Improved observation of colonized roots reveals the regulation of arbuscule development and senescence by drought stress in the arbuscular mycorrhizae of citrus

Citrus is the typical mycorrhizal fruit tree species establishing symbiosis with arbuscular mycorrhizal (AM) fungi. However, arbuscule development and senescence in colonized citrus roots, especially in response to drought stress, remain unclear, which is mainly due to the difficulty in clearing and staining lignified roots with the conventional method. Here, we improved the observation of colonized roots of citrus plants with the sectioning method, which enabled the clear observation of AM fungal structures. Furthermore, we investigated the effects of one week of drought stress on arbuscule development and senescence with the sectioning method. Microscopy observations indicated that drought stress significantly decreased mycorrhizal colonization (F%and M%) although it did not affect plant growth performance. Fluorescence probes (WGA 488 and/or Nile red) revealed that drought stress inhibited arbuscule development by increasing the percentage of arbuscules at the early stage and decreasing the percentages of arbuscules at the midterm and mature stages. Meanwhile, drought stress accelerated arbuscule senescence, which was characterized by the increased accumulation of neutral lipids. Overall, the sectioning method developed in this study enables the in-depth investigation of arbuscule status, and drought stress can inhibit arbuscule development but accelerate arbuscule senescence in the colonized roots of citrus plants. This study paves the way to elaborately dissecting the arbuscule dynamics in the roots of fruit tree species in response to diverse abiotic stresses.

Efficacy of Mycorrhizae Based Manure on the Vegetative Growth of Rice Grown within Bauchi State, Nigeria

Background: Rice is one of the staple crops in the African continent for its ability to give maximum yields which can help to achieve food security under the sustainable development goals (SDGs);to those effects, the incessant use of inorganic fertilizer has been employed which proved to have devastating effect in the environment and the ecosystem at large. Therefore, the thirst for an alternative method to ensure bumper production of rice cannot be overemphasized so as to prevent soil alteration and environmental damage. Objective: This study aimed at determining the efficacy of mycorrhizae-based manure on the vegetative growth of rice as compared to inorganic fertilizer and its sustainability. Methods: Soil samples were collected from seven (7) locations (M1 - M7). Mycorrhiza were isolated from the soils and mass produced, mixed with organic waste to form manure (biofertilizer) and were applied at concentrations of 50 g, 100 g and 150 g to the potted rice in tree (3) replicates. Growth parameters observed were plant height, girth diameter, leaf broadness and leaf number. Results: The result revealed mycorrhizal spore count ranging from 1.7 × 107 - to 4.1 × 107 across the locations. The mycorrhizae-based manure gives the highest plant height of 45.33 cm as compared with the least plant height of 18.5 cm from the inorganic fertilizer. Furthermore, the biofertilizer gives a positive influence on the other parameters observed in comparison with the inorganic fertilizer. Statistical analysis shows that, the means of all the parameters except for leaf numbers were significantly different at p ≤ 0.05 across the sampling locations. Conclusions: Mycorrhizae-based manure proves to be an effective replacement of inorganic fertilizer that can boost rice production at a cheaper cost.

Effects of metal lead on growth and mycorrhizae of an invasive plant species (Solidago canadensis L.)

It is less known whether and how soil metal lead （Pb） impacts the invasion of exotic plants. A greenhouse experiment was conducted to estimate the effects of lead on the growth and mycorrhizae of an invasive species （Solidago canadensis L.） in a microcosm system. Each microcosm unit was separated into HOST and TEST compartments by a replaceable mesh screen that allowed arbuscular mycorrhizal （AM） fungal hyphae rather than plant roots to grow into the TEST compartments. Three Pb levels （control, 300, and 600 mg/kg soil） were used in this study to simulate ambient soil and two pollution sites where S. canadensis grows. Mycorrhizal inoculum comprised five indigenous arbuscular mycorrhizal fungal species （ Glomus mosseae, Glomus versiform, Glomus diaphanum, Glomus geosporum, and Glomus etunicatum）. The ^15N isotope tracer was used to quantify the mycorrhizally mediated nitrogen acquisition of plants. The results showed that S. canadensis was highly dependent on mycorrhizae. The Pb additions significantly decreased biomass and arbuscular mycorrhizal colonization （root length colonized, RLC%） but did not affect spore numbers, N （including total N and ^15N） and P uptake. The facilitating efficiency of mycorrhizae on nutrient acquisition was promoted by Pb treatments. The Pb was mostly sequestered in belowground of plant （root and rhizome）. The results suggest that the high efficiency of mycorrhizae on nutrient uptake might give S. canadensis a great advantage over native species in Pb polluted soils.

