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1.
Rock phosphate （RP） is a low efficiency P fertilizer that is directly applied to the soil and can be solubilized by phosphate-solubilizing microorganisms （PSMs） in fermentation or soil conditions. This study investigated dynamic solubilization of 2 concentrations of rock phosphate in a liquid culture with different dosages of glucose by two fungal isolates,Aspergillus niger P39 and Penicillium oxalicum P66, from soybean and wheat rhizosphere soil. Although during the 20 day culture period A. niger P39 had a stronger ability to acidify the culture media than P. ozalicum P66, soluble P concentrations at glucose dosages of 30 and 50 g L^-1 with RP of 15 g L^-1 in the culture solution were much higher by P. oxalicum P66. The greater effectiveness of P. oxalicum P66 compared to A. niger P39 in the solubilization of RP was strongly associated with the production of organic acids. This study suggested that for RP solubilization the type rather than the concentration of PSM-produced organic acids was more important.  相似文献   

2.
Many soil microorganisms are able to transform insoluble forms of phosphorus to an accessible soluble form, contributing to plant nutrition as plant growth-promoting microorganisms (PGPM). The objective of this work was to isolate, screen and evaluate the phosphate solubilization activity of microorganisms in maize rhizosphere soil to manage soil microbial communities and to select potential microbial inoculants. Forty-five of the best isolates from 371 colonies were isolated from rhizosphere soil of maize grown in an oxisol of the Cerrado Biome with P deficiency. These microorganisms were selected based on the solubilization efficiency of inorganic and organic phosphate sources in a modified Pikovskaya's liquid medium culture containing sodium phytate (phytic acid), soybean lecithin, aluminum phosphate (AlPO4), and tricalcium phosphate (Ca3(PO4)2). The isolates were identified based on nucleotide sequence data from the 16S ribosomal DNA (rDNA) for bacteria and actinobacteria and internal transcribed spacer (ITS) rDNA for fungi. Bacteria produced the greatest solubilization in medium containing tricalcium phosphate. Strains B17 and B5, identified as Bacillus sp. and Burkholderia sp., respectively, were the most effective, mobilizing 67% and 58.5% of the total P (Ca3(PO4)2) after 10 days, and were isolated from the rhizosphere of the P efficient L3 maize genotype, under P stress. The fungal population was the most effective in solubilizing P sources of aluminum, phytate, and lecithin. A greater diversity of P-solubilizing microorganisms was observed in the rhizosphere of the P efficient maize genotypes suggesting that the P efficiency in these cultivars may be related to the potential to enhance microbial interactions of P-solubilizing microorganisms.  相似文献   

3.
A range of low-molecular-weight organic acids were identified in rhizosphere soil, leaf litter, and poultry manure compost. Laboratory and greenhouse experiments were carried out to examine the effects of seven low-molecular-weight organic acids on phosphate adsorption by soils, and the solubilization and plant uptake of P from soil pre-incubated with monocalcium phosphate and North Carolina phosphate rock. Acetic, formic, lactic (monocarboxylic), malic, tartaric, oxalic (dicarboxylic), and citric (tricarboxylic) acids were used in the study. The addition of organic acids decreased the adsorption of P by soils in the order tricarboxylic acid>dicarboxylic acid>monocarboxylic acid. The decreases in P adsorption with organic acid addition increased with an increase in the stability constant of the organic acid for Al (logK Al). Organic acids extracted greater amounts of P from soils meubated with both monocalcium phosphate and phosphate rock than water did. Although more phosphate was extracted by the organic acids from monocalcium phosphate — than from phosphate rock — treated soils in absolute terms, when the results were expressed as a percentage of dissolved phosphate there was little difference between the two fertilizers. The amount of P extracted by the organic acids from both fertilizers increased with an increase in logK Al values. The addition of oxalic and citric acids increased the dry matter yield of ryegrass and the uptake of P in soils treated with both fertilizers. The agronomic effectiveness of both fertilizers increased in the presence of organic acids and the increase was greater with the phosphate rock than with the monocalcium phosphate. The results indicated that organic acids increase the availability of P in soils mainly through both decreased adsorption of P and increased solubilization of P compounds.  相似文献   

