Arbuscular Mycorrhizal Fungi Bio-fertilizers Research Articles

The Effects of Bio-Fertilizer by Arbuscular Mycorrhizal Fungi and Phosphate Solubilizing Bacteria on the Growth and Productivity of Barley under Deficit of Water Irrigation Conditions

Bio-fertilizers are the most important and effective method used to reduce the quantities of chemical fertilizers consumed and reduce dependence on them in agricultural production to avoid their harmful effects on the environment and public health as well as reduce the cost of agricultural production in light of increasing pollution and under adverse conditions for production and climate change. A bio-fertilizer depends primarily on the use of beneficial microorganisms such as arbuscular mycorrhizal fungi (AMF) to improve the uptake of nutrients, improve plant growth, productivity, and grain yield. Crop production faces many challenges, and drought is one of the majority of the significant factors limiting crop production worldwide, especially in semi-arid regions. The objective of this study was to evaluate the effects of AMF and phosphate solubilizing bacteria (PSB), plus three rates of the recommended dose of phosphorus (RDP) fertilizer on yield, yield components, and nutrients uptake, in addition to evaluating the beneficial effects of these combinations to develop Phosphorus (P) management under three levels of irrigation water, i.e., three irrigations (normal or well-watered), two irrigations (moderate drought), and one irrigation (severe drought) on barley (Hordeum vulgare L.). The results showed that the treatment with AMF bio-fertilizer yielded the highest values of plant height, spike length, spike weight, number of grains/spike, 1000-grain weight, grain yield, straw yield, biological yield, and harvest index. Moreover, the grain and straw uptake of nitrogen (N), P, and potassium (K) (kg ha−1) in the two seasons under the three levels of irrigation, respectively, were superior followed by the inoculation by PSB. While the treatment without bio-fertilizer yielded the lowest values of these traits of barley, the treatment with bio-fertilizer yielded the increased percentage of the grain yield by 17.27%, 17.33% with applying AMF, and 10.31%, 10.40% with treatment by PSB. Treatment with AMF or PSB (Phosphorien), plus rates of phosphorus fertilizer under conditions of irrigation water shortage, whether irrigation was performed once or twice, led to an increase in grain yield and other characteristics compared to the same fertilization rates without inoculation. The results of this study showed that the use of bio-fertilizers led to an increase in plant tolerance to drought stress, and this was demonstrated by an increase in various traits with the use of treatments that include bio-fertilizers. Therefore, it is suggested to inoculate the seeds with AMF or PSB plus adding phosphate fertilizers at the recommended dose under drought conditions.

Test the viability and effectiveness of the AMF biofertilizer prototypes using different spore carrier media on production of organic cocoa

Increasing consumer demand for healthy food products has an impact on increasing demand for organic cocoa, but it is difficult for farmers to fulfil it because the production per hectare is still very low. Development of indigenous Arbuscular Mycorrhizal Fungi (AMF) as biological fertilizers is expected to relieve farmers’ difficulties. This study aimed to find the best AMF biofertilizer prototype that can increase organic cocoa production while increasing soil fertility. The research was conducted through 2 stages. Stage 1 made prototypes of biological fertilizers from 7 indigenous AMF species isolated from cocoa roots using different spore carrier media and then tested the spore viability during storage, and stage 2 selected 2 of the best AMF biofertilizer prototypes to test their effectiveness on organic cocoa plantations. The results showed the AMF biofertilizer prototype with spore’s carrier media volcanic sand and zeolite gave the viability of spores remained high after being stored for 1 month, reaching 91.78% and 90.67%. The effectiveness test on organic cocoa plantations showed that the AMF biofertilizer prototype with different spore-carrying media had no significant effect on the yield and yield components of organic cocoa beans, but AMF biofertilizer prototype with volcanic sand spore-carrying media tended to increase the yield and improves soil fertility. It was concluded that the AMF biofertilizer prototype with volcanic sand spore carrier media was the best prototype, but it is necessary to carry out tests at several locations to determine the consistency of the effect.

From soil to plant: strengthening carrot defenses against Meloidogyne incognita with vermicompost and arbuscular mycorrhizal fungi biofertilizers.

