Root Colonization Rate Research Articles

Does arbuscular mycorrhizal fungus affect cadmium uptake and chemical forms in rice at different growth stages?

Effects of the arbuscular mycorrhizal fungus (AMF) - Rhizophagus intraradices (a mix of root pieces, mycelium pieces and spores) on the temporal variation of Cd uptake and chemical forms in rice at four growth periods (tillering, jointing, flowering, and ripening stages) were investigated in soil added with 0, 2 and 10mgCdkg−1. Results showed that the interactions amongst rice growth stages, soil Cd concentrations and mycorrhizal inoculation had significant effects (P˂0.001) on root biomass, straw and root Cd concentrations, and straw Cd chemical forms in rice. Root colonization rates fluctuated with growth stages, reaching its peak at jointing stage and then decreasing at flowering and ripening stages. AMF increased the grain yield in rice plant grown in soil added with 10mgCdkg−1, whereas no effect was found in soil added with 2mgCdkg−1. In soil added with 2mgCdkg−1, the concentrations of ethanol and d-H2O extractable Cd at flowering stage was significantly reduced in mycorrhizal treatments, which subsequently induce less Cd accumulation in grains due to the positive correlations between ethanol or d-H2O extractable Cd and grain Cd concentrations at flowering stage. In soil added with 10mgCdkg−1, AMF significantly elevated the proportions of NaCl extractable Cd at ripening stage which also lead to the reduced grain Cd concentrations, since there was a negative correlation between the percentage of NaCl extractable Cd and grain Cd concentration at this stage. Our study indicated that flowering and ripening stages were important periods for AMF to limit the grain Cd concentrations in rice, when grown in Cd-contaminated soil.

Inoculum production of arbuscular mycorrhizal fungi native to soils under different forest covers

ABSTRACT The low natural fertility of Brazilian soils requires the use of inoculants that facilitate the absorption of nutrients by plants. Arbuscular mycorrhizal fungi such as obligatory biotrophics of active roots perform this function, but access to this resource is limited by the difficulty in producing inoculants. The objective of this study was to investigate the production of AMF inoculants native of soils under different forest covers in Vitória da Conquista, BA, by means of spore quantification, colonization rate and species identification. For this purpose, soils were collected from sites under Mata Nativa (native forest) and plantations of Madeira Nova (Pterogyne nitens) and Eucalyptus, placed into separate 500 mL disposable cups with seeds of Brachiaria sp. and cultivated for five months. Spores were quantified and the AMF species identified in the control soil (without brachiaria) and in the cups cultivated with brachiaria at each month. From the first month, the colonization rate of brachiaria roots was evaluated. The inoculants produced showed differences in the number of spores and species, in the AMF species identified, and in the root colonization rate as a function of the forest cover. Thus, considering the increase in the number of spores, species and colonization over time, the inoculant produced from the soil under native forest was more promising for utilization.

Tracing of Two Pseudomonas Strains in the Root and Rhizoplane of Maize, as Related to Their Plant Growth-Promoting Effect in Contrasting Soils.

TaqMan-based quantitative PCR (qPCR) assays were developed to study the persistence of two well-characterized strains of plant growth-promoting rhizobacteria (PGPR), Pseudomonas fluorescens Pf153 and Pseudomonas sp. DSMZ 13134, in the root and rhizoplane of inoculated maize plants. This was performed in pot experiments with three contrasting field soils (Buus, Le Caron and DOK-M). Potential cross-reactivity of the qPCR assays was assessed with indigenous Pseudomonas and related bacterial species, which had been isolated from the rhizoplane of maize roots grown in the three soils and then characterized by Matrix-Assisted Laser Desorption Ionization (MALDI) Time-of-Flight (TOF) mass spectrometry (MS). Sensitivity of the qPCR expressed as detection limit of bacterial cells spiked into a rhizoplane matrix was 1.4 × 102 CFU and 1.3 × 104 CFU per gram root fresh weight for strain Pf153 and DSMZ 13134, respectively. Four weeks after planting and inoculation, both strains could readily be detected in root and rhizoplane, whereas only Pf153 could be detected after 8 weeks. The colonization rate of maize roots by strain Pf153 was significantly influenced by the soil type, with a higher colonization rate in the well fertile and organic soil of Buus. Inoculation with strain DSMZ 13134, which colonized roots and rhizoplane to the same degree, independently of the soil type, increased yield of maize, in terms of biomass accumulation, only in the acidic soil of Le Caron, whereas inoculation with strain Pf153 reduced yield in the soil Buus, despite of its high colonization rate and persistence. These results indicate that the colonization rate and persistence of inoculated Pseudomonas strains can be quantitatively assessed by the TaqMan-based qPCR technique, but that it cannot be taken for granted that inoculation with a well-colonizing and persistent Pseudomonas strain has a positive effect on yield of maize.

