Elección de planta trampa y sustrato para la producción de inóculo micorrízico

In the course of our research, aimed at improving sugar beets phosphorus nutrition, we isolated and characterized Streptomyces sp. strains, endemic from sugar beet fields of the Beni-Mellal region, which are able to use natural rock phosphate (RP) and tricalcium phosphate (TCP) as sole phosphate sources. Ten Streptomyces sp. isolates yielded a comparable biomass in the presence of these two insoluble phosphate sources, indicating that they were able to extract similar amount of phosphorus (P) from the latter for their own growth. Interestingly, five strains released soluble P in large excess from TCP in their culture broth whereas only two strains, BP, related to Streptomyces bellus and BYC, related to Streptomyces enissocaesilis, released a higher or similar amount of soluble P from RP than from TCP, respectively. This indicated that the rate of P released from these insoluble phosphate sources exceeded its consumption rate for bacterial growth and that most strains solubilized TCP more efficiently than RP. Preliminary results suggested that the solubilization process of BYC, the most efficient RP and TCP solubilizing strain, involves both acidification of the medium and excretion of siderophores. Actinomycete strains possessing such interesting RP solubilizing abilities may constitute a novel kind of fertilizers beneficial for plant nutrition and more environmentally friendly than chemical fertilizers in current use.

ABSTRACTIn order to study the effect of plant growth promoting rhizobacteria (PGPR), vermicompost and phosphate sources on the growth and nutrients uptake by lettuce, a greenhouse experiments was conducted. Treatments consisted of PGPR (Pseudomonas fluorescens) (with and without inoculation), vermicompost (0 and 1% w/w) and phosphate sources (control, rock phosphate (RP), tricalcium phosphate and triple super phosphate (TSP) at 25 mg P kg−1 level). Biological fertilizers, RP and TSP significantly increased shoot dry matter (SDM) and some measured nutrients uptake. Co-application of PGPR and RP, in non-vermicompost treatments significantly increased SDM, shoot nitrogen, phosphorus (P), potassium, zinc and manganese uptake rates. Shoot P uptake had no significant difference between TSP and RP treatments. Co-application of PGPR, vermicompost and TSP significantly decreased SDM, which may be due to the P toxic levels in the plant aerial parts and/or the inhibition of the bacterial activities in the rhizosphere soil.

Phosphorus is one of the essential elements limiting vegetative production in the world. Although phosphorus is abundant in soils, a tiny part is available for plants. With phosphate solubilizing bacteria (PSB), phosphorus, insoluble in soils, is transformed into a suitable form for plants. This study aimed to determine tricalcium phosphate (TCP) activities and rock phosphate (RP) used to isolate PSMs. 118 bacterial isolates, which can phosphate solubilizing, were incubated for 72 h in National Botanical Research Institute phosphate (NBRIP) medium using TCP and RP as phosphate sources. At the end of the incubation, the amount of inorganic phosphorus (Pi) in the medium and the pH of the medium was determined. As a result of bacterial incubation, an average of 57.87 mg L−1 Pi was detected in rock phosphate medium, while this rate was found to be 421 mg L−1 in TCP medium. After 72 h of incubation, it was determined that the pH of the NBRIP media varied between 3.60 and 5.05, and TCP dissolved seven times more to rock phosphate. This study has shown that TCP alone in determining the isolation and effectiveness of PSMs is not indigenous.

Phosphate solubilizing microorganisms (PSMs) were isolated from rhizoplane, rhizosphere and non-rhizosphere of different leguminous plants. To isolate efficient phosphate solubilizers the rhizosphere and non-rhizosphere soil samples were enriched with different phosphate sources like tricalcium and rock phosphate. PSMs were detected in all the regions, but their number gradually decreased from rhizosphere, rhizoplane and non-rhizosphere soil. When compared to fungal population, bacterial population was more in number. Tephrosia purpurea recorded the highest bacterial population of 30.15 × 106 cfu/g, 50.51 × 106 cfu/g and 21.10 × 106 cfu/g in the rhizoplane, rhizosphere and non-rhizosphere regions respectively. In enrichment culture technique, highest phosphate solubilizing bacterial population was recorded in the rhizosphere soil of Clitoria ternatea (23 × 103 cfu/g) in tricalcium phosphate containing Pikovskaya's (PVK) medium. In a plate assay method solubilization zone diameter produced by microorganisms was varied from 0.2 cm to 1.0 cm. The phosphate solubilization ability of the isolated microorganisms in a liquid PVK medium varied from 11.85 mg to 61.96 mg P2O5. The medium turned acidic during the incubation period. The pH varied among the organisms from the initial 6.5 to the final 3.2 during 15 days of incubation. Citric acid, fumaric acid, gluconic acid, glutaric acid, glyoxalic acid, ketobutyric acid, ketoglutaric acid, malic acid, malonic acid, succinic acid and tartaric acid are produced by the isolated PSMs. Seed or soil inoculation with phosphate solubilizing bacteria (PSB) is known to improve solubilization of fixed and applied phosphates in soil bring about higher crop yield. The PSM are effective as biofertilizers in enhancing crop yields in phosphate deficient soils. They are environmentally friendly and supply phosphate to plants in a sustainable manner.