Sustainable agricultural practices for controlling crop pests are urgently needed to reduce the reliance on chemical pesticides, which have long-term detrimental effects on ecosystems. In this study, we assessed the effectiveness of arbuscular mycorrhizal fungi (AMF) and vermicompost (Vc) supplementation, alone and in combination, in mitigating the negative impacts of Meloidogyne incognita infestation on carrot (Daucus carota L.) growth, development, and physiology. We measured different plant growth parameters such as plant height and biomass accumulation, several plant physiological parameters such as the levels of photosynthetic pigments, phenolics, and the activity of defense enzymes such as peroxidases and polyphenol oxidases, and evaluated the severity of Meloidogyne incognita nematode infestation on plants treated or not treated with vermicompost (Vc) and/or arbuscular mycorrhizal fungi (AMF). Our findings show that M. incognita significantly affects plant growth, biomass accumulation, and photosynthetic pigment and carotenoid content. The incorporation of Vc and AMF into the soil, either individually or in combination, significantly alleviates the negative effects of nematode infestation on carrot plants. This was accompanied by the induction of phenolic compounds and defense enzymes such as peroxidases (+15.65%) and polyphenol oxidases (29.78%), and by a reduction in the severity of nematode infestation on Vc and AMF-treated plants compared to nematode-infested plants. Principal component analysis (PCA) shows significant correlations between various of the studied parameters. In particular, we observed negative correlations between the application of AMF and Vc alone and in combination and disease severity, and positive correlations between plant growth, photosynthetic pigments phenol content, and activity of defense enzymes. Our study highlights the relevance of cultural practices and beneficial microorganisms for the sustainable and environmentally friendly management of agricultural pests.

Engineering Approach for Production of Arbuscular Mycorrhizal Inoculum Adapted to Saline Soil Management

(1) Background: Soil salinity impacts plant growth and productivity in steppic regions. Thus, the current study aims at producing, at low cost, an inoculum composed of native arbuscular mycorrhizal fungi (AMF) strains adapted to saline soil management. (2) Methods: The propagation of the native AMF strains was carried out in three natural saline soils presenting increasing salinity levels (4.5, 8.5 and 9.3 dS·m−1 in Boughzoul (BG), Salt Rocket (SR) and Zaafrane (ZA) sites, respectively). Three host plant species (alfalfa, clover and leek) were tested as trap cultures. AMF spore richness and diversity, the quantification of soil microbial biomass and the determination of the most probable number (MPN) were carried out before and after 24 months culture. Moreover, the mycorrhizal rates of the host plant species were assessed. (3) Results: The moderate saline soil (SR) planted with alfalfa was found to be the most suitable for AMF inoculum production with a maximum of 650 spores, 10 g−1 of soil, a mycorrhizal rate of 86%, 70 propagules·g−1 of soil and the highest microbial biomass content. (4) Conclusion: This study points out the best combination for the production of a more adapted AMF biofertilizer for saline soil management and proposes several indicators for biofertilizer quality evaluation.

PRODUCTION OF OIL PALM (Elaeis guineensis Jack) FLOWER BUNCHES IN ULTISOL ON APPLICATION OF BIOFERTILIZERS AND IN ORGANIC FERTILIZERS

One of the efforts to increase the production of oil palm flower bunches in ultisols is applying biofertilizers and inorganic fertilizers. Biofertilizers can reduce the use and adverse effects of inorganic fertilizers. Arbuscular Mycorrhizal Fungi (AMF) is one of the biofertilizers that can help plants absorb nutrients and increase plant resistance to various environmental stresses. This study aimed to examine the role of AMF (as biofertilizer) and inorganic fertilizers in increasing the production of oil palm flower bunches in Ultisol. This experiment is a factorial experiment using a Randomized Block Design. The first factor is the application of biofertilizers, which consists of two levels without biofertilizers (AMF) and with biofertilizers (AMF). The second factor is the dose of inorganic fertilizer, composed of 5 levels, no inorganic fertilizer, 25, 50, 75, and 100% recommended doses of inorganic fertilizer. The variables observed were the number of sheaths, the percentage of broken sheaths, the number of male flower bunches, the number of female flower bunches, the percentage of male and female flower bunches, sex ratio per plant, and AMF colonization. The results showed that AMF biofertilizer saved 25% of inorganic fertilizers and increased 29.33% of female flowers production. The highest production of oil palm flower bunches was obtained from the application of AMF biofertilizer and 75% of inorganic fertilizers (1.5 kg Urea, 1.1 kg SP-36, 1.2 kg MOP, 0.7 kg Kisserite per plant). Oil palm with AMF had a higher average sex ratio than plants without AMF biofertilizers. The average sex ratio in oil palm plants applying AMF biofertilizer and inorganic fertilizers ranged from 0.42 to 0.73.

