首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
Bacillus and Pseudomonas are the dominant groups of bacteria known for their antagonistic potential against many plant and animal pathogens. Presently, exploration of these genera with antagonistic property for disease management of aquaculture system is gaining more importance to overcome the use of antibiotics and related resistance issues. Rapid screening and identification of these genera from diverse bacterial populations by conventional methods is laborious, cost-intensive, and time-consuming. To overcome these limiting factors, in the present study, a colony multiplex PCR (cmPCR) method was developed and evaluated for the rapid detection of Bacillus and Pseudomonas. The technique amplifies the partial 16S rRNA gene of Bacillus and Pseudomonas with a product size of ~1,100 and ~375 bp, respectively, using single forward (BSF2) and two reverse primers (PAGSR and BK1R). Reliability of the cmPCR method was confirmed by screening 472 isolates obtained from ten different eco-stations, of which 133 isolates belonged to Bacillus and 32 to Pseudomonas. The cmPCR method also helped to identify six different Pseudomonas spp. and 14 different Bacillus spp. from environmental samples. Of the total 472 isolates studied, 46 showed antagonistic activity, among which 63 % were Bacillus and 17.4 % were Pseudomonas. Thus, the newly developed molecular approach provides a quick, sensitive, and potential screening tool to detect novel, antagonistically important Bacillus and Pseudomonas genera for their use in aquaculture. Further, it can also act as a taxonomic tool to understand the distribution of these genera from wide ecological niches and their exploitation for diverse biotechnological applications.  相似文献   

2.
Bacteria of the genus Bacillus are well known to possess antagonistic activity against numerous plant pathogens. In the present study, 11 strains of Bacillus spp. were isolated from a brackish environment and assayed for biocontrol activity under in vitro and in vivo conditions. Among the 11 isolates tested, nine isolates effectively inhibited the growth of various plant pathogens, namely Phytophthora capsici, Phytophthora citrophthora, Phytophthora citricola, Phytophthora sojae, Colletotrichum coccodes, Colletotrichum gloeosporioides, Colletotrichum acutatum, Rhizoctonia solani, Fusarium solani, Fusarium graminearum, Pyricularia spp., and Monilina spp. The effective isolates were further screened for suppression of Phytophthora blight of pepper plants under greenhouse conditions. The isolate SB10 exhibited the maximum (72.2%) ability to reduce the disease incidence and increased (32.2%) the vigour index of Capsicum annuum L. plants. Antifungal compounds produced by isolate SB10 were highly thermostable (100°C for 30 min). Matrix-Assisted Laser Desorption Ionization-Time of Flight mass spectrometry of the antifungal compounds revealed three lipopeptide complexes, namely the surfactins, the iturins, and the fengycins, which are well-known antifungal compounds produced by Bacillus spp.  相似文献   

3.
We attempted to isolate Lactobacillus spp. from the marine oyster (Crassostrea gigas) and select stress resistant strains for development of a future marine aquaculture feed adjuvant. A total of 83 lactobacilli strains were isolated from oyster. They were all Gram-positive, rod-shaped and catalase-negative. By performing a stress resistance assay, we selected eighteen isolates. Based on 16S rRNA gene sequencing, Lactobacillus paracasei was the most prevalent species among the selected isolates. The in vitro antagonistic effect of the selected strains against fish pathogens was assayed by measurement of inhibition diameters. Except for MH44, MH51, MH53 and MH62, most of the isolates showed inhibition of Vibrio alginolyticus and Vibrio proteolyticus (diameters over 15 mm). Lactobacillus rhamnosus MH22 was selected as the most stress resistant strain showing the MICs of 1.8 M NaCl, 14% ethanol and 0.014% hydrogen peroxide. L. rhamnosus MH22 isolated from oyster has a potential to be applied as a microbial feed adjuvant for marine aquaculture.  相似文献   