در فرمولاسیون کودهای میکروبی فسفاته که غالبا به فرم گرانوله تهیه می‌شوند از باکتری‌های حل‌کننده فسفات استفاده می‌شود. از جمله محدودیت‌های تولید این نوع کود، از بین رفتن باکتری‌ها در فرایند تهیه و خشک نمودن گرانول‌ها می‌باشد. بر این اساس در این تحقیق اقدام به جداسازی باکتری‌های حل‌کننده فسفات مقاوم به دما شد و تحمل دمایی و توانایی انحلال فسفات (از منابع سنگ فسفات و تری‌کلسیم فسفات) در باکتری‌های بومی جدا شده از خاک، مورد ارزیابی قرار گرفت. از پنج باکتری (جدایه‌های RPS4، RPS6، RPS7، RPS8 و RPS9) با قابلیت تولید هاله شفاف تنها دو باکتری (RPS7 و RPS9) قادر به تحمل دمای 55 درجه سلسیوس به مدت 16ساعت بودند. در محیط اسپربر جامد حاوی تری‌‌کلسیم ‌فسفات، باکتری RPS9 و RPS7 به ترتیب با دارا بودن مقادیر 60/2 و 27/2 برای نسبت (HD/CD) بعد از گذشت 12روز، قدرت بالایی در امر انحلال فسفات معدنی نامحلول داشتند. میزان انحلال فسفات کم‌محلول در روش کمی نیز برای دو باکتری RPS9 و RPS7 به ترتیب 8/531 و 1/324 میلی‌گرم بر لیتر بدست آمد. نتایج زنده‌مانی باکتری‌ها نیز نشان داد که زنده‌مانی جمعیت میکروبی در حالت بدون تیمار دمایی تا 6 ماه و در حالت تیمار دمایی به 4 ماه کاهش یافت. شناسایی مولکولی RPS7 و RPS9 حاکی از آن بود که هر دو جدایه متعلق به گونه Pantoea agglomerans هستند.

The implementation of autotrophic in vitro culture systems is revealed as a crucial strategy for the multiplication of native arbuscular mycorrhizal fungi, as it plays a fundamental role in restoring the sustainability of agricultural systems that have suffered degradation. The objective of the research was to establish an autotrophic in vitro culture method using two trap plants of native arbuscular mycorrhizal fungi under laboratory conditions. Inoculum native to Bidens pilosa and Tagetes patula were collected, spores were disinfected and cultured in vitro using a modified Murashige and Skoog medium. The results showed mycorrhization percentages greater than 50% in the trap plants and a significant reduction in microbial contamination with the use of antibiotics. The autotrophic in vitro culture system was feasible with Tagetes patula and Bidens pilosa, proving to be a promising strategy to produce mycorrhizal inoculum under laboratory conditions. In conclusion, spore disinfection and selection of suitable trap plants guarantee the success of in vitro culture inoculated with native arbuscular mycorrhizal fungi.

