تأثیر قارچ های میکوریزایی و علفکش ترفلان بر سبز شدن، رشد و درصد کلونیزاسیون ریشه در گیاه شبدر سفید (Trifolium repens L)

Arbuscular mycorrhiza is an ancient symbiosis between the majority of land plants and fungi
\nfrom the phylum Glomeromycota. Arbuscular mycorrhizal fungi (AMF) colonize plant roots
\nand contribute to the mineral nutrient uptake of the hosts in exchange for carbohydrates. AMF
\nspecies diversity and identity was reported to have a decisive influence on the composition
\nand productivity of natural plant communities. Only around 200 glomeromycotan species
\ndescribed so far were thought to colonize the majority of higher plant species and thus, their
\nhost specificity was thought to be very low.
\nIn this thesis, molecular methods were used to investigate ecological aspects of root
\ncolonizing AMF. The community composition of these fungi was analyzed in two plant
\nspecies-rich grasslands facing different environmental conditions and harboring different
\nplant communities. One site consisting of two meadows located close to each other was
\nsituated in the upper montane zone of the Swiss Alps. The other was located in the lowland in
\nFrance on the edge of the Jura mountains. The roots were analyzed using AMF-specific
\nnested PCR, RFLP screening and sequencing of rDNA small subunit and internal transcribed
\nspacer regions. AMF sequences were analyzed phylogenetically and used to define
\nmonophyletic sequence types.
\nOverall, 27 different AMF sequence types were detected in the root samples from both
\nfield sites. The overlap between the AMF communities in the alpine and lowland site was
\nrelatively small - they shared just six sequence types. These results indicate strong
\ngeographical differences in the AMF community composition, reflecting different
\nenvironmental conditions and plant species communities in each site.
\nThe question was adressed, whether different host plant species co-occurring in the same
\narea host distinct or similar AMF communities. Gentiana verna, G. acaulis and Trifolium spp.
\ngrowing in two alpine species-rich meadows harbored significantly different AMF
\ncommunities, whereas the differences between the two sites were negligible. These results
\nindicate that within a relatively small area with similar soil and climatic conditions, the host
\nplant species can have a major influence on the AMF communities within the roots. In these
\nalpine sites, there was also a focus on green plants from the family Gentianaceae. In contrast
\nto their mycoheterotrophic relatives, the green gentians did not show a high level of
\nspecificity towards AMF. The plants sampled harbored AMF communities comprising
\nmultiple phylotypes from different fungal lineages.
\nIn the lowland site – a calcareous grassland – different culturing methods and their
\ninfluence on the AMF community composition in the roots were adressed. Four plant species
\nwere sampled i) directly in the field, ii) in a bait plant bioassay conducted directly in that
\n
\ngrassland and iii) in a greenhouse trap experiment using soil and a transplanted whole plant
\nfrom that grassland as inoculum. The community composition in their roots was strongly
\ninfluenced by the experimental approach, with additional influence of cultivation duration,
\nsubstrate and host plant species in some experiments.
\nSome fungal phylotypes, e.g. Glomus mosseae and several members of Glomus group B,
\nappeared predominantly in the greenhouse experiment or in bait plants. These phylotypes can
\nbe considered r strategists, rapidly colonizing uncolonized ruderal habitats in early
\nsuccessional stages of the fungal community. Other phylotypes as Glomus badium and
\nGLOM-A16 were detected almost exclusively in roots sampled from plants naturally growing
\nin the grassland or from bait plants exposed in the field, indicating that they preferentially
\noccur in late successional stages of fungal communities and thus represent the K strategy. The
\nonly phylotype found with high frequency in all three experimental approaches as well as in
\nthe alpine site was GLOM A-1 (Glomus intraradices), which is assumed to be a generalist.
\nThese ecological strategies of different AMF species or phylotypes should be considered
\nin AMF experimental work. In greenhouse trap experiments it is difficult to establish a rootcolonizing
\nAMF community reflecting the diversity of these fungi in the field roots, because
\nfungal succession in such artificial systems may bias the results. However, the field bait plant
\napproach might be a convenient way to study the influence of different environmental factors
\non AMF community composition directly under the field conditions.
\nFinally, the co-existence of the Glomeromycota in the root samples with fungi from the
\nbasidiomycotan order Sebacinales was addressed. These fungi are widely distributed and
\nknown to form various types of presumable mycorrhizal associations of different morphology
\n(ecto-, ectendo-, orchid, ericoid, jungermannoid) with a broad range of host plant species.
\nHowever, their presence in plants forming arbuscular mycorrhiza has not been reported yet.
\nTherefore, the root samples originating from the two species-rich grasslands mentioned above
\nwere analyzed with Sebacinales-specific primers for the D1/D2 region of the nuclear 28S
\nrDNA subunit. Fungi from the order Sebacinales were present in the majority of the root
\nsamples from both sites, where they co-existed with the Glomeromycota. In agreement with
\nstudies targeting the Sebacinales in ericoid plants, the phylogenetic analysis of sebacinoid
\nsequences from our samples did not reveal any patterns according to their host plant species
\nor geographical origin.