Dry-Season Soil and Co-Cultivated Host Plants Enhanced Propagation of Arbuscular Mycorrhizal Fungal Spores from Sand Dune Vegetation in Trap Culture.

The use of arbuscular mycorrhizal fungi (AMF) as biofertilizer in agriculture is a sustainable approach to fertilization. The first step in the production of AMF biofertilizer is inoculation of mycotrophic plants with a composite of soil and native plant roots, containing potentially viable AMF spores from natural habitats, to a trap culture. A single host plant or a consortium of host plants can be used to propagate AMF spores. However, the difference in the comparative efficiency of mono- and co-cultivated host plants used for the production of AMF spores and the maintenance of original AMF community composition has not been well elucidated. Here, we prepared trap culture with nutrient-poor soil from coastal sand dune vegetation collected during the dry season when the AMF spore density and relative abundance of Glomeromycota ITS2 sequences were significantly higher (p = <0.05) than in the wet season. The AMF communities in the soil were mainly composed of Glomus spp. Maize (Zea mays L.) and/or Sorghum (Sorghum bicolor (L.). Moench) were grown in trap cultures in the greenhouse. Our results demonstrated that co-cultivation of the host plants increased the production of AMF spores but, compared to mono-cultivation of host plants, did not better sustain the native AMF community compositions in the coastal sand dune soil. We propose that the co-cultivation of host plants in a trap culture broadens AMF-host plant compatibilities and thus sustains the symbiotic association of the natively diverse AMF. Therefore, the results of this study suggest that further research is needed to confirm whether the co-culturing of more than one host plant is as efficient a strategy as using a monoculture of a single host plant.

Effect of water stress and mixed types of the genus Arbuscular Mycorrhizal Fungi from cocoa roots on spore propagation and root colonization used corn as the host

Biofertilizer with Arbuscular Mycorrhizal Fungi (AMF) as the inoculants is needed in organic cocoa cultivation on smallholder plantations in Indonesia. AMF biofertilizer requires a sufficient number of spore inoculants, so it is necessary to multiply isolated spores. Research objective was determining the effect of water stress and mixed types of AMF genus from cocoa roots on spore propagation and root colonization used corn as the host plant. The study used a 2-factors randomized block design and 3 replications. The first factor was water stress consisting of 3 levels (without water stress as a control, soil moisture content 100% of field capacity; light water stress, soil moisture content 70% of field capacity; and heavy water stress, soil moisture content 40% of field capacity), while the second factor was mixed types of AMF genus also consisting of 3 levels (inoculant of genus Glomus only, mixed inoculants of the genus Glomus + Acaulospora, and mixed inoculants of the genus Glomus + Scutelospora. Result of research showed, the interaction of water stress and mixed types of the AMF genus had no significantly affect on the number of spores reproduced, root colonization and host plant growth. The best way of propagation of AMF spores was by heavy water stress treatment with a soil moisture content of 40% of field capacity producing 6,713.40 spores or an increase of 13,326.82%. Mixed inoculants of the genus Glomus + Scutelospora gave the highest number of spores after propagation (6,263.40 pieces) or an increase of 12,427.77%.

