conducive to pathogen spread than its use in a top-irrigated cultural system, but may still serve as efficient means of inoculum movement in the absence of control measures.

Phenotypic and molecular characterization of species hybrids derived from induced fusion of zoospores of Phytophthora capsici and Phytophthora nicotianae

Phenotypes of species hybrids created from in vitro fusion of zoospores from Phytophthora nicotianae and P. capsici were characterized and compared. The species hybrids were created as part of a study of sources of genetic variation in populations of the parent species that are pathogenic over a similar range of plants. Four isolates of species hybrids proved to be similar to both P. capsici and P. nicotianae in relation to vegetative and reproductive morphologies. As in a previous study, DNA of P. capsici was detected more readily than that of P. nicotianae in all hybrid isolates. In the present study, DNA of P. nicotianae was detected in three of four hybrids by hybridization of RAPD-PCR products with species-specific DNA from P. nicotianae. By thermal denaturation analyses, DNA melting temperatures and GC contents of parent species and species hybrids were similar. The mean GC content of 47.2% was similar to GC contents reported for other Phytophthora spp. Additionally, the distributions of GC-rich regions of hybrids were more similar to the distribution in P. capsici than in P. nicotianae. By these molecular analyses, the hybrids were shown to be more similar to P. capsici than to P. nicotianae. Even though interspecific somatic fusion is likely to occur rarely under natural conditions, it could contribute to the genetic diversity of heterothallic species of Phytophthora.

Relationship of Phytophthora Fruit Rot to Fruit Maturation and Cuticle Thickness of New Mexican-type Peppers

Experiments were conducted to determine the relationship between pepper fruit susceptibility to Phytophthora fruit rot and fruit maturity. Pepper fruits were harvested weekly throughout the 1991 growing season and were dipped in a suspension of Phytophthora capsici zoospores (5×10 3 zoosporesl/ml). The susceptibility of nonwounded fruit to infection decreased with increased ripening. Lesion elongation in nonwounded fruit decreased from 14.1 mml/day in green fruit to 10.7 mm/day in nondehydrated red fruit. Nonwounded fruit (immature green, mature green, and red) inoculated with 5×10 3 zoospores in a 100-μl drop also exhibited less infection as the fruit ripened [...]

An ultrastructural study of the effect of metalaxyl on Phytophthora capsici infected stems of Capsicum annuum

AbstractStems of pepper seedlings were inoculated with zoospores of Phytophthora capsici 18 h after a soil‐drench with metalaxyl solution (5 μg ml−1) or water. Infected stem tissues were examined by electron microscopy 24 h after inoculation. Compared with untreated controls, in which the fungal cells were generally normal in shape and ultrastructure, the most conspicuous effects of metalaxyl treatment on the fungal ultrastructure in the stem tissue were an abnormal shrinking of the fungal cell, a separation of the plasma membrane from the hyphal wall, a peculiar invagination and breakdown of the plasma membrane, the presence of vesicles in the invaginated spaces and within the damaged fungal cells, and an indistinct structure of cell organelles. In metalaxyl‐treated stems, an electron‐dense material was apposed in those sites of the host cell wall in most intimate contact with the fungal cell wall, indicating that the deposition of these substances from the host cell walls may function as a plant defence reaction to the fungus, whereas in untreated controls, the dark‐stained host cytoplasm did not aggregate around the sites of fungal contact. The haustorium was encased by the extra‐haustorial matrix in treated stems. These results suggest that metalaxyl treatment not only changes the fine structure of P. capsici, but may also induce the plant defence reaction.

Aggregation of Phytophthora capsici Zoospores and their Interaction with Zoospores of P. palmivora

Zoospores of Phytophthora palmivora Butler aggregated without encysting within 2 min when they were suspended in water (Ko & Chase, 1973). Such zoospore behaviour was temperature-dependent with an optimum temperature of 16 °C. Aggregate formation also depended on both zoospore concentration and depth of suspension. We now report a similar behaviour of zoospores of Phytophthora capsici Leonian in water. The interaction between zoospores of P. palmivora and P. capsici was also investigated.

The flagella of zoospores of Phytophthora capsici Leonian as viewed with the phase contrast microscope

Examinations of living zoospores of Phytophthora capsici with the phase contrast microscope reveal a small spherical body on many of the flagella. Before the zoospores emerge from the sporangia, they have two flagella already. Immediately after the zoospores emerge from sporangia, they move about rapidly and no small spherical bodies are visible on the flagella. One of the flagella swings severely foreward and the other slowly afterward. Later, as the zoospores begin to swim more slowly, a small spherical body appears on the middle part of the flagella. The flagella suddenly fold in two at the point of the spherical body and take an appearance of earpick shape. The flagella seem to wither completely or remain earpick-like. The zoospores stop their movement and the flagella, now being only spherical bodies or earpick-like structures, become detached and float away. Some different ways on transformations of flagella were observed in these examinations.