4.
In vitro antagonistic effects of rhizobacteria associated with Coffea arabica L. against some fungal coffee pathogens were studied. The aims were to screen indigenous coffee‐associated isolates for their inherent antagonistic potential against major coffee wilt diseases induced by Fusarium spp. Antagonistic effects, siderophore, HCN and lytic enzyme production were determined on standard solid media. Chemical methods were employed to categorize the major types of siderophores. From a total of 212 rhizobacterial isolates tested, over 10 % (all Pseudomonas and Bacillus spp.) exhibited remarkable inhibition against Fusarium spp. One isolate AUPB24 (P. chlororaphis) showed maximum inhibition of mycelial growth against all fungal pathogens tested, whereas other isolates were mostly inhibitory to F. stilboides and F. oxysporum. The isolate AUBB20 (B. subtilis) was most antagonistic to F. xylarioides. Of the rhizobacterial isolates tested, 67 % produced siderophores and 35 % produced HCN. Many strains (all Pseudomonas spp.) produced siderophores of the hydroxamate type and only a small proportion produced those of the catecholate type. Few antagonists showed chitinase activity. The production of siderophores and HCN by Pseudomonas spp., lipase and protease by all antagonists and β‐1,3‐glucanase by several Bacillus spp. could be considered the major mechanisms involved in the inhibition of fungal growth. The in vitro results provide the first evidence of an antagonistic effect of coffee‐associated rhizobacteria against the emerging fungal coffee pathogens F. stilboides and F. xylarioides and indicate the potential of both bacterial groups for biological control of coffee wilt diseases.  相似文献   

5.
Fungi in the genus Lecanicillium (formerly classified as the single species Verticillium lecanii) are important pathogens of insects and some have been developed as commercial biopesticides. Some isolates are also active against phytoparasitic nematodes or fungi. Lecanicillium spp. use both mechanical forces and hydrolytic enzymes to directly penetrate the insect integument and the cell wall of the fungal plant pathogen. In addition to mycoparasitism of the plant pathogen, the mode of action is linked to colonization of host plant tissues, triggering an induced systemic resistance. Recently it was demonstrated that development of Lecanicillium hybrids through protoplast fusion may result in strains that inherit parental attributes, thereby allowing development of hybrid strains with broader host range and other increased benefits, such as increased viability. Such hybrids have demonstrated increased virulence against aphids, whiteflies and the soybean cyst nematode. Three naturally occurring species of Lecanicillium, L. attenuatum, L. longisporum, and an isolate that could not be linked to any presently described species based on rDNA sequences have been shown to have potential to control aphids as well as suppress the growth and spore production of Sphaerotheca fuliginea, the causal agent of cucumber powdery mildew. These results suggest that strains of Lecanicillium spp. may have potential for development as a single microbial control agent effective against several plant diseases, pest insects and plant parasitic nematodes due to its antagonistic, parasitic and disease resistance inducing characteristics. However, to our knowledge, no Lecanicillium spp. have been developed for control of phytopathogens or phytoparasitic nematodes.  相似文献   

6.
In this study, more than 150 bacteria showing antagonistic properties against bacterial and fungal pathogens of the tomato plant were isolated and characterized. The most efficient agents against these phytopathogenic microorganisms belong to the genus Bacillus: the best biocontrol isolates were representatives of Bacillus subtilis, B. mojavensis and B. amyloliquefaciens species. They intensively produced fengycin or/and surfactin depsipeptide antibiotics and also proved to be excellent protease secretors. It was proved, that the selected strains were able to use ethylenethiourea (ETU) as sole nitrogen source. These antagonistic and ETU-degrading Bacillus strains can be applied as biocontrol and also as bioremediation agents.  相似文献   

