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At least 19 recordsLinked to original sources
PubMed2000

Solid formulations of binucleate Rhizoctonia isolates suppress Rhizoctonia solani and Pythium ultimum in potting medium.

Two isolates of binucleate Rhizoctonia spp., previously selected for efficacy in suppression of Rhizoctonia solani and Pythium spp., as well as plant growth promotion, were incorporated into various solid substrate formulations. These formulated products were assayed at three doses in three glass-house experiments for biocontrol of damping-off diseases in Capsicum annuum. R. solani anastomosis group 4 or Pythium ultimum var. sporangiiferum were incorporated into pasteurized potting medium with each formulated binucleate Rhizoctonia product. All formulations were effective against both pathogens in at least two experiments, but some formulations of one isolate of binucleate Rhizoctonia did not give consistent control of R. solani in one experiment. The most consistent formulation, which provided control of both pathogens at all doses of binucleate Rhizoctonia, was the simple substrate of rice hulls. The implications for commercialization of a biocontrol product are discussed.

Capsicum↗
PubMed2005

[Effects of fungicide on temporal and spatial niches of Rhizoctonia solani].

This paper studied the variation of the temporal and spatial niches of rice sheath blight-causing Rhizoctonia solani under spraying fungicide. The results showed that between fungicide treatments and control, the spatial niche breadth of Rhizoctonia solani was different, while its temporal niche breadth was similar. The spatial niche breadth of Rhizoctonia solani was 0.5240 when spraying fungicide at booting and full heading stages, 0.5742 at booting and milkfilling stages, and 0.8577 at tillering stage, while the control was 0.8563. Spraying fungicide had little effect on temporal niche breath. The spatial niche breath, percentage of diseased leaves and sheathes, index of disease, and control effect all suggested that spraying fungicide two times in rice growth period was better than spraying it one time. Spraying fungicide at booting and full heading stages and at booting stage and milkfilling stages had the best effects. Fungicide could not only narrow the spatial niche breadth, limit the spread of Rhizoctonia solani on top leaves which were important for the yield, but also narrow the temporal niche breadth, limit the spread of Rhizoctonia solani during the yield formation period of rice. But, spraying fungicide only changed the distribution of the fungus niches and narrowed the niches during rice yield formation period, with no changes in the whole niches of Rhizoctonia solani.

Fungicides, Industrial↗
PubMed2003

Genetic diversity and virulence of Rhizoctonia species associated with plantings of Lotus corniculatus.

Species of Rhizoctonia cause a blight of Lotus corniculatus, a perennial forage legume. We characterized genetic variation and virulence in populations of R. solani and binucleate Rhizoctonia's associated with diseased L. corniculatus in field plantings over several years. Isolates of anastomosis groups AG-1 and AG-4 accounted for the R. solani recovered from diseased leaf and shoot tissues. Isolates of binucleate Rhizoctonia were recovered predominantly from soil and associated plant debris. Isolates of R. solani were more virulent on leaves and shoots of L. corniculatus than were binucleate Rhizoctonia isolates. Numerous unique DNA restriction patterns were observed among binucleate isolates and anastomosis groups of R. solani. Variation in restriction patterns was greater among isolates of AG-1 from the lower plant canopy than from the upper canopy. No restriction pattern was shared by any isolate from AG-1 and AG-4. Allelic and genotypic heterogeneity of AG-1 isolates were also greater in the lower plant canopy. Binucleate isolates exhibited greater heterogeneity than AG-1 isolates from either canopy region. L. corniculatus offers significant opportunities for investigating temporal and spatial dynamics of genetic structure of Rhizoctonia populations in perennial plant systems.

DNA, Bacterial↗
PubMed2005

An alpha-glucan elicitor from the cell wall of a biocontrol binucleate Rhizoctonia isolate.

