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1.
Ectomycorrhizal fungi can produce antifungal compounds in vitro as well as in symbiosis with the host plant that can reduce root diseases. The objective of this study was to isolate antifungal compounds from culture filtrate of Paxillus sp. 60/92, which can form mycorrhizas with Picea glehnii seedlings. Culture filtrate of Paxillus sp. 60/92 showed antifungal activity against Pythium vexans at pH 3–4 but not at pH 5–10, although sterile MMN-b liquid medium (pH 3–10) did not show antifungal activity. Upon separation of antifungal compounds in the culture filtrate, antifungal activity was detected in the organic acid and water-soluble phenolics fractions adjusted to pH 3. Although antifungal activity of individual fractions was lower than that of the culture filtrate, a mixture of these fractions showed antifungal activity similar to that of the culture filtrate. Furthermore, antifungal activity of oxalic acid, which is known to be produced by Paxillus involutus, was increased by mixing with the water-soluble phenolic fraction. Our findings indicate that Paxillus sp. 60/92 produces organic acids and water-soluble phenolics that together show antifungal activity at pH 3–4 against P. vexans. 相似文献
2.
Sergio Saia Paolo Ruisi Veronica Fileccia Giuseppe Di Miceli Gaetano Amato Federico Martinelli 《PloS one》2015,10(6)
Arbuscular mycorrhizal fungi (AMF) have a major impact on plant nutrition, defence against pathogens, a plant’s reaction to stressful environments, soil fertility, and a plant’s relationship with other microorganisms. Such effects imply a broad reprogramming of the plant’s metabolic activity. However, little information is available regarding the role of AMF and their relation to other soil plant growth—promoting microorganisms in the plant metabolome, especially under realistic field conditions. In the present experiment, we evaluated the effects of inoculation with AMF, either alone or in combination with plant growth–promoting rhizobacteria (PGPR), on the metabolome and changes in metabolic pathways in the roots of durum wheat (Triticum durum Desf.) grown under N-limited agronomic conditions in a P-rich environment. These two treatments were compared to infection by the natural AMF population (NAT). Soil inoculation with AMF almost doubled wheat root colonization by AMF and decreased the root concentrations of most compounds in all metabolic pathways, especially amino acids (AA) and saturated fatty acids, whereas inoculation with AMF+PGPR increased the concentrations of such compounds compared to inoculation with AMF alone. Enrichment metabolomics analyses showed that AA metabolic pathways were mostly changed by the treatments, with reduced amination activity in roots most likely due to a shift from the biosynthesis of common AA to γ-amino butyric acid. The root metabolome differed between AMF and NAT but not AMF+PGPR and AMF or NAT. Because the PGPR used were potent mineralisers, and AMF can retain most nitrogen (N) taken as organic compounds for their own growth, it is likely that this result was due to an increased concentration of mineral N in soil inoculated with AMF+PGPR compared to AMF alone. 相似文献
3.
Claudia M. Ribaudo Evelyn M. Krumpholz Fabricio D. Cassán Rubén Bottini María L. Cantore José A. Curá 《Journal of Plant Growth Regulation》2006,25(2):175-185
Tomato seeds were inoculated with the plant growth–promoting rhizobacteria Azospirillum brasilense FT326, and changes in parameters associated with plant growth were evaluated 15 days after inoculation. Azospirilla were localized on roots and within xylematic tissue. An increase in shoot and root fresh weight, main root hair length, and
root surface indicated that inoculation with A. brasilense FT 326 resulted in plant growth improvement. The levels of indole-3-acetic acid (IAA) and ethylene, two of the phytohormones related
to plant growth, were higher in inoculated plants. Exogenously supplied ethylene mimicked the effect of inoculation, and the
addition of an inhibitor of its synthesis or of its physiological activity completely blocked A. brasilense growth promotion. Based on our results, we propose that the process of growth promotion triggered by A. brasilense inoculation involves a signaling pathway that has ethylene as a central, positive regulator. 相似文献
4.
New strains of Beijerinckia mobilis and Clostridium sp. isolated from the pea rhizosphere were studied with respect to their promoting effect on the growth and development of some agricultural crops. Seed soaking in bacterial suspensions followed by the soil application of the suspensions or their application by means of foliar spraying was found to be the most efficient method of bacterization. The application of B. mobilis andClostridium sp. cultures in combination with mineral fertilizers increased the crop production by 1.5–2.5 times. The study of the population dynamics of B. mobilis by the method of genetic marking showed that this bacterium quickly colonized the rhizoplane of plants and, therefore, had characteristics of an r-strategist. At the same time, Clostridiumsp. was closer to K-strategists, since this bacterium slowly colonized the econiches studied. The introduction of the bacteria into soil did not affect the indigenous soil bacterial complex. The presence of Clostridium sp. slowed down the colonization of roots by the fungal mycelium. The possible mechanisms of the plant growth–promoting activity of B. mobilisand Clostridiumsp. are discussed. 相似文献
5.