Diversity and abundance of arbuscular mycorrhizal fungi under different plant and soil properties in Sidama, southern Ethiopia

In Sidama, agroforestry represents land-use systems with deliberate management of multipurpose trees and shrubs that grow in intimate association with annual and perennial agricultural crops and/or livestock. The interaction of microbiota with the trees, shrubs and crops may make the system fertile, productive and sustainable. One of the beneficial microbiota which has symbiotic association with most of the plants in agroforestry is arbuscular mycorrhizal fungi (AMF). In November and December of 2012, root and rhizosphere soil samples of 21 plant species from nine peasant associations (PAs) (villages within districts where 300–500 families live) were collected from the agroforestry practices in Sidama of Southern Ethiopia for the determination of diversity and abundance of AMF under selected soil parameters and plant species density. Findings on the diversity of AMF based on soil properties showed that at moderate to low P and N concentrations the rate of AMF root colonization and spore density was high in comparison with the rhizosphere soils with the highest P and N concentration. The highest percentage of total AMF colonization was recorded for shade trees Millettia ferruginea (84 %) and Erythrina brucei (80 %) followed by intercropped perennial crops Ensete ventricosum (86 %), Catha edulis (85 %) and Coffea arabica (80 %) and the lowest percentage AMF colonization was recorded for Rhamnus prinoides (53 %) and Colocasia esculenta (52 %). Though found in almost all homegarden agroforestry practices and with broad coverage in Sidama agroforestry, some crops and vegetables such Brassica integrifolia and Cucurbita pepo, grown intercropped were found to be non-mycorrhizal as none of the AMF structures were recorded. The highest number of AM spore population was recorded in rhizosphere soils of Croton macrostachyus (1066 ± 19.33) and Catha edulis (1054 ± 53.12) and the lowest spore density was recorded for Dioscorea alata (100.00 ± 2.89) spore per 100 g of dry soil. The percentage fungal colonization in any individual plant species and spore population in the rhizosphere soils of that species did not correlate to each other and percentage AM root colonization and spore density of all plants in the agroforestry of Sidama were found significantly different at P < 0.05 level.

Inoculation with a Pb-tolerant strain of Paxillus involutus improves growth and Pb tolerance of Populus\u2009\xd7\u2009canescens under in vitro conditions

AimsEctomycorrhizal fungi can improve poplar growth and tolerance to heavy metal stress, and may be useful during the afforestation and phytoremediation of polluted regions with poplar trees. In this study, we determined the effects of the symbiotic interaction between Populus × canescens trees and Paxillus involutus strains different in their tolerance to lead.MethodsIn vitro inoculated and non-inoculated plants were treated with 0.75 mM Pb(NO3)2. The root colonization rate of the two fungal strains, as well as their impacts on poplar health and lead accumulation were examined.ResultsBased on the colonization level, the roots were classified into one of three categories: non-mycorrhized, changed (ie, fungal cells were present on the root surface, but the Hartig net did not fully develop), and fully mycorrhized. The lead-tolerant P. involutus strain colonized roots better than the non-tolerant strain (ie, changed and fully mycorrhized roots). Moreover, plants inoculated with the tolerant fungal strain grew better than the control plants (217 % increase in dry weight over the controls), and accumulated lead in the roots and stems.ConclusionsInoculation of P. × canescens trees with a Pb-tolerant strain of P. involutus improves host plant growth and may increase Pb phytostabilization potential.