Binucleate Rhizoctonia (BNR) isolate (232-C6) is an effective biocontrol agent for protection of potato from Rhizoctonia canker, a disease caused by Rhizoctonia solani. Production of hydrolytic enzymes is one of the best known inducible defense responses following microbial infection. We isolated and characterized a cell wall alpha-glucan from BNR, which induces beta-1,3 glucanase activities in potato sprouts, the primary site of infection by R. solani. An autoclaving method, previously reported for isolation of oligosaccharide elicitors was used, and the glucan purified by chromatographic techniques. Maximal induction of beta-1,3 glucanase activity in potato sprouts was obtained with 250 microg of the alpha-glucan elicitor after 6 days from inoculation time. Both, BNR mycelium and the alpha-glucan produced a similar kinetic response of beta-1,3 glucanase. However, the alpha-glucan did not induce phytoalexin accumulation, previously correlated with the defense response. Uronic acids (approximately 10% with respect to total neutral sugars) were determined and identified as glucuronic acid by high-pH anion-exchange chromatography. Methylation analysis showed that the glucan consists of (1-->3) and (1-->4)-linked glucose units with preponderance of the first ones. Some of the (1-->4) linkages were branched at position 6. The glucan was partially degraded with amyloglucosidase. This, together with the NMR spectra data and the high optical rotation of the original (+195 degrees ) and degraded glucans (+175 degrees ) proved the alpha configuration. Further methylation of the amyloglucosidase degraded glucans indicated that they consist of (1-->3)-linked glucoses. The present study is the first report on the isolation and characterization of an alpha-glucan from Rhizoctonia, that may be important as a biocontrol factor.

Cell Wall↗
PubMed2006

Fungal antagonists of the plant pathogen Rhizoctonia solani: selection, control efficacy and influence on the indigenous microbial community.

A broad spectrum of fungal antagonists was evaluated as potential biocontrol agents (BCAs) against the soil-borne pathogen Rhizoctonia solani using a new combination of in vitro and in vivo assays. The in vitro characterisation of diverse parameters including the ability to parasitise mycelium and to inhibit the germination of Rhizoctonia sclerotia at different temperatures resulted in the selection of six potential fungal antagonists. These were genotypically characterised by their BOX-PCR fingerprints, and identified as Trichoderma reesei and T. viride by partial 18S rDNA sequencing. When potato sprouts were treated with Trichoderma, all isolates significantly reduced the incidence of Rhizoctonia symptoms. Evaluated under growth chamber conditions, the selected Trichoderma isolates either partly or completely controlled the dry mass loss of lettuce caused by R. solani. Furthermore, the antagonistic Trichoderma strains were active under field conditions. To analyse the effect of Trichoderma treatment on indigenous root-associated microbial communities, we performed a DNA-dependent SSCP (Single-Strand Conformation Polymorphism) analysis of 16S rDNA/ITS sequences. In this first assessment study for Trichoderma it was shown that the pathogen and the vegetation time had much more influence on the composition of the microbiota than the BCA treatment. After evaluation of all results, three Trichoderma strains originally isolated from Rhizoctonia sclerotia were selected as promising BCAs.

Base Sequence↗
PubMed2004

Pectic zymogram variation and pathogenicity of Rhizoctonia solani AG-4 to bean (Phaseolus vulgaris) isolates in Isfahn, Iran.

Rhizoctonia disease, caused by Rhizoctonia solani is one of the most important fungal diseases in bean fields in Isfahan, Iran. Bean plants showing stem and root cankers were collected and Rhizoctonia-like fungi obtained from the samples were identified by anastomosis. Pure cultures of bean isolates of R. solani were identified as AG-4. There were also AG-4 isolates from tomato, potato, cucumber, alfalfa and sugar beet in the areas sampled. A total of 163 isolates of R. solani AG-4 originating from stem and root cankers of beans were examined using pectic zymogram electrophoresis. Polygalacturonase (PG) and pectin estrase isozymes were observed in all AG-4 isolates tested. One (PG) and one pectic esterase (PE) band was found in common between all isolates examined. The electrophoretic patterns were grouped into seven zymogram groups (ZGs) according to the diagnostic PG and PE bands. One ZG occurred in a high frequency throughout the areas sampled. A pathogenicity test was conducted and representative isolates of each ZG were used to inoculate healthy bean plants. The results showed that each ZG caused different symptoms with varying severity. Isolates belonging to two ZGs were highly pathogenic causing root, stem and hypocotyl cankers whereas isolates of the other ZGs produced weak or no symptoms.

Electrophoresis, Agar Gel↗
PubMedDate not supplied

Changes in ribonuclease with age in the fungus Rhizoctonia solani.

The enzyme ribonuclease (RNase) which was isolated from Rhizoctonia solani Kuehn degraded ribonucleic acid from both Torula yeast and from Rhizoctonia solani mycelia. As the Rhizoctonia mycelia aged, there was an increase in both the total and the specific activities of the RNase present in the mycelia. This change is discussed in relation to the age dependent decrease in protein synthesis in this fungus.

Cryptococcus↗
PubMed2006

Phylogenetic utility of indels within ribosomal DNA and beta-tubulin sequences from fungi in the Rhizoctonia solani species complex.