Contribution to Confirmed &Synthesized on Mycorrhizae of <i>Tuber indicum</i>s.l. with Two Dominated &Subalpine Broadleaf Trees in Southwestern China

The ascomata and mycorrhizae of Tuber indicum s.l. were collected under the forest of broad-leaf species Populus yunnanensis and Quercus pannosa in the field respectively. The symbiotic relationships of both trees with T. indicum were examined and affirmed based on morphology and ITS-rDNA sequences. These two mycorrhizal combinations were successfully produced on artificially controlled substrates and cultural condition. This is the first report of a mycorrhizal association and synthesis between Chinese black truffles and poplars. A hyphal net covering the mantle’s surface of the mycorrhizae was detected in both mycorrhizal combinations. The mycorrhizal colonization of P. yunnanensis and Q. pannosa suggests that T. indicum s.l. has a broader host range and that additional corresponding wood species would be used as candidates for the cultivation of T. indicum. The nuclear-ITS sequences of the mycorrhizae included in the phylogeny of the T. indicum complex revealed that the two clades within the complex do not markedly differ with respect to their preferences for host species or geographical origin. Our results help to explain the wide distribution of both clades of the T. indicum complex. It would be more important for truffle conservation and Chinese black truffle plantation development with these two dominated & alpestrine Populus yunnanensis and Quercus pannosa at subalpine limestone areas in China.

Soil compaction and arbuscular mycorrhizae affect seedling growth of three grasses

Soil compaction is a limitation to establishment of native forest species on reclaimed surfacemined lands in Appalachia. Previously, non-native forage species such as tall fescue (Schedonorus arundinaceus(Schreb.) Dumort., nom. cons.) have been planted because they easily established on reclaimed mine soil. There is now interest in establishing robust native prairie species to enhance biodiversity and provide greater potential for root activity in the compacted soil. We conducted a 10-week glasshouse study comparing growth of “Pete” eastern gamagrass (Tripsacum dactyloidesL.), “Bison” big bluestem (Andropogon gerardiiVitman), and “Jesup MaxQ” tall fescue at soil bulk densities (BD) of 1.0, 1.3, and 1.5 g·cm-3. We also examined effects of arbuscular-mycorrhizal fungi (AMF) on plant growthin relation to compaction. Sources of AMF were a reclaimed surface coal mine soil and a native tallgrass prairie soil. Shoot and root biomass of tall fescue and big bluestem were reduced at 1.5 BD while eastern gamagrass growth was not affected. Growth ofbig bluestem and eastern gamagrass was greaterwith AMF than without, butsimilar between AMF sources. Tall fescue growthwas not enhanced by AMF. Overall, tall fescue biomass was 3 times greater than eastern gamagrass and 6 times greater than big bluestem when comparing only AMF-colonized grasses. Eastern gamagrass and big bluestem are both slower to establish than tall fescue. Eastern gamagrass appears to be more tolerant of compaction, while big bluestem appears somewhat less tolerant.

Interactions between a Root Knot Nematode (<i>Meloidogyne exigua</i>) and Arbuscular Mycorrhizae in Coffee Plant Development (<i>Coffea arabica</i>)