Impact of a natural soil salinity gradient on fungal endophytes in wild barley (Hordeum maritimum With.)

Occurrence and distribution pattern of fungal endophytes in different tissues of halophytic plants across saline depressions are poorly studied. We investigated the endophytic fungal communities inhabiting roots, stems and leaves of Hordeum maritimum collected in a soil salinity gradient, i.e. non-saline, slightly saline and saline, using a culture-dependent approach. A total of 20 taxa belonging to Ascomycota phylum were identified by ITS rRNA gene sequence. Pyronema domesticum and Alternaria spp. were the most frequently isolated. Roots host higher diversity and were more frequently colonized by endophytes than aboveground organs. Endophytic composition of all organs surveyed differed according to salinity gradient. Contrary to expectations, the colonization rate of roots increased with soil salinity, indicating that under salt stress the endophyte-plant association is promoted. All the isolates exhibited in vitro saline tolerance, especially those belonging to genera Xylaria, Chalastospora, Alternaria and Pyronema. Fungal tolerance to NaCl under in vitro conditions appears to be more dependent on the isolates than on the sites of their isolation, suggesting that under natural conditions other factors, beyond soil salinity, should be taken into account. These findings highlight the importance of fungal endophytes in the protection and/or adaptation of both interacting species (plant-fungus) to salt stress under natural conditions.

The Role of the Arbuscular Mycorrhizal Maize (Zea mays L.) and Phosphorus levels in the phytoremediation of zinc contaminated soil.

The factorial experiment under greenhouse condition was conducted to investigate the effects of AMF on phytoremediation of zinc contaminated soil. Maize plants inoculated and non-inoculated with Glomus mossea were grown under five levels of Zinc addition (0, 100, 300, 600, and 900〖 mg kg〗^(-1) ) and three levels of phosphorus addition (0, 25, 50 mg kg^(-1)). No mycorrhizal colonization was detected in the roots of non-inoculated plants. The higher value of colonized roots in inoculated plants was in treatment (+MP0Zn4) 69% while the lower value was in the treatment (+MP2Zn3) 35%. An addition of phosphorus fertilization significantly decrease colonization rate of roots. Inoculation with AMF increased shoots and roots dry matter weight, Zn uptake in shoots and phosphorus concentration and uptake in shoots and roots. Inoculation with AMF decreases Zn concentration in shoots and increases Zn concentration in roots in moderate and high levels of Zn addition. Dry matter weight of shoots and roots significantly decreases with increase of Zinc addition in non mycorhizal plants; however, there is no significant effect of the zinc addition on shoots and roots dry matter weight in mycorrhizal plants. These results are good evidence that AMF increases host plant tolerance to Zn contamination. An addition of phosphorus increases shoots and roots dry matter, phosphorus concentration and uptake. This study suggests that AMF protect maize plants from Zn toxicity and enhance phytoremediation of Zn contaminated soil by two mechanisms: dilutions effects and accumulate Zn in roots and fungi mycelium

