Phytopathogenic Fungal Species Research Articles

Spectroscopic and biochemical studies of chromium(III) and manganese(II) complexes with p-vanillin containing thiosemicarbazone and semicarbazone ligands

A new series of chromium(III) and manganese(II) complexes with p-vanillin thiosemicarbazone (L1) and p-vanillin semicarbazone (L 2 ) have been synthesized and characterized. The nature of bonding and stereochemistry of the complexes have been deduced from elemental analysis, conductivity measurements, mass, magnetic susceptibility, infrared and electronic spectral studies. On the basis of these spectral studies, an octahedral geometry has been assigned for all the complexes. The antimicrobial activities of the free ligands and their metal complexes were evaluated on different species of phytopathogenic fungi and their biopotency has been discussed.

Characterization of Pseudomonas corrugata Strain P94 Isolated from Soil in Beijing as a Potential Biocontrol Agent

In an attempt to obtain biologic control agents for grey mildew of tomato, a total of 628 bacterial strains were isolated from agricultural soil samples in Beijing, China, and screened for in vitro antibiosis toward Botrytis cinerea. Strain P94 exhibited the most obvious antagonistic activity. It P94 had no pathogenicity and was identified as Pseudomonas corrugata by the Biolog identification system combined with 16S rDNA sequence analysis and biochemical and physiologic characteristics. The specific products of polymerase chain reaction with two pairs of specific primers indicated that P94 belonged to P. corrugata genomic group II. Strain P94 inhibited the growth of a number of phytopathogenic fungal and bacterial species and showed inhibition activity to tomato grey mildew by tomato leaf testing in vitro. Strain P94 showed a positive reaction for HCN, protease, phosphatase, and indole acetic acid tests and a negative reaction for siderophore-, chitinase-, and cellulase-production tests. Therefore, the secondary metabolites producing novel P. corrugata strain P94 exhibited an innate potential of biocontrol activities in vitro.

Phylogenetic analysis of Phoma species

The cosmopolitan Phoma genus contains mainly phytopathogenic, opportunistic parasites, and saprophyte fungal species. Up to now, the characterization of Phoma species and other taxa of Phoma has been determined on the basis of morphology on standardized media, and gene sequence analysis was only used as a confirmative or distinctive complement.In this study, we tried to find molecular markers which can be used as phylogenetics markers in the molecular based classification in the Phoma genus.We employed a part of the translation elongation factor 1 subunit alpha (EF-1α=tef1) containing both introns and exons and ITS region containing the internal transcribed spacer regions 1 and 2 and the 5.8S rDNA, as potential genetic markers to infer phylogenetic relationships among different Phoma taxa. Twelve different Phoma species sequences were analysed together with the closely related Ascochyta ones. The constructed phylogenetic trees, based on tef1 and ITS sequences, do not support the traditional Phoma sections based on morphological characterization. However, we managed to distinguish between the Phoma strains and Ascochyta species by comparing their tef1 sequences through parsimony analysis. We proved that a tef1 can be a useful phylogenetic marker to resolve phylogenetic relationships at species level in Phoma genus.Both parsimony sequence analyses confirmed that the Phyllosticta sojicola species is identical to the Phoma exigua var. exigua species as Kövics et al. (1999) claimed. However, the evolutionary distance by ITS sequences within Phoma species is too small to get well based consequences for the phylogenetic relationships of Phoma genus.Further investigations would be necessary to clarify whether the tef1 and ITS sequences as phylogenetic molecular markers are well suited for the classification of Phoma species.

Identification of Fungi Associated with Grapevine Decline in Castilla y León (Spain)

