Plant regeneration from callus cultures of Valeriana wallichii DC.

Petiole expiants of Valeriana wallichii. DC., a threatened medicinal plant, were used for inducing callus. Optimum callus formation was observed on Murashige and Skoogs' (1962) medium supplemented with 3.0 mg/l NAA and 0.25 mg/l Kn. Shoot regeneration was achieved upon transferring the callus to medium containing 1.0 mg/l Kn and 0.25 mg/l NAA. Complete plantlets were obtained on the same medium or upon transfer of the regenerated shoot buds to medium containing 5.0 mg/l Kn and 1.0 mg/l IAA. Nearly a thousand callus regenerated plants were successfully transferred to the field following previously standardized hardening procedures.Abbreviations BAP 6-Benzylaminopurine - 2,4-D 2,4-dichloro phenoxyaceticacid - 2iP 2-isopentenyladenine - IAA indole-3-acetic acid - IBA indole-3-butyric acid - Kn Kinetin - MS Murashige and Skoog's medium (1962) - NAA -napthalene aceticacid - Z Zeatin     

40种杂草的丙酮提取物对3种植物病原真菌的抑菌活性

在离体条件下研究了40种杂草的丙酮提取物对辣椒疫霉(Phytophthora capsici Leonian)、尖孢镰刀菌(Fusarium oxysporium Schl.)和灰葡萄孢(Botrytis cinerea Pets.)3种植物病原真菌的抑菌活性.结果表明,有7种杂草的丙酮提取物至少对1种供试病原菌的抑制率在60%以上.其中,黄花蒿(Artemisia annua L.)、苍耳(Xanthiumsibiricum Patrin)和荔枝草(Salvia plebeia R. Br.)的丙酮提取物对3种病原菌的抑制率都在60%以上;鳢肠(Ecliptaprostrata L.)的丙酮提取物对辣椒疫霉和尖孢镰刀霉的抑制率在60%以上;车前(Plantago asiatica L.)、夏至草[Lagopsis supina(Steph.)IK.-Gal.]和泽漆(Euphorbia helioscopia L.)的丙酮提取物对灰葡萄孢的抑菌效果较好.     

Fumigant antifungal activity of essential oil components from Acorus gramineus against three phytopathogenic fungi

Analysis by gas chromatography-mass spectrometry led to the identification of 26 compounds in Acorus gramineus essential oil. The antifungal activity of the identified compounds was tested singularly by using standard compounds. Allyl isothiocyanate and cis-asarone showed inhibition rates of 100% against P. cactorum at 28 mg/l air. In a test with C. parasitica and E. circinatum, allyl isothiocyante and cis-asarone showed moderate activity at 28 mg/l air.     

Chitinase-mediated destructive antagonistic potential of Pseudomonas aeruginosa GRC1 against Sclerotinia sclerotiorum causing stem rot of peanut

Pseudomonas aeruginosa GRC₁ exhibited strong antagonistic activity against Sclerotinia sclerotiorum, in vitro and in vivo. Scanning electron microscopic (SEM) studies showed morphological abnormalities such as perforation, lysis and fragmentation of hyphae of S. sclerotiorum caused by P. aeruginosa GRC₁. This strain produced extracellular chitinase enzyme, the role of which was clearly demonstrated through Tn5 mutagenesis. Bacterization of peanut seeds with GRC₁ resulted in increased seed germination and reduced stem-rot of peanut in S. sclerotiorum-infested soil by 97%. Other vegetative and yield plant parameters such as nodules per plant, pods and grain yield per plant were enhanced with a statistical significance in comparison to control. Neomycin resistant (GRC₁^neo+) bacterium was a good root colonizer and frequently isolated from rhizosphere of peanut plants. These findings showed P. aeruginosa GRC₁ as a potential biocontrol agent against S. sclerotiorum.     

