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Rhizoctonia Solani (rhizoctonia + solani)
Selected AbstractsPotential Applications of Oxidoreductases for the Re-oxidation of Leuco Vat or Sulfur Dyes in Textile DyeingENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 3 2008F. Xu Abstract Conventional textile dyeing by vat and sulfur dyes includes reduction and re-oxidation steps (with chemical reductants and oxidants), so that the insoluble dyes can be solubilized in the dyeing solution, adsorbed by the fabric, and fixed onto the dyed fabric. The treatments often involve hazardous chemicals, expensive catalysts, or conditions that are suboptimally effective, energy-intensive, caustic, or polluting. Improving these steps with enzyme technology could be of significant interest in terms of better dyeing, handling of hazardous chemicals, disposal of waste, or production economy. The idea of an enzymatic re-oxidation step for vat and sulfur dyeings was tested under simplified laboratory conditions. Selected vat and sulfur dyes, including Vat Blue,43, Vat Orange,7, Vat Green,3, Vat Orange,2, Vat Red,13, Vat Yellow,2, and Sulfur Black,1, were first chemically reduced. The reduced (leuco) dyes were then re-oxidized by aerated buffer solutions or H2O2, in the presence or absence of an oxidoreductase, selected from seven laccases from Myceliophthora thermophila, Scytalidium thermophilum, Coprinus cinereus, Trametes villosa, Rhizoctonia solani, Pycnoporus cinnabarinus, Botrytis cinerea, a bilirubin oxidase from Myrothecium verrucaria, and a heme peroxidase from Coprinus cineresu. It was shown that the enzymes were able to catalyze and accelerate the re-oxidation of the reduced dyes, even when they were adsorbed on cotton fabric, by dissolved air (O2) or H2O2. Small redox-active mediators could facilitate the enzymatic re-oxidation. For Sulfur Black,1, a higher conversion of the leuco dye was achieved with laccase-catalyzed re-oxidation. The further development of this potential enzyme application is discussed. [source] Fungal pathogens associated with melon collapse in Spain,EPPO BULLETIN, Issue 2 2000J. García-Jiménez Spain produces 43 200 ha of melons with a considerable export to European markets. In the last 10 years, melon cultivation in Spain has decreased more than 40% due mainly to collapse of the vines caused by soil-borne diseases. Serious economic losses have resulted. In order better to understand the aetiology of this disease, a survey of 217 melon fields throughout the melon production areas of Spain was conducted from 1987 to 1996 to analyse the fungal population associated with roots. In addition, the presence of melon necrotic spot carmovirus (MNSV) was studied in 93 fields. This virus is present mainly in southeastern Spain. The predominant fungal species isolated from 82.5% of sampled fields with symptoms of collapse was Acremonium cucurbitacearum. Roots affected by this fungus show corky brown areas soon after transplanting. Small secondary roots and root hairs become necrotic, although there is continuous production of new rootlets. This process continues until the late stages of the disease. As the fruits approach maturity, the entire plant wilts and dies. Other fungal species associated with melon collapse are: Monosporascus cannonballus (isolated from 29.5% of sampled fields), Macrophomina phaseolina (32.7%) and Rhizoctonia solani (31.8%). Of these, the incidence of M. cannonballus isolated from diseased melons has increased substantially over the past 10 years. Melon collapse in Spain is complex because several fungi capable of causing collapse of the vines are prevalent and often isolated from roots in the same field. In addition, other minor pathogens, such as Rhizopycnis vagum and Plectosporium tabacinum, are frequently isolated from symptomatic vines and may also contribute to the death of the plants. [source] NtKTI1, a Kunitz trypsin inhibitor with antifungal activity from Nicotiana tabacum, plays an important role in tobacco's defense responseFEBS JOURNAL, Issue 19 2010Hao Huang A cDNA library from tobacco inoculated with Rhizoctonia solani was constructed, and several cDNA fragments were identified by differential hybridization screening. One cDNA clone that was dramatically repressed, NtKTI1, was confirmed as a member of the Kunitz plant proteinase inhibitor family. RT-PCR analysis revealed that NtKTI1 was constitutively expressed throughout the whole plant and preferentially expressed in the roots and stems. Furthermore, RT-PCR analysis