Summary. A number of phytopathogenic fungal species are associated with grapevine decline. Esca, eutypa dieback, black dead arm, and other grapevine decline diseases affecting vine wood have a worldwide distribution. The external symptoms of these diseases, however, can be erratic; even asymptomatic infections are known. Grapevine decline causes economic losses, the size of which depends on factors that still remain unclear, but in all cases the productive life of affected plants is shortened. Grapevine decline is present throughout Castilla y Leon (Spain). In the present work, the fungi potentially associated with grapevine decline were isolated and identified. Botryosphaeria-like spp., Phaeomoniella chlamydospora and Phaeoacremonium spp. were common. Cylindrocarpon spp. were found mainly in young plants, while Phomopsis viticola, Fomitiporia mediterranea, Eutypa lata and Stereum hirsutum were found only occasionally. Particular attention was given to the identification of the Botryosphaeria-like species, of which several were found. By comparing restriction endonuclease patterns (ITS1-NL4) and the sequences of the internal transcribed spacer fragments (ITS4-ITS5), Diplodia seriata (=B. obtusa), Diplodia mutila (=B. stevensii), Neofusicoccum parvum (=B. parva), B. dothidea, Dothiorella iberica (=B. iberica) and Dothiorella sarmentorum (=Diplodia sarmentorum) were all identified. D. seriata and D. mutila were identified on plants older than five years. The incidence of infection by “Botryosphaeria” species in young plants was very variable.

Biological control of two phytopathogenic fungal species isolated from the rhizoplane of soybean (Glycine max).

Biological control of two phytopathogenic fungal species isolated from the rhizoplane of soybean (<i>Glycine max</i>).

Chemical structure, surface properties and biological activities of the biosurfactant produced by Pseudomonas aeruginosa LBI from soapstock.

Pseudomonas aeruginosa LBI isolated from petroleum-contaminated soil produced rhamnolipids (RL(LBI)) when cultivated on soapstock as the sole carbon source. HPLC-MS analysis of the purified culture supernatant identified 6 RL homologues (%): R(2) C(10) C(10) 28.9; R(2) C(10) C(12:1) 23.0; R(1) C(10) C(10) 23.4; R(2) C(10) C(12) 11.3; R(2) C(10) C(12) 7.9; R(2) C(10) C(12) 5.5. To assess the potential antimicrobial activity of the new rhamnolipid product, RL(LBI), its physicochemical properties were studied. RL(LBI) had a surface tension of 24 mN m(-1) and an interfacial tension of 1.31 mN m(-1); the cmc was 120 mg l(-1). RL(LBI) produced stable emulsions with hydrocarbons and vegetable oils. This product showed good antimicrobial behaviour against bacteria: MIC for Bacillus subtilis, Staphylococcus aureus and Proteus vulgaris was 8 mg l(-1), for Streptococcus faecalis 4 mg l(-1), and for Pseudomonas aeruginosa 32 mg l(-1). RL(LBI) was active against phytopathogenic fungal species, MIC values of 32 mg l(-1) being found against Penicillium, Alternaria, Gliocadium virens and Chaetonium globosum. Due to its physicochemical properties and antimicrobial behaviour, RL(LBI) could be used in bioremediation treatment and in the food, cosmetic and pharmaceutical industries.

Physicochemical characterization and antimicrobial properties of rhamnolipids produced by Pseudomonas aeruginosa 47T2 NCBIM 40044.

Pseudomonas aeruginosa 47T2, grown in submerged culture with waste frying oil as a carbon source, produced a mixture of rhamnolipids with surface activity. Up to 11 rhamnolipid homologs (Rha-Rha-C(8)-C(10); Rha-C(10)-C(8)/Rha-C(8)-C(10);Rha-Rha-C(8)-C(12:1); Rha-Rha-C(10)-C(10); Rha-Rha-C(10)-C(12:1); Rha-C(10)-C(10); Rha-Rha-C(10)-C(12)/Rha-Rha-C(12)-C(10); Rha-C(10)-C(12:1)/Rha-C(12:1)-C(10); Rha-Rha-C(12:1)-C(12); Rha-Rha-C(10)-C(14:1); Rha-C(10)-C(12)/Rha-C(12)-C(10)) were isolated from cultures of P. aeruginosa 47T2 from waste frying oil and identified by HPLC-MS analysis. This article deals with the production, isolation, and chemical characterization of the rhamnolipid mixture RL(47T2). The physicochemical and biological properties of RL(47T2) as a new product were also studied. Its surface tension decreased to 32.8 mN/m; and the interfacial tension against kerosene to 1 mN/m. The critical micellar concentration for RL(47T2) was 108.8 mg/mL. The product showed excellent antimicrobial properties. Antimicrobial activity was evaluated according to the minimum inhibitory concentration (MIC), the lowest concentration of an antimicrobial agent that inhibits development of visible microbial growth. Low MIC values were found for bacteria Serratia marcescens (4 microg/mL), Enterobacter aerogenes (8 microg/mL), Klebsiella pneumoniae (0.5 microg/mL), Staphylococcus aureus and Staphylococcus epidermidis (32 microg/mL), Bacillus subtilis (16 microg/mL), and phytopathogenic fungal species: Chaetonium globosum (64 microg/mL), Penicillium funiculosum (16 microg/mL), Gliocadium virens (32 microg/mL) and Fusarium solani (75 microg/mL).

