Solani Hyphae Research Articles

Polycyclic aromatic hydrocarbons storage by Fusarium solani in intracellular lipid vesicles

Accumulation and elimination of polycyclic aromatic hydrocarbons (PAHs) were studied in the fungus Fusarium solani. When the fungus was grown on a synthetic medium containing benzo[ a]pyrene, hyphae of F. solani contained numerous lipid vesicles which could be stained by the lipid-specific dyes: Sudan III and Rhodamine B. The fluorescence produced by Rhodamine B and PAH benzo[ a]pyrene were at the same locations in the fungal hyphae, indicating that F. solani stored PAH in pre-existing lipid vesicles. A passive temperature-independent process is involved in the benzo[ a]pyrene uptake and storage. Sodium azide, a cytochrome c oxidation inhibitor, and the two cytoskeleton inhibitors colchicine and cytochalasin did not prevent the transport and accumulation of PAH in lipid vesicles of F. solani hyphae. F. solani degraded a large range of PAHs at different rates. PAH intracellular storage in lipid vesicles was not necessarily accompanied by degradation and was common to numerous other fungi.

Biological control of Rhizoctonia solani by two Trichoderma species isolated from South African composted soil

Strains of two Trichoderma species isolated from composted soil were evaluated for biological control of Rhizoctonia solani. Macroscopic observations of in vitro bioassays revealed that the Trichoderma isolates overgrew the pathogen completely and that a brownish discolouration occurred at the initial point of interaction. Ultrastructural studies demonstrated that the Trichoderma isolates coiled around the R. solani hyphae and subsequently caused cell wall lysis. Application of Trichoderma formulations to cucumber seeds in the greenhouse significantly increased the percentage germination, survival and overall dry weight biomass of seedlings compared to a diseased control. Chitinase activity was detected on agar plates supplemented with colloidal chitin. The mycoparasitism of the two Trichoderma isolates indicates that there may be a reservoir of Trichoderma isolates which may be used as biological control agents for local South African soil conditions.

Biological control of damping-off caused by Rhizoctonia solani using chitinase-producing Paenibacillus illinoisensis KJA-424

A bacterium having strong chitinolytic activity was isolated from a coastal soil in Korea and identified as Paenibacillus illinoisensis KJA-424 on the basis of the nucleotide sequence of a 16S rRNA gene. By activity staining after SDS–PAGE, three major chitinase bands with chitinolytic activity, approximate molecular weight of 63, 54 and 38 kDa were detected. On co-culture Rhizoctonia solani with KJA-424, abnormal swelling and deformation of R. solani hyphae were observed, where the release of N-acetyl- d-glucosamine was detected. The bacterium suppressed the symptom of damping-off cucumber seedlings caused by R. solani, in greenhouse trial.

Molecular cloning, characterization, and expression of a cDNA encoding an endochitinase gene from the mycoparasite Stachybotrys elegans

Stachybotrys elegans is a mycoparasite of the soilborne plant pathogenic fungus Rhizoctonia solani. The mycoparasitic activity of S. elegans is correlated with the production of cell wall degrading enzymes such as chitinases. This report details the cloning by RACE-PCR and characterization of a full-length cDNA clone, sechi44, that appears to encode an extracellular endochitinase. An analysis of the sechi44 sequence indicates that this gene contains a 1269-bp ORF and encodes a 423-aa polypeptide. The SECHI44 protein has a calculated molecular weight of 44.1 kDa and p I of 5.53. Since the SECHI44 protein also appears to encode a signal peptide, an extracellular location for the corresponding protein is predicted. Comparison of SECHI44 sequence with known sequences of fungal endochitinases revealed that SECHI44 is grouped with endochitinases from other mycoparasites. Real-time quantitative RT-PCR analysis showed an elevated level of expression of sechi44 (21-fold) in chitin-rich (induced) as compared to no-carbon (non-induced) culture conditions. In dual culture, the temporal expression of sechi44 increased after 2 days of contact with R. solani, reaching a 10-fold increase after 9 days, followed by a decrease to basic expression level at 12 days. Interestingly, inhibition of sechi44 expression was observed when S. elegans hyphae were in close proximity with R. solani hyphae.