Mycorrhiza and Phosphate Solubilizing Bacteria: Potential Bioagents for Sustainable Phosphorus Management in Agriculture

Phosphorus (P) is a critical nutrient that plays an essential role in improving soil fertility for optimum plant growth and productivity. It is one of the most deficient macro-nutrients in agricultural soils after nitrogen and is considered inadequate for plant growth and production. To P availability in soils, the farmers are applying huge amounts of synthetic P fertilizers that adversely affect the wider environment, groundwater, soil fertility and microbial population. Many beneficial microbes are known to release and supply soluble P for improving growth and yield of a variety of plants in a sustainable manner in P deficient soils. Thus, inoculation of these microbes, including arbuscular mycorrhizal fungi (AMF) and phosphate solubilizing bacteria (PSB) to soil to enhance crop production without harming the environment, is an alternative approach to chemical fertilizers. The combined role of AMF and PSB in P solubilization is not well understood and the application and mode of action of these microbial groups are often naive due to variation in the environment. Therefore, the current review article would develop a better understanding of the interactive role and mechanisms of AMF and PSB in improving P availability from both organic and inorganic sources in a sustainable crop production system. Finally, the current review would loop out further avenues for researchers interested to commercially produce effective AMF and PSB-based biofertilizers for sustainable management of phosphorus over a wide range of agricultural crops worldwide.

Growth, physiological, and biochemical responses of thyme (Thymus vulgaris L.) to the application of arbuscular mycorrhizal fungi under cadmium stress conditions

Thyme (Thymus vulgaris L.) is one of the most important medicinal plants used in various pharmaceutical, osmotic, health, and food industries. Arbuscular mycorrhizal fungi (AMF) symbiosis is viewed as one of the several methods to improve growth under heavy metals stress. To investigate the effects of cadmium (Cd) and AMF bio-fertilizers on the growth and morpho-physiological characteristics of thyme, a greenhouse experiment was performed in three replications. Experimental treatments included Cd at three levels 0, 75, and 150 mg/kg of soil and AMF at three levels without inoculation, inoculation with Funneliformis etunicatum, and Funneliformis mosseae. Cadmium stressed plant showed reduced plant height, number of leaves, stem fresh and dry weight, and root fresh and dry weight while AMF inoculation enhanced the increased means of these traits considerably. Inoculation with F. mosseae also ameliorated the Cd stress (150 mg/kg) induced reduction in plant height, number of leaves, and stem and root dry weight by 13.41%, 8.42%, 30.3%, and 22.2%, respectively. Cadmium stress reduced membrane stability index while AMF inoculation enhanced membrane stability index considerably. An increase in soluble carbohydrate and proline content was observed due to Cd stress and AMF inoculation caused a further increase in these two metabolite contents ensuring better growth under Cd stressed conditions. Results indicated that F. mosseae had a higher efficiency in increasing morphological traits and improving physiological characteristics than F. etunicatum. Overall, AMF inoculation, especially F. mosseae significant ameliorative potential for Cd toxicity in thyme plants.

English

Soil degradation, one of the causes associated with declining maize productivity is an environmental concern whose consequences are felt most strongly by poor people in developing countries. Indeed, the production of maize on soil fertilized with a combination of mycorrhizal fungi and half a dose of NPK has resulted in a production like that of the extension practice in Benin. This study aims, through an analysis of the financial profitability, to highlight the interest that maize production can generate with the production system using biofertilizer based on arbuscular mycorrhizal fungi (AMF) in Benin. The study was conducted among 100 randomly selected maize producers in 9 villages in South-Benin, Central-Benin and North-Benin. Economic profitability indicators including net margin, average labor productivity, and profit-cost ratio were determined. The results showed that regardless of the production area, maize cultivation with the AMF biofertilizer-based system was more profitable for producers (63,830 FCAF of net margin against 43,730 FCAF for vulgarized practice). Thus, agricultural policies could be oriented towards the promotion of maize inputs based on AMF bio-fertilizers to facilitate their availability to producers. Key words: Arbuscular mycorrhizal, Zea mays L., crop production systems; economic efficiency, farm development, Benin.

Effects of Nitroxin and arbuscular mycorrhizal fungi on the agro-physiological traits and grain yield of sorghum (Sorghum bicolor L.) under drought stress conditions.