Antifungal potential of extracellular metabolites produced by Streptomyces hygroscopicus against phytopathogenic fungi

Indigenous actinomycetes isolated from rhizosphere soils were assessed for in vitro antagonism against Colletotrichum gloeosporioides and Sclerotium rolfsii. A potent antagonist against both plant pathogenic fungi, designated SRA14, was selected and identified as Streptomyces hygroscopicus. The strain SRA14 highly produced extracellular chitinase and β-1,3-glucanase during the exponential and late exponential phases, respectively. Culture filtrates collected from the exponential and stationary phases inhibited the growth of both the fungi tested, indicating that growth suppression was due to extracellular antifungal metabolites present in culture filtrates. The percentage of growth inhibition by the stationary culture filtrate was significantly higher than that of exponential culture filtrate. Morphological changes such as hyphal swelling and abnormal shapes were observed in fungi grown on potato dextrose agar that contained the culture filtrates. However, the antifungal activity of exponential culture filtrates against both the experimental fungi was significantly reduced after boiling or treatment with proteinase K. There was no significant decrease in the percentage of fungal growth inhibition by the stationary culture filtrate that was treated as above. These data indicated that the antifungal potential of the exponential culture filtrate was mainly due to the presence of extracellular chitinase enzyme, whereas the antifungal activity of the stationary culture filtrate involved the action of unknown thermostable antifungal compound(s).     

Bacillus strains isolated from rhizosphere showed plant growth promoting and antagonistic activity against phytopathogens

Seven bacterial isolates screened from rhizosphere of common bean growing at Uttarakhand Himalaya showed potential plant growth promoting (PGP) and antagonistic activities. Based on 16S rRNA gene sequence the isolate BPR7 was identified as Bacillus sp. BPR7. The strain BPR7 produced IAA, siderophore, phytase, organic acid, ACC deaminase, cyanogens, lytic enzymes, oxalate oxidase, and solubilized various sources of organic and inorganic phosphates as well as potassium and zinc. Strain BPR7 strongly inhibited the growth of several phytopathogens such as Macrophomina phaseolina, Fusarium oxysporum, F. solani, Sclerotinia sclerotiorum, Rhizoctonia solani and Colletotricum sp. in vitro. Cell-free culture filtrate of strain BPR7 also caused colony growth inhibition of all test pathogens. PGP and antifungal activities of Bacillus sp. BPR7 suggest that it may be exploited as a potential bioinoculant agent for P. vulgaris.     

Antibiotics potentiating potential of catharanthine against superbug Pseudomonas aeruginosa

Multidrug resistance (MDR) put an alarming situation like preantibiotic era which compels us to invigorate the basic science of anti-infective chemotherapy. Hence, the drug resistant genes/proteins were explored as promising drug targets. Keeping this thing in mind, proteome of Pseudomonas aeruginosa PA01 was explored, which resulted in the identification of tripartite protein complexes (MexA, MexB, and OprM) as promising drug target for the screening of natural and synthetic inhibitors. The purpose of present investigation was to explore the drug resistance reversal potential mechanism of catharanthine isolated from the leaves of Catharanthus roseous. Hence, the test compound catharanthine was in silico screened using docking studies against the above receptors, which showed signi?cant binding affinity with these receptors. In order to validate the in silico findings, in vitro evaluation of the test compound was also carried out. In combination, catharanthine reduced the minimum inhibitory concentration MIC of tetracycline (TET) and streptomycin up to 16 and 8 folds, respectively. Further, in time kill assay, catharanthine in combination with TET reduced the cell viability in concentration dependent manner and was also able to reduce the mutation prevention concentration of TET. It was also deduced that drug resistance reversal potential of catharanthine was due to inhibition of the efflux pumps.     