The genus Rhizoctonia consists of a diverse assemblage of anamorphic fungi frequently associated with plants and soil throughout the world. Some anamorphs are related with teleomorphs (sexual stage) in different taxonomic classes, orders, and families. The fungus may exist as pathogen, saprophyte, or mycorrhizal symbiont and shows extensive variation in characteristics such as geographic location, morphology, host specificity, and pathogenicity. In this study, phylogenetic analyses were performed in the Rhizoctonia solani species complex with individual and combined data sets from three gene partitions (ITS, LSU rDNA, and beta-tubulin). To explore whether indels were a source of phylogenetically informative characters, single-site indels were treated as a new state, while indels greater than one contiguous nucleotide were analyzed by including them as ambiguous data (Coding A); excluding them from the analyses (Coding B), and with three distinct codes: multistate for different sequence (Coding C); multistate for different length (Coding D) and different characters for each distinct sequence (Coding E). Results suggest that indels in noncoding regions contain phylogenetic information and support the fact that the R. solani species complex is not monophyletic. Six clades within R. solani (teleomorph=Thanatephorus) representing distinct anastomosis groups and five clades within binucleate Rhizoctonia (teleomorph=Ceratobasidium) were well supported in all analyses. The data suggest that clades with representatives of R. solani fungi belonging to anastomosis groups 1, 4, 6, and 8 should be recognized as phylogenetic species.

Base Sequence↗
PubMed2000

Antifungal characteristics of a fluorescent Pseudomonas strain involved in the biological control of Rhizoctonia solani.

A plant growth-promoting isolate of a fluorescent Pseudomonas spp. EM85 was found strongly antagonistic to Rhizoctonia solani, a causal agent of damping-off of cotton. The isolate produced HCN (HCN+), siderophore (Sid+), fluorescent pigments (Flu+) and antifungal antibiotics (Afa+). Tn5::lacZ mutagenesis of isolate EM85 resulted in the production of a series of mutants with altered production of HCN, siderophore, fluorescent pigments and antifungal antibiotics. Characterisation of these mutants revealed that the fluorescent pigment produced in PDA and the siderophore produced in CAS agar were not the same. Afa- and Flu- mutants had a smaller inhibition zone when grown with Rhizoctonia solani than the EM85 wild type. Sid- and HCN mutants failed to inhibit the pathogen in vitro. In a pot experiment, mutants deficient in HCN and siderophore production could suppress the damping-off disease by 52%. However, mutants deficient in fluorescent pigments and antifungal antibiotics failed to reduce the disease severity. Treatments with mutants that produced enhanced amounts of fluorescent pigments and antibiotics compared with EM85 wild type, exhibited an increase in biocontrol efficiency. Monitoring of the mutants in the rhizosphere using the lacZ marker showed identical proliferation of mutants and wild type. Purified antifungal compounds (fluorescent pigment and antibiotic) also inhibited the fungus appreciably in a TLC bioassay. Thus, the results indicate that fluorescent pigment and antifungal antibiotic of the fluorescent Pseudomonas spp. EM85 might be involved in the biological suppression of Rhizoctonia-induced damping-off of cotton.

Antibiosis↗
PubMed1999

Biocontrol of Rhizoctonia solani and Pythium ultimum on Capsicum by Trichoderma koningii in potting medium.

Two isolates of Trichoderma koningii were evaluated for efficacy in control of damping-off diseases in seedlings of Capsicum annuum grown in pasteurized potting medium in a glasshouse. A selected isolate of binucleate Rhizoctonia and two fungicides were also included as standards for control of Rhizoctonia solani and Pythium ultimum var. sporangiiferum. Both isolates of T. koningii reduced seedling death caused by R. solani in one of two experiments, and by P. u. sporangii-ferum in two of three experiments. Neither isolate of T. koningii suppressed damping-off caused by either pathogen as consistently as the binucleate Rhizoctonia or fungicides. The implications of these results for commercial disease management are discussed.

Fungicides, Industrial↗
PubMed2004

Rhizoctonia solani, an elicitor of 6-pentyl-alpha-pyrone production by Trichoderma harzianum in a two liquid phases, extractive fermentation system.

6-pentyl-alpha-pyrone (6PP) production by Trichoderma harzianum, in an extractive fermentation system, was elicitated by Rhizoctonia solani. The extent of 6PP elicitation was related to the state of Rhizoctonia and to the Trichoderma inoculum type. The use of non-viable Rhizoctonia solani mycelium in mycelium-inoculated Trichoderma harzianum culture, yielded the maximal 6PP production (474 mg l(-1)) compared to control cultures (147 mg l(-1)) and decreased the process time from 192 to 96 h.

