1,720,999 research outputs found
Biological control of Monilinia laxa and Fusarium oxysporum f. sp. lycopersici by a lytic enzyme-producing Penicillium purpurogenum
No full textBiological control experiments were conducted with the lytic enzyme- producing fungus Fenicillium purpurogehum against the plant pathogens Monilinia laxa and Fusarium oxysporum f. sp. lycopersici. Applications of P. purpurogenum to peach shoots previously inoculated with M. laxa reduced lesion length and extent of pathogen colonization of shoots by 90 and 80% (P ≤ 0.05), respectively, comparable to the level of disease control obtained with the fungicide captan. Disease severity in tomato plants inoculated with F. oxysporum f. sp. lycopersici was decreased by 30% (P ≤ 0.05) with the biological treatment. The fungus P. purpurogenum produced β-1,3- glucanase and chitinase activities in liquid culture that were inducible by cell walls and live mycelium of M. laxa but not of F. oxysporum f. sp. lycopersici. Crude filtrates or crude enzyme preparations of P. purpurogenum cultures with lytic enzyme activities produced lysis of hyphae and spores of M. laxa and F. oxysporum f. sp. lycopersici. These lytic effects were strong in M. laxa and ended in complete dissolution of mycelium. The induction of lytic enzymes by M. laxa and the effects of lytic enzymes on mycelia of the pathogens in relation to the different degrees of biological control obtained are discussed
The lytic enzymatic complex of Penicillium purpurogenum and its effects on Monilinia laxa
No full textAn isolate of Penicillium purpurogenum produces lytic enzymes which are directly implicated in the degradation of fungal cell walls and are associated with its own growth and autolysis. Maximal β-1,3-glucanase activity was detected after 45 d of growth (2347 mU mg−1 protein) in a stationary culture, and after 12 d of incubation (1533 mU mg−1 protein) in a shake culture. Other enzymatic activities detected in stationary liquid cultures were β-1,3,(4)-glucanase (with two maxima of approx 100–120 mU mg−1 protein at 14 and 50 d of growth), β-1,6-glucanase (317 and 270 mU mg−1 protein at days 3 and 13, respectively) and polymethyl-galacturonase (914 and 951 mU mg−1 protein at days 5 and 12, respectively). The chitinase activity was low. P. purpurogenum directly attacked the mycelium of Monilinia laxa when the two fungi were grown together. The enzymatic complex of P. purpurogenum also attacked the mycelium of M. laxa lysing its hyphae and spores, resulting in complete destruction of the mycelia. © 1993, British Mycological Society. All rights reserved
Genetic diversity in Monilinia laxa populations in peach orchards in Spain
No full textOne-hundred and forty-four random amplified polymorphic DNA markers, of which 59 were polymorphic and 85 monomorphic, were used to assess the genetic diversity and to study the structure of Monilinia laxa populations in Spain. Twenty-one isolates collected from several orchards (subpopulations), in various years and in various hosts, were used. The analysis of population structure revealed that genetic diversity within orchards (HS) accounted for 97% of the total genetic diversity (HT), while genetic diversity among the orchards represented only 3%. The relative magnitude of gene differentiation between subpopulations (GST) and the estimate of the number of migrants per generation (Nm) averaged 0.032 and 15.1 respectively. The results obtained in dendrograms were in accordance with the gene diversity analysis. Grouping of isolates in the dendrogram was independent of whether they came from the same or different orchards. There was no relationship between clustering among isolates from distinct years and hosts. The relative importance of several evolutionary forces in populations of M. laxa is discussed, together with implications for the management of brown rot. © 2007 The Authors
Editorial: Impact of novel omic technologies on biological control against plant pathogens
No full text2 Pág.Peer reviewe
First report on the detection and quantification of Verticillium dahliae from Estonian strawberry fields using quantitative real-time PCR
No full textThe main aim of this investigation was to develop a SYBRGreen real-time polymerase chain reaction (PCR) assay for detection and quantification of Verticillium dahliae directly from affected strawberry roots and soils. The proposed assay utilizes a specifically designed primer pair on the basis of an internal transcribed spacer (ITS) sequence. During 2014-2015, plant and soil samples were randomly collected from different areas including Vasula, Rohu, Unipiha, Utsu and Marjamaa in Estonia and analyzed for V. dahliae. Real-time PCR technique using primers designed to the rDNA ITS1 was highly sensitive and accurate and so allowed reliable quantification of the pathogen DNA at low inoculation in soils (3 × 10-1 pg µl-1) and even in root of symptomless plants (5 × 10-1 pg µl-1). This is the first study of using this technique to quantify the population of V. dahliae in strawberry fields from Estonia. © 2016, Lithuanian Institute of Agriculture. All rights reserved.Peer reviewe