Plant growth promoting potential of endophytic bacteria isolated from Piper nigrum

Piper nigrum is an interesting plant to study the endophytic microbial factors affecting plant growth because of its unique features. Endophytic bacterial isolation from the plant resulted in the isolation of twelve bacterial isolates which were screened for various plant growth promoting properties like phosphate solubilization, ACC deaminase production, siderophore production etc. Interestingly, seven isolates were found to have IAA biosynthetic potential. Bacterial isolates with multiple plant growth promoting properties were studied for their growth promoting effect on Vigna radiata seedlings. This resulted in the identification of Klebsiella sp. (PnB 10) and Enterobacter sp. (PnB 11) as the isolates with excellent growth promoting properties. The results confirm promising applications of the endophytic bacterial isolates obtained in the study and also their possible growth promoting effect in P. nigrum.     

Effect of a preparation from Chaetomium fungi on the growth of phytopathogenic fungi

We studied the fungicidal activity of a biological preparation from the fungi of the genus Chaetomium against soil phytopathogenic fungi Rhizoctonia solani and Fusarium oxysporum. The inhibitory effect of the preparation under study depended on its concentration, duration of storage, and growth characteristics of pure cultures of the phytopathogens. The highest (98.8%) inhibitory activity was observed on day 3 of the interaction with Rhizoctonia solani. After a 2-year storage, this preparation was capable of inhibiting the growth of the phytopathogens only at high doses. The preparation precluded the development of bare patch and increased the productivity of potato plants. The preparation may serve as an alternative to chemical fungicides for plant protection.     

Endophytic fungi from Chilean native gymnosperms: antimicrobial activity against human and phytopathogenic fungi

Thirty-eight endophytic fungi were isolated from eight Chilean gymnosperms. Isolates were characterized and grouped according to culture characteristics, colony growth, and conidia morphology. Thirteen isolates were identified: Acremonium bacillisporum, A. bactrocephalum, A. strictum, Alternaria alternata, Aureobasidium pullulans, Chaetomium funicola, Cladosporium tenuissimum, Curvularia protuberata, C. tritici, Microsphaeropsis olivacea, Penicillium chrysogenum, P. janczewskii, and Triblidiopycnis pinastri. Malbranchea and Stegonosporium were identified at the genus level. Fourteen isolates, considered to be sterile mycelia, did not fructify in the culture medium. Crude extracts of liquid cultures from endophytes were examined for antibacterial and antifungal activity against bacteria and phytopathogenic fungi using agar diffusion. Antifungal activity against pathogenic fungi was determined by microdilution assays. Extracts of Acremonium bactrocephalum, Microsphaeropsis olivacea, and isolate E-3 inhibited growth of selected pathogenic organisms, indicating they merit further study. This is the first comparative report on the antimicrobial activity of endophytic fungi from Chilean gymnosperms.     

Chitinolytic actinomycetes from a Brazilian tropical soil active against phytopathogenic fungi

Five Streptomyces spp. isolated from a Brazilian forest soil showed endochitinase activity in the alkaline range with optima between 40 and 50°C. Three were highly active against three phytopathogenic fungi by in vitro experiments. Preliminary experiments suggested that the isolates may belong to a new taxon.     

The effect of a preparation from Chaetomium fungi on the growth of phytopathogenic fungi

We studied the fungicidal activity of a biological preparation from the fungi of the genus Chaetomium against soil phytopathogenic fungi Rhizoctonia solani and Fusarium oxysporum. The inhibitory effect of the preparation under study depended on its concentration, duration of storage, and growth characteristics of pure cultures of the phytopathogens. The highest (98.8%) inhibitory activity was observed on the third day of the interaction with Rhizoctonia solani. After a 2-year storage, this preparation was capable of inhibiting the growth of phytopathogens only at high doses. The preparation precluded the development of a bare patch but increased the productivity of potato plants. The preparation may serve as an alternative to chemical fungicides for plant protection.     