showed that NtKTI1 expression was repressed after R. solani inoculation, mechanical wounding and salicylic acid treatment, but was unaffected by methyl jasmonate, abscisic acid and NaCl treatment. In vitro assays showed that NtKTI1 exerted prominent antifungal activity towards R. solani and moderate antifungal activity against Rhizopus nigricans and Phytophthora parasitica var. nicotianae. Bioassays of transgenic tobacco demonstrated that overexpression of NtKTI1 enhanced significantly the resistance of tobacco against R. solani, and the antisense lines exhibited higher susceptibility than control lines towards the phytopathogen. Taken together, these studies suggest that NtKTI1 may be a functional Kunitz trypsin inhibitor with antifungal activity against several important phytopathogens in the tobacco defense response. [source] Composition and antifungal activity of essential oils isolated from Hypericum hyssopifolium and Hypericum heterophyllumFLAVOUR AND FRAGRANCE JOURNAL, Issue 1 2004A. Cakir Abstract The composition of the hydrodistilled essential oils obtained from the aerial parts of Hypericum hyssopifolium subsp. elongatum var. elongatum and H. heterophyllum Vent. were analysed by means of GC and GC,MS, and 66 compounds were determined in total. The oils showed remarkable differences in chemical composition. The oil of H. hyssopifolium, which is rich in monoterpenes, consists primarily of , -pinene (57.3%), , -pinene (9.0%), limonene (6.2%) and , -phellandrene (4.4%). The oil of H. heterophyllum was a complex mixture consisting mainly of sesquiterpenes (72.9% of the total oil). In this oil, isocaryophyllene (17.1%), , -pinene (11.6%), , -cadinene (9.5%), , -muurolene (8.2%), n -decane (5.8%), , -cadinene (5.5%) and , -caryophyllene (4.5%) were found to be major constituents. The two essential oils were tested for antifungal activity using microbial growth inhibition assays in vitro against 10 agricultural pathogenic fungi, which consisted of ,ve Fusarium species (F. oxysporum, F. culmorum, F. sambucinum, F. solani and F. acuminatum) and ,ve anastomosis groups of Rhizoctonia solani (AG-3, AG-4, AG-5, AG-9 and AG-11). In general, the oils showed moderate activity against several fungal species, viz F. acuminatum, AG-5 and AG-11. The most signi,cant results were obtained against AG-11 for H. heterophyllum oil. However, both oils increased the growth of some fungal species. In addition, the antifungal activity of 13 pure compounds identi,ed as major components in the essential oils of the Hypericum species studied were determined using microbial growth inhibition assays against the 10 fungal species mentioned above. Among these compounds, both , -caryophyllene oxide and , -terpineol were inhibitory to the growth of all fungi. Copyright © 2003 John Wiley & Sons, Ltd. [source] Studies on anastomosis groups of Rhizoctonia solani isolates causing disease in two forest nurseries in PolandFOREST PATHOLOGY, Issue 2 2006S. St, pniewska-Jarosz Summary Thirty-eight isolates of Rhizoctonia spp. were isolated from Scots pine (Pinus sylvestris) seedlings with damping-off symptoms, originating from two forest nurseries in central-west Poland (Wronczyn and Jarocin) and from diseased seedlings grown in soil from Wronczyn nursery. Majority of these isolates (79%) had multinucleate cells and were identified as Rhizoctonia solani. The remaining isolates were recognized as binucleate Rhizoctonia spp. R. solani isolates were characterized using hyphal anastomosis and were divided into five anastomosis groups (AG). The most prevalent was AG5 (37% of isolates), followed by AG2-1 (30%) and 27% of the isolates were identified as AG4. Groups AG1-IB and AG2-2 were only represented by single isolates. The virulence recorded as mortality (in percentage) was comparatively high for binucleate and multinucleate isolates of Rhizoctonia spp. Sequence analysis of the polymerase chain reaction (PCR)-amplified internal transcribed spacer (ITS) rDNA region was used for phylogenetic analysis. The dendrogram showed that isolates were distinctly separated based on their AG types and there was no relationship between pathogenicity on Scots pine seedlings and the AG to which the isolates belong to. The results are discussed with respect to pathogenic potential of the various AG groups. Résumé Trente-huit isolats de Rhizoctonia spp. ont été isolés de semis de Pin sylvestre (Pinus sylvestris) présentant des symptômes de fonte, dans deux pépinières forestières du Centre-Ouest de la Pologne (Wronczyn and Jarocin) et