Potential for improving pea production by co-inoculation with fluorescent Pseudomonas and Rhizobium 总被引:2,自引:0,他引:2
Seed bacterization with five plant growth promoting fluorescent Pseudomonas strains isolated from Indian and Swedish soils and three Rhizobium leguminosarumbiovar viceae strains isolated from Swedish soils were shown to promote plant growth in Pisum sativum L. cv. Capella. Co-inoculation of the fluorescent pseudomonads and Rhizobium improved plant growth in terms of shoot height, root length and dry weight. Both the fluorescent pseudomonads and Rhizobium were shown to exhibit a wide range of antifungal activity against pathogens specific to pea. Seed bacterization with plant growth promoting strains alone and together with a rhizobial isolate, R 361-27 reduced the number of infected peas grown in Fusarium oxysporum infested soils. We found that the introduced organisms were able to colonize the roots, which was confirmed using immunofluorescence staining and drug resistant mutant strains. In a synthetic culture medium, all the plant growth promoting fluorescent pseudomonads strains produced siderophores, which shown to express antifungal and antibacterial activity. Our results suggest the potential use of these bacteria to induce plant growth and disease suppression in sustainable agriculture production systems. 相似文献
6.
Qualitative enzyme assays were used as a tool to investigate the stability of freeze-dried mycorrhizal fungi. Both lyophilized (L) and non-lyophilized (NL) mycelia of individual isolates showed identical response for all the enzymes tested (nitrate reductase, protease, pectinase, and nuclease). All the isolates showed positive nitrate reductase activity, except two isolates of Thelephora terrestris (both L and NL). Both L and NL cultures of individual isolates showed substrate specificity (between gelatin and casein) for protease activity. Though both L and NL mycelia of all the culture isolates grew upon pectin substrate, there was no pectinase activity expressed. RNAase activity was variously exhibited (little activity, little growth–no activity, and no growth–no activity) by individual test cultures. The consistencies in growth and enzyme activity of the cultures before and after lyophilization imply the stability of the freeze-dried vegetative mycelium. 相似文献
7.
Aseptic tomato and radish roots were found to exude, respectively, 2.8–5.3 and 290–390 ng tryptophan per seedling per day. The inoculation of radish plants with rhizosphere pseudomonads increased the root biomass by 1.4 times. The inoculation of tomato plants with the same pseudomonads was ineffective. The beneficial effect of bacterial inoculation on the radish plants can be explained by the fact that the introduced rhizobacteria produce the plant growth–stimulating hormone indole-3-acetic acid. In pot experiments, the addition of this phytohormone to the soil increased the mass of radish roots by 36%. The phytohormonal action of the rhizosphere microflora was found to be efficient provided that the concentration of tryptophan in the rhizosphere is sufficiently high. 相似文献
8.
Wim Grunewald Giel van Noorden Gert Van Isterdael Tom Beeckman Godelieve Gheysen Ulrike Mathesius 《The Plant cell》2009,21(9):2553-2562
The plant rhizosphere harbors many different microorganisms, ranging from plant growth–promoting bacteria to devastating plant parasites. Some of these microbes are able to induce de novo organ formation in infected roots. Certain soil bacteria, collectively called rhizobia, form a symbiotic interaction with legumes, leading to the formation of nitrogen-fixing root nodules. Sedentary endoparasitic nematodes, on the other hand, induce highly specialized feeding sites in infected plant roots from which they withdraw nutrients. In order to establish these new root structures, it is thought that these organisms use and manipulate the endogenous molecular and physiological pathways of their hosts. Over the years, evidence has accumulated reliably demonstrating the involvement of the plant hormone auxin. Moreover, the auxin responses during microbe-induced de novo organ formation seem to be dynamic, suggesting that plant-associated microbes can actively modify their host''s auxin transport. In this review, we focus on recent findings in auxin transport mechanisms during plant development and on how plant symbionts and parasites have evolved to manipulate these mechanisms for their own purposes. 相似文献
9.