The effects of a superphosphate (SP) and a rock phosphate (RP), with equal total P contents, on the growth and mineral nutrition responses of mycorrhizal and nonmycorrhizal cowpea, pigeon pea and groundnut were investigated in a pot experiment using an air-dry gamma ray-sterilized (1.5Mrad) Andisol subsoil. Adequate amounts of micronutrients were added to the pot soils as supplements. The plants were inoculated with surface-sterilized 100 spores/pot of Glomus etunicatum or none and with Rhizobium strains. At their maturities, dry weights of plant parts and nodule number, root length, arbuscular mycorrhizal fungal (AMF) colonization of roots and AMF spore production were also measured. Shoot nitrogen and phosphorus concentrations were determined by the Micro-Kjeldahl distillation and ammonium-molybdenum blue methods, respectively. Shoot copper and iron concentrations were measured by the atomic absorption spectrophotometry. Mycorrhiza formation was greater with superphosphate than with rock phosphate treatments. Rock phosphate enhanced mycorrhization in cowpea and pigeon pea but it decreased it in groundnut. Superphosphate-treated cowpea and pigeon pea plants were larger than RP-treated plants whether mycorrhizal or not but in groundnut growth increased only when the plant was treated with SP and inoculated with AMF. Mycorrhizal enhancement of shoot growth in superphosphate-fertilized groundnut could be a direct consequence of improved P nutrition resulting from increased hyphal uptake and/or enlarged absorptive root surface due to increased root fineness. There were similarities in shoot dry matter yields as well as shoot P uptakes of both mycorrhizal and non-mycorrhizal RP-treated plants suggesting that the legumes were so unresponsive to the RP that even mycorrhization could not trigger any response in them. The increased contents of N, Cu and Fe in the shoots of mycorrhizal SP-fertilized plants were observed to be the result of larger shoot sizes except with Fe in groundnut shoot whose enhancement could be related to a good mycorrhiza formation and a concomitant improvement in P nutrition which may further have been influenced by its fine root structure. There was a very close interdependency of fine root structure, AMF colonization, AMFspore production and improved P and Fe nutrition in groundnut as a result of soluble phosphate application.Journal of Science & Technology (Ghana) Vol. 27 (2) 2007: pp. 43-56

Quicklime treatment and stirring of different poultry litter substrates for reducing pathogenic bacteria counts

Phosphorus plays a major role in plant growth, but only a small portion of phosphorus in soil is taken up by plants and the remaining part becomes unavailable for plants. Phosphate solubilizing microorganisms play a vital role in dissolving the complex form of phosphates to the accessible forms. The present paper reports the solubilization of tricalcium phosphate (TCP), single super phosphate (SSP), rock phosphate (RP), iron phosphate (FeP) and aluminum phosphate (AlP) by Streptomyces sp . KP109810 (S) with the production of organic acids as well as acid phosphatase. The amount of phosphate released (562 mg l–1) was found to be the highest in the case of single super phosphate, as compared to the other phosphate sources. The highest phosphatase activity was observed in the presence of iron phosphate (0.033 Uml–1). The proposed thin layer chromatography (TLC) method was used to analyze the organic acids in culture broths of the following P sources. The numbers of these organic acids were six organic acids from SSP, seven from RP, four organic acids from FeP and two for each of AlP and TCP. The effects of Streptomyces sp. KP109810 on P solubilization from different P sources, plant biomass production, and P content of maize (Zea mays L.) were examined in a greenhouse study. A complementary greenhouse experiment was conducted in pots by growing maize as a test crop. Our findings showed a great efficient promotion of maize growth and P content compared to un-inoculated plants. Furthermore, single supper phosphate showed better results than rock phosphate, the latter performed comparably upon Streptomyces inoculation. These findings demonstrate that Streptomyces sp. KP109810 can improve crop growth and P nutrition.