4.
黑土区高效溶磷真菌筛选及其溶解磷矿粉效果的研究   总被引：6，自引：1，他引：6  
黑土区高效溶P真菌筛选及其溶解磷矿粉效果的试验结果表明 ,溶P真菌溶P效果高于溶P细菌 ,且其溶P性状稳定。曲霉菌“P39”、“P37”和青霉菌“P6 6”、“P1”溶P效果高于其他供试菌 ,菌株之间溶P活性与培养液pH值和有机酸含量间不存在必然相关性 ,推测不同菌株间溶P活性差异与菌株产生的有机酸种类和数量有关  相似文献   

5.
 The phosphate-solubilizing potential of the rhizosphere microbial community in mangroves was demonstrated when culture media supplemented with insoluble, tribasic calcium phosphate, and incubated with roots of black (Avicennia germinans L.) and white [Laguncularia racemosa (L.) Gaertn.] mangrove became transparent after a few days of incubation. Thirteen phosphate-solubilizing bacterial strains were isolated from the rhizosphere of both species of mangroves: Bacillus amyloliquefaciens, Bacillus licheniformis, Bacillus atrophaeus, Paenibacillus macerans, Vibrio proteolyticus, Xanthobacter agilis, Enterobacter aerogenes, Enterobacter taylorae, Enterobacter asburiae, Kluyvera cryocrescens, Pseudomonas stutzeri, and Chryseomonas luteola. One bacterial isolate could not be identified. The rhizosphere of black mangroves also yielded the fungus Aspergillus niger. The phosphate-solubilizing activity of the isolates was first qualitatively evaluated by the formation of halos (clear zones) around the colonies growing on solid medium containing tribasic calcium phosphate as a sole phosphorus source. Spectrophotometric quantification of phosphate solubilization showed that all bacterial species and A. niger solubilized insoluble phosphate well in a liquid medium, and that V. proteolyticus was the most active solubilizing species among the bacteria. Gas chromatographic analyses of cell-free spent culture medium from the various bacteria demonstrated the presence of 11 identified, and several unidentified, volatile and nonvolatile organic acids. Those most commonly produced by different species were lactic, succinic, isovaleric, isobutyric, and acetic acids. Most of the bacterial species produced more than one organic acid whereas A. niger produced only succinic acid. We propose the production of organic acids by these mangrove rhizosphere microorganisms as a possible mechanism involved in the solubilization of insoluble calcium phosphate. Received: 21 April 1999  相似文献   

6.
This study determined the cell density in the field and the biological activity of culturable phosphate-solubilizing microorganisms (PSMs) present in the Elaeis guineensis Jacq. rhizosphere at two locations in a commercial plantation. Promising isolates found in two soils under different agronomic management conditions were selected. We first calculated the cell density of cultivable PSMs grown in SRS medium (Sundara-Rao and Sinha, 1963) supplemented with the insoluble phosphate sources Ca3(PO4)2, AlPO4, and FePO4. Twenty-two bacteria, ten filamentous fungi, and eight yeast isolates were found. The 16 isolates with the clearest P solubilization halo in Petri dishes were selected to estimate their P solubilization potential in SRS medium with Ca3(PO4)2. No solubilization activity was registered using AlPO4 or FePO4 as the P sources. Ten of the isolates presented solubilization efficiencies between 20 and 82%. Some of these isolates showed high percentages of identity with the 16S and ITS rDNA sequences of the genera Aspergillus, Penicillium, Klebsiella, Burkholderia, and Staphylococcus according to the NCBI and EzTaxon-e databases. The solubilization activity of the isolates was associated with a decrease in the pH and the release of organic acids, such as gluconic, citric, succinic, and acetic acids. Gluconic acid was mainly released by the genera Aspergillus and Penicillium, and these isolates also showed the highest solubilization activities (82 and 80%, respectively). Therefore, these isolates were selected as the most promising isolates present in the oil palm rhizosphere for phosphate solubilization.  相似文献   