Plant defensins are small, highly stable, cysteine-rich antimicrobial proteins that are thought to constitute an important
component of plant defense against fungal pathogens. There are a number of such defensins expressed in various plant tissues
with differing antifungal activity and spectrum. Relatively little is known about the modes of action and biological roles
of these proteins. Our previous work on a virally encoded fungal toxin, KP4, from Ustilago maydis and subsequently with the plant defensin, MsDef1, from Medicago sativa demonstrated that some of these proteins specifically blocked calcium channels in both fungi and animals. The results presented
here demonstrate that KP4 and three plant defensins, MsDef1, MtDef2, and RsAFP2, all inhibit root growth in germinating Arabidopsis seeds at low micromolar concentrations. We have previously demonstrated that a fusion protein composed of Rab GTPase (RabA4b)
and enhanced yellow fluorescent protein (EYFP) is dependent upon calcium gradients for localization to the tips of the growing
root hairs in Arabidopsis thaliana. Using this tip-localized fusion protein, we demonstrate that all four proteins rapidly depolarize the growing root hair
and block growth in a reversible manner. This inhibitory activity on root and root hair is not directly correlated with the
antifungal activity of these proteins and suggests that plants apparently express targets for these antifungal proteins. The
data presented here suggest that plant defensins may have roles in regulating plant growth and development.
A. Allen and A.K. Snyder contributed equally. 相似文献
10.
Different promoter regions control level and tissue specificity of expression of Agrobacterium rhizogenes rolB gene in plants 总被引:6,自引:0,他引:6
I. Capone M. Cardarelli D. Mariotti M. Pomponi A. De Paolis P. Costantino 《Plant molecular biology》1991,16(3):427-436
Expression of the rolB gene of A. rhizogenes T-DNA triggers root differentiation in transformed plant cells. In order to study the regulation of this morphogenetic gene, the GUS reporter gene was placed under the control of several deleted fragments of the rolB 5 non-coding region: carrot disc transformations and the analysis of transgenic tobacco plants containing these constructions identified the presence of distinct regulatory domains in the rolB promoter. Two regions (located from positions –623 to –471 and from –471 to –341, from the translation start codon) control the level but not the tissue specificity of rolB expression: progressive deletions of the rolB promoter starting from position –1185 to –341, although at different levels, maintained the same pattern of GUS expression — maximal in root meristems and less pronounced in the vascular tissue of aerial organs. Further deletion of 35 bp, from –341 to –306, drastically affected tissue specificity: GUS activity was still clearly detectable in the vascular tissue of the aerial organs while expression in the root meristem was totally suppressed. Analysis of transgenic embryos and seedlings confirmed that distinct promoter domains are responsible for meristematic (root) and differentiated (vascular) expression of rolB. Finally, we present data concerning the effects of plant hormones on the expression of rolB-GUS constructions. 相似文献
11.
Pishchik V.N. Vorobyev N.I. Chernyaeva I.I. Timofeeva S.V. Kozhemyakov A.P Alexeev Y.V. Lukin S.M. 《Plant and Soil》2002,243(2):173-186
Bacterial inoculants of the commercially available plant growth promoting rhizobacteria (PGPR) Arthrobacter mysorens 7, Flavobacterium sp. L30, and Klebsiella mobilis CIAM 880 were selected to obtain ecologically safe barley crop production on cadmium (Cd) polluted soils. All the PGPR immobilized 24–68% soluble cadmium from soil suspension. A. mysorens 7 and K. mobilis CIAM 880 were highly resistant to Cd and grew in up to 1 and 3 mmol CdCl2 on DAS medium respectively. All PGPR were able to fix nitrogen (276–1014 nmol mg–1 bacterial DW) and to produce indole acetic acid (IAA) (126–330 nmol mg–1 bacterial DW) or ethylene (4.6–13.5 nmol bacterial DW). All the PGPR actively colonized barley root system and rhizosphere and significantly stimulated root elongation of barley seedlings (up to 25%), growing on soil containing 5 or 15 mg Cd kg–1 of soil. Created in the simulation mathematical model confirms our hypothesis that PGPR beneficial effect on barley growing under Cd-stress is a complex process. One of mechanisms underlying this effect might be increase of bacterial migration from rhizoplane to rhizosphere, where PGPR bind soluble free Cd ions in biologically unavailable complex forms. Among the studied PGPR K. mobilis CIAM 880 was the most effective inoculant. Inoculation with K. mobilis CIAM 880 of barley plants growing on Cd contaminated soil (5 mg Cd kg–1 of soil) under field conditions increased by 120% grain yield and 2-fold decreased Cd content in barley grain. The results suggest that the using K. mobilis CIAM 880 is an effective way to increase the plant yield on poor and polluted areas. 相似文献
12.