Extending chestnut blight hypovirus host range within diaporthales by biolistic delivery of viral cDNA.

Biolistic bombardment was used to successfully transform three phytopathogenic fungal species with an infectious cDNA clone of the prototypic hypovirus, CHV1-EP713, a genetic element responsible for the virulence attenuation (hypovirulence) of the chestnut blight fungus, Cryphonectria parasitica. The fungal species included two strains each of C. parasitica and Valsa ceratosperma, as well as one strain of Phomopsis G-type (teleomorph Diaporthe Nitschke); all are members of the order Diaporthales but classified into three different genera. A subset of transformants for each of the fungal species contained CHV1-EP713 dsRNA derived from chromosomally integrated viral cDNA. As has been reported for CHV1-EP713 infection of the natural host C parasitica, biolistic introduction of CHV1-EP713 into the new fungal hosts V ceratosperma and Phomopsis G-type resulted in altered colony morphology and, more importantly, reduced virulence. These results suggest a potential for hypoviruses as biological control agents in plant-infecting fungal pathogens other than the chestnut blight fungus and closely related species. In addition, the particle delivery technique offers a convenient means of transmitting hypoviruses to potential host fungi that provides new avenues for fundamental mycovirus research and may have practical applications for conferring hypovirulence directly on infected plants in the field.

Antifeedant and toxic effects of sesquiterpenes fromSenecio palmensis to colorado potato beetle

A bioassay-guided fractionation of the aerial parts ofSenecio palmensis resulted in the isolation of two sesquiterpenes, 2,10-bisaboladien-1-one and 11β-acetoxy-5-angeloyloxy-silphinen-3-one. The bisabolene and the silphinene represented 0.012% and 0.024% of the plant dry weight, respectively. Both compounds showed antifeedant activity againstLeptinotarsa decemlineata larvae and adults in short-term choice and no-choice bioassays. Both compounds were also tested against different species of phytopathogenic fungi. The beetles were more sensitive to these compounds in choice than in no-choice assays, with a gradient of increasing sensitivity from second instars to adults. Bisabolene was 45 times less active as an antifeedant than juglone, which was tested as a positive control. The silphinen was more active than the bisabolene, with a range of activity similar to juglone. Furthermore, exposure of fourth instars to these compounds over a 24-hr period resulted in reduced feeding and growth rates. To distinguish between antifeedant and toxic effects, growth efficiencies were calculated as the slope of the regression of relative growth rate on relative consumption rate. The comparison of these results with those of antifeedant simulation and contact toxicity bioassays indicates that feeding inhibition is the primary mode of action of the bisabolene, while the silphinene shows both antifeedant and toxic effects.

Discriminating Synergism and Antagonism of Spores Within Species of Phytopathogenic Fungi

Synergism and antagonism of spores of phytopathogenic fungi can be detected by comparison of the changes in the infection probabilities at different inoculum densities. In this paper, we describe a model, developed from the formula of the multiple infection transformation and probability theory, that can be used to discriminate the synergism and antagonism of spores. A function was derived that allows the easy evaluation of synergism and antagonism. The model was used to analyze the experimental data of Puccinia striiformis spores and winter wheat. The definition of antagonism is broader than that used by Vanderplank

Allelopathic effects of green fronds of Pteridium aquilinum on cultivated plants, weeds, phytopathogenic fungi and bacteria