7.
A study was carried out to test direct and indirect antagonistic effect against Fusarium wilt, caused by Fusarium oxysporum f. sp. ciceri (FOC), and plant growth-promoting (PGP) traits of bacteria isolated from rhizosphere soils of chickpea (Cicer arietinum L.). A total of 40 bacterial isolates were tested for their antagonistic activity against FOC and of which 10 were found to have strong antagonistic potential. These were found to be Streptomyces spp. (five isolates) and Bacillus spp. (five isolates) in the morphological and biochemical characterisation and 16S rDNA analysis. Under both greenhouse and wilt sick field conditions, the selected Streptomyces and Bacillus isolates reduced disease incidence and delayed expression of symptoms of disease, over the non-inoculated control. The PGP ability of the isolates such as nodule number, nodule weight, shoot weight, root weight, grain yield and stover yield were also demonstrated under greenhouse and field conditions over the non-inoculated control. Among the ten isolates, Streptomyces sp. AC-19 and Bacillus sp. BS-20 were found to have more potential for biocontrol of FOC and PGP in chickpea. This investigation indicates that the selected Streptomyces and Bacillus isolates have the potential to control Fusarium wilt disease and to promote plant growth in chickpea.  相似文献   

8.
《Biological Control》2013,64(3):287-295
Establishment of alfalfa crops is continuously threatened by seedling diseases caused by soilborne pathogens. The use of plant beneficial bacteria as inoculants is a feasible and environmentally friendly means to control soil pathogens. Identifying effective plant growth-promoting strains to use on local crops under local environmental conditions requires the screening of large collections of native isolates. A collection of 738 rhizospheric fluorescent Pseudomonas isolates was obtained from alfalfa plants from three agroecological regions representative of Uruguayan agricultural systems. The isolates were evaluated for in vitro pathogen inhibition, biosurfactant production, phosphate solubilization and the presence of genes involved in antibiotic synthesis. Isolates with strong in vitro antagonistic activity toward Pythium debaryanum were more abundant in alfalfa plants established in a previously natural ecosystem while biosurfactant producers were less abundant in that location. A subset of isolates was selected for genotypic characterization by rep-PCR using BOX primers. Twenty-four genotypes were defined, sixteen from a single geographical origin and eight composed of isolates from multiple origins. Genotypic profiles correlated well with phenotypic traits. A subset of isolates was assayed to determine their ability to protect alfalfa against P. debaryanum damping-off and to promote plant growth. Five native Pseudomonas isolates showed significant effects on alfalfa by increasing plant biomass and/or protecting from pathogen infection. Plant growth promoting isolates from each location were genotypically similar. Our work contributes to the knowledge of the phenotypic and genotypic diversity of rhizospheric fluorescent pseudomonads of forage legumes and the frequency of plant growth promoting traits associated with this group of bacteria in different agricultural systems.  相似文献   

9.
Summay Soil samples were taken from 48 fields in the southern part of Thailand in which either bambara groundnut (Vigna subterranea) or groundnut (Arachis hypogeae) had been planted. Bacillus spp. were isolated using soil dilution plates and heat treatment to screen for endospore-producing bacteria. Among 342 Bacillus spp. isolates tested, 168 isolates were not antagonistic to Bradyrhizobium sp. strain NC-92 using dual culture technique. Further testing found 16 isolates of Bacillus spp. had the ability to inhibit mycelial growth of Rhizoctonia solani, a causal agent of leaf blight of bambara groundnut. Among these isolates, Bacillus spp. isolate TRV 9-5-2 had the greatest activity in anti-microbial tests against R. solani. This isolate was later identified as B. firmus. A powder formulation of B. firmus was developed by mixing bacterial endospores, talcum, sodium carboxymethylcellulose (SCMC) and polyvinylpyrolidone (PVP). The formulations contained bacterial levels ranging from 108 to 1010 c.f.u./g and the viability of bacteria in all formulations remained high after 1 year storage at room temperature (26–32 °C). All formulations showed satisfactory effectiveness in vitro in suppressing mycelial growth of R. solani using dual culture technique. The application of formulations as seed treatment showed that these formulations did not cause abnormality of seedling shape and had no effect on the germination of bambara groundnut seeds.  相似文献   

