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To determine the mycorrhizal status and to identify the fungi colonising the roots of the plants, common buckwheat (Fagopyrum esculentum) and tartary buckwheat (F. tataricum) were inoculated with an indigenous fungal mixture from a buckwheat field. Root colonisation was characterised by the hyphae and distinct microsclerotia of dark septate endophytes, with occasional arbuscules and vesicles of arbuscular mycorrhizal fungi. Sequences of arbuscular mycorrhizal fungi colonising tartary buckwheat clustered close to the Glomus species group A. Sequences with similarity to the Ceratobasidium/Rhizoctonia complex, a putative dark septate endophyte fungus, were amplified from the roots of both common and tartary buckwheat. To the best of our knowledge, this is the first report of arbuscular mycorrhizal colonisation in tartary buckwheat and the first molecular characterisation of these fungi that can colonise both of these economically important plant species.

Abstract: The effects of biofumigation and soil heating on arbuscular mycorrhizal fungi (AMF) colonisation, strawberry growth and strawberry yield in pot experiments compared with untreated soil and chemical fumigation with dazomet were tested. Three different Brassicaceae species (Brassica juncea, Eruca sativa, Sinapis alba) were used as biofumigant plant green manure and soil heating was applied to simulate soil solarisation. Half of the plants were inoculated with indigenous arbuscular mycorrhizal fungi inoculum. With one exception (E. sativa) among the uninoculated plants, the treatments significantly decreased the mycorrhizal colonisation parameters compared with the untreated control. Dazomet displayed the greatest inhibitory effects on AMF establishment. In addition, the intensity and number of bands corresponding to Glomus spp. obtained with temporal temperature-gradient gel electrophoresis were lower for strawberry plants from biofumigant treatments than from the control. For the inoculated plants, there were almost no significant differences among the mycorrhizal colonisation parameters. The mass of leaves for the uninoculated and inoculated plants was higher for almost all non-chemical soil fumigant treatments compared with the control, except for heating of the uninoculated treatments. The number of strawberry fruits for the uninoculated biofumigant treatments was the highest, being higher than the values observed for the heating treatments, the chemical disinfection treatments and the control. There were no significant differences among the inoculated treatments. Biofumigation with Brassicaceae species resulted in higher soil organic matter and mineral nutrients and had a relatively small effect on AMF colonisation (F% = 59.0, 80.3, 47.3 for Bj, Es and Sa, respectively) compared with uninoculated controls (F% = 84.3). Despite the reduced AMF colonisation, biofumigation resulted in a higher fruit number and mass of leaves. Therefore, it represents a non-chemical soil fumigation method that should be applied in sustainable strawberry production. [Copyright &y& Elsevier]

Thlaspi praecox (Brassicaceae) is a recently discovered metal hyperaccumulating plant species colonized by arbuscular mycorrhizal fungi (AMF). The identity and diversity of the AMF colonizing its roots have not been determined so far. Therefore, T. praecox was inoculated with an indigenous fungal mixture from a metal polluted site and grown in original polluted soil/ commercial substrate mixtures (i.e., 100%, 50%, and 25%). Low to moderate mycorrhizal frequencies (F = 33-68%) and only rare arbuscules were observed. Densities of vesicles and microsclerotia, typical structures of dark septate endophytes (DSE), were greater in pots with 100% original polluted soil. In contrast, the highest diversity of fungal genotypes was observed in the roots from 25% polluted soil/ commercial substrate mixture, with the lowest soil concentrations of Cd, Zn, and Pb. The sequences obtained corresponded to Glomus species (Glomeromycota), to putative DSE Phialophora verrucosa and Rhizoctonia sp. and to some other fungi from Asco- and Basidiomycota, that are known to associate with plants, namely Capnobotryella sp., Penicillium brevicompactum, Rodotorula aurantiaca and Rodotorula slooffiae. This is the first report of DSE occurrence in roots of hyperaccumulating T. praecox, a promising candidate for phytoextraction. [ABSTRACT FROM AUTHOR]

Significant hyperaccumulation of Zn, Cd and Pb in field samples of Thlaspi praecox Wulf. collected from a heavy metal polluted area in Slovenia was found, with maximal shoot concentrations of 14 590mgkg-1 Zn, 5960mgkg-1 Cd and 3500mgkg-1 Pb. Shoot/root ratios of 9.6 for Zn and 5.6 for Cd show that the metals were preferentially transported to the shoots. Shoot bioaccumulation factors exceeded total soil Cd levels 75-fold and total soil Zn levels 20-fold, further supporting the hyperaccumulation of Cd and Zn. Eighty percent of Pb was retained in roots, thus indicating exclusion as a tolerance strategy for Pb. Low level colonisation with arbuscular mycorrhizal fungi (AMF) of a Paris type was observed at the polluted site, whereas at the non-polluted site Arum type colonisation was more common. To our knowledge this is the first report of Cd hyperaccumulation and AMF colonisation in metal hyperaccumulating T. praecox. [Copyright &y& Elsevier]