In nutrient-limited high-elevation ecosystems, plants rely on arbuscular mycorrhizal (AM) fungi to provide mineral phosphorus (P) in the form of phosphate (PO43-). AM fungi gather these nutrients from phosphorus-cycling bacteria (PCBs) that can mineralize PO43- from organic matter and solubilize mineral-bound P. How climate, soil factors, and nutrient limitation influence AM fungi and PCB assembly remains unclear. We collected soil from montane meadows across a 1,000-m elevation gradient on three replicate mountainsides and analyzed AM fungal marker genes, P-cycling genes from shotgun metagenomes, and edaphic measurements. High-elevation soils had nearly 50-fold less soil PO₄³⁻ and 60% more AM fungal hyphae than low-elevation soils. AM fungal turnover was linked to changes in pH, organic carbon, and PO₄³-. The composition of 198 P-cycling genes was influenced by the AM fungal community structure. Drivers of individual PCB functional genes, including pH and organic carbon, varied with gene phylogeny. We found a trade-off in P-cycling strategies across elevation: P-rich, low-elevation soils supported root-colonizing AM fungi and organic P-mineralizing bacteria. P-poor, high-elevation soils were dominated by stress-tolerant AM fungi and mineral P-solubilizing bacteria. Our results suggest that AM fungi and PCB community turnover across elevation are both shaped by pH, organic carbon, and P availability. With continued climate warming, the structure and function of mountaintop ecosystems might shift to resemble lower elevations, disrupting long-established and specialized microbial assemblages, with consequences for P-cycling dynamics and the total P available to plant communities.IMPORTANCEPhosphorus (P) limits plant productivity in high-elevation ecosystems, yet the microbial networks that mobilize P, including arbuscular mycorrhizal (AM) fungi and phosphorus-cycling bacteria (PCBs), remain under-characterized in these nutrient-poor soils. We show that across a 10,00-m elevation gradient, AM fungi and P-cycling gene assemblages shift predictably with pH, organic carbon, and phosphate availability. Higher elevations, with less available P, select for stress-tolerant AM fungal taxa and PCB strategies geared toward mineral solubilization, while low-elevation sites favor root colonization by AM fungi and organic P mineralization. These results suggest that nutrient limitation can constrain microbial community assembly in consistent ways across landscapes. High mountain soils are low in P and rely on a network of underground AM fungi and PCB to deliver nutrients to plants. This study shows how those underground relationships reorganize with elevation and how climate change could collapse long-standing microbial strategies by pushing high-elevation ecosystems toward lowland conditions. As soils warm and dry, the microbial scaffolding that supports alpine plant life may become increasingly unstable.