7.
In this study we found that Penicillium spp. exhibiting P-solubilizing activity are common both on and in the roots of wheat plants grown in southern Australian agricultural soils. From 2,500 segments of washed and surface-disinfested root pieces, 608 and 223 fungi were isolated on a selective medium, respectively. All isolates were screened for P solubilization on solid medium containing hydroxyapatite (HA); 47 isolates (5.7%) solubilized HA and were identified as isolates of Penicillium or its teleomorphs. These isolates were evaluated for solubilization of Idaho rock phosphate (RP) in liquid culture. Penicillium bilaiae strain RS7B-SD1 was the most effective, mobilizing 101.7 mg P l–1 after 7 days. Other effective isolates included Penicillium simplicissimum (58.8 mg P l–1), five strains of Penicillium griseofulvum (56.1–47.6 mg P l–1), Talaromyces flavus (48.6 mg P l–1) and two unidentified Penicillium spp. (50.7 and 50 mg P l–1). A newly isolated strain of Penicillium radicum (KC1-SD1) mobilized 43.3 mg P l–1. RP solubilization, biomass production and solution pH for P. bilaiae RS7B-SD1, P. radicum FRR4718 or Penicillium sp. 1 KC6-W2 was determined over time. P. bilaiae RS7B-SD1 solubilized the greatest amount of RP (112.7 mg P l–1) and had the highest RP-solubilizing activity per unit of biomass produced (up to 603.2 g P l–1 mg biomass–1 at 7 days growth). This study has identified new isolates of Penicillium fungi with high mineral phosphate solubilizing activity. These fungi are being investigated for the ability to increase crop production on strong P-retaining soils in Australia.  相似文献   

8.
三种溶磷真菌对不同磷源溶解效果的比较研究   总被引：2，自引：0，他引：2  
报道了溶磷菌株P39(Aspergilusspp.)和P66、P2.3(Penicilliumspp.)在液体培养条件下对5种难溶性磷源的溶解效果。试验结果表明,3种溶磷菌株在所有磷源培养基中生长良好,但它们之间的溶磷量相差很大,菌株P39对不同磷源的溶磷效果为磷酸铁>磷酸铝>磷酸钙>宜昌磷矿粉>摩洛哥磷矿粉,其溶磷率分别达到96.60%、84.00%、66.05%、61.43%和41.52%;P66菌株对不同磷源的溶磷效果为磷酸铝>磷酸钙>摩洛哥磷矿粉>宜昌磷矿粉>磷酸铁,溶磷率分别为78.18%、58.45%、41.09%、33.00%和14.27%;而菌株P2.3对不同磷源的溶磷效果要小于菌株P39和P66,研究结果表明P2.3菌株对磷酸铁不具有溶磷活性,对其它4种不同磷源的溶磷效果为磷酸钙>磷酸铝>摩洛哥磷矿粉>宜昌磷矿粉。对不同菌株培养滤液可滴定酸含量和pH测定结果发现,菌株P39的培养滤液可滴定酸含量与pH值之间存在直线相关,菌株P66和P2.3处理的二者相关性不显著,表明不同的溶磷菌株在不同磷源条件下,可能从有机酸组成和含量两方面发生了变化而影响对难溶性磷的溶解。  相似文献   

9.
《Soil biology & biochemistry》2001,33(12-13):1741-1747
Two Venezuelan phosphate rocks (PRs), apatite deposits from Monte-Fresco and Navay areas, and two minerals, Florida apatite and Utah variscite were used to investigate phosphate solubilization by the wild type strain IR-94MF1 of Penicillium rugulosum initially selected for its high mineral phosphate activity (Mps+) and two of its mutants Mps++ and Mps−. In liquid cultures, the three fungal strains showed better growth on the Navay PR than on Monte Fresco PR. The Utah variscite was the best phosphorus (P) source for the growth of the wild type and the Mps++ mutant. Solubilization of the various P sources by the wild-type IR-94MF1 and the Mps++ mutant resulted mostly from the action of organic acids. Citric acid seemed to be more active agent for the solubilization of the Utah variscite while gluconic acid appeared to be responsible for the solubilization of the Florida apatite and the Monte Fresco PR. Both organic acids are likely involved in the solubilization of the Navay PR. The Mps- mutant did not produce any organic acid when grown on all the P sources used.  相似文献   