Phosphorus (P) is one of the key bio elements that limits agricultural production. Although Sri Lanka is endowed with rock phosphate deposits, practical means to utilize this resource are limited. Phosphate-solubilizing fungi (PSF) play an important role in enhancing the bioavailability of soil phosphorus to plants. In this study, fungi from eight soil samples in Kaikawala, Sri Lanka, were isolated using spread plate method and analyzed for its phosphate solubility capacity. One fungal isolate with significant halo zones on Pikovskaya’s agar (PVK) plates, containing 0.5% tricalcium phosphate, was identified. After purification, the isolate was transferred to three media setups: PVK with 0.5% apatite (ERP) as the phosphate source, PVK with 0.5% tricalcium phosphate as a positive control, and PVK without P source as a negative control and analyzed for the solubilization index (SI). DNA sequences of the internal transcribed spacers with 5.8S region of ribosomal DNA (ITS1-5.8S-ITS2) was analyzed with universal primer pair ITS4-F/ITS5-R to determine the identity of the species. Fungal isolate PSF01 showed a phosphate solubilizing activity on both PVK media, ERP (1.07 ± 0.03 cm SI) and tricalcium phosphate (1.07 ± 0.01 cm), with similar effects (p > 0.05). However, the SI in the negative control was 1.00 ± 0.00 cm without halo zone (p < 0.05). The fungal strain is fast growing with initially white but quickly changing to black colonies after producing conidial spores on potato dextrose agar with distinctive conidial heads and pale-yellow lower surface characterized as Aspergillus. Sanger DNA sequencing identified the fungus as Aspergillus niger (99%) and a phylogenetic tree was constructed using MEGA11 software using reference data obtained from NCBI GenBank data to identify the isolated PSF01. Consequently, our preliminary studies demonstrate the importance of examining more soil samples to identify PSF for sustainable agricultural applications in the future.

The major objective of this study was to quantify the effects of substrate depth and substrate composition on the development of sedum etc., in a sloped rooftop (6 : 12 pitch) environment during a 4-year period. The experiment was conducted from 2006 October to 2010 December under several conditions without soil erosion control : two substrate depth (5cm, 10cm), four substrate composition (A5N3C2, A3N3C4, A6C4, G5L3C2: A: artificial lightweight soil, N : natural soil, G : granite decomposed soil, C : leave composite, L : loess), four sloped roof direction (, , , ). In this experiment 4 sedum etc., were used: Sedum sarmentosum, Sedum kamtschaticum, Sedum rupestre, Sedum telephium, flowering herbs (mixed seed : Taraxacum platycarpum, Lotus corniculatus, Aster yomena, Aster koraiensis), western grasses (mixed seed : Tall fescue, Creeping redfescue, Bermuda grass, Perennial ryegrass). The establishment factor had two levels : succulent shoot establishment (sedum), seeding (flowering herbs, western grasses). 1. Enkamat, as it bring about top soil exfoliation, was unsuitable material for soil erosion control. 2. Sedum species exhibited greater growth at a substrate depth of 10cm relative to 5cm. All flowering herbs and western grasses established only at a substrate depth of 5cm were died. A substrate depth of 5cm was not suited in sloped rooftop greening without maintenance. If additional soil erosion control will be supplemented, a substrate depth of 10cm in sloped rooftop greening without maintenance was considered suitable. 3. For all substrate depth and composition, the most abundant species was Sedum kamtschaticum. The percentage of surviving Sedum kamtschaticum was 73.4% at a substrate depth of 10cm in autumn 2007 one year after the roof vegetation had been established. But the percentage of surviving other sedum were 33.3%~51.9%, therefor mulching for soil erosion control was essential after rooftop establishment in extensive sloped roof greening was proved. To raise the ratio of plant survival, complete establishment of plant root at substrate was considered essential before rooftop establishment. 4. There was a significant interaction between biomass and substrate moisture content. There were also a significant difference of substrate moisture and erosion among substrate composition. The moisture content of A6C4 was highest, the resistance to erosion of A5N3C2 was highest among substrate composition. The biomass of plants were not significantly higher in A5N3C2 and A6C4 relative to A3N3C4 and G5L3C2, For substrate moisture and erosion resistance, A5N3C2 and A6C4 were considered suitable in sloped rooftop greening without maintenance. 5. There were significant difference among roof slope direction on the substrate moisture. Especially, the substrate moisture content of was lower relative to that of , that guessed by solar radiation and erosion.

Affordable technologies are needed to allow smallholder farmers to effectively use the phosphate rocks (PRs) found in many African countries. A pot study was conducted in Tanzania using two PRs (Panda and Minjingu) and two soils (an Alfisol and an Andisol) to assess responses of several types of crops to these PRs and to determine whether changes in crop responses to PR with time are due to crop sequence or merely contact time with soil. The Panda PR had no effect on growth or tissue P content in maize (Zea mays L.), bean (Phaseolus vulgaris L.), and pigeon pea [Cajanus cajan (L.) Millsp.], but it nearly tripled these parameters for cabbage (Brassica oleracea L.) on the Alfisol. Freshly applied Minjingu PR only slightly stimulated maize and pigeon pea, but nearly tripled cabbage yield in both soils. Previous crop had a greater effect than previously applied PR on second crop maize. Yields and P content of maize were always lowest following cabbage and highest following pigeon pea. Minjingu PR, but not Panda PR, had residual benefits on maize. Severe Mn toxicity occurred in all crops on the unamended Andisol. The calcareous Minjingu PR, but not the Panda PR, increased yields dramatically on the Andisol, partly by raising the soil pH in water enough (from 4.6 to 5.6) to alleviate Mn toxicity. Future P fertility work in Africa should pay adequate attention to the effects of crop sequences and soil biological properties.