Interactions of human phagocytes with mouldsFusariumspp. andVerticilliumnigrescenspossessing different pathogenicity1

Fusarium spp. are emerging as important causes of invasive fungal infections. They tend to have decreased susceptibility to antifungal agents, making host defences very important. The ability of human phagocytes to cause damage to hyphae of Fusarium solani, F. oxysporum and Verticillium nigrescens, a mould with very low pathogenicity, was assessed using the 2,3-bis[2-methoxy-4-nitro-5-sulphophenyl]2H-tetrazolium-5-carboxanilide (XTT) metabolic assay. The oxidative burst, evidenced as superoxide anion (O2-) production, of phagocytes in response to hyphae was also investigated, as well as phagocytosis of conidia by monocyte (MNC)-derived macrophages (MDM). Hyphal damage by polymorphonuclear leukocytes (PMNL) and MNC showed a linear trend increasing with effector cell:target cell (E:T) ratio. Although no significant differences were observed for PMNL, MNC-induced damage to F. solani hyphae was lower than that seen with F. oxysporum hyphae at an E:T ratio of 20:1 and with V. nigrescens hyphae at ratios of 1:1, 5:1 and 20:1 (P < 0.05). In contrast, levels of O2- production by phagocytes in response to F. oxysporum were lower than those induced in response to the other fungi (P < 0.01). The average number of V. nigrescens conidia ingested by MDM was higher than that of conidia of the other fungi (P < 0.01). Phagocytes respond to the test fungi differentially, with F. solani being the least susceptible to damage by MNC. This may correlate with the observation that, compared to the other fungi studied, it causes a relatively high incidence of infections in neutropenic patients.

Purification and Partial Characterization of aβ-1,3-Glucanase Secreted by the MycoparasiteStachybotrys elegans

A β-1,3-glucanase secreted by Stachybotrys elegans, when grown on minimal synthetic medium containing Rhizoctonia solani cell wall fragments, was purified to homogeneity. The purification method involved ammonium sulfate precipitation and ion-exchange and size-exclusion chromatographies. The molecular mass of the enzyme was estimated under denaturing conditions to be about 94 kDa. The enzyme had an optimum pH of 5.0 and was most active between 40 and 50°C. Except for Mn2+, the enzyme activity was not sensitive to the metal ions tested and Km of 0.18 mg/ml was estimated for laminarin as a substrate. Cell wall lytic activity of purified β-1,3-glucanase was tested on actively growing R. solani hyphae. β-1,3-Glucanase induced morphological changes such as hyphal tip swelling, bursting, leakage of cytoplasm, and formation of numerous septae.

Biological control of soilborne plant pathogens by a β-1,3 glucanase-producing Pseudomonas cepacia

A β-1,3 glucanase-producing bacterium identified as Pseudomonas cepacia was isolated on a synthetic medium with laminarin as sole carbon source. In biocontrol experiments carried out under greenhouse conditions, this bacterium decreased the incidence of diseases caused by Rhizoctonia solani, Sclerotium rolfsii and Pythium ultimwn by 85, 48 and 71%, respectively. A determination of lytic enzymes revealed no chitinolytic activity. However, an active and stable β-1,3 glucanase was detected. The optimal temperature and pH values for its activity were 60°C and 5.0, respectively. The induction of this β-1,3 glucanase by different fungal cell walls as sole carbon source in synthetic medium was correlated with the biocontrol of the respective fungi by Pseudomonas cepacia. The damage caused to R. solani hyphae was observed under light and electron microscopes. The role of the β-1,3 glucanase produced by Pseudomonas cepacia in the biological control of soilborne plant pathogens is discussed.

Characteristics of Inhibition of Suppressive Soil Created hy Monoculture with Radish in the Presence of Rhizoctonia solani

AbstractSoils collected from five districts of Hawaii county were infested with Rhtzoctonia solani in small inoculum particles and successfully planted with radish to induce suppression, Suppressiveness was induced in some, but not all, replicates of all. soils. When fresh inoculum was added, suppressiveness was demonstrated in some, but not all, replicates of two soils, but not in the other three soils. Acidity of soil was not important in successful induction of suppression. Characteristics of induced suppression in soil from one site (S. Kohala) were further investigated.Reduction of microbial population by heat treatment of suppressive soil completely nullified its inhibitory effect. The populations of actinomycetes, fungi in general and Trichoderma spp. in suppressive and conducive soil were not significantly different. However, the population of bacteria in suppressive soil was almost four times higher than that in conducive soil. The survival time of R. solani in suppressive soil was shorter than that in conducive soil. Hyphae of R. solani also lysed faster in suppressive soil than in conducive soil. It is suggested that suppressiveness of the South Kohala soil created by monoculture is due to enhanced competitive pressure generated by an increased bacterial population, which in turn causes the rapid autolysis of R. solani hyphae.