English

In Sidama, agroforestry represents land-use systems with deliberate management of multipurpose trees and shrubs that grow in intimate association with annual and perennial agricultural crops and/or livestock. The interaction of microbiota with the trees, shrubs and crops make the system fertile, productive and sustainable. One of the beneficial microbiota which has symbiotic association with most of the plants in agroforestry is arbuscular mycorrhizal fungi (AMF). In November and December of 2012, root and rhizosphere soil samples of 21 plant species from nine peasant associations (PAs) (villages within districts where 300 to 500 families live) were collected from the agroforestry practices in Sidama of Southern Ethiopia for the determination of diversity of AMF based on selected soil parameters and plant species density. Findings on the diversity of AMF based on soil properties showed that at moderate to low P and N concentrations the rate of root colonization and spore density was high in comparison with the rhizosphere soils with the highest P and N concentration. The highest percentage of total colonization was recorded for shade trees Millettia ferruginea (84%) and Erythrina brucei (80%) followed by intercropped perennial crops Ensete ventricosum (86%), Catha edulis (85%) and Coffea arabica (80%) and the lowest percentage colonization was recorded for Rhamnus prinoides (53%) and Colocasia esculenta (52%). Though found in almost all homegarden agroforestry practices and with broad coverage in Sidama agroforestry, some crops and vegetables such Brassica integrifolia and Cucurbita pepo, grown intercropped were found to be non-mycorrrhizal as none of the AMF structures were recorded. The highest number of AM spore population was recorded in rhizosphere soils of Croton macrostachyus (1066±19.33) and Catha edulis (1054±53.12) and the lowest spore density was recorded for Dioscorea alata (100.00±2.89) spore per 100 g of dry soil. The percentage fungal colonization in any individual plant species and spore population in the rhizosphere soils of that species did not correlate to each other and percentage root colonization and spore density of all plants in the agroforestry of Sidama were found significantly different at P<0.05 level. Key words: Arbuscular mycorrhizal fungi (AMF), dependency, rhizosphere, parameters, colonization, density.

Soil and seasons affect arbuscular mycorrhizal fungi associated with Tamarix rhizosphere in arid and semi-arid steppes

The arbuscular mycorrhizal fungi (AMF) diversity associated to Tamarix articulata and Tamarix gallica rhizosphere was investigated in the Algerian steppic area. Evaluation of species diversity revealed the presence of 10 glomoid and one gigasporoid spore types of AMF species from the ten studied sites. Shannon biodiversity index showed that AMF species diversity varied according to soil physico-chemical characteristics of the different sites. However, seasonal variation affected abundance but not AMF species biodiversity. Significant effect of soil and seasons on AMF root colonization rate was also observed. Overall, AMF Tamarix root colonization rates varied according to the species ranging from 0.88 to 75.26% in T. articulata and from 1.90 to 12.96% in T. gallica. This study highlighted the complexity of Tamarix species/AMF symbiosis through seasons associated with plant phenology and soil physico-chemical composition in arid and semi-arid steppes.

Effect of Funneliformis mosseae on growth, mineral nutrition, biochemical indexes and chlorophyll content of Ziziphus spina-christi seedlings at different salinities

Vast area of the land around the world is saline. Knowledge of plant behavior and their interaction with mychorrizal fungi in saline areas may help seedling establishment in such environments. This study aimed to determine the effects of the inoculation of the fungus Funneliformis mosseae (FM) on Ziziphus spina-christi (Rhamnaceae) plants grown under salt stress. Mycorrhizal and non-mycorrhizal seedlings were exposed to different levels of NaCl in the soil (0, 50, 100, and 150 mM). The following parameters were measured in both inoculated and non-inoculated plants: root colonization rate, seedling height, root diameter, root and shoot dry weights, chlorophyll a and b, total nitrogen (N), phosphorus (P), potassium (K) and sodium (Na+) content, proline accumulation in roots and leaves, superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activities. The results showed that soil salinity hampered the root colonization by the fungus, and decreased basal diameter, seedling height, root and shoot dry weights, as well as some nutrients and chlorophyll a concentration, while increased leaves and roots Na+, SOD and POD activity, proline accumulation, as well as CAT activity in the roots. Contrastingly, no significant effect of soil salinity were detected on K and CAT of leaves, root N, and chlorophyll b. Inoculated plants had higher basal diameter, leaves and roots P, root and shoot dry weights, chlorophyll a and lower SOD content, proline accumulation in leaves and Na+, as compared with non-inoculated plants. Seedling height, root N, CAT and POD content, and chlorophyll b were not affected by inoculation with FM. These results demonstrated that FM inoculation is a promising method for improving the growth of Z. spina-christi seedlings under salt stress.