This paper focuses on parasitic root knot nematodes (Meloidogyne exigua) and how to decrease their pathogenic effect on coffee plants (Coffea arabica), by examining the behaviour of and the interactions between nematodes, coffee plant and arbuscular mycorrhizae (AM). The experiment was carried out at the seedling stage, with six (6) treatments (plants with M. exigua, plants with arbuscular mycorrhizae, plants with both organisms, and the same time, first mycorrhizae plants, then nematodes were inoculated and vice versa). After 5 months the measured variables were: dry biomass (roots and shoot), nematode knots caused by M. exigua in root, nematode juvenile (J2) found in 100.0 g of soil, and mycorrhizal percentage. Plant nutrients (P and N) contents were analysed. Significant differences were found in all the variables, but concentration N content in plants. Plants with mycorrhizae and plants with mycorrhizae and then inoculated with nematodes have the same behaviour. Control plants and plants with nematode and then inoculated with mycorrhizae behave similarly. It is thought that arbuscular mycorrhizae are formed before the nematode infestation, allowing coffee plants to regain the energy lost by the parasitic interaction. AM may help coffee plants with lignifications of the plant cell wall cuticle. As the cuticle thickens it is more difficult for nematodes to penetrate and enter into plant roots. Therefore, arbuscular mycorrhizae help coffee plants to uptake and transport nutrients, improving its nutritional status and stabilizing nematode attacks. It is suggested that symbiotic interactions help neutralize parasitic interactions.

Applications of beneficial plant growth promoting rhizobacteria and mycorrhizae in rhizosphere and plant growth:A review

Because of climate change and the highly growing world population,it becomes a huge challenge to feed the whole population.To overcome this challenge and increase the crop yield,a large number of fertilizers are applied but these have many side effects.Instead of these,scientists have discovered beneficial rhizobacteria,which are environmentally friendly and may increase crop yield and plant growth.The microbial population of the rhizosphere shows a pivotal role in plant development by inducing its physiology.Plant depends upon the valuable interactions among the roots and microbes for the growth,nutrients availability,growth promotion,disease suppression and other important roles for plants.Recently numerous secrets of microbes in the rhizosphere have been revealed due to huge development in molecular and microscopic technologies.This review illustrated and discussed the current knowledge on the development,maintenance,interactions of rhizobacterial populations and various proposed mechanisms normally used by PGPR in the rhizosphere that encouraging the plant growth and alleviating the stress conditions.In addition,this research reviewed the role of single and combination of PGPR,mycorrhizal fungi in plant development and modulation of the stress as well as factors affecting the microbiome in the rhizosphere.

Root-associated endophytic fungi modulate endogenous auxin and cytokinin levels to improve plant biomass and root morphology of trifoliate orange

Root-associated endophytic fungi like Serendipita indica and arbuscular mycorrhizal(AM) fungi can improve plant growth and root construction, but the potential mechanism is unclear. In this study, Funneliformis mosseae(an AM fungus) and S. indica, singly or in combination were inoculated into trifoliate orange(Poncirus trifoliata) seedlings, to assess changes in biomass and root morphological traits, coupled with auxins and cytokinins concentrations in leaves and roots and the expression of auxin synthesis and transporter protein genes. After 20 weeks of inoculation with these fungi, shoot and root biomass, root total length, taproot length, average diameter, surface area, volume, and the number of lateral roots in 1st-, 2nd-, and 3rd-order were improved, and S. indica showed a relatively greater effect than F. mosseae and dual inoculation. Endophytic fungal inoculation also significantly increased the concentration of indoleacetic acid, indole butyric acid, trans-zeatin,dihydrozeatin, and isopentenyl adenine in leaves and roots, whilst F. mosseae and S. indica exhibited relatively greater effects on leaves and roots, respectively. Correlation analysis revealed that both biomass and root morphological traits(except root projected area) were significantly positively associated with endogenous auxins and cytokinins. In addition, the inoculated plants recorded comparatively higher expression levels of indoleacetic acid synthesis genes(PtTAA1, PtTAR2, PtYUC3, PtYUC4, PtYUC6, and PtYUC8) and indoleacetic acid transporter protein genes(PtAUX1, PtLAX1, PtLAX2, PtLAX3, PtPIN1, PtPIN3, PtPIN4, PtABCB1, and PtABCB19) than the non-inoculated plants, among which F. mosseae and S. indica showed better effects in leaves and roots, respectively. These results suggest that root-associated endophytic fungi improved plant growth and root architecture, which were associated with changes in endogenous auxins and cytokinins.