F. Vinale E.L. Ghisalberti G. Flematti R. Marra M. Lorito K. Sivasithamparam 《Letters in applied microbiology》2010,50(4):380-385
Aims: A sterile red fungus (SRF) isolated from cortices of roots of both wheat (Triticum aestivum cv. Gamenya) and ryegrass (Lolium rigidum cv. Wimmera) was found to protect the hosts from phytopathogens and promote plant growth. In this work, the major secondary metabolites produced by this SRF were analysed, and their antibiotic and plant‐growth‐promoting activities investigated. Methods and Results: Two main compounds, veratryl alcohol (VA) and 4‐(hydroxymethyl)‐quinoline, were isolated from the culture filtrate of the fungus. In antifungal assays, VA inhibited the growth of Sclerotinia sclerotiorum and Pythium irregulare even at low amounts, while high concentrations (>100 μg per plug) of 4‐(hydroxymethyl)‐quinoline were needed. Both metabolites revealed weak inhibition of Rhizoctonia solani. Furthermore, both compounds showed a growth promotion activity on canola (Brassica napus) seedlings used as bioassays. Conclusions: Isolation and characterization of the main secondary metabolites from culture filtrates of a root‐inhabiting sterile fungus are reported. The biological assays indicate that these secondary metabolites may have a role in both plant growth regulation and antifungal activity. Significance and Impact of the Study: This study provides a better understanding of the metabolism of a cortical fungus that may have a useful role in the biological suppression of root‐infecting soil‐borne plant pathogens. 相似文献
13.
A hydroxamate type siderophore producing fluorescent Pseudomonas strain, isolated from the rhizoplane of paddy root showing plant growth promoting activity, exhibited a decreased in vitro antibiosis, production of siderophore and suppression of collar rot in presence of metham sodium. Use of herbicide had a detrimental effect on the plant growth promoting activity of this organism. The multiple drug resistant mutant strain derived from this rhizobacteria colonized the roots, but the herbicide application had a negative effect on their population. HPLC analysis of the siderophore showed five peaks of which the peak number three confirmed the antifungal activity. 相似文献
14.
Kravchenko LV Azarova TS Leonova-Erko EI Shaposhnikov AI Makarova NM Tikhonovich IA 《Mikrobiologiia》2003,72(1):48-53
The study of the effect of the root exometabolites of tomato plants on the growth and antifungal activity of the plant growth-promoting Pseudomonas strains showed that the antifungal activity of plant growth-promoting rhizobacteria in the plant rhizosphere may depend on the sugar and organic acid composition of root exudates. 相似文献
15.
The ecophysiological characteristics of fine roots of mature forest plants are poorly understood because of difficulties of measurement. We explored a root in-growth approach to measure respiration and nitrate uptake of woody plant roots in situ. Roots of seven species were grown into sand-filled chambers. Root-associated respiration was measured as CO 2 emission on four dates and nitrate uptake was quantified using 15N. All the roots were younger than 3 months at the time of measurement. Fine root respiration measured over the temperature range of 14.5–15.5 °C averaged 18.9–36.5 nmol gDM –1 s –1 across species. Nitrate uptake rates by these fine roots (1.3–6.8 nmol gDM –1 s –1) were comparable to other studies of forest trees. The root respiration rates were several times higher than measurements on detached roots of mature trees, concurring with literature observations that young roots respire much more rapidly than older roots. The root in-growth approach appears promising for providing information on the metabolic activity of fine roots of mature forest trees growing in soil. 相似文献
16.
Arvind Gulati Natasha Sharma Pratibha Vyas Swati Sood Praveen Rahi Vijaylata Pathania Ramdeen Prasad 《Archives of microbiology》2010,192(11):975-983
An efficient phosphate-solubilizing plant growth–promoting Acinetobacter rhizosphaerae strain BIHB 723 exhibited significantly higher solubilization of tricalcium phosphate (TCP) than Udaipur rock phosphate (URP),
Mussoorie rock phosphate (MRP) and North Carolina rock phosphate (NCRP). Qualitative and quantitative differences were discerned
in the gluconic, oxalic, 2-keto gluconic, lactic, malic and formic acids during the solubilization of various inorganic phosphates
by the strain. Gluconic acid was the main organic acid produced during phosphate solubilization. Formic acid production was
restricted to TCP solubilization and oxalic acid production to the solubilization of MRP, URP and NCRP. A significant increase
in plant height, shoot fresh weight, shoot dry weight, root length, root dry weight, and root, shoot and soil phosphorus (P)
contents was recorded with the inoculated treatments over the uninoculated NP0K or NPTCPK treatments. Plant growth promotion as a function of phosphate solubilization suggested that the use of bacterial strain
would be a beneficial addition to the agriculture practices in TCP-rich soils in reducing the application of phosphatic fertilizers. 相似文献
17.