10.
ABSTRACT

Dissolution of phosphate rocks (PR) in soils requires an adequate supply of acid (H+) and the removal of the dissolved products [calcium (Ca2 +) and dihydrogen phosphate (H2PO4 ?)]. Plant roots may excrete H+ or OH? in quantities that are stoichiometrically equal to excess cation or anion uptake in order to maintain internal electroneutrality. Extrusion of H+ or OH? may affect rhizosphere pH and PR dissolution. Differences in rhizosphere acidity and solubilization of three PRs were compared with triple superphosphate between a grass (Brachiaria decumbens) and a legume (Stylosanthes guianensis) forage species at two pH levels (4.9 and 5.8) in a phosphorus (P)-deficient Ultisol with low Ca content. The experiment was performed in a growth chamber with pots designed to isolate rhizosphere and non-rhizosphere soil. Assessment of P solubility with chemical extractants led to ranking the PRs investigated as either low (Monte Fresco) or high solubility (Riecito and North Carolina). Solubilization of the PRs was influenced by both forage species and mineral composition of the PR. The low solubility PR had a higher content of calcite than the high solubility PRs, which led to increased soil pH values (> 7.0) and exchangeable Ca, and relatively little change in bicarbonate-extractable soil P. Rhizosphere soil pH decreased under Stylosanthes but increased under Brachiaria. The greater ability of Stylosanthes to acidify rhizosphere soil and solubilize PR relative to Brachiaria is attributed to differences between species in net ion uptake. Stylosanthes had an excess cation uptake, defined by a large Ca uptake and its dependence on N2 fixation, which induced a significant H+ extrusion from roots to maintain cell electroneutrality. Brachiaria had an excess of anion uptake, with nitrate (NO3 ?) comprising 92% of total anion uptake. Nitrate and sulfate (SO4 2 ?) reduction in Brachiaria root cells may have generated a significant amount of cytoplasmic hydroxide (OH?), which could have increased cytoplasmic pH and induced synthesis of organic acids and OH? extrusion from roots.  相似文献   

11.
Organic acid concentration in the proteoid rhizosphere of White Lupin in different soil samples (Oxisol-Ap = Ox, Luvisol-Ap and Luvisol-C = LA and LC) was determined in order to study the influence of root-released carboxylates on the mobilization of phosphate, aluminum, and iron in the rhizosphere. In the LC, organic acids were accumulated as Casalts extractable with water. In the proteoid rhizosphere of this soil sample 55 μmol citrate and 8 μmol malate per g soil were found. In the Ox, no water extractable organic acids were present. However, determination of citrate in the solid phase of this soil by Diffuse Reflectance Infrared Fourier Transform Spectroscopy gave concentrations of 88 and 68 μmol citrate per g soil without and with P application, respectively. Displaced soil solution from the proteoid root rhizosphere of the Ox and the LA increased in Fe and Al concentrations from <50 μmol/L (soil from reference pots without plants) to more than 600 μmol Fe+Al/L. The concentration of P was increased by a factor of 2 despite of P uptake by the proteoid roots. The mobilization of Al, Fe, and P is attributed to ligand exchange of phosphate against citrate and to the solubilization of Al and Fe as carboxylate complexes.  相似文献   