The arbuscular mycorrhizal (AM) symbiosis enhances plant tolerance to water deficit through the alteration of plant physiology and the expression of plant genes. These changes have been postulated to be caused (among others) by different contents of abscisic acid (ABA) between AM and non-AM plants. However, there are no studies dealing with the effects of exogenous ABA on the expression of stress-related genes and on the physiology of AM plants. The aim of the present study was to evaluate the influence of AM symbiosis and exogenous ABA application on plant development, physiology, and expression of several stress-related genes after both drought and a recovery period. Results show that the application of exogenous ABA had contrasting effects on AM and non-AM plants. Only AM plants fed with exogenous ABA maintained shoot biomass production unaltered by drought stress. The addition of exogenous ABA enhanced considerably the ABA content in shoots of non-AM plants, concomitantly with the expression of the stress marker genes Lsp5cs and Lslea and the gene Lsnced. By contrast, the addition of exogenous ABA decreased the content of ABA in shoots of AM plants and did not produce any further enhancement of the expression of these three genes. AM plants always exhibited higher values of root hydraulic conductivity and reduced transpiration rate under drought stress. From plants subjected to drought, only the AM plants recovered their root hydraulic conductivity completely after the 3 d recovery period. As a whole, the results indicate that AM plants regulate their ABA levels better and faster than non-AM plants, allowing a more adequate balance between leaf transpiration and root water movement during drought and recovery.

Variation in the trypsin inhibitors (TIs) and the chymotrypsin inhibitors (CIs) among 69 pigeonpea [Cajanus cajan (L.) Millsp.] strains from a wide geographical distribution and among 17 accessions representing seven wild Cajanus species was studied by electrophoretic banding pattern comparisons and by spectrophotometric activity assays. The TI and CI electrophoretic migration patterns among the pigeonpea strains were highly uniform but varied in the inhibitor band intensities. The migration patterns of the inhibitors in the wild Cajanus species were highly species specific. The mean TI activity of pigeonpea strains (2279 units) was significantly higher than that of the wild Cajanus species (1407 units). However, the mean CI activity in the pigeonpea strains (62 units) was much lower than that in the wild species (162 units). Kenya 2 and ICP 9151 were the lowest and the highest, respectively, in both the TI and CI activities among all the pigeonpea strains used in this study. A highly-significant positive correlation was observed between the TI and CI activities. The Bowman-Birk type inhibitors with both TI and CI activities were identified in all the pigeonpea strains and also in the accessions of all the wild species except C. volubilis (Blanco) Blanco. The C. volubilis accession ICPW 169 was found to be 'null' for both CI bands and CI activity. Environment, strain, and environment x strain interaction showed highly-significant effects on both the TI and CI activities. Growing the pigeonpea strains at a different environment from their area of adaptation increased TI and CI activities and also altered the maturity period.

Phosphorus is abundant in soil but its availability is limited due to its immobilization and complexation with mineral ions. The sources of phosphate are sustainable only when they are in receipt of solubilized by rhizospheric microorganisms. Phosphate solubilizing microorganisms (PSMs) such as rhizospheric or endophytic bacteria, free-living fungi, or vesicular -arbuscular mycorrhiza (VAM) have potency to solubilize mineral phosphate source by secretion of acids, enzymes, chelation of metal ions, and H+ ion extrusion. The isolation and screening of these PSMs is done on Pikovskaya medium, NBRIP medium, or Tris minimal agar medium with application of different sources of phosphate like tricalcium phosphate, apatite, or rock phosphate and detected by either zone of solubilization or color of zone around the colony. The amount of released phosphate in the solution is determined by measuring the reduction of phosphomolybdate or vanadomolybdate complex in acidic condition. The amount of reduced complex is directly proportional to soluble phosphate.