Diversity and Abundance of Arbuscular Mycorrhizal Fungi Under Different Plant and Soil Properties in Sidama, Southern Ethiopia

In Sidama, agroforestry represents land-use systems with deliberate management of multipurpose trees and shrubs that grow in intimate association with annual and perennial agricultural crops and/or livestock. The interaction of microbiota with the trees, shrubs and crops make the system fertile, productive and sustainable. One of the beneficial microbiota which has symbiotic association with most of the plants in agroforestry is arbuscular mycorrhizal fungi (AMF). In November and December of 2012, root and rhizosphere soil samples of 21 plant species from nine peasant associations (PAs)(villages within districts where 300-500 families live) were collected from the agroforestry practices in Sidama of Southern Ethiopia for the determination of diversity and abundance of AMF under selected soil parameters and plant species density. Findings on the diversity of AMF based on soil properties showed that at moderate to low P and N concentrations the rate of AMF root colonization and spore density was high in comparison with the rhizosphere soils with the highest P and N concentration. The highest percentage of total AMF colonization was recorded for shade trees Millettia ferruginea (84%) and Erythrina brucei (80%) followed by intercropped perennial crops Ensete ventricosum (86%), Catha edulis (85%) and Coffea arabica (80%) and the lowest percentage AMF colonization was recorded for Rhamnus prinoides (53%) and Colocasia esculenta (52%). Though found in almost all homegarden agroforestry practices and with broad coverage in Sidama agroforestry, some crops and vegetables such Brassica integrifolia and Cucurbita pepo, grown intercropped were found to be non-mycorrrhizal as none of the AMF structures were recorded. The highest number of AM spore population was recorded in rhizosphere soils of Croton macrostachyus (1066±19.33) and Catha edulis (1054±53.12) and the lowest spore density was recorded for Dioscorea alata (100.00±2.89) spore per 100 g of dry soil. The percentage fungal colonization in any individual plant species and spore population in the rhizosphere soils of that species did not correlate to each other and percentage AM root colonization and spore density of all plants in the agroforestry of Sidama were found significantly different at P<0.05 level.

Effects of Arbuscular Mycorrhizal Fungi on the production of tomato in Togo

A field study was conducted to assess the effectiveness of the Arbuscular Mycorrhizal Fungus (AMF) Glomus sp. on the plant growth, the flowering and the fruit yield of tomato (Lycopersicon esculentum, Mill.). Thus, 4 strains of Glomus sp. (M233, M353, B3 and Gd) were tested in comparison with NPK fertilizer on 3 tomato varieties ICRIXINA, TROPIMECH and PETO76, using a complete randomized block design with three replications. The results revealed that 84 days after transplanting (DAT), the rate of root colonization by the fungus did not exceed 25%, and the plant height was not affected by AMF inoculation, whereas M353 induced late flowering on ICRIXINA at 69 DAT and PETO76 at 74 DAT. Also the four AMF strains induced similar fruit yields as that of NPK for each of the 3 tomato varieties used. However, the response of tomato plants to AMF varied with the varieties.Keywords: AMF strains, effectiveness, tomato production, Togo.

Interaction between earthworms and arbuscular mycorrhizal fungi on the degradation of oxytetracycline in soils

The interactive impact of earthworms (Eisenia fetida) and arbuscular mycorrhizal fungi (Rhizophagus intraradices, AM fungi) on the degradation of oxytetracycline (OTC) in soils was studied under greenhouse conditions. Treatments included maize plants inoculated vs. not inoculated with AM fungi and treated with or without earthworms at low (1 mg kg−1 soil DM) or high (100 mg kg−1 soil DM) OTC rates. The root colonization rate, the hyphal density of mycorrhizae, the residual OTC concentration in soils, catalase, dehydrogenase, urease, soil microbial biomass C, Shannon–Wiener index (H) for microbial communities from T-RFLP profiles were measured at harvest. The results indicated that earthworms and AM fungi would individually or interactively enhance OTC decomposition and significantly decreased the residual OTC concentration at both high and low OTC rates. Both earthworms and AM fungi could promote the degradation of OTC by increasing soil microbial biomass C at both high and low OTC rates. The effect of soil enzyme activity and soil microbial diversity on OTC decomposition was different between high and low OTC rates. Hyphomicrobium and Bacillus cereus were dominant bacteria, and Thielavia and Chaetomium were dominant phyla of fungi at all occasions. Earthworm activity stimulated the growth of Hyphomicrobium and Thielavia, while AM fungi may stimulate B. cereus, Thielavia and Chaetomium, resulting in greater OTC decomposition. The interaction between earthworms and AM fungi in affecting the degradation of OTC may be attributed to different mechanisms, depending on soil microbial biomass, function (enzyme activity) and communities (the abundance of Hyphomicrobium, B. cereus, Thielavia and Chaetomium) in the soil.