A test of the mycorrhizal-associated nutrient economy framework in two types of tropical rainforests under nutrient enrichments

Shifts in tree species and their mycorrhizal associations driven by global change play key roles in biogeochemical cycles. In this paper, we proposed a framework of the mycorrhizal-associated nutrient economy(MANE), and tested it using nutrient addition experiments conducted in two tropical rainforests. We selected two tropical rainforests dominated by arbuscular mycorrhizal(AM) and ectomycorrhizal(ECM) trees, and established eighteen20 m×20 m plots in each rainforest. Six nitrogen(N) and phosphorus(P) addition treatments were randomly distributed in each rainforest with three replicates. We examined the differences in soil carbon(C) and nutrient cycling, plant and litter productivity between the two rainforests and their responses to 10-year inorganic N and P additions. We also quantified the P pools of plants, roots, litter, soil and microbes in the two rainforests. Overall,distinct MANE frameworks were applicable for tropical rainforests, in which soil C, N and P were cycled primarily in an inorganic form in the AM-dominated rainforest, whereas they were cycled in an organic form in the ECMdominated rainforest. Notably, the effects of mycorrhizal types on soil P cycling were stronger than those on C and N cycling. The intensified N and P deposition benefited the growth of AM-dominated rainforests instead of ECMdominated rainforests. Our findings underpin the key role of mycorrhizal types in regulating biogeochemical processes, and have important implications for predicting the ecological consequences of global changes.

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Mycorrhizal synthesis between Pisolithus arhizus and adult clones of Arbutus unedo in vitro and in nursery

Arbutoid mycorrhizae were synthesized between adult se- lected clones of Arbutus unedo L. and Pisolithus arhizus. Two micro- propagated clones were tested： ALl, in vitro and C1 （acclimatized plants） in nursery and later in a field trial. In vitro, rooted shoots were trans- ferred to test tubes containing the substrate previously inoculated with mycelium cultured on agar. In the nursery, two inoculation treatments were tested （vegetative inocula or dry sporocarps） and compared to con- trol plants. In the field trial, plants from nursery inoculation treatments were compared and an additional control treatment using seedlings was implemented. Plant height was evaluated 4 months later in the nursery and 20 months later in the field trial.

Inoculation with arbuscular mycorrhizal fungi improves seedlings growth of two sahelian date palm cultivars (<i>Phoenix dactylifera</i>L., cv. Nakhla hamra and cv. Tijib) under salinity stresses

This study presents an analysis of the impact of mycorrhizal inoculation on growth under salt stress of date palms cultivars Nakhla hamra (NHH) and Tijib known in the Sahel for their earliness in flowering and fruiting. The seedlings were grown in a greenhouse on a sandy substrate watered to field capacity every two days and were subjected to increasing levels of NaCl (0, 1, 2, 4, 6, 8 and 16 g·L-1) and then inoculated with 5 strains of Glomus (G. aggregatum, G. intraradices, G. verriculosum, G. mosseae, G. fasciculatum). The experimental design was a randomized complete block with three factors (cultivars: Tijib and Nakhla Hamra x seven levels of NaCl concentrations x six levels of inoculum). The results showed that in the absence of NaCl, G. verriculosum significantly enhanced shoot growth: 33.5 cm against 30.3 cm in the control and roots growth: 81.5 cm against 78 cm in NHH, while in Tijib, the growth is stimulated by Glomus fasciculatum: 33.8 cm against 32.7 cm for stems and 90 cm against 86 cm for the roots of inoculated plants and controls. In contrast, in the presence of NaCl 8 g·L-1, NHH has a better growth in the presence of G. intraradices: 37.3 cm against 30.6 cm for stems and 77 cm against 73 for roots, while Tijib grows better in the presence of G. fasciculatum with respectively 31.9 cm against 31.7 cm and 51.27 cm against 51.6 cm for stems and roots of inoculated plants and controls. Biochemical analysis revealed that changes in levels of proline depend on the cultivar, the mycorrhizal strain used and concentrations of NaCl applied. These results open the prospect of using mycorrhizal fungi to improve the productivity of palm trees in the Sahel.