The use of bio-fertilizers in agro-ecosystems is considered to have the potential to improve plant growth in extreme environments featuring water shortages. However, while arbuscular mycorrhizal fungi (AMF) and bacteria bio-fertilizers have been used in other plants to enhance stress tolerance, little is known about their symbiotic effect on sorghum (Sorghum bicolor L.) growth under drought stress conditions. Therefore the aim of this study was to investigate the inoculation of sorghum with Nitroxin and Glomus mosseae and their interaction effects on the agro-physiological characteristics and grain yield of sorghum under drought stress conditions. Nitroxin is a bio-fertilizer that consists of a mixture of Azospirillum and Azotobacter bacteria. The results showed that co-inoculation of sorghum seeds with Nitroxin and AMF improved the chlorophyll (a, b and total) content, soluble proteins, water use efficiency) WUE(, relative water content (RWC), nitrogen (N) content in the plant, AMF spore density, proline content, grain yield, panicle length, the number of panicles per plant, grain number per panicle, 1000-grain weight and decreased the electrolyte leakage and water saturation deficit (WSD) in drought stress and non-stress conditions. Under drought stress conditions, there was a 27% increase in grain yield under the synergistic effects of bacteria and fungi compared to the non-application of these microorganisms. The results of this experiment show that Nitroxin and AMF bio-fertilizers can mitigate the negative effects of stress on plants in drought stress conditions by increasing the amount of photosynthetic pigments, soluble proteins and osmotic regulation and decreasing electrolyte leakage. We found that the combination of bacteria and AMF for sorghum growth and yield increment is a promising method to cope with the stress caused by drought.

Arbuscular mycorrhizal fungi biofertilizer improves American ginseng (Panax quinquefolius L.) growth under the continuous cropping regime

Continuous cropping of American ginseng (Panax quinquefolius L.) is often associated with the scarcity or unavailability of soil nutrients and an imbalance of rhizosphere microbiota, resulting in low yield and poor plant quality. Inoculation with arbuscular mycorrhizal fungi (AMF) improves plant growth and production by facilitating nutrient acquisition and by modifying the abundance and diversity of rhizosphere microorganisms. In the present study, we investigated the mechanisms by which continuous cropping of American ginseng caused growth inhibition and how AMF biofertilizer application relieved these cropping obstacles. The results showed that: 1) continuous cropping of American ginseng significantly decreased the emergence rate, shoot and root dry weight, rhizosphere soil pH, the contents of ammonium, available phosphorus (P), and available potassium (K) in the rhizosphere, while increasing the root rot disease index and the soil content of nitrate; 2) continuous cropping of American ginseng decreased the diversity of bacteria, while increasing the diversity of fungi, and increased the relative abundances of Acidobacteria and Ascomycota, while decreasing the relative abundances of Actinobacteria, Firmicutes and Zygomycota; 3) in contrast, the application of AMF biofertilizer relieved the negative effects of continuous cropping American ginseng; 4) significant positive correlations were found between Pseudarthrobacter, Streptomyces and the content of ammonium, between Bacillus and the content of available K, and between Mortierella elongata and the content of available P, suggesting that the increase of rhizosphere plant-beneficial bacteria and fungi promoted the contents of available nutrients in the rhizosphere; 5) application of AMF biofertilizer significantly decreased the abundances of soil-borne pathogenic fungi Fusarium oxysporum, F. solani and the deleterious bacteria Candidatus Solibacter. In summary, our results suggest that AMF biofertilizer application improved the continuous cropping of American ginseng growth by increasing the AMF inoculation rate, by recruiting rhizosphere beneficial bacteria and fungi that promote plant-uptake of nitrogen (N) and P, and by suppressing soil-borne pathogens. Therefore, AMF biofertilizer is a probiotic agent that prevents microbial imbalances and nutrient deficiencies during continuous cropping of American ginseng.