de semis malades élevés dans du sol provenant de la pépinière de Wronczyn. La majorité de ces isolats (79%) ont des cellules multi-nucléées et ont été identifiés comme des Rhizoctonia solani. Le reste des isolats ont été reconnus comme des Rhizoctonia spp. binucléés. Les isolats de R. solani ont été caractérisés en utilisant l'anastomose d'hyphes et répartis dans cinq groupes d'anastomoses (AG). Le plus important est le groupe AG5 (37% des isolats), suivi par AG2-1 (30%) et AG4 (27%). Les groupes AG1-IB et AG2-2 sont représentés chacun par seulement un isolat. La virulence, estimée par le pourcentage de mortalité, est relativement forte pour les isolats binucléés et multinucléés de Rhizoctonia spp. L'analyse des séquences de la région ITS de l'ADNr amplifiées par PCR a été utilisée pour l'analyse phylogénétique. Le dendrogramme montre que les isolats sont séparés selon leur groupe d'anastomose mais il n'y a pas de relation entre le groupe d'anastomose et la virulence sur semis de Pin sylvestre. Les résultats sont discutés dans la perspective du pouvoir pathogène des différents groupes d'anastomoses. Zusammenfassung Von Kiefernsämlingen (Pinus sylvestris) mit Umfallkrankheit, die aus zwei Forstbaumschulen in Zentral-Westpolen stammten (Wronczyn und Jarocin) und aus erkrankten Sämlingen, die in Bodenproben aus der Baumschule Wronczyn kultiviert worden waren, wurden 38 Stämme von Rhizoctonia spp. isoliert. Die meisten dieser Isolate (79%) hatten vielkernige Zellen und wurden als R. solani identifiziert. Die restlichen Isolate waren zweikernige Rhizoctonia spp. Die Isolate von R. solani wurden durch Anastomosierungstests charakterisiert und fünf Anastomosierungsgruppen zugeordnet. Die häufigste Gruppe war AG5 (37% der Isolate), gefolgt von AG2-1 (30%) und AG4 (27%). Die Gruppe AG1-IB und AG2-2 waren nur durch einzelne Isolate vertreten. Die Virulenz (gemessen als % Mortalität) war sowohl für zweikernige als auch für vielkernige Isolate vergleichsweise hoch. Mit den Sequenzen der PCR-amplifizierten ITS-rDNA-Region wurde eine phylogenetische Analyse durchgeführt. Das Dendrogramm zeigte, dass die Isolate aufgrund ihrer Zugehörigkeit zu den Anastomosierungsgruppen deutlich voneinander getrennt waren, und es bestand keine Beziehung zwischen ihrer Virulenz gegenüber Kiefernsämlingen und der Gruppenzugehörigkeit. Die Befunde werden im Hinblick auf das pathogene Potential der verschiedenen Anastomosierungsgruppen diskutiert. [source] Rhizoctonia solani AG 2-1 as a causative agent of cotyledon rot on European beech (Fagus sylvatica)FOREST PATHOLOGY, Issue 6 2005A. M. Hietala Summary Rhizoctonia solani was frequently isolated in the Italian Alps from nursery-grown European beech (Fagus sylvatica) seedlings displaying symptoms of cotyledon rot. Koch's postulates were verified and mode of infection of the associated isolates was investigated with light and scanning electron microscopy. Population structure of the pathogen was investigated by scoring the anastomosis reaction type in pairings between different isolates from the same seedbed. One pathogen genotype showed a large distribution area within the seedbed, this implying that the inoculum had been building up in the seedbed over a longer time period. Hyphal anastomosis tests and sequence analysis of the internal transcribed spacer (ITS) region of ribosomal DNA indicated that the pathogen belongs to AG 2-1 of R. solani. ITS sequence analysis indicates that the isolates from beech are closely related to R. solani isolates causing a disease on tulip. The striking similarities between the two diseases are discussed. Résumé Rhizoctonia solani a fréquemment été isolé de semis de hêtre (Fagus sylvatica) présentant des symptômes de pourriture des cotylédons dans une pépinière forestière des Alpes italiennes. Les postulats de Koch ont été vérifiés et le mode d'infection étudié par microscopie optique et électronique à balayage. La structure de la population de l'agent pathogène a étéétudiée en examinant les réactions d'anastomoses dans les confrontations par paires des isolats d'un même lit de semences. Un génotype particulier s'est avéré largement distribué dans le lit de semence, suggérant soit une accumulation de l'inoculum pendant une longue période soit que ce génotype est capable de reproduction homocaryotique, favorisant sa dispersion. Les tests d'anastomose et l'analyse de la séquence de la région ITS de l'ADN ribosomal indiquent que l'agent pathogène appartient au groupe AG 2-1 de R. solani. L'analyse de la séquence de l'ITS montre