Arbuscular mycorrhizal (AM) fungi reside in the rhizosphere and form mutualistic associations with plant roots. They promote photosynthesis, improve stress resistance, and induce secondary metabolite biosynthesis in host medicinal plants. The AM fungi that are symbiotic with medicinal plants comprise a wide array of species and have abundant germplasm resources. Though research on the AM fungi in medicinal plants began relatively recently, it has nonetheless become an investigative hot spot. Several scholars have explored the diversity and the growth-promoting effects of mycorrhizal fungi in hundreds of medicinal plants. Current research on symbiotic AM fungi in medicinal plants has focused mainly on the effects of inoculating host plants with symbiotic mycorrhizal fungi. However, research on the symbiotic AM fungi in medicinal plants continues to expand, and further study is required to determine the mechanisms by which AM fungi interact with host plants. This paper introduces the diversity of symbiotic AM fungi of medicinal plants and the effects of AM fungi on rhizosphere soil of medicinal plants, including soil structure, microbiota, enzyme activities, etc. This review focuses on the effects of AM fungi on medicinal plants, including antioxidant enzyme systems, drought resistance, nutrient absorption profiles of macro- and micronutrients, accumulation of secondary metabolites such as terpenes, phenolic compounds, and nitrogenous compounds, and prevention of diseases. This review is expected to provide a reference for the application of AM fungi in medicinal plant cultivation, biological control, resource conservation, and the sustainable development of the traditional Chinese medicine industry.

Stoklosa, A., Nandanavanam, R., Puczel, U. and Upadhyaya, M. K. 2011. Influence of isoxaflutole on colonization of corn (Zea mays L.) roots with arbuscular mycorrhizal fungus Glomus intraradices. Can. J. Plant Sci. 91: 143-145. In a greenhouse pot culture study, corn plants were grown in sterilized soil containing mycorrhizal fungus Glomus intraradices and different concentrations of Converge Pro® herbicide (19.8, 39.6, 79.2, and 158.4 µg a.i. isoxaflutole L-1 soil). Mycorrhizal colonization of corn roots was observed to be 10 to 20% at 6 wk (exp. I) and 50 to 60% at 8 wk (exps. II and III) of plant growth. Isoxaflutole did not inhibit mycorrhizal colonization in any of the three experiments. These results show that the use of isoxaflutole does not affect corn plants by influencing mycorrhizal colonization for up to 8 wk of growth.

The 20thcentury witnessed an augmentation in agricultural production, mainly through the progress and use of pesticides, fertilizers containing nitrogen and phosphorus, and developments in plant breeding and genetic skills. In the naturally existing ecology, rhizospheric soils have innumerable biological living beings to favor the plant development, nutrient assimilation, stress tolerance, disease deterrence, carbon seizing and others. These organisms include mycorrhizal fungi, bacteria, actinomycetes, etc. which solubilize nutrients and assist the plants in up taking by roots. Amongst them, arbuscular mycorrhizal (AM) fungi have key importance in natural ecosystem, but high rate of chemical fertilizer in agricultural fields is diminishing its importance. The majority of the terrestrial plants form association with Vesicular Arbuscular Mycorrhiza (VAM) or Arbuscular Mycorrhizal fungi (AMF). This symbiosis confers benefits directly to the host plant’s growth and development through the acquisition of Phosphorus (P) and other mineral nutrients from the soil by the AMF. They may also enhance the protection of plants against pathogens and increases the plant diversity. This is achieved by the growth of AMF mycelium within the host root (intra radical) and out into the soil (extra radical) beyond. Proper management of Arbuscular Mycorrhizal fungi has the potential to improve the profitability and sustainability of agricultural systems. AM fungi are especially important for sustainable farming systems because AM fungi are efficient when nutrient availability is low and when nutrients are bound to organic matter and soil particles.