A collection of bacterial strains obtained from a wide-range origin was screened for ability to promote growth in two types of Prunus rootstocks in a commercial nursery. Only few strains promoted growth significantly and consistently, and a strong specificity for the rootstock cultivar was observed. Irrigation of plants with Pseudomonas fluorescens EPS282 and Pantoea agglomerans EPS427 significantly increased plant height and root weight of the plum Marianna 2624 and the peach–almond hybrid GF-677, respectively. Plant height showed a higher rate of growth in early stages of development (2.6–3.5 times the non-treated controls), but the effect decreased with plant age. However, in aged plants growth promotion was more significant on root weight (1.9 times the non-treated controls) than on plant height. The efficacy of growth promotion and the persistence of strains in the root environment were dependent on the bacterial inoculum concentration applied. Increases in root development were maximum at inoculum concentrations of up to 8 log10 CFU ml–1 (ca 10 log10 CFU L–1 of potting mix). Population levels at the optimum inoculum concentration were around 7 log10 CFU g f.w.–1 root material at early stages of development and decreased to 4 log10 CFU g f.w.–1 after several months of development. The best plant growth-promoting strains were very diverse in secondary metabolite production and antagonistic ability against several plant pathogens. 相似文献
18.
Plant defensins are small, highly stable, cysteine-rich antimicrobial peptides produced by the plants for inhibiting a broad-spectrum
of microbial pathogens. Some of the well-characterized plant defensins exhibit potent antifungal activity on certain pathogenic
fungal species only. We characterized a defensin, TvD1 from a weedy leguminous herb, Tephrosia villosa. The open reading frame of the cDNA was 228 bp, which codes for a peptide with 75 amino acids. Expression analyses indicated
that this defensin is expressed constitutively in T. villosa with leaf, stem, root, and seed showing almost similar levels of high expression. The recombinant peptide (rTvD1), expressed
in the Escherichia coli expression system, exhibited potent in vitro antifungal activity against several filamentous soil-borne fungal pathogens.
The purified peptide also showed significant inhibition of root elongation in Arabidopsis seedlings, subsequently affecting the extension of growing root hairs indicating that it has the potential to disturb the
plant growth and development. 相似文献
19.
To test whether plant growth–promoting bacteria might be useful in facilitating the growth of Phragmites australis, the common reed, in the presence of metals and organic compounds, P. australis seeds were treated with plant growth–promoting bacteria. The bacterium Pseudomonas asplenii AC was genetically transformed to express a bacterial gene encoding the enzyme 1-aminocyclopropane-1-carboxylate deaminase,
and both the native and transformed bacteria were tested in conjunction with P. australis. Inoculation of seeds, which were subsequently grown in the presence of copper or creosote, with transformed P. asplenii AC significantly increased seed germination. Moreover, the addition of either native or transformed P. asplenii AC to P. australis seeds enabled the plants (shoots and roots) to attain a greater size than noninoculated plants after growth in soil in the
presence of either copper or creosote. 相似文献
20.
Summary The effect of exogenous applications of gibberellins (GAs) or the growth retardant -chloroethyltrimethylammonium chloride (CCC) on root nodule formation and activity (C2H2-reduction) in soya was studied. Daily foliar application of GA3 (2.89×10–6
M) delayed the formation of nodule initials and reduced the numbers mass nodule–1 and specific activity of nodules by 43%, 31% and 47% respectively, without affecting plant growth. Similar effects on nodulation were produced by foliar application of GA4 (3.01×10–5
M) or GA7 (3.03×10–5
M), or by the addition of GA3 (2.89×10–6
M) to the rooting medium. GA effectiveness in reducing nodule numbers was decreased by delaying its application until after the initial infection process had occurred, but the nodules formed were smaller and less active than those of the untreated control plants. The GA effect on nodulation and nodule activity was not associated with alterations in root exudate or due to a direct inhibitory effect of the hormone on the nitrogenase system. When the endogenous root content of GA-like substances was reduced (86% decrease) by foliar application of CCC (6.30×10–5
M), nodule numbers were increased by 56%, but nodule size and total nodule activity were similar to those of control plants. The GA and CCC treatments had no effect on rhizobial growth in liquid culture nor on root colonisation by rhizobia.The results suggest that the endogenous content of root GA may have a regulatory role in both the infection process and in subsequent nodule morphogenesis, thus controlling both the number and effectiveness of the root nodules formed. 相似文献