que les isolats de hêtre sont proches d'isolats de R. solani pathogènes sur tulipe. Les ressemblances frappantes entre les deux maladies et la gestion de la maladie sur hêtre sont discutées. Zusammenfassung In einer Forstbaumschule in den italienischen Alpen wurde Rhizoctonia solani häufig aus Buchenkeimlingen (Fagus sylvatica) mit Symptomen einer Kotyledonenfäule isoliert. Die Koch'schen Postulate wurden erfüllt und die Art der Infektion der beteiligten Isolate wurde licht- und rasterelektronen-mikroskopisch untersucht. Die Populationsstruktur des Pathogens wurde anhand der Reaktionstypen (Anastomosierungsverhalten) in Paarungsversuchen mit den unterschiedlichen Isolaten aus demselben Saatbeet untersucht. Ein Kompatibilitätstyp war innerhalb des Saatbeetes weit verbreitet, was darauf hindeutet, dass sich das Inokulum über einen längeren Zeitraum dort angereichert hatte und/oder der Genotyp homokaryotisch fruchtet, was seine Ausbreitung fördert. Die Anastomosierungstests und die ITS-Sequenzanalyse der ribosomalen DNA ergaben, dass der Erreger zu der AG 2-1 Gruppe R. solani gehört. Die ITS-Sequenzen deuten darauf hin, dass die Isolate von Buche mit den R. solani, Isolaten verwandt sind, die an Tulpen pathogen sind. Die auffallende Ähnlichkeit der beiden Krankheiten und das Management der Erkrankung an Buche wird diskutiert. [source] Functional, genetic and chemical characterization of biosurfactants produced by plant growth-promoting Pseudomonas putida 267JOURNAL OF APPLIED MICROBIOLOGY, Issue 2 2009Marco Kruijt Abstract Aims:, Plant growth-promoting Pseudomonas putida strain 267, originally isolated from the rhizosphere of black pepper, produces biosurfactants that cause lysis of zoospores of the oomycete pathogen Phytophthora capsici. The biosurfactants were characterized, the biosynthesis gene(s) partially identified, and their role in control of Phytophthora damping-off of cucumber evaluated. Methods and Results:, The biosurfactants were shown to lyse zoospores of Phy. capsici and inhibit growth of the fungal pathogens Botrytis cinerea and Rhizoctonia solani. In vitro assays further showed that the biosurfactants of strain 267 are essential in swarming motility and biofilm formation. In spite of the zoosporicidal activity, the biosurfactants did not play a significant role in control of Phytophthora damping-off of cucumber, since both wild type strain 267 and its biosurfactant-deficient mutant were equally effective, and addition of the biosurfactants did not provide control. Genetic characterization revealed that surfactant biosynthesis in strain 267 is governed by homologues of PsoA and PsoB, two nonribosomal peptide synthetases involved in production of the cyclic lipopeptides (CLPs) putisolvin I and II. The structural relatedness of the biosurfactants of strain 267 to putisolvins I and II was supported by LC-MS and MS-MS analyses. Conclusions:, The biosurfactants produced by Ps. putida 267 were identified as putisolvin-like CLPs; they are essential in swarming motility and biofilm formation, and have zoosporicidal and antifungal activities. Strain 267 provides excellent biocontrol activity against Phytophthora damping-off of cucumber, but the lipopeptide surfactants are not involved in disease suppression. Significance and Impact of the Study:,Pseudomonas putida 267 suppresses Phy. capsici damping-off of cucumber and provides a potential supplementary strategy to control this economically important oomycete pathogen. The putisolvin-like biosurfactants exhibit zoosporicidal and antifungal activities, yet they do not contribute to biocontrol of Phy. capsici and colonization of cucumber roots by Ps. putida 267. These results suggest that Ps. putida 267 employs other, yet uncharacterized, mechanisms to suppress Phy. capsici. [source] Biotransformation of l -menthol by twelve isolates of soil-borne plant pathogenic fungi (Rhizoctonia solani) and classification of fungiJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 6 2003Mitsuo Miyazawa Abstract The microbial transformation of l -menthol (1) was investigated by using 12 isolates of soil-borne plant pathogenic fungi, Rhizoctonia solani (AG-1-IA Rs24, Joichi-2, RRG97-1; AG-1-IB TR22, R147, 110.4; AG-1-IC F-1, F-4, P-1; AG-1-ID RCP-1, RCP-3, and RCP-7) as a biocatalyst. Rhizoctonia solani F-1, F-4 and P-1 showed 89.7,99.9% yields of converted product from 1, RCP-1, RCP-3, and RCP-7 26.0,26.9% and the other isolates 0.1,12.0%. In the cases of F-1, F-4 and P-1, substrate 1 was converted to (,)-(1S,3R,4S,6S)-6-hydroxymenthol (2), (,)-(1S,3R,4S) -1-hydroxymenthol (3) and (+)-(1S,3R,4R,6S)-6,8-dihydroxymenthol (4), which was a new compound. Substrate 1 was converted to 2 and/or 3 by RRG97-1, 110.4, RCP-1, RCP-3 and RCP-7. The structures of the metabolic products were elucidated on the basis of their spectral data. In addition, metabolic pathways of the biotransformation of 1 by Rhizoctonia solani are discussed. Finally, from the main component analysis and the differences in the yields of converted product from 1, the 12 isolates of Rhizoctonia solani were divided into three groups based on an analysis of the metabolites. Copyright © 2003 Society of Chemical Industry [source] Purification of Angularin, A Novel Antifungal Peptide from Adzuki BeansJOURNAL OF PEPTIDE SCIENCE, Issue 3 2002Dr X. Y. Ye Abstract An antifungal peptide was isolated from the adzuki bean with a procedure involving affinity chromatography on Affi-gel blue gel and ion exchange chromatography on CM-Sepharose. The protein designated angularin was adsorbed on both types of chromatographic media and possessed a molecular weight of 8 kDa. Angularin exhibited antifungal activity against a variety of fungal species including Mycospharella arachidiocola and Botrytis cinerea. It inhibited mycelial growth in B. cinerea with an IC50 of 14.3 µM. Fusarium oxysporum and Rhizoctonia solani were not inhibited. Angularin demonstrated inhibitory activity on translation in the rabbit reticulocyte lysate system (IC50 = 8.0 µM) but did not affect proliferation of splenocytes. The activity of HIV-1 reverse transcriptase was inhibited in the presence of angularin. Its N -terminal sequence was GEPGQKE. Copyright © 2002 European Peptide Society and John Wiley & Sons, Ltd. [source] First Report of Rhizoctonia solani AG-7 on Cotton in EgyptJOURNAL OF PHYTOPATHOLOGY, Issue 4 2010Kamel A. Abd-Elsalam Abstract Eighty-two isolates of Rhizoctonia solani were recorded from roots of naturally-infected seedlings of the Egyptian cotton (Gossypium barbadense L.). Anastomosis groups (AGs) of the isolates were determined by using 13 different AGs testers. Three (3.7%) of the isolates were identified as R. solani AG7, while the remaining isolates were belonging to the AG 2-1, AG4 and AG5. The identification of the three isolates was based on the frequency of the C2 reaction with the AG7 tester isolate. No fusion was observed between AG7 and isolates representing the other 13 AGs. Colonies of AG7 isolates grown on potato dextrose agar (PDA), malt yeast agar (MYA) and melt peptone agar (MPA) were brown to dark brown with aerial mycelium and sclerotia. The isolates had pitted sclerotial clusters and brownish exudates after 21 days of culturing on PDA, but without clear zonation. Pathogenicity test under greenhouse conditions revealed that AG7 caused the common symptoms of damping,off, which included seed rot, lesions on the hypocotyls and root rot. [source] Development of a Sensitive Serological Method for Specific Detection of Latent Infection of Macrophomina phaseolina in CowpeaJOURNAL OF PHYTOPATHOLOGY, Issue 1 2009Leonard Afouda Abstract A double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) was developed for the specific detection and quantification of Macrophomina phaseolina in plant tissue. Both polyclonal antisera produced against immunogens from mycelium and culture filtrate of M. phaseolina detected the fungus in mycelial and plant extracts, although the antibodies raised against mycelium were more sensitive. No cross-reaction occurred with Rhizopus stolonifer, Pythium ultimum, Mucor hiemalis, Fusarium oxysporum, Septoria nodorum, Rhizoctonia solani, Sclerotinia sclerotiorum, Phytophthora infestans and Aspergillus niger. In enzyme assays, activity of the endo-acting hydrolytic enzymes 1,3-,-glucanase and, less, cellulase, but not xylanase was detected in infected plants. DAS-ELISA was more sensitive than the 1,3-,-glucanase assay. In polyacrylamide gel electrophoresis (PAGE) up to 18 protein bands were observed, with four bands occurring in the 12 tested isolates deriving from various geographical origin in Niger and Nigeria. The enzyme assays and protein patterns were considered not suitable for specific M. phaseolina detection. Macrophomina phaseolina was essentially located in the roots and hypocotyls, and less in epicotyls and leaves of infected plants. The antibodies were also useful to detect latent infection and the infection of cowpea seeds. [source] Suppression of Root Rotting Fungi and Root Knot Nematode of Chili by Seaweed and