Antagonists and parasites of Rhizoctonia solani and their efficacy in reducing stem canker of potato under controlled conditions

A number of fungi and bacteria isolated from sclerotia on potato tubers were antagonistic to or parasitic on Rhizoctonia solani in vitro . The parasitism of R. solani hyphae by Penicillium cyclopium, P. nigricans, Gliocladium deliquescens, Fusarium culmorum, F. moniliforme, Epicoccum nigrum, Trichothecium roseum, Cylindrocarpon destructans and C. olivaceum are new records. These fungi, Pseudomonas fluorescens , and a Streptomyces sp. were also effective in reducing stem canker under laboratory conditions.

Helminthosporium solani Dur. &amp; Mont. development on potato periderm

Development ofHelminthosporium solani Dur. & Mont. on artificially inoculated, excised potato tuber periderm, incubated in darkness and high humidity at 20 to 24°C, was studied using light and scanning electron microscopy. Spore germination occurred within 16 hours, and appressoria were observed 2 days after inoculation. Penetration of periderm was evident 4 days after inoculation. Conidiophores with young conidia developed on the periderm surface within 7 days of inoculation. Well-developed conidia were visible often by 9 days after inoculation. Rudimentary stromata were observed beneath conidiophore groupings at later stages of development. In histological studies,H. solani hyphae were found in the phellem, phelloderm, and cortex of infected tuber sections. Basal cells of conidiophores or stromata were observed on the surface and in the outer tangential cork cell layers. Several layers of suberized and sometimes collapsed cortical cells were observed beneath disrupted and collapsed, infected periderm. Cavities sometimes formed between periderm and cortex, and callosities were observed on cell walls of some cortical cells beneath infected periderm.

Mycoparasitism ofFusarium SPP. onRhizoctonia solani Kühn

Experiments on nutrient and staled agar were carried out to investigate the mycoparasitic activity of some fusaria againstRhizoctonia solani Kuhn. Penetration and coiling byFusarium oxysporum Sch.,F. semitectum Berk & Rav. andF. udum Butler in and around theR. solani hyphae was observed. Lysis ofF. udum hyphae was observed inside theR. solani hyphae showing the reverse of the normal direction of necrotrophic mycoparasitic relationships. The mycoparasitic activity ofFusarium spp. was much affected in staled agar plates.

Estimation of the generation time and peripheral growth zone of Aspergillus nidulans and Alternaria solani hyphae from radial growth rates and ranges in apical cell length.

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Susceptibility and resistance of several fungi to microbial lysis.

Potgieter, H. J. (Cornell University, Ithaca, N.Y.), and M. Alexander. Susceptibility and resistance of several fungi to microbial lysis. J. Bacteriol. 91:1526-1532. 1966.-Strains of Streptomyces, Nocardia, and Pseudomonas capable of lysing hyphae of Fusarium solani or Neurospora crassa were obtained by selective culture, but attempts to isolate an organism lysing Rhizoctonia solani failed. When provided with F. solani or N. crassa as carbon sources, the actinomycetes tested produced beta-(1 --> 3) glucanase and chitinase. A mixture containing purified chitinase and beta-(1 --> 3) glucanase induced spheroplast formation in F. solani, caused some morphological changes in N. crassa, but had almost no effect on R. solani hyphae. The polysaccharides in R. solani walls, which contain a large amount of glucose as well as galactose, mannose, and glucosamine, were not hydrolyzed appreciably by the two enzymes. Laminaribiose and laminaritriose were released by enzymatic hydrolysis of F. solani and N. crassa walls, and gentiobiose was liberated from R. solani and N. crassa walls. Melaninlike materials were found in R. solani walls, accounting for 8.50% of the wall weight. A role for melanin in protecting hyphae from microbial lysis is suggested.