10.
Dothistroma septosporum is the causal agent of Dothistroma needle blight of pine trees. A novel green fluorescent protein (GFP)-based screening method was developed to assess the potential of microorganisms for biocontrol of Dothistroma. The screen utilizes GFP expression as an indicator of metabolic activity in the pathogen and hygromycin resistance selection to determine if the interaction is fungistatic or fungicidal. Results suggested that six of eight Trichoderma isolates tested have the potential to control Dothistroma in vitro, via a fungicidal action. Because D. septosporum produces a broad-spectrum toxin, dothistromin, the inhibition of Trichoderma spp. by D. septosporum was determined by growth rate measurements compared to controls. Inhibition of the Trichoderma spp. ranged from no inhibition to 30% inhibition and was influenced by the assay medium used. The GFP screening method was also assessed to determine if it was suitable for screening bacteria as potential biocontrol candidates. Although a method involving indirect-contact had to be used, two of four Bacillus strains showed antagonistic activity against D. septosporum in vitro, via a fungistatic interaction. The four bacterial strains inhibited D. septosporum growth by 14.0 to 39.8%. This GFP-based method represents a novel approach to screening fungi and bacteria for antagonistic activity.  相似文献   

11.
An in vitro antagonism test is a typical procedure for the selection of potential biocontrol strains. However, the traditional method of screening antagonistic bacteria in vitro is a time consuming method when conducting large-scale screening trials. In this study, an improved method for the selection of antagonistic bacteria in vitro from compost was established based on the traditional method. 21 Antagonistic bacteria out of 33 target strains isolated from vinegar waste compost using the improved method. The 16S rDNA gene showed the 21 strains all belonged to the Bacillus genus and 18 different types of fingerprints were obtained by enterobacterial repetitive inter-genic consensus (ERIC)-PCR. 18 Selected strains which had the unique fingerprints all exhibited broad-spectrum antagonism towards the tested fungi and at least two enzyme activities in vitro. Among them, majority of the isolates were siderophore producer, some of them showed nitrogen-fixing ability and small of them were IAA producer. Four out of five selected strains were found both to be effective in controlling wilt and damping-off disease and four strains showed strong growth-promoting activities for cucumber seedlings under greenhouse conditions. Thus, these results demonstrated that the improved method was an effective and rapid means to screen potential antagonistic microorganisms in vitro. The results also showed that Bacillus sp. strains in vinegar waste compost exhibited antibiosis against fungal pathogens and promoted the growth of cucumber seedlings.  相似文献   

12.
Endophytes play an important role in protection of host plants from infection by phytopathogens. Endophytic bacteria were isolated from five different parts (root, stem, petiole, leaf and seed) of Panax notoginseng and evaluated for antagonistic activity against Fusarium oxysporum, Ralstonia sp. and Meloidogyne hapla, three major pathogens associated with root-rot disease complex of P. notoginseng. From 1000 endophytic bacterial strains evaluated in vitro, 104 strains exhibited antagonistic properties against at least one of these three pathogens. Phylogenetic analyses of their 16S rRNA gene sequences showed that these 104 antagonistic bacteria belong to four clusters: Firmicutes, Proteobacteria, Actinobacteria and Bacteroidetes/Chlorobi. Members of the Firmicutes, in particular the Bacillus spp., were predominant in all analyzed tissues. The root was the main reservoir for antagonistic bacteria. Of the 104 antagonists, 51 strains showed antagonistic activities to one pathogen only, while 43 and 10 displayed the activities towards two and all three pathogens, respectively. The most dominant species in all tissues were Bacillus amyloliquefaciens subsp. plantarum and Bacillus methylotrophicus, which were represented by eight strains with broad antagonistic spectrum to the all three test pathogens of root-rot disease complex of P. notoginseng.  相似文献   

13.
The ubiquitous freshwater pathogen Saprolegnia parasitica has long been considered a true generalist, capable of infecting a wide range of fish species. It remains unclear, however, whether different isolates of this pathogen, obtained from distinct geographic locations and host species, display differences in host preference. To assess this, the current study examined the induced zoospore encystment responses of four S. parasitica isolates towards the skin of four fish species. While three of the isolates displayed ‘specialist’ responses, one appeared to be more of a ‘generalist’. In vivo challenge infections involving salmon and sea trout with the ‘generalist’ (salmon isolate EA001) and a ‘specialist’ (sea trout isolate EA016) pathogen, however, did not support the in vitro findings, with no apparent host preference reflected in infection outcomes. Survival of sea trout and salmon though was significantly different following a challenge infection with the sea trout (EA016) isolate. These results indicate that while S. parasitica isolates can be considered true generalists, they may target hosts to which they have been more frequently exposed (potential local adaptation). Understanding host preference of this pathogen could aid our understanding of infection epidemics and help with the development of fish management procedures.  相似文献   