Utilization of Biourine and Arbuscular Mycorrhizal Fungi as Biotechnological Agents for Improving Land Productivity of Ex-Coal Mines and Testing Their Effects on the Content of Forage Fiber Fractions [Hymenachne amplexicaulis (Rudge) Nees

Abstract Background and Objective: Liquid biourine organic fertilizer can affect the physical, chemical and biological fertility of soil. Mycorrhizal biofertilizers can help plants to supply and absorb nutrients, especially phosphorus, which is low in availability in acidic/critical soils. The aim of this study was to characterize, test and prove that the administration of biourine liquid organic fertilizer and Arbuscular mycorrhizal Fungi biofertilizer (AMF) as a biotechnology agent, was able to improve the productivity of ex-coal mine lands and also affect the content of forage fiber feed fractions. Materials and Methods: An experiment using a completely randomized design with 4 types of treatment and 5 repetitions was conducted. The treatments consisted of: (1) Biourine concentration of 0%+AMF 20 g potG1, (2) Biourine concentration of 15%+AMF 20 g potG1, (3) Biourine concentration of 30%+AMF 20 g potG1 and (4) Biourine concentration of 45%+AMF 20 g potG1. Variables observed were Acid Detergent Fiber (ADF), Neutral Detergent Fiber (NDF), hemicellulose, cellulose and lignin. Results: The results of various analyses showed that the treatment had a highly significant effect (p<0.01) on all variables observed. The treatment with 45% biourine+AMF 20 g potG1 resulted in lower ADF, NDF and lignin contents and produced higher cellulose and hemicellulose content than the treatments with 30% biourine+AMF 20 g potG1, 15% biourine+AMF 20 g potG1 and 0% biourine+AMF 20 g potG1. Conclusion: Biourine liquid organic fertilizer and Arbuscular mycorrhizal Fungi biofertilizer (AMF) are biotechnology agents that improve the productivity of ex-coal mine land and also affect the content of forage fiber feed fractions. Key words: ADF, arbuscular mycorrhizal fungi, biourine, fiber fraction, hymenachne amplexicaulis (Rudge) nees., lignin, NDF Received: Accepted:

Effects of Different Irrigation Levels and Arbuscular Mycorrhizal Fungi (AMF), Photosynthesis Activator, Traditional Fertilizer on Yield and Growth Parameters of Dry Bean (Phaseolus Vulgaris L.) in Arid Climatic Conditions

ABSTRACTA field experiment has been conducted to determine the effects of different irrigation water and AMF (Arbuscular Mycorrhizal Fungi) biofertilizer, photosynthesis activator and traditional fertilizer dry bean (Phaseolus vulgaris L.) on yield and growth parameters in Nevsehir Province of Turkey in 2015. The experiment has been carried out using three replications in a split plot design with three different irrigation types as main plots and AMF biofertilizer (ERS), photosynthesis activator (Multigreen-Mg), traditional fertilization (TF-Control), ERS + Mg, ERS + TF and TF + Mg applied as subplots. The number of pods per plant, the length of pods, the number of grains per pod, the weight of grains per plant, the yield of grains, 1000 seed weight, the number of grains per plant, protein yield, arbuscular mycorrhizal fungi rate have been evaluated as yield and growth criteria in the study. In the experiment, as well as the treatment x irrigation interaction, the plant height, pod number per plant, pod lenght, grain number per pod, grain weight per plant, grain yield, 1000 seed weight, grain number per plant, protein rate/grain, protein yield, root weight and AMF colonization parameters, were the other studied properties that were found to be significant. The results obtained were 877.6 mm for I100 irrigation treatment, 512.2 mm for I50 irrigation treatment and 40.19 mm water for I30 irrigation treatment. Regarding the growth parameters of dry bean, the highest PH was in ERS + Mg (67.66 cm), the lowest PH was in ERS (54.33 cm); In I50, the highest Plant Height (PH) was in ERS + Mg (65.66 cm), the lowest PH was in TF-Control (53.00 cm); and in I30, the highest PH was in TF-Control (50.66 cm), and the lowest PH was again in ERS + Mg (44.33 cm). For protein yield (PY) value, ERS + Mg, ERS + TF, TF + Mg have been placed in the same group, in I100 and I50 irrigation treatment. The highest value was ERS + TF (34.90 kg da−1) in I100, The lowest value was TF-control (19.90 kg da−1) in I30 irrigation treatment. In terms of mycorrhiza colonization ratio, ERS has been ranked first in all irrigation treatments, while the highest mycorrhiza colonization has been observed in I30 irrigation treatment (26.30%). ERS was followed by ERS + Mg (23.33%). As expected, the lowest mycorrhiza colonization ratio in all irrigation treatments have been observed in TF-control treatment, while the highest mycorrhiza colonization ratio has been respectively observed in I30 and I50 irrigation topics. The highest root weight (RW) in I100 irrigation treatment was observed in ERS (15.06 g plant−1) and it was observed in ERS (19.05 g plant−1; 26.30 g plant−1) in I50 and I30 irrigation treatments. The lowest RW in all irrigation treatments has been observed in TF + Mg (4.43 g plant−1, 6.40 g plant−1, 10.26 g plant−1), respectively.