Plant growth promoting potentials of Pseudomonas spp. strain OG isolated from marine water

Abstract

Bacterium Pseudomonas spp. olive green (OG) was isolated from marine water, yet, it was characterized as plant growth promoting bacterium (PGPB). Multiple plant growth promoting traits of OG isolate were determined in vitro. It was tested positive for Indole-3-acetic acid (IAA) production with 29 µg ml^?1 of IAA yield, phosphate solubilization with 34 µg ml^?1 solubilization of Tri-calcium-phosphate and it showed maximum of 32 µg ml^?1 of ammonia production. OG isolate was affirming siderophore production, hydrocyanic acid (HCN) production and catalase production. 16S rRNA gene sequence comparison was used to identify the isolate which showed its closest neighbor to be Pseudomonas fluoroscens strain BCPBMS-1. Efficacy of this PGPB was tested on the seedling growth of two test plants chickpea and green gram. Both the test plants treated with OG-based talc bioformulation showed significant growth promotion. Chickpea showed enhanced overall fresh biomass by 24%, overall dry biomass by 27% was observed after 15 days of seeded in pots. Green gram showed enhanced overall dry biomass by 28% was observed after 10 days of seeded in pots.     

Purification,characteristics and identification of chitinases synthesized by the bacterium Serratia plymuthica MP44 antagonistic against phytopathogenic fungi

Applied Biochemistry and Microbiology - Once isolated from the rhizosphere, the chitinolytic bacterium Serratia plymuthica MP44 showed strong antagonistic action against such phytopathogenic fungal...     

In vitro evaluation of solvent extracted compounds from edible macromycetes against phytopathogenic fungi

Extraction of antimicrobial compounds from medicinal mushrooms, namely, Auricularia polytricha (Jew's ear), Lentinulla edodes (Shiitake) and Volvariella volvacea (paddy straw), has been done with different solvent systems (chloroform, ethyl acetate, ether and methanol) and tested against a wide range of phytopathogens by filter paper disk assay. All the three basidiomycetes inhibited the phytopathogens tested so far. This enumeration was based on the number of organisms inhibited and the diameter of inhibitory zones produced. From the results obtained, it could be observed that ethyl acetate was the best solvent for extracting antimicrobial substances from these medicinal mushrooms. Thin layer chromatography revealed the presence of several compounds with different Retention Factor (RF) values. Sodium dodecyl sulphate–polyacrylamide gel electrophoresis profiling of V. volvacea showed the presence of several antimicrobial proteins with various molecular weights. Western blotting revealed the presence of thaumatin-like glycoproteins of molecular weight more than 45 kDa.     

Fungicidal property of active component derived from Acorus gramineus rhizome against phytopathogenic fungi

The fungicidal property of Acorus gramineus rhizome-derived materials against Botrytis cineria, Erysiphe graminis, Phytophthora infestans, Puccinia recondita, Pyricularia grisea, and Rhizoctonia solani was tested using a whole plant method in vivo, and was compared with a synthetic fungicide and seven commercially available A. gramineus rhizome-derived components. The responses varied according to the plant pathogen tested. At 2000 mg/l, the hexane fraction of A. gramineus rhizomes showed strong fungicidal activities against R. solani and P. infestans. The results indicated at least one of the fungicidal actions of alpha-asarone and asaronaldehyde derived from A. gramineus rhizomes.     

Mycoparasitism studies of Trichoderma species against three phytopathogenic fungi: evaluation of antagonism and hydrolytic enzyme production

Trichoderma spp. are used for biocontrol of several plant pathogens. However, their efficient interaction with the host needs to be accompanied by production of secondary metabolites and cell wall-degrading enzymes. Three parameters were evaluated after interaction between four Trichoderma species and plant-pathogenic fungi: Fusarium solani, Rhizoctonia solani and Sclerotinia sclerotiorum. Trichoderma harzianum and T. asperellum were the most effective antagonists against the pathogens. Most of the Trichoderma species produced toxic volatile metabolites, having significant effects on growth and development of the plant pathogens. When these species were grown in liquid cultures with cell walls from these plant pathogens, they produced and secreted β-1,3-glucanase, NAGAse, chitinase, acid phosphatase, acid proteases and alginate lyase.