We established a 13‐week greenhouse experiment based on replicated microcosms to test whether the effects of defoliation on grassland plants and soil organisms depend on plant species composition and the presence of arbuscular mycorrhizal (AM) fungi. The experiment constituted of three treatment factors – plant species composition, inoculation of an AM fungus and defoliation – in a fully factorial design. Plant species composition had three levels: (1) Trifolium repens monoculture (T), (2) Phleum pratense monoculture (P) and (3) mixture of T. repens and P. pratense (T+P), while the AM inoculation and the defoliation treatment had two levels: (1) no inoculation of AM fungi and (2) inoculation of the AM fungus Glomus claroideum BEG31, and (1) no trimming, and (2) trimming of all plant material to 6 cm above the soil surface three times during the experiment, respectively. At the final harvest, AM colonization rate of plant roots differed between the plant species compositions, being on average 45% in T, 33% in T+P and 4% in P. Defoliation did not affect the colonization rate in T but raised the rate from 1% to 7% in P and from 20% to 45% in T+P. Shoot production and standing shoot and root biomass were 48%, 85% and 68% lower, respectively, in defoliated than in non‐defoliated systems, while the AM fungus did not affect shoot production and root mass but reduced harvested shoot mass by 8% in non‐defoliated systems. Of the plant quality attributes, defoliation enhanced the N concentration of harvested shoot biomass by 129% and 96% in P and T+P, respectively, but had no effect in T, while the C concentration of shoot biomass was on average 2.7% lower in defoliated than in non‐defoliated systems. Moreover, defoliation reduced shoot C yield (the combined C content of defoliated and harvested shoot biomass) on average by 47% across all plant species compositions and shoot N yield by 37% in T only. In contrast to defoliation, the AM fungus did not affect shoot N and C concentrations or shoot N yield, but induced 10% lower C yield in non‐defoliated systems and 17% higher C yield in defoliated T. In roots, defoliation led to 56% and 21% higher N concentration in P and T+P, respectively, and 28% higher C concentration in P, while the mycorrhizal fungus lowered root N concentration by 9.7% in defoliated systems and had no effect on root C concentrations. In the soil, the nematode community was dominated by bacterivores and the other trophic groups were found in a few microcosms only. Bacterivores were 45% more abundant in defoliated than in non‐defoliated systems, but were not affected by plant species composition or the AM fungus. Soil inorganic N concentration was significantly increased by defoliation in T+P, while the mycorrhizal fungus reduced NH 4 –N concentration by 40% in T. The results show that defoliation had widespread effects in our experimental systems, and while the effects on plant growth were invariably negative and those on bacterivorous nematodes invariably positive, most effects on plant C and N content and soil inorganic N concentration varied depending on the plant species present. In contrast, the effects of defoliation did not depend on the presence of the AM fungus, which suggests that while the relative abundance of legumes and grasses is likely to have a significant role in the response of legume–grass communities to defoliation, the role of AM fungi may be less important. In line with this, the AM fungus had only a few significant effects on plant and soil attributes in our systems and each of them was modified by defoliation and/or plant species composition. This suggests that the effects of AM fungi in legume–grass communities may largely depend on the plant species present and whether the plants are grazed or not.

Leaf water content (LWC) of crops is a suitable parameter for evaluation of plant water status and arbuscular mycorrhizal effect on the host plant under drought stress. Remote sensing technology provides an effective avenue to estimate LWC in crops. However, few LWC retrieval models have been developed specifically for the arbuscular mycorrhizal inoculated crops. In this study, soybean with inoculation and non-inoculation treatments were planted under the severe drought, moderate drought and normal irrigation levels. The LWC changes under different treatments at the 30th, 45th and 64th day after the inoculation were investigated, and the spectral response characteristics of inoculated and non-inoculated soybean leaves under the three drought stresses were analyzed. Five types of spectral variables/indices including: raw spectral reflectance (R), continuum-removed spectral reflectance (RC), difference vegetation index (DVI), normalized difference vegetation index (NDVI) and ratio vegetation index (RVI) were applied to determine the best estimator of LWC. The results indicate that LWC decreased as the aggravating of drought stress levels. However, LWC in inoculated leaves was higher than that in the counterparts under the same drought stress level, and the values of raw reflectance measured at inoculated leaves were lower than the non-inoculated leaves, especially around 1900 nm and 1410 nm. These water spectral features were more evident in the corresponding continuum-removed spectral reflectance. The newly proposed DVIC(2280, 1900) index, derived from the continuum-removed spectral reflectance at 2280 nm and the raw spectral reflectance at 1900 nm in DVI type of index, was the most robust for soybean LWC assessment, with R2 value of 0.72 (p < 0.01) and root mean square error (RMSE) and mean absolute error (MAE) of 2.12% and 1.75%, respectively. This study provides a means to monitor the mycorrhizal effect on drought-induced crops indirectly and non-destructively. Keywords: leaf water content, remote sensing, arbuscular mycorrhizal fungi, drought, crops DOI: 10.25165/j.ijabe.20191206.4950 Citation: Kong W P, Huang W J, Zhou X F, Mortimer H, Ma L L, Tang L L, et al. Estimating leaf water content at the leaf scale in soybean inoculated with arbuscular mycorrhizal fungi from in situ spectral measurements. Int J Agric & Biol Eng, 2019; 12(6): 149–155.