14.
The association of Rhizoctonia spp. with insect-damaged and diseased tissue of the invasive perennial Lepidium draba was documented throughout the range of L. draba that was surveyed in Europe, including Hungary, Austria, Switzerland and France. Samples that could be both maintained under cooled conditions after collection and promptly processed consistently yielded Rhizoctonia solani, 11 isolates of which anastomosed with AG-4, one with AG-2-1 and one isolate was determined to be binucleate. Comparative virulence among the isolates was analyzed using nonparametric survival analysis for interval-censored data. This analysis indicated that there were significant differences among the isolates. These findings provide further evidence that both root-attacking insects and soilborne pathogens are associated with the lower density of a perennial invasive species in its native range. Prioritization of prospective biocontrol agents should include the ability to engage in insect/plant pathogen synergisms. The application of nonparametric maximum likelihood estimation to interval-censored data for the assessment of comparative virulence among several strains of a plant pathogen is more accessible than calculation of the area under the disease progress curve.  相似文献   

15.
Mango (Mangifera indica L.) is considered as one of the most popular fruits among millions of people in the tropical area and increasingly in the developed countries. Anthracnose, caused by the fungus Colletotrichum gloeosporioides, is the most important pre- and post-harvest disease of mango. The objective of this research was to evaluate the prevalence of different promising antagonistic Trichoderma and Bacillus spp. on phyloplane of mango in Ethiopia and to evaluate their antagonistic potential against the pathogen. A total of 19 mango fields were surveyed and anthracnose affected all fields. Culture studies on potato dextrose agar for evaluation of antibiosis activity of Trichoderma spp. and Bacillus spp. revealed that they have inhibitory and lytic effect on C. gloeosporioides, which is an indication of their potential biocontrol agent for management of mango anthracnose as an alternative to chemical control. Significant differences (p?<?0.05) were observed among Bacillus isolates in causing lysis of pathogen mycelium, when inoculated on actively growing colony of C. gloeosporioides. Maximum reduction in growth rate of pathogen was observed with Bacillus spp. (B50), which restricted the growth to 2.7?mm compared to 8.3?mm in the control with 67.5% efficacies. There were similar effects (p?<?0.05) among Trichoderma spp. in formation of inhibition zones and lysis by varying degrees up to 59.7% efficacies in reducing linear growth of the pathogen in dual culture.  相似文献   

16.
Bacillus spp. has emerged as the most effective alternative to synthetic chemical fungicides. To get a better insight in the antagonistic potential of Bacillus strains, rhizospheric soil samples of healthy tomato plants from Indo-gangetic plain regions of India were analysed. A total of 108 Bacillus strains were obtained from preliminary screening. Potent strains identified on the basis of in vitro antagonistic and biochemical assays were subjected to diversity analysis using 16S-rDNA, BOX and ERIC-PCR. Furthermore, the four best performing antagonistic Bacillus strains under in vitro plant growth promotion and antagonistic assay were selected for pot experiment. In field study, Bacillus amyloliquefaciens MB101 and Bacillus subtilis MB14 showed drastic reduction in disease index by 55.7 and 41.74% with significant elevation in fruit yield up to 220 and 184 qha–1, respectively. The present study was successful in selecting effective Bacillus strains by performing phenotypic and genotypic characterisation of Bacillus strains that can be used as an integral component of integrated disease management of tomato root rot and damping-off.  相似文献   