A rapid diagnostic assay for detection and quantification of the causal agent of strawberry wilt from field samples
No full textVerticillium dahliae Kleb, the cause of Verticillium wilt disease, is a destructive pathogen that leads to severe yield losses in strawberry fields and thus considerable economic damages. Although rapid identification and detection methods are becoming available more, pathogen quantification remains one of the main challenges in the disease management. In this study, a real-time polymerase chain reaction (rtPCR) assay was developed to quantitatively assess V. dahliae abundance directly from affected roots and soil collected from different areas in Estonia. A specific primer pair based on the ribosomal DNA (rDNA) internally transcribed spacer was designed for SYBR Green-based assay. Strawberry plant and soil samples were randomly collected from different areas in Estonia and analyzed for V. dahliae by soil plating technique and rtPCR assay. The assay was specific for V. dahliae so that the minimum detection limit was 0.93 pg µl−1 of pathogen DNA and the lowest amount of V. dahliae detected in soil was 10.48 pg µl−1 of target DNA corresponding to one microsclerotia per gram of soil. This technique allowed rapid detection and quantification of the pathogen DNA at the picogram level in soils and even in symptomless plants, facilitating the screening of the pathogen in diverse areas. This is the first study about the rtPCR technique being used successfully to assess populations of V. dahliae with high specificity and sensitivity in Estonia strawberry fields. Results of this research can be useful for growers and agricultural organizations to improve available disease management strategies against Verticillium wilt. © 2016 Informa UK Limited, trading as Taylor & Francis Group
Effects of stabilizers on shelf-life of Epicoccum nigrum formulations and their relationship with biocontrol of postharvest brown rot by Monilinia of peaches
No full textAim To find a formulation of Epicoccum nigrum conidia that maintains a high viability over time and which proves efficient to biocontrol peach rot caused by Monilinia spp. Methods and Results We tested the effect of stabilizers and desiccants on the shelf-life of Epicoccum nigrum conidia. Conidial samples were dried for 40 min at 40°C in a fluidized bed-dryer to obtain moisture contents <15%. The toxicity of additives was tested by assaying production of conidia in fermentations and germinability of the produced conidia 50% PEG300, 10%-5% KCl (stabilizers) and 95.24% Cl 2Ca (desiccant) significantly (P = 0.05) reduced conidial germination. To enhance shelf-life of dried conidia, nontoxic stabilizers were added at the following different stages of the production-drying process (i) to substrate contained in bags before production, (ii) to conidial centrifuge pellets obtained after production, before filtering and drying, (iii) to conidial centrifuge pellets obtained after production, before adding talc and drying, and (iv) to conidial centrifuge pellets obtained after production, before adding silica powder and drying. Conidial germinability was tested at 0, 180 and 365 days after storage at room temperature. Shelf-life of formulations retaining the highest viability were conidia produced with 1% KCl or 50% PEG 8000, conidia dried with 2.5% methylcellulose, and conidia dried with 1% KCl + silica powder. All these formulations improved the shelf-life of E. nigrum conidia and significantly reduced brown rot on peaches. Conclusions Our results show that additives improve the shelf-life of E. nigrum and assist controlling brown rot on peaches. Significance and Impact of the Study New improved formulations of a biocontrol agent have been obtained which will improve the control of Monilinia on peach. © 2007 The Authors
Production, survival, and evaluation of solid-substrate inocula of Penicillium oxalicum, a biocontrol agent against Fusarium wilt of tomato
No full textProduction of conidia of Penicillium oxalicum (ATCC number pending), a biocontrol agent of Fusarium oxysporum f. sp. lycopersici, was tested in liquid and solid fermentation. P. oxalicum produced 250-fold more conidia in solid than in liquid fermentation at 30 days after inoculation of substrate. Solid fermentation was carried out in plastic bags (600 cm3) especially designed for solid fermentation (VALMIC) containing 50 g of peat/vermiculite (PV) (11, wt/wt) with 40% moisture, sealed, sterilized, and then inoculated with 1 ml of a conidial suspension of P. oxalicum (105 conidia g-1 dry substrate), sealed again, and incubated in darkness at 20 to 25°C for 30 days. Addition of amendments to PV in a proportion of 0.5 (wt/wt) significantly increased conidial production of P. oxalicum. The best production was obtained on PV plus meal of cereal grains (barley) or leguminous seeds (lentil) (100-fold higher). Conidial production