Pseudomonas aeruginosaJOURNAL OF PHYTOPATHOLOGY, Issue 7-8 2008V. Sultana Abstract Solvent fractions (i.e. n -hexane, chloroform and methanol) of the ethanol extracts of the seaweeds Codium iyengarii, Jania capillacea, Stokeyia indica and Solieria robusta caused more than 50% mortality of Meloidogyne javanica juveniles within 24 h at 10 mg/ml. Nematode mortality increased with an increase in fraction concentration or exposure time. The n -hexane fractions from S. indica, J. capillacea and C. iyengarii and the chloroform fraction from S. robusta also resulted in more than 50% mortality within 48 h at 1.0 mg/ml. In a screen-house experiment application of S. indica and S. robusta as soil amendments alone or with Pseudomonas aeruginosa, a plant growth promoting rhizobacterium (PGPR), significantly suppressed infection of chili roots by root-infecting fungi Macrophomina phaseolina, Rhizoctonia solani, Fusarium solani and the root knot nematode Meloidogyne javanica. Seaweed alone or with PGPR also increased plant growth. Suppressive effect on root pathogens and growth enhancement potential of seaweeds and P. aeruginosa were also effective in field plots. [source] Morphological and Pathological Variability in Rice Isolates of Rhizoctonia solani and Molecular Analysis of their Genetic VariabilityJOURNAL OF PHYTOPATHOLOGY, Issue 11-12 2007S. Guleria Abstract Nineteen isolates of Rhizoctonia solani collected from different rice varieties grown in various regions of Punjab were studied for their morphological and pathological characterization. Majority of the isolates were fast growing with raised and fluffy colonies and hyphal width of 9.6 ,m while four exhibited moderate growth rate. Colony colour in all except two isolates was light yellowish brown. While sclerotial number per 5.0 mm culture disc of the test isolates ranged between 2.1 and 11.2 mm, their size varied between 1.31 and 2.08 mm. Sclerotial colour in all except two isolates was dark brown and most of these were found scattered in the colony. There was no relationship between morphologically similar isolates and their pathogenic behaviour. Majority of the isolates produced lesion length between 45.6 and 58.2 mm on detached rice leaves (cv. PR116). Molecular characterization of genetic diversity in the test isolates was studied by using 10 inter simple sequence repeats (ISSR) and eight random amplified polymorphic DNA (RAPD) markers. The size of amplified DNA bands ranged from 0.25,3.0 to 0.5,4.0 kb with ISSR and RAPD markers, respectively. Combined data set of 155 DNA markers were analysed with UPGMA resulting five clusters with 49,89% genetic similarity. Most of the isolates showed grouping specific to the host variety. Out of these two types of DNA markers, RAPD markers were able to detect more genetic variability when compared to ISSR markers. [source] Characterization and Pathogenicity of Rhizoctonia spp. from Onion in Amasya, TurkeyJOURNAL OF PHYTOPATHOLOGY, Issue 2 2006I. Erper Abstract Forty-two isolates of Rhizoctonia spp. were obtained from onion in Amasya, Turkey. Of these, 29% were Rhizoctonia solani (AG-4), 69% were Waitea circinata var. zeae (Rhizoctonia zeae) and 2% were binucleate Rhizoctonia (AG-B). Most of the isolates were recovered from rhizosphere soil. In pathogenicity tests on onion, R. solani AG-4 caused the greatest disease severity, those of W. circinata var. zeae were moderately virulent but binucleate Rhizoctonia isolates were of low virulence. This is the first report of binucleate Rhizoctonia AG-B and W. circinata var. zeae occurring on onion in Turkey. [source] Incidence of Cotton Seedling Diseases Caused by Rhizoctonia solani and Thielaviopsis basicola in Relation to Previous Crop, Residue Management and Nutrients Availability in Soils in SW SpainJOURNAL OF PHYTOPATHOLOGY, Issue 11-12 2005A. Delgado Abstract Cotton seedling damping-off is considered a disease complex, in which several pathogens can be involved. In SW Spain, postemergence damping-off seems to be mainly associated with Rhizoctonia solani and Thielaviopsis basicola, posing a serious limitation for crop, especially in cold springs. Ninety-seven commercial plots, where postemergence damping-off of cotton seedlings was observed during previous years, were selected in April 2001. In each plot, plants were randomly sampled between cotyledon to three true-leaf stage and soil samples besides the plants were taken. Symptomatic plants were separated according to the main observable seedling disease symptom: black necrosis (black root