果树抗冻研究现状

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Effectivity of arbuscular mycorrhizal fungi collected from reclaimed mine soil and tallgrass prairie

We examined suitability of arbuscular mycorrhizal fungi (AMF) associated with cool-season nonnative forages on reclaimed surface-mined land in southeast Ohio for establishment of native warm-season grasses. The goal of establishing these grasses is to diversify a post-reclamation landscape that is incapable of supporting native forest species. A 16-week glasshouse study compared AMF from a 30-year reclaimed mine soil (WL) with AMF from native Ohio tallgrass prairie soil (CL). Four native grasses were examined from seedling through 16 weeks of growth. Comparisons were made between CL and WL AMF on colonized (+AMF) and non-colonized plants (–AMF) at three levels of soil phosphorus (P). Leaves were counted at 4 week intervals. Shoot and root biomass and percent AMF root colonization were measured at termination. We found no difference between WL and CL AMF. Added soil P did not reduce AMF colonization, but did reduce AMF efficacy. Big bluestem (Andropogon gerardii Vitman), Indiangrass (Sorghastrum nutans (L.) Nash), and tall dropseed (Sporobolus asper (Michx.) Kunth) benefited from AMF only at low soil P while slender wheatgrass (Elymus trachycaulus (Link) Gould ex Shinners) exhibited no benefit. Establishment of tallgrass prairie dominants big blue-stem and Indiangrass would be supported by the mine soil AMF. It appears that the non-native forage species have supported AMF equally functional as AMF from a regionally native tallgrass prairie. Tall dropseed and slender wheatgrass were found to be less dependent on AMF than big bluestem or Indiangrass and thus would be useful in areas with little or no AMF inoculum.

我国的早实核桃

我国的早实核桃杨卫昌，高尚峰（陕西省果树研究所，杨陵７１２１００）（陕西黄龙县干果服务站）核桃（ＪｕｇｌａｎｓｒｅｇｉａＬ．）属胡桃科、胡桃属，是世界著名的干果树种。我国以其分布广、面积大，名列世界首位。在核桃生产中，除部分产区外，绝大部分产区都是采...

Arbuscular Mycorrhizal Fungus Mediate Changes in Mycorrhizosphere Soil Aggregates

Many studies have shown that arbuscular mycorrhizal (AM) fungus has an important role in soil aggregate formation and stabilization. While most studies about the effects of AM fungus on soil aggregate have experimental set-ups in single pots or containers with two compartments, these studies cannot differentiate the effects of roots, mycorrhizal roots or hyphae. In this study we used containers with four compartments to split the roots and quantitatively compare the change of soil aggregate in the mycorrhizosphere soil, rhizosphere soil, hyphosphere soil and bulk soil. Our results demonstrate a significant positive correlation among hyphal length density, easily extractable glomalin (EEG) and aggregate mean weight diameter (MWD), geometric mean diameter (GMD) and percentage of soil macroaggregate with a diameter larger than 0.25 mm (R0.25). The GMD and MWD of R0.25 in the hyphal compartment were higher than those in the non-inoculated root compartment, but were lower than those in the mycorrhizal compartment. This suggests the mycorrhizal hyphae had a greater effect than the non-inoculated roots, but less of an effect than the mycorrhizal roots on the formation and stabilization of soil aggregate. The results reveal that plant roots, mycorrhizal roots and mycorrhizal hyphae contribute to aggregate stability in individual ways and that their effects are additive, creating a synergistic stabilizing effect.

Effect of Arbuscular Mycorrhizal (AM) Fungi on the Physiological Performance of Phaseolus vulgaris Grown under Crude Oil Contaminated Soil

An experiment was conducted to assess the influence of arbuscular mycorrhizal (AM) fungi on the performance of Phaseolus vulgaris under crude oil contaminated soil. P. vulgaris was grown on soil under 2%, 4% and 8% (v/w) crude oil contamination. The experimental units were biostimulated with 2 g NPK fertilizer pot-1 and were inoculated with 12 g AM inoculum pot-1. Non inoculated pots served as control. The results showed that AM inoculated pots recorded higher and significantly (P < 0.05) different dry matter yields and chlorophyll content than non AM inoculated pots. Residual total petroleum hydrocarbon (TPH) increased as percent crude oil contamination increased. Total petroleum hydrocarbon decomposition and removal was higher on pots inoculated with AM than non inoculated pots. With AM colonization, physiological characteristics of P. vulgaris and TPH decomposition improved. This is evinced by the linear regression analysis between colonization and TPH (R2 = 0.77).

松坪无核柿调查报告

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