Soil solarization, the process of heating soil by covering fields with clear plastic, is a promising method to reduce populations of soilborne pests and weeds without the use of pesticides. However, the destruction of beneficial organisms such as arbuscular mycorrhizal (AM) fungi also may occur, thereby reducing positive effects of solarization. We compared the effects of solarization and chemical fumigants on the survival of indigenous AM fungi in 1995 and 1996. The infectivity of AM fungi was monitored before and after solarization using a greenhouse bioassay with Sorghum bicolor L. for both years. AM colonization of roots was also monitored in the field 8months after solarization in 1995. Weed densities were measured 8months after treatment in 1996. Solarization increased the average daily soil temperature 6-10°C and the maximum soil temperature reached by 10-16°C (5-20cm depth). Solarization did not reduce the infectivity of AM fungi immediately after the solarization period in either year, as determined by the greenhouse bioassay. Infectivity was greatly reduced in solarized plots 8months after solarization (over winter) in both years as assessed in the field (1995) or with the greenhouse bioassay (1996). Fumigation with metam sodium at 930l ha(-1) (350kg active ingredient ha(-1)) reduced the infectivity of AM fungi in both years, and fumigation with methyl bromide at 800kg ha(-1) eliminated infection by AM fungi. Solarization was as effective as methyl bromide and metam sodium at 930l ha(-1) in controlling winter annual weeds measured 8months after treatment. Solarization apparently reduced AM fungi in soil indirectly by reducing weed populations that maintained infective propagules over the winter. Fumigation with metam sodium or methyl bromide directly reduced AM fungi in soil.

There are many tangerine (Citrus reticulata) orchards in northern Thailand. These orchards are supplied with different levels of fertilizers. The objective of this study is to investigate arbuscular mycorrhizal (AM) fungi associated with tangerine in Chiang Mai province, northern Thailand, and the effect of AM fungi on the growth of the air layered tangerine variety 'Sai Num Phung' with different levels of nitrogen (N) and phosphorus (P) fertilizers in a pot experiment. Percentage of AM colonization in the tangerine roots and spore density in the rhizosphere varied significantly with the available P levels in the orchard soil. Means of root colonization and spore density were significantly depressed at >500 mg P/kg soil. Twenty-two species of AM fungi were found to be associated with tangerine in orchards of the Chiang Mai province. The effects of AM fungi, and N and P fertilizers on air layered tangerine plants were investigated in pots for ten months. AM fungi increased growth of the host plant especially in pots with N but without P fertilizers. AM fungi increased concentrations of P and Mg in leaves of tangerine. Application of N and P fertilizers depressed root colonization of AM fungi in the pot experiment. This study has shown that a wide range of AM fungi is associated with tangerine in commercial orchards, but with high levels of N and P fertilizers the increase in growth of tangerine trees due to the association with AM fungi may be limited.