rot), brown necrosis and other symptoms. Thielaviopsis basicola inoculum was estimated in soil samples. Soil samples were also analysed for nutrient availability (N, P, K, Ca, Mg, Fe, Cu, Mn and Zn). All the sampled plants showed some seedling disease symptom. Macroscopic symptoms can provide a reasonable distinction between these two major pathogens involved in seedling disease symptoms in the studied area: the percentage of T. basicola isolates (18%) from black necrosis symptomatic plants was significantly higher than that of R. solani (4.1%), whereas in brown necrosis symptomatic plants, the situation was reversed (10.7 vs. 12.8%). The percentage of plants with black necrosis symptoms was inversely related to the portion of plants with brown necrosis in each plot. The mean incidence of black necrosis was significantly lower in plots with residue incorporation (sugar beet as the preceding crop) than in plots without residue incorporation. No significant effect of preceding crop or residue management on brown necrosis incidence was observed. Incidence of black necrosis was negatively correlated with available N measured as NO3 -N when corn or sunflower were the preceding crop. The incidence of black necrosis was positively related to Fe availability in soil after cotton as preceding crop, whereas brown necrosis was negatively related to the availability of this micronutrient. [source] Antifungal property of the essential oils and their constituents from Cinnamomum osmophloeum leaf against tree pathogenic fungiJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 12 2005Han-Chung Lee Abstract This study compares the chemical constituents of leaf essential oils from various geographical provenances of Cinnamomum osmophloeum and investigates their antifungal activities against six tree pathogenic fungi. According to GC-MS and cluster analyses, the leaf essential oils obtained from different geographical provenances and their relative contents were classified into six chemotypes: cinnamaldehyde type, cinnamaldehyde,cinnamyl acetate type, cinnamyl acetate type, linalool type, camphor type, and mixed type. Results from the antifungal tests show that the leaf essential oils of cinnamaldehyde type and cinnamaldehyde,cinnamyl acetate type have excellent inhibitory effect against Rhizoctonia solani, Collectotrichum gloeosporioides, Ganoderma australe and Fusarium solani. Furthermore, among the fourteen constituents of C osmophloeum leaf essential oils, Z -cinnamaldehyde, eugenol, geraniol and citral display the best antifungal properties. Comparisons of the antifungal properties of Z -cinnamaldehyde congeners reveal that Z -cinnamaldehyde exhibits the best antifungal property of this group. Copyright © 2005 Society of Chemical Industry [source] Pathogenesis of Streptoverticillium albireticuli on Caenorhabditis elegans and its antagonism to soil-borne fungal pathogensLETTERS IN APPLIED MICROBIOLOGY, Issue 5 2002J.-O. Park Aims: To examine the biological activity of Streptoverticillium albireticuli. Methods: Isolation of S. albireticuli was carried out using the dry-heat technique. Nematicidal and pathogenic activity on Caenorhabditis elegans was measured by mortality in metabolites and colonization rate on fishmeal extract agar. Antifungal and enzymatic activities of S. albireticuli were measured by the agar plate method and the semidefined solid media method, respectively. Results:S. albireticuli showed strong nematicidal activity against C. elegans . Pathogenic activity was also evident with the colonized nematode by the isolate on fishmeal extract agar. It also showed antifungal activity against certain fungal pathogens such as Rhizoctonia solani , Phytophthora cinnamomi and Fusarium oxysporum . Significance and Impact of the Study: The discovery of an actinomycete showing pathogenic activity against the nematode may indicate the potential for it to be used as a biocontrol agent of parasitic nematodes, in addition to its ability to suppress fungal pathogens. [source] Enhanced fungal resistance in transgenic cotton expressing an endochitinase gene from Trichoderma virensPLANT BIOTECHNOLOGY JOURNAL, Issue 5 2003Chandrakanth Emani Summary Mycoparasitic fungi are proving to be rich sources of antifungal genes that can be utilized to genetically engineer important crops for resistance against fungal pathogens. We have transformed cotton and tobacco plants with a cDNA clone encoding a 42 kDa endochitinase from the mycoparasitic fungus, Trichoderma virens. Plants from 82 independently