Is the arbuscular mycorrhizal fungus Rhizophagus irregularis able to fulfil its life cycle in the presence of diesel pollution?

The present work examined the impact of increasing diesel concentrations (0.05, 0.1, 0.25, 0.5 and 1%) on the development of both partners of the arbuscular mycorrhizal symbiosis: Rhizophagus irregularis and chicory roots (Cichorium intybus L.) grown in vitro. Our findings showed that although the different diesel concentrations tested (0.05, 0.1, 0.25, 0.5%) affect negatively the main stages of R. irregularis development (germination, germinative hyphal elongation, root colonization rate, extraradical hyphae development, sporulation) and the chicory root growth, they are not completely inhibited, except at 1%. The arbuscular mycorrhizal fungus was able to fulfil its life cycle in the presence of the pollutant. No increase in malondialdehyde (MDA) production – a biomarker of lipid peroxidation – was detected in diesel-exposed mycorrhizal or non-mycorrhizal roots, suggesting that the negative effect of diesel on the chicory roots growth could not result from the alteration of membrane lipids. Moreover, our results pointed out that the diesel toxic effect on the growth of chicory roots is less noticeable when they are mycorrhized, indicating a protective effect of mycorrhization. This protection could be related to induction of antioxidant enzyme peroxidase activity, but not to superoxide dismutase activity. Taken together, our results demonstrated the toxic effect of diesel on the mycorrhizal symbiosis and suggest a probable involvement of the mycorrhizal fungus in the protection of chicory roots against oxidative stress induced by diesel.

Effects of arbuscular mycorrhizal fungi on ecological restoration in coal mining areas

In the coal mining subsidence areas in arid and barren locations in western China where plants are difficult to grow, the root of A. fruticosa was inoculated with arbuscular mycorrhizal fungi (AMF). The effects of inoculation with AMF on the growth of A. fruticosa and improvement of the degraded soil were determined. Results showed that the selected AMF and A. fruticosa had a strong symbiotic relation. Sixteen months after inoculation, the root colonization rate in A. fruticosa reached 88%. Inoculation with AMF was shown to promote the growth and root development of A. fruticosa and improve rhizospheric soil and fertilization of A. fruticosa. After the inoculation, the contents of organic matters and glomalin-associated proteins in the rhizospheric soil of A. fruticosa increased significantly. Sixteen months after the inoculation, the acidic phosphatase activity in the rhizosphere of A. fruticosa in the inoculated plots increased by 44% compared with that of the control plot, and the content of available phosphorus was 2.5 times that of the control. Hence, inoculation with AMF improves the rhizosphere of A. fruticosa, promotes a stable ecosystem in the mining area.

Synergistic effects between Suilllus luteus and Trichoderma virens on growth of Korean spruce seedlings and drought resistance of Scotch pine seedlings