17.
Aims: This work was aimed at identifying strains which can degrade quorum‐sensing (QS) molecules from fish gut, with properties suitable for use as probiotic in aquaculture. Methods and Results: A total of 200 strains were obtained from the intestine gut of Carassius auratus gibelio after enrichment in KG medium contained 500 μg l?1 of C6‐HSL as the sole source of carbon and nitrogen; one strain named QS inhibitor (QSI)‐1 was identified as the genus Bacillus spp. by morphological phenotypes, and the strain also possessed an aiiA homologue gene using PCR amplification. In vitro, QSI‐1 strongly interfered with violacein production by Chromobacterium violaceum. Coculture of QSI‐1 with fish pathogen effectively reduced the amount of acyl‐homoserine lactones (AHLs) and the extracellular proteases activity of Aeromonas hydrophila YJ‐1. The oral LD50 of QSI‐1 to fish was more than 1011 CFU shown that it was avirulent to fish. Fish fed diet supplemented with QSI‐1 had good survival, suggesting that QSI‐1 showed protection against Aer. hydrophila infection. Conclusions: The results indicate that the isolate QSI‐1 might have the potential possibility to be used as a probiotic in aquaculture. Significance and Impact of the Study: This is the first report to describe a bacterium isolated from the intestine gut of C. auratus gibelio which can degrade AHLs and has the probiotic characteristics for its use in aquaculture.  相似文献   

18.
We studied the diversity and biocontrol potential of 100 fungal endophytes isolated from Espeletia spp., endemic plant species from the Paramo in the Andean mountain range. Our sample was genotypically highly diverse at all ITS similarity levels. The antagonistic properties of these isolates were tested against common crop pathogens in Colombia, including Pectobacterium carotovorum, Ralstonia solanacearum, Pseudomonas syringae, Xanthomonas campestris, Rhizoctonia solani, Botrytis cinerea, Fusarium oxysporum, and Phytophthora infestans. All endophytic isolates were able to significantly inhibit the growth of at least one of the plant pathogens tested (P?<?0.05). Three main types of endophyte/pathogen interactions were observed. However, only those endophytes that produced an evident inhibition halo were further studied using their crude extracts to confirm that the inhibitory effect was due to the production of endophytic bioactive metabolites. From these experiments, nine promising isolates were selected for co-inoculation tests with R. solani in tomato plants. The isolates identified as Aureobasidium pullulans and Paraconiothyrium sporulosum not only protected the plants against this pathogen but also allowed them to exhibit similar growth and development as the uninoculated control. This work explores new alternatives for disease management without the application of chemical pesticides.  相似文献   

19.
Two outdoor pot experiments were carried out to evaluate the reaction of 11 commercial Egyptian cotton cultivars Macrophomina phaseolina, the incitant of ashy stem in cotton and to evaluate the antagonistic ability of 27 isolates of Trichoderma sp. against pathogen cotton cultivars Giza 85, Giza 87, Giza 89 and Giza 90 were resistant to M. phaseolina because both survival and plant height of these cultivars was not affected when the soil was infested with the pathogen. None of the cultivars were found to be immune to highly pathogenic of M. phaseolina isolate. Of the 27 isolate’s of Trichoderma that were evaluated, the best antagonistic performance was given by isolates nos. 2, 10, and 16 were promising for commercialization because they significantly increased survival and improved plant height and dry weight of the surviving cotton seedlings.  相似文献   

20.
Trichoderma, soil-borne filamentous fungi, are capable of parasitising several plant pathogenic fungi. Twelve isolates of Trichoderma spp. isolated from different locations of South Andaman were characterized for their cultural, morphological and antagonistic activity against soil borne and foliar borne pathogens. The sequencing of these isolates showed seven different species. The isolates revealed differential reaction patterns against the test pathogens viz., Sclerotium rolfsii, Colletotrichum gloeosporioides and C. capsici. However, the isolates, TND1, TWN1, TWC1, TGD1 and TSD1 were most effective in percentage inhibition of mycelial growth of test pathogens. Significant chitinase and β-1,3-glucanase activities of all Trichoderma isolates has been recorded in growth medium. T. viride was found with highest chitinase whereas T. harzianum was recorded with highest β-1,3-glucanase activities.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号