Six species of arbuscular mycorrhizal (AM) fungi (Glomus aggregatum, G. clarum, G. etunicatum, G. intraradices, G. mosseae and G. versiforme) were evaluated, in three greenhouse experiments, for their effects on reproduction of the root-lesion nematode, Pratylenchus penetrans, and growth of Ottawa 3 apple rootstock. Glomus mosseae increased total dry weights of nematode-inoculated and non-inoculated rootstock in all three greenhouse experiments, and G. intraradices increased dry weights in two of three greenhouse experiments. Plants inoculated with G. mosseae generally supported fewer P. penetrans per gram of root than plants inoculated with other AM fungi, but did not differ significantly from the controls in any greenhouse experiment. Colonization of roots by AM fungi was reduced by P. penetrans at initial inoculum densities greater than 250 nematodes/L soil. In field trials, preplant inoculation with either G. intraradices or G. mosseae increased rootstock growth and leaf concentrations of P, Mg, Zn and Cu in fumigated plots but not in non-fumigated plots, indicating that colonization by native AM fungi in non-fumigated plots may have been sufficient for adequate nutrient acquisition. The abundance of vesicles and arbuscules was greater in roots of plants inoculated with AM fungi before planting than in roots of non-inoculated plants, in both fumigated and non-fumigated plots. P. penetrans per gram of root and per 50 ml soil were significantly lower for G. mosseae- inoculated plants than for non-inoculated plants in fumigated soil but not in non-fumigated soil.

Summary The composition of communities of arbuscular mycorrhizal (AM) fungi can have a large effect on the performance of their plant hosts. The role of individual fungal species in shaping this response is as yet unresolved. We have used the fungicide benomyl to alter the community of AM fungi in undisturbed monoliths of soil in a natural community. Changes in the community were characterized by root colonization (%RLC), cloning, sequencing and tRFLP of a partial SSUrDNA fragment. Eleven plant species were sufficiently abundant in the monoliths to be examined. In the highly mycorrhiza‐dependent perennial herb Ajuga reptans, phosphate concentration was significantly reduced after benomyl treatment over a full growing season. The other plant species showed low colonization and no significant difference in phosphate concentration after benomyl treatment. Although colonization in A. reptans was reduced, many mycorrhizal fungi survived in the roots. Some became more abundant following fungicide treatment, suggesting competitive release. Fungi that increased were generalists that have been identified in field samples from published studies colonizing a wide range of plant species. Those that declined were specialists with a narrow host range; five types had not been recorded previously in field samples. AM fungi in this study differed greatly in their response to perturbation, independent of the identity of the host plant. If such functional diversity is widespread, then elucidating the part played by AM fungal diversity in regulating plant community structure will be key to our understanding and management of ecosystems.

Interactions between two arbuscular mycorrhizal fungi and fungivorous nematodes and control of the nematode with fenamifos

Gene induction during plant-microbe interactions : the role of chitinases during fungal infection and the investigation of mycorrhiza-induced genes in the model plant "M. truncatula"

AM fungi root colonization increases the production of essential isoprenoids vs. nonessential isoprenoids especially under drought stress conditions or after jasmonic acid application

Heavy metal (HM) pollution is a major worldwide environmental concern. Phytoremediation has become a promising remediation technique that include the use of selected plant species to remove or to stabilize a range of pollutants. Plant tolerance to HM stress is improved by arbuscular mycorrhizal (AM) fungi. Thus, suitable plant fungus combinations may contribute to the success of phytoremediation of HM polluted soil. Metallothioneins (MTs) and polyamines (PAs) are implicated in the response and tolerance to HM stress in several plant species, but whether the response is modulated by AM fungi remains to be clarified. Populus alba AL35 plants were grown in pots containing either soil collected from a HM polluted or unpolluted soil; they were pre-inoculated or not with Glomus mosseae or G. intraradices. At the first and the second growth season, the expression of MT and PA biosynthetic genes was analysed in leaves using quantitative RT-PCR, and free and conjugated foliar PA concentrations were detected. Results indicate that on polluted soil, AM fungi restored plant biomass despite higher Cu and Zn accumulation in plant organs. P. alba mycorrhizal plants exhibit increased capacity for stabilization of soil HMs, and improved stress tolerance through the transcriptional up-regulation of stress-related genes and the protective role of PAs.