Cell Culture Techniques↗
PubMed2004

An immunological approach to quantifying the saprotrophic growth dynamics of Trichoderma species during antagonistic interactions with Rhizoctonia solani in a soil-less mix.

Studies of the saprotrophic growth dynamics of Trichoderma species and their fungal hosts during antagonistic interactions are severely hampered by the absence of methods that allow the unambiguous identification and quantification of individual genera in complex environments such as soil or compost containing mixed populations of fungi. Furthermore, methods are required that allow discrimination between active hyphal growth and other components of fungal biomass such as quiescent spores that are produced in large numbers by Trichoderma species. This study details the use of monoclonal antibodies to quantify the saprotrophic growth dynamics of the soil-borne plant pathogen Rhizoctonia solani and biological control strains of Trichoderma asperellum and Trichoderma harzianum during antagonistic interactions in peat-based microcosms. Quantification was based on the immunological detection of constitutive, extracellular antigens that are secreted from the growing tip of Rhizoctonia and Trichoderma mycelium and, in the case of Trichoderma harzianum, from quiescent phialoconidia also. The Trichoderma-specific monoclonal antibody (MF2) binds to a protein epitope of the enzyme glucoamylase, which was shown by immunofluorescence and immunogold electron gold microscopy studies of Trichoderma virens in vitro to be produced at the origin of germ tube emergence in phialoconidia and from the growing tip of germ tubes. In addition, a non-destructive immunoblotting technique showed that the enzyme was secreted during active growth of Trichoderma asperellum mycelium in peat. The Rhizoctonia solani-specific monoclonal antibody (EH2) similarly binds to a protein epitope of a glycoprotein that is secreted during active mycelial growth. Extracts derived from lyophilized mycelium were used as a quantifiable and repeatable source of antigens for construction of calibration curves. These curves were used to convert the absorbance values obtained in ELISA tests of peat extracts to biomass equivalents, which allowed comparisons of the saprotrophic growth dynamics of the pathogen and antagonists to be made in single or mixed species microcosms. Trichoderma species were able to compete successfully with R. solani for nutrients and to prevent saprotrophic growth of the pathogen. Specificity of the Trichoderma quantitative assay was tested in non-sterile soil-based microcosms artificially inoculated with T. asperellum. The assay was highly specific and only detected T. asperellum population dynamics. No cross-reactivity was found with extracts from soil samples containing contaminant fungi.

Animals↗
PubMed2004

Strategy to select and assess antagonistic bacteria for biological control of Rhizoctonia solani Kühn.

A screening strategy was developed to assess the potential of plant-associated bacteria to control diseases caused by Rhizoctonia solani Kühn. About 434 already characterized antagonistic bacterial strains isolated from diverse plant species and microenvironments were evaluated for biocontrol and plant growth promotion by a hierarchical combination of assays. Analyzing in vitro antagonism towards different Rhizoctonia isolates resulted in a selection of 20 potential biocontrol agents. The strains were characterized by their antagonistic mechanisms in vitro as well as their production of the plant growth hormone indole-3-acetic acid. The plant growth promoting effect by antagonistic bacteria was determined using a microtiter plate assay on the basis of lettuce seedlings. Lettuce and sugar beet as host plant were included in the biocontrol experiments in which the antagonistic effect of 17 bacterial isolates could be confirmed in vivo. Sequencing of the 16S rDNA gene and (or) fatty acid methyl ester gas chromatography was used to identify the antagonistic isolates. Molecular fingerprints of isolates obtained by BOX-polymerase chain reaction were compared to avoid further investigation with genetically very similar strains and to obtain unique molecular fingerprints for quality control and patent licensing. According to our strategy, an assessment scheme was developed and four interesting biological control agents, Pseudomonas reactans B3, Pseudomonas fluorescens B1, Serratia plymuthica B4, and Serratia odorifera B6, were found. While S. plymuthica B4 was the best candidate to biologically control Rhizoctonia in lettuce, P. reactans B3 was the best candidate to suppress the pathogen in sugar beet.

Antibiosis↗
PubMed1977

Mycotic keratitis due to Rhizoctonia sp.

A case of mycotic keratitis due to Rhizoctonia sp. is reported for the first time. Fungal hyphae were detected in corneal scrapings and cultures were found positive for Rhizoctonia sp. on two occasions. Species could not be identified and it has been disposed in Herb. IMI as Rhizoctonia sp. (IMI 200029). The isolate grew faster at 37 degrees C than at 28 degrees C and its pathogenicity was established in rabbit's eye.

Animals↗