In experiments on spruce we have shown that jasmonic acid (JA), a cyclopentanone fatty acid, influences the ectomycorrhizal formation: we therefore also applied it to an endomycorrhizal symbiosis. Garlic (Allium sativum (L.)) bulbs were potted into substrates inoculated or not with arbuscular mycorrhizal fungi (AMF), and one half of the plants was foliar-treated with 5 μM JA. A synergistic effect of JA treatment and AMF inoculation on shoot length was found. Root growth of inoculated plants was accelerated especially when JA was applied. Either JA or AMF inoculation significantly enhanced bulb development. Mycorrhizal colonization was promoted and the development of arbuscules and vesicles was enhanced upon JA application. [ABSTRACT FROM AUTHOR]

Abstract: Maize root residues that remain in the field after harvesting are a source of water-soluble compounds, which can inhibit growth of succeeding maize crops through autotoxicity. The aim of this study was to test whether the formation of symbiosis between maize and arbuscular mycorrhizal fungi (AMF) alleviates negative effects of autotoxicity. Maize root extracts containing water-soluble compounds were used to simulate the release of autotoxic compounds from decomposing root residues in soil under experimental conditions and were applied at increasing concentrations to maize seedlings. The 0.15% (w/v) root extract treatment decreased root biomass and increased guaiacol peroxidase (G-POD) activity and concentrations of the major water-soluble compound benzoxazinone 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA) in roots of maize seedlings. As such, 0.15% concentration was used in subsequent inoculation experiment. The effects of maize root extracts seen in non-inoculated seedlings were lost in AMF-inoculated maize, even though the AMF colonization was reduced in the root extract-treated seedlings. These data indicate that AMF can alleviate the negative effects induced in maize seedlings by water-soluble compounds from maize roots and show potential importance of AMF in extensive agricultural practice. [Copyright &y& Elsevier]

Abstract: A better understanding of the mechanisms that govern copper (Cu) uptake, distribution and tolerance in Brassica carinata plants in the presence of chelators is needed before significant progress in chelate-assisted Cu phytoextraction can be made. The aims of this study were therefore to characterise (S,S)-N,N′-ethylenediamine disuccinic acid (EDDS)-assisted Cu uptake, and to compare the spatial distribution patterns of Cu in the roots and leaves of B. carinata plants. The plants were treated with 30μM or 150μM CuSO4 or CuEDDS in hydroponic solution. Quantitative Cu distribution maps and concentration profiles across root and leaf cross-sections of the desorbed plants were obtained by micro-proton induced X-ray emission. In roots, the 30μM treatments with both CuSO4 and CuEDDS resulted in higher Cu concentrations in epidermal/cortical regions. At 150μM CuSO4, Cu was mainly accumulated in root vascular bundles, whereas with 150μM CuEDDS, Cu was detected in endodermis and the adjacent inner cortical cell layer. Under all treatments, except with a H+-ATP-ase inhibitor, the Cu in leaves was localised mainly in vascular tissues. The incubation of plants with 150μM CuEDDS enhanced metal translocation to shoots, in comparison to the corresponding CuSO4 treatment. Inhibition of H+-ATPase activity resulted in reduced Cu accumulation in 30μM CuEDDS-treated roots and 150μM CuEDDS-treated leaves, and induced changes in Cu distribution in the leaves. This indicates that active mechanisms are involved in retaining Cu in the leaf vascular tissues, which prevent its transport to photosynthetically active tissues. The physiological significance of EDDS-assisted Cu uptake is discussed. [Copyright &y& Elsevier]

Abstract: Sečovlje salterns are an important protected area of biotic diversity in the Mediterranean. They represent an extreme environment with high salinity and drought that severely influence the growth of organisms. In the present study, diversity of plant halophytes and their mycorrhizal status were screened at eight different locations, which were mostly dikes and salt ponds, and which were deliberately selected for their distinct properties (e.g. soil salinity ranging from 105 to 2627 μS cm−1, vegetation type and management practice of the salterns). Twelve different halophytic plant species were recorded, of which eleven are designated as vulnerable. With few exceptions, they were found at the abandoned (Fontanigge) and sustained (Lera) locations of the Sečovlje salterns, distributed according to their tolerance to the salinity and waterlogging. The highest diversity of halophytes was listed at Fontanigge, in the abandoned, periodically flooded and gradually overgrown salt ponds. All of the examined species were colonised with either arbuscular mycorrhizal fungi (AMF) and/or dark septate endophytes (DSEs). High levels of colonisation were however detected only for species belonging to the Asteraceae and Plantaginaceae families. Higher root colonisation frequencies were generally seen for plants growing