Korean spruce (Picea koraiensis Sieb. El Zucc.) is one of the main afforestation species in northern China. Seedling quality is a critical factor at planting time. To test whether the synergistic growth enhancement of Scotch pine (P. sylvestris var. mongolica) seedlings brought by the plant beneficial fungus Trichoderma virens (J.H. Mill., Giddens and A.A. Foster) Arx and ectomycorrhizal fungus (Suillus luteus (L.) Roussel.) can also benefit Korean spruce seedlings, we examined the effects of S. luteus and T. virens on the growth of P. koraiensis seedlings and drought resistance of P. sylvestris var. mongolica in peat soils. The two fungi were added to sterilized peat soil in pots, and the plants were grown for 4 months. Seedling growth and physiological variables, including mycorrhizal colonization rate of roots, biomass, and chlorophyll content, were examined. The colonization rate of the mycorrhizal fungus on P. koraiensis exceeded 65 %, and the synergism between S. luteus and T. virens enhanced most of the variables for P. koraiensis seedlings after inoculation with S. luteus then 30 days later with T. virens as in our published results for seedlings of P. sylvestris var. mongolica. When seedlings of P. sylvestris var. mongolica were inoculated with this sequence, they became more drought tolerant. T. virens also induced S. luteus to produce -1,3-glucanase and chitinase. This inoculation sequence at planting can thus improve the quality of P. sylvestris var. mongolica and P. koraiensis seedlings and substantiates our previous results.

Impact of soil salinity on arbuscular mycorrhizal fungi biodiversity and microflora biomass associated with Tamarix articulata Vahll rhizosphere in arid and semi-arid Algerian areas

Soil salinization is an increasingly important problem in many parts of the world, particularly under arid and semi-arid areas. Unfortunately, the knowledge about restoration of salt affected ecosystems using mycorrhizae is limited. The current study aims to investigate the impact of salinity on the microbial richness of the halophytic plant Tamarix articulata rhizosphere. Soil samples were collected from natural sites with increasing salinity (1.82–4.95 ds.m−1). Six arbuscular mycorrhizal fungi (AMF) species were isolated from the different saline soils and identified as Septoglomus constrictum, Funneliformis mosseae, Funneliformis geosporum, Funneliformis coronatum, Rhizophagus fasciculatus, and Gigaspora gigantea. The number of AMF spores increased with soil salinity. Total root colonization rate decreased from 65 to 16% but remained possible with soil salinity. Microbial biomass in T. articulata rhizosphere was affected by salinity. The phospholipid fatty acids (PLFA) C16:1ω5 as well as i15:0, a15:0, i16:0, i17:0, a17:0, cy17:0, C18:1ω7 and cy19:0 increased in high saline soils suggesting that AMF and bacterial biomasses increased with salinity. In contrast, ergosterol amount was negatively correlated with soil salinity indicating that ectomycorrhizal and saprotrophic fungal biomasses were reduced with salinity. Our findings highlight the adaptation of arbuscular and bacterial communities to natural soil salinity and thus the potential use of mycorrhizal T. articulata trees as an approach to restore moderately saline disturbed arid lands.

Arbuscular mycorrhizal fungal symbiosis with Sorbus torminalis does not vary with soil nutrients and enzyme activities across different sites

Effects of soil chemical properties on arbuscular mycorrhizal fungal (AMF) symbiosis with wild service tree (Sorbus torminalis L. Crantz) were examined for study the rates of root colonization at three forest sites: Kheiroud, Lalis, and Takrin in northern Iran. Soil characteristics including pH, available phosphorus (P), potassium (K), organic matter, total nitrogen, acid and alkaline phosphatase activities, CaCO3, spore density (SD) and AMF colonization of soil and root samples were analyzed. The study sites were investigated in spring and autumn to highlight the effects of soil chemical properties on AMF statues for better nurseries and reforestation management of this rare tree species in forests. Changes in soil pH, P, K, organic matter, total nitrogen, acid and alkaline phosphatase, CaCO3, SD, and AMF colonization of soil and root samples were analyzed at the study sites. K, pH, root colonization, SD and acid phosphatase activity showed no significant differences among sites in spring and autumn, while total nitrogen, P, organic matter and alkaline phosphatase activities showed significant differences among sites and seasons. AMF colonization rates were more than 51% and 32% of roots in spring and autumn, respectively. No correlation between root colonization and soil chemical parameters in spring and autumn were detected. There was no correlation between percentage of AM root colonization and SD nor other soil parameters in spring and autumn. SD and CaCO3 were significantly negatively correlated in spring and autumn. Despite differences in soil characteristics, the results showed that SD and root colonization were not significantly different among the sites. They also showed that wild service trees had strong symbiosis with AMF, while soil properties might not have a significant effect on this symbiosis. Therefore, colonized seedlings can be considered as an appropriated method for reforestation and conservation of this rare tree species.