transformed callus lines of cotton were regenerated and analysed for transgene expression. Several primary transformants were identified with endochitinase activities that were significantly higher than the control values. Transgene integration and expression was confirmed by Southern and Northern blot analyses, respectively. The transgenic endochitinase activities were examined in the leaves of transgenic tobacco as well as in the leaves, roots, hypocotyls and seeds of transgenic cotton. Transgenic plants with elevated endochitinase activities also showed the expected 42 kDa endochitinase band in fluorescence, gel-based assays performed with the leaf extracts in both species. Homozygous T2 plants of the high endochitinase-expressing cotton lines were tested for disease resistance against a soil-borne pathogen, Rhizoctonia solani and a foliar pathogen, Alternaria alternata. Transgenic cotton plants showed significant resistance to both pathogens. [source] Induced systemic resistance against three foliar diseases of Agrostis stolonifera by (2R,3R)-butanediol or an isoparaffin mixtureANNALS OF APPLIED BIOLOGY, Issue 2 2010A.M. Cortes-Barco Induced systemic resistance (ISR) is a type of plant defence mechanism typically activated by non-pathogenic root-associated micro-organisms and systemic priming of gene expression in response to subsequent pathogen challenge. ISR was found to be activated by PC1, a mixture of food-grade synthetic isoparaffins and (2R,3R)-butanediol, a volatile organic compound produced by bacteria. In controlled environment tests, application of PC1 or (2R,3R)-butanediol to the soil reduced the diseased leaf area of Agrostis stolonifera by 20,40% for the fungal pathogens, Microdochium nivale, Rhizoctonia solani or Sclerotinia homoeocarpa compared to the water control. In A. stolonifera, expression of the jasmonate synthesis-related genes, AsAOS1, encoding an allene oxide synthase, and AsOPR4, encoding a 12-oxo-phytodienoic acid reductase, and expression of a pathogenesis-related protein gene, AsGns5, encoding an acidic , -1,3-glucanase, were primed for increased expression by PC1 or (2R,3R)-butanediol when M. nivale was inoculated 7 days later. However, the compounds differed in their ability to induce expression prior to pathogen challenge. PC1 induced AsAOS1 expression upon treatment, whereas (2R,3R)-butanediol induced expression of AsOPR4 and AsGns5 upon treatment. These results indicate that both (2R,3R)-butanediol and PC1 can produce ISR in A. stolonifera but may do so through different mechanisms. [source] Effect of Elicitation on Growth, Respiration, and Nutrient Uptake of Root and Cell Suspension Cultures of HyoscyamusmuticusBIOTECHNOLOGY PROGRESS, Issue 2 2002Edgard B. Carvalho The elicitation of Hyoscyamus muticus root and cell suspension cultures by fungal elicitor from Rhizoctonia solani causes dramatic changes in respiration, nutrient yields, and growth. Cells and mature root tissues have similar specific oxygen uptake rates (SOUR) before and after the onset of the elicitation process. Cell suspension SOUR were 11 and 18 ,mol O2/g FW·h for non-elicited control and elicited cultures, respectively. Mature root SOUR were 11 and 24 ,mol O2/g FW·h for control and elicited tissue, respectively. Tissue growth is significantly reduced upon the addition of elicitor to these cultures. Inorganic yield remains fairly constant, whereas yield on sugar is reduced from 0.532 to 0.352 g dry biomass per g sugar for roots and 0.614 to 0.440 g dry biomass per g sugar for cells. This reduction in yield results from increased energy requirements for the defense response. Growth reduction is reflected in a reduction in root meristem (tip) SOUR, which decreased from 189 to 70 ,mol O2/g FW·h upon elicitation. Therefore, despite the increase in total respiration, the maximum local oxygen fluxes are reduced as a result of the reduction in metabolic activity at the meristem. This distribution of oxygen uptake throughout the mature tissue could reduce mass transfer requirements during elicited production. However, this was not found to be the case for sesquiterpene elicitation, where production of lubimin and solavetivone were found to increase linearly up to oxygen partial pressures of 40% O2 in air. SOUR is shown to similarly increase in both bubble column and tubular reactors despite severe mass transfer limitations, suggesting the possibility of metabolically induced increases in tissue convective transport during elicitation. [source] | ||||||||||||||||||||||||||||