obtained after 5 days of inoculation was similar to that obtained at 30 days. However, viability of conidia produced in PV plus lentil meal was 35% higher than that of conidia produced in PV plus barley meal. Changes in proportions (110.5, wt/wt/wt; 111, wt/wt/wt; 10.50,5, wt/wt/wt; 1:1:0.5, vol/vol/vol) of components of the substrate (peat/vermiculite/lentil meal) did not enhance production or viability of conidia. Optimal initial moisture in the substrate was 30 to 40%. At lower moistures, significant reductions of production of conidia were observed, particularly at 10%. There was a general decline in the number of conidia in bags with time of storage at -80, -20, 4, and 25°C, or at room temperature (range from 30 to 15°C), with the highest decline occurring from 60 to 180 days. Conidial viability also was reduced with time, except for conidia stored at -20°C. Fresh conidia produced in solid fermentation system or those conidia stored at -20°C for 180 days reduced Fusarium wilt of tomato by 49 and 61%, respectively
Enhancing the adhesion of Epicoccum nigrum conidia to peach surfaces and its relationship to the biocontrol of brown rot caused by Monilinia laxa
No full textAims To find a formulation of Epicoccum nigrum conidia that enhances its adhesion to peach surfaces and improves its biocontrol efficacy against brown rot caused by Monilinia laxa. Methods and Results The stickers, glycerol, sodium alginate and methylcellulose; the desiccants, silica powder and talc; and a commercial adhesive (NU FILM 17®) were added at two different points during the production of an E. nigrum conidial formulation to improve conidial adhesion to peach surfaces. Conidial adhesion levels were determined from the number of E. nigrum conidia that adhered to glass slides or peach surfaces and conidial viability of adherent E. nigrum conidia was determined from the number of colony-forming units of glass or peach-adherent E. nigrum that grew on Petri dishes that contained potato dextrose agar. Compared to dried E. nigrum conidia without additives, the adhesion and viability of adherent E. nigrum conidia to peach surfaces were enhanced when either 1·25% sodium alginate or 2·5% methylcellulose was added to the conidial mass after fluid-bed drying, and when 2·5% methylcellulose was added to the conidial mass after its production and before fluid-bed drying. Epicoccum nigrum conidial formulations with 2·5% methylcellulose were more effective than dried E. nigrum conidia without additives in reducing the incidence of brown rot in peaches caused by M. laxa. Conclusions When 2·5% methylcellulose is incorporated into an E. nigrum conidial formulation, the adhesion of E. nigrum conidia to peach surfaces improves and results in efficacious biocontrol of brown rot. Significance and Impact of the Study A new improved formulation of a biocontrol agent has been developed to improve the control of M. laxa on peaches. © 2010 The Society for Applied Microbiology
Solid substrate production of Epicoccum nigrum conidia for biological control of brown rot on stone fruits
No full textProduction of conidia of Epicoccum nigrum, a biocontrol agent of the fungal pathogen Monilinia laxa, was tested in liquid- and solid-state fermentation. Liquid fermentation was conducted in 250 ml Erlenmeyer flasks containing 50 ml of a mineral medium (containing per litre 20 g lactose, 10 g NO3K, 1 g K2HPO4, 0.5 g MgSO4·7H2O, and 1 ml of a minor-element solution), inoculated with 2×105 E. nigrum conidia ml-1, and incubated at 20-25°C and 150 rpm for 7 days. Solid-state fermentation was carried out in specially designed plastic bags (600 cm3) (VALMIC®) containing either 50 g of peat/vermiculite (11, w/w), or 50 g of peat/vermiculite/lentil meal (111, w/w/w) with 40% (v/w) initial moisture content. Substrate was inoculated with a conidial suspension of E. nigrum to give 105 conidia g-1 substrate, and bags were incubated at 20-25°C for 7 days in darkness. The amount of conidia of E. nigrum obtained in solid-state fermentation with substrate based on peat/vermiculite/lentil meal was 10-fold higher than with substrate based on peat/vermiculite or in liquid fermentation. Conidial production under these conditions was maintained in the range of 108 conidia g-1 substrate from 10 to 150 days after inoculation. Germinability of these conidia was >90%. Addition of other nutrients than lentil meal to peat/vermiculite did not enhance production of conidia. Presence of peat in the substrate was necessary for good conidia production, but change in the kind of peat or vermiculite did not improve conidial production. Conidial production was similar when the substrate was inoculated with 105, 106 or 107 conidia g-1 dry substrate. Incubation of bags in light conditions did not enhance conidial production. Fresh conidia produced in this solid-state fermentation system reduced the incidence and lesion diameter induced by M. laxa on peaches. © 2004 Elsevier B.V. All rights reserved
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