The effects of aqueous and methanolic extracts of the fronds of Pteridium aquilinum and of the macerated fronds on the germination and radicle growth of eight species of cultivated plants and five weed species were tested. The results indicate that the growth of four out of the five weed species was markedly inhibited in the test with macerated fronds. The aqueous extract had no significant effect on either the cultivated or the weed species. Mustard and tomato appeared to be the most susceptible species to the methanolic extract of the fern's fronds. The effect on the growth of four species of phytopathogenic fungi and four phytopathogenic bacteria was also tested. Fungi were tested with aqueous, methanolic and ethanolic extracts of the fronds. Bacteria were tested with aqueous extract. The fungal growth was strongly inhibited by the aqueous extract, and this inhibitory activity was maintained throughout the course of the experiment. In the bioassays with methanolic and ethanolic extracts, a tendency towards recuperation could be observed in some of the fungi tested. The diluted aqueous fraction (1:10) of the methanolic extract produced a stimulating effect on the growth of all the fungi tested. The aqueous extract inhibited only the growth of the sole gram-positive bacteria among the species tested.

Prevention of a plant disease by specific inhibition of fungal polyamine biosynthesis.

DL-alpha-Difluoromethylornithine (DFMO), an inhibitor of the polyamine biosynthetic enzyme ornithine decarboxylase (EC 4.1.1.17), strongly retards the growth of several species of phytopathogenic fungi in vitro. Such inhibition can be completely reversed by putrescine or spermidine, confirming the essentiality of polyamines for growth of fungal hyphae. We now show that DFMO can protect bean plants (Phaseolus vulgaris Linnaeus cv. Pinto) against infection by uredospores of the bean rust fungus, Uromyces phaseoli Linnaeus, race O. Unifoliolate leaves of 10-day-old greenhouse-grown seedlings were sprayed with 400 microliter per leaf of DFMO at various concentrations in 0.01% Tween 20 at pH 7.0 before or after inoculation with uredospores of Uromyces. After 16 hr in darkness in dew chambers to facilitate spore germination, plants were transferred to the greenhouse, arranged randomly, and examined for local lesions 7 days later. All concentrations of DFMO 0.50 mM or higher gave complete protection against the pathogen; at lower concentrations, postinoculation treatments with DFMO were generally more effective than preinoculation. The appearance of lesions on plants treated with lower concentrations of DFMO was retarded 2-6 days. DFMO also confers protection on unsprayed parts of treated plants, indicating the translocation of some protective effect from sprayed areas. DL-alpha-Difluoromethylarginine, an analogous inhibitor of arginine decarboxylase (EC 4.1.1.19), which is the rate-limiting enzyme in an alternative pathway for polyamine biosynthesis in higher plants, confers no protection even at 5 mM. This emphasizes ornithine decarboxylase as the biochemical locus of choice for the prevention of plant diseases by inhibiting polyamine metabolism.

An antibiotic substance purely isolated from the culture filtrates of Gloeosporium olivarum which was grown in the presence of MCP.

An antibiotic substance has been purely isolated from the culture filtrates of Gloeosporium olivarum Alm. which was grown for 12 days in the presence of 0.03% 2-methyl-4 chlorophenoxyacetic acid (MCP). The yield was 0.181mg/ml of the original filtrate. This compound of white needle-shaped crystals, m. p. 55°C, is thermostable, nearly insoluble in cold water, but soluble in hot water and many organic solvents. It contains C, H, O, Cl and the hydroxyl group characteristic to a primary or secondary alcohol, but does not contain S, P and N·The one-dimensional paper-partition chromatogram of the antibiotic developed by ascending technique with acetone-methanol-water mixtures (30:5:65v/v) showed a single inhibiting zone at Rf 0.73. When the antibiotic was incorporated into agar media at the dilution of 1:5, 000, the growth of G. olivarum and Cochliobolus miyabeanus was almost completely inhibited, the dilution end-point being about at I:40, 000 and 1:30, 000 against the former fungus and Corticium centrifugum respectively. Conidial germination of G. olivarum was entirely inhibited at 1:3, 000. In the other experiment by paper disk method, it also exerted a toxicity against other 5 species of phytopathogenic fungi and 5 species of bacteria. The inhibitory activity of MCP in vitro on G. olivarum is considered to be attributable to this antibiotic produced by addition of MCP rather than to its direct effect on the pathogen.