Use of Trichoderma spp. and arbuscular mycorrhizal fungi to increase soil beneficial population of bacteria in a nectarine commercial orchard: Effect on root growth, nutrient acquisition and replanting disease

ABSTRACTThe aim of the present experiment was to evaluate the effect of commercial Trichoderma and arbuscular mycorrhizal fungi (AMF)-based bio-fertilizers on nectarine root growth, nutrient acquisition and replanting disease. The experiment was performed from 2008 to 2012 in an A. mellea-infected nectarine orchard subjected to the following treatments: 1) untreated control; 2) AMF-biofertilizer applied at planting (120 kg ha−1) and every year in spring and autumn at the rate of 6 kg ha−1; 3) Trichoderma spp applied at planting (5 g plant−1) and every year (in April, May and September) at 2.5 kg ha−1. AMF bio-fertilizers decreased root diameter and increased root survivorship. Leaf phosphorus concentration increased in AMF bio-fertilizers plots, while no significant treatments effects were observed on other leaf nutrient concentration. Although biofertilizer application did not affect soil microbial population, at the end of the trial (2012) the application of Trichoderma alone increased the population of the fungus.

Synergistic interaction of Rhizobium leguminosarum bv. viciae and arbuscular mycorrhizal fungi as a plant growth promoting biofertilizers for faba bean (Vicia faba L.) in alkaline soil

Egyptian soils are generally characterized by slightly alkaline to alkaline pH values (7.5–8.7) which are mainly due to its dry environment. In arid and semi-arid regions, salts are less concentrated and sodium dominates in carbonate and bicarbonate forms, which enhance the formation of alkaline soils. Alkaline soils have fertility problems due to poor physical properties which adversely affect the growth and the yield of crops. Therefore, this study was devoted to investigating the synergistic interaction of Rhizobium and arbuscular mycorrhizal fungi for improving growth of faba bean grown in alkaline soil. A total of 20 rhizobial isolates and 4 species of arbuscular mycorrhizal fungi (AMF) were isolated. The rhizobial isolates were investigated for their ability to grow under alkaline stress. Out of 20 isolates 3 isolates were selected as tolerant isolates. These 3 rhizobial isolates were identified on the bases of the sequences of the gene encoding 16S rRNA and designated as Rhizobium sp. Egypt 16 (HM622137), Rhizobium sp. Egypt 27 (HM622138) and Rhizobium leguminosarum bv. viciae STDF-Egypt 19 (HM587713). The best alkaline tolerant was R. leguminosarum bv. viciae STDF-Egypt 19 (HM587713). The effect of R. leguminosarum bv. viciae STDF-Egypt 19 and mixture of AMF (Acaulospora laevis, Glomus geosporum, Glomus mosseae and Scutellospora armeniaca) both individually and in combination on nodulation, nitrogen fixation and growth of Vicia faba under alkalinity stress were assessed. A significant increase over control in number and mass of nodules, nitrogenase activity, leghaemoglobin content of nodule, mycorrhizal colonization, dry mass of root and shoot was recorded in dual inoculated plants than plants with individual inoculation. The enhancement of nitrogen fixation of faba bean could be attributed to AMF facilitating the mobilization of certain elements such as P, Fe, K and other minerals that involve in synthesis of nitrogenase and leghaemoglobin. Thus it is clear that the dual inoculation with Rhizobium and AMF biofertilizer is more effective for promoting growth of faba bean grown in alkaline soils than the individual treatment, reflecting the existence of synergistic relationships among the inoculants.