Physiological responses of halophytic C&lt;sub&gt;4&lt;/sub&gt; grass Aeluropus littoralis to salinity and arbuscular mycorrhizal fungi colonization

The halophytic C4 grass, Aeluropus littoralis, was cultivated under low (50 mM) and high (200 mM) NaCl salinity and inoculated with the arbuscular mycorrhizal fungi (AMF) Claroideoglomus etunicatum in a sand culture medium for 20 weeks. Shoot and root dry mass increased under salinity conditions up to 24 and 86%, respectively. Although the root colonization rate significantly decreased in the presence of salt, AMF-colonized (+AMF) plants had higher biomass compared with plants without AMF colonization (-AMF) only under saline conditions. Net CO2 assimilation rate increased significantly by both salinity levels despite stable stomatal opening. In contrast, AMF-mediated elevation of the net CO2 assimilation rate was associated with a higher stomatal conductance. Unexpectedly, leaf activity of phosphoenolpyruvate carboxylase decreased by salinity and AMF colonization. Transpiration rate was not affected by treatments resulting in higher water-use efficiency under salinity and AMF conditions. Concentrations of soluble sugars and free α-amino acids increased by both salinity and AMF treatments in the shoot but not in the roots. Proline concentration in the leaves was higher in the salt-treated plants, but AMF colonization did not affect it significantly. Leaf activity of nitrate reductase increased by both salinity and AMF treatments. Mycorrhizal plants had significantly higher Na+ and K+ uptake, while Ca2+ uptake was not affected by salt or AMF colonization. The ratio of K+/Na+ increased by AMF in the shoot while it decreased in the roots. Leaf osmotic potential was lowered under salinity in both +AMF and -AMF plants. Our results indicated that higher dry matter production in the presence of salt and AMF could be attributed to higher CO2 and nitrate assimilation rates in the leaves. Higher leaf accumulation of soluble sugars and α-amino acids but not proline and elevated water-use efficiency were associated with the improved growth of A. littoralis inoculated with AMF.

Long-term fertilizer application effects on the soil, root arbuscular mycorrhizal fungi and community composition in rotation agriculture

Arbuscular mycorrhizal fungi (AMF) play key roles in plant growth, ecosystem sustainability and stability. However, it is still unclear how the soil, root AMF growth and community composition are affected by fertilizer application in subtropical wheat–rice rotation agro-ecosystems. We investigated the impact of different organic and/or inorganic fertilizers on AMF growth and community composition in a long-term experiment field in Zhejiang Province, east China. AMF biomass was determined using 16:1ω5 phospholipid fatty acids (PLFAs) and neutral lipid fatty acids (NLFAs) content. Soil and root AMF community compositions were determined by DGGE analysis, cloning, sequencing and phylogenetic analyses. The root colonization rate was not significantly affected by different fertilizer regimes. Manure amendment significantly enhanced both AMF hyphal (i.e., 16:1ω5 PLFA) and spore (i.e., 16:1ω5 NLFA) biomass content, while inorganic fertilizer only increased the AMF spore biomass. A total of 10 and 11 Glomeromycota phylotypes were detected in soil and root samples, respectively. Glomus was the dominant genus in both soil and root samples, while Acaulospora genus occurred in roots only. Although the different fertilizers altered soil AMF communities, the root AMF community structure was not significantly altered. Soil pH (F=5.695, P<0.01) and available K (F=4.888, P<0.01) contributed to both soil and root AMF community composition, while the C/P ratio (F=3.893, P<0.01) only contributed to soil AMF community. The data suggests that high soil organic C content benefits AMF growth, while soil pH and available K concentration strongly influence AMF community. The root AMF community was much more resilient to the changes caused by long-term fertilizer application than the soil community.