12.
Ericoid mycorrhizal fungi increase the ability of their host plants to colonize soils polluted with toxic metals, although the underlying mechanisms are not clearly understood. Two mycorrhizal strains of Oidiodendron maius isolated from contaminated soil were previously shown to tolerate high concentrations of toxic metals. We investigated further the biological mechanisms that may explain metal tolerance, focussing on the interactions between insoluble metal species and extracellular fungal metabolites. In particular, we demonstrate that fungal strains derived from polluted and unpolluted soils mobilize insoluble inorganic zinc compounds to different extents. Strains from polluted soils showed in fact little ability to solubilize Zn from both ZnO and Zn3(PO4)2, whereas strains from unpolluted soils showed a higher solubilization potential. This different behaviour was confirmed when the solubilization abilities of a wider range of fungal strains (25 isolates) was examined. Induction of organic acids (malate and citrate) by the metal compounds was at least in part responsible for metal solubilization. Our results suggest that ericoid mycorrhizal strains from polluted and unpolluted soils may interact differently with metal compounds. We speculate that this may reflect specific strategies to maintain homeostasis of essential metals under different soil conditions.  相似文献   

13.
ABSTRACT

Arbuscular mycorrhizal (AM) fungi can improve plant phosphorus (P) uptake; however, information about how AM fungi affect rhizosphere organic acid and microbial activity to alleviate citrus low P stress is limited. Here, a pot experiment was conducted to evaluate the effect of AM fungi (Rhizophagus intraradices, Ri) inoculation on rhizosphere organic acid content, microbial biomass (MB) and enzyme activity of trifoliate orange (Poncirus trifoliata L. Raf.) seedlings grown under three low P conditions. The results showed that mycorrhizal seedlings all recorded higher P concentrations, plant biomass and better root morphology with more lateral and fine roots, but lower root mass ratios, irrespective of P conditions. Mycorrhizal P absorption contribution did not differ significantly among three P conditions. Mycorrhizal seedling rhizosphere soil exhibited lower organic acid content, soil organic P content and ratio of MB-carbon (C)/MB-P, but higher MB and enzyme activity. Additionally, the main organic acids showed a negative relationship with mycorrhizal colonization rate and hyphal length; however, phosphatase and phytase activity had a significantly positive relationship with MB. Therefore, the results suggest that AM fungi inoculation may help citrus to efficiently utilize organic P source by improving microbial activity under low available P conditions.  相似文献   

14.
C、N源及C/N比对微生物溶磷的影响   总被引：19，自引：1，他引：19  
以不同的氮源 (NH4+、NO3- 、尿素 )、不同的碳源 (葡萄糖、蔗糖、糖蜜和淀粉 )及碳氮比 (34∶1、20∶1、5∶1)为培养基研究不同C、N源和C/N比对微生物溶磷的影响。结果发现 ,曲霉 2TCiF2和 4TCiF6在以NO3-为氮源的培养基中表现出强的解磷活力 ,而节杆菌 1TCRi7和 1TCRi14的溶磷活性则在NO3-存在时降低 ,青霉 1TCRiF5、2TCRiF4、肠杆菌 1TCRi15和欧文氏菌 4TCRi2 2则只有在供给NH4+时 ,才具有溶解磷矿粉的能力。加入少量可溶性磷对大多数微生物的溶磷能力没有显著的影响。曲霉 2TCiF2在蔗糖为碳源时溶磷活力最高 ,节杆菌 1TCRi7只有在葡萄糖为碳源时才具有溶磷能力。培养基的C/N比越高 ,曲霉和欧文氏杆菌的溶磷活力越高 ,而青霉和肠杆菌则在C/N比最低时 ,其溶磷活力最强。这些微生物之所以具有溶解磷矿粉的能力 ,主要是由于分泌有机酸 ,但非有机酸物质的络合和螯合作用 ,可能在肠杆菌和欧文氏菌溶磷中起重要作用。氮源、碳源和碳氮比极大地影响微生物的代谢 ,尤其对分泌有机酸等物质的种类可能产生很大的影响。  相似文献   

15.
The species‐specific microbial root and rhizosphere colonization contributes essentially to the plant nutrient supply. The species number and colonization densities of cultivable saprotrophic microfungi and the activities of nutrient‐releasing soil enzymes (protease, acid and alkaline phosphatase, arylsulfatase) were investigated in the rhizosphere of one low mycorrhizal (Salix viminalis) and one higher mycorrhizal (S. × dasyclados) willow clone at a Eutric Cambisol in N Germany. After soil washing, in total 32 and 28 saprotrophic microfungal species were isolated and identified microscopically from the rhizosphere of S. viminalis and S. × dasyclados, respectively. The fungal species composition changed within the growing season but the species number was always lower under S. × dasyclados than under S. viminalis. Under both willow clones, the fungal colonization density was largest in spring, and the species number was largest in autumn. Acid‐phosphatase activity (p < 0.001) and protease activity (p < 0.003) were significantly affected by the Salix clone, whereas arylsulfatase and alkaline‐phosphatase activities did not show clone‐specific differences. All enzyme activities reached their maxima in the summer sampling. Rhizosphere colonization with Acremonium butyri, Cladosporium herbarum, and Penicillium janthinellum contributed significantly to explain the activities of acid phosphatase. Rhizosphere colonization with Cylindrocarpon destructans, Penicillium spinulosum, Plectosphaerella cucumerina, and Trichoderma polysporum contributed significantly to explain the arylsulfatase activities. Effects of the saprotrophic fungal colonization densities on the protease activities in the rhizosphere were low. Acid‐ and alkaline‐phosphatase and arylsulfatase activities in the rhizosphere soil were stronger affected by the composition of the saprotrophic fungal communities than by the Salix clone itself. In conclusion, the colonization density of some saprotrophic microfungi in the rhizosphere contributed to explain shifts in soil‐enzyme activities of the P and S cycles under different willow clones.  相似文献   

16.
ABSTRACT

The exploitation of phosphate mines generates an important quantity of phosphate sludge that remains accumulated and not valorized. In this context, composting with organic matter and rhizospheric microorganisms offers an interesting alternative and that is more sustainable for agriculture. This work aims to investigate the synergetic effect of arbuscular mycorrhizal fungi (AMF), phosphate-solubilizing bacteria (PSB) and phospho-compost (PC), produced from phosphate-laundered sludge and organic wastes, and their combination on plant growth, phosphorus solubilization and phosphatase activities (alkaline and acid). Inoculated mycorrhizae and bacteria strains used in this study were selected from plant rhizosphere grown on phosphate-laundered sludge. Significant (p < .05) increases in plant growth was observed when inoculated with both consortia and PC (PC+ PSB+ AMF) similar to those recorded in plants amended with chemical fertilizer. Tripartite inoculated tomato had a significantly (p < .05) higher shoot height; shoot and root dry weight, root colonization and available P content, than the control. Co-inoculation with PC and AMF greatly increased alkaline phosphatase activity and the rate of mycorrhizal intensity. We conclude that PC and endophytic AMF and PSB consortia contribute to a tripartite inoculation in tomato seedlings and are coordinately involved in plant growth and phosphorus solubilization. These results open up promising prospects for using formulate phospho-compost enriched with phosphorus-solubilizing microorganisms (PSM) in crop cultivation as biofertilizers to solve problems of phosphate-laundered sludge accumulation.  相似文献   

17.
Four most efficient phytase and phosphatase producing fungi belonging to genera Aspergillus, Trichoderma, and Penicillium were isolated from the rhizosphere soil of leguminous, cereal, and vegetable crops. Efficacy order of fungi in terms of phytate hydrolysis under laboratory conditions was Aspergillus > Penicillium > Trichoderma. The test fungi released more of extracellular (E) phytase than intracellular (I) phytase (E: I- 3.44 - 6.03:1) and produced acid phosphatase activity ranging from 367- 830 μmol pNP ml?1 h?1. Aspergillus niger possessed the twin ability of phosphate mineralization and solubilization. The incubation studies in compost-amended soil exhibited the higher competence of Penicillium chrysogenum to improve the soil available P and increase the level of extractable organic P under alkaline soil to benefit P nutrition. Developing microbial inoculant using P. chrysogenum strain and its subsequent application to soil may help the marginal farmer to replenish soil P more economically compared to chemical fertilizer.  相似文献   

18.
Desert soils are infertile, and the ability to improve them by P-fertilization is limited by the solubility of phosphate. We aimed to understand the function of phosphate solubilizing bacteria and the mechanisms behind phosphate solubilization in desert soils. Vegetated and barren desert soils, mine spoil and a fertile temperate grassland loam were sampled. Bacteria and fungi were isolated and identified, and their phosphate-solubilizing abilities were measured in vitro. The release of plant available PO4, SO4, NO3 and NH4 from desert soils did not compare with that of a grassland soil. Desert soils had substantially lower solubilization than grassland, 162 and 99–121 µg PO4-P g?1 dry soil, respectively. Phosphate-solubilizing bacteria and fungi were inhabiting the soils. Si addition increased phosphate solubilization of fungi by 50%. The isolated microbes were shown, using 31P nuclear magnetic resonance (NMR) analysis, to rapidly take-up both intracellular and extracellular phosphate during the phosphate solubilizing process. Desert soil had potentially active microbial populations that are capable to solubilize inorganic phosphorus; S and Si as the limiting factors. Acidification as the main mechanism to solubilize mineral phosphate was not as evident in our desert soils as in former studies dealing more fertile soils.  相似文献   

19.
Corn samples and different commercial dry‐milled fractions collected from an industrial mill in Argentina were surveyed for fungal contamination. The percentage of Fusarium isolates in whole corn kernels among all fungi recovered was 2.0–97.0%; in corn grits, it was 2.6–50.0%. Maximum levels in the other fractions were 5.2 × 105 colony forming units per gram (CFU/g) in germ and bran, 5.0 × 103 CFU/g in C flour, and 2.7 × 103 CFU/g in corn meal. The high initial contamination from whole corn is reflected in germ and bran, which is destined for animal consumption, but not in corn meal. F. verticillioides and Aspergillus flavus were the most frequent species in the whole corn kernel, but F. verticillioides was prevalent in all the other industrial fractions. Other potentially toxigenic fungi that were isolated included Aspergillus parasiticus, Alternaria alternata, Penicillium citrinum, and P. funiculosum. In this first report about mold contamination in corn industrial dry‐milled fractions in Argentina, the high fungal contamination level observed in the stored corn could indicate the necessity to improve the hybrid quality and the storage conditions to diminish the risk of mycotoxin occurrence.  相似文献   

20.
Soil phosphorous (P) deficiency is a major constraint to plant production which is overcome by adding inorganic-phosphate as chemical fertilizers. Fluorescent pseudomonads are the diverse group of bacteria able to mobilize sparingly soluble phosphate form. Total three hundred seven fluorescent Pseudomonas isolates were obtained from the Aloe barbadensis (Miller) rhizosphere. These Pseudomonas strains were further evaluated in vitro for their ability to solubilize phosphate and to produce indole acetic acid (IAA), hydrogen cyanide (HCN), siderophore and 1-aminocyclopropane 1- carboxylate (ACC) deaminase. Fifty three (36.8%) isolates produced IAA and 52 (36.1%) isolates produced siderophores whereas 36 (25.0%) and 31 (21.5%) isolates produced HCN and ACC deaminase, respectively. A positive correlation existed between siderophore and ACC deaminase producers. Cluster analysis showed rhizosphere as the major factor influencing the ecological distribution and physiological characterization of phosphate solubilizing bacteria (PSB). Based on partial 16S rRNA gene sequencing PSB were identified as Pseudomonas putida, Pseudomonas sp. and Pseudomonas plecoglossicida with highest phosphate solubilization ability. In conclusion, these phosphate solubilizing fluorescent pseudomonads would help in understanding their role in phosphorus solubilization and identification of potent phosphorus solubilizers from the rhizosphere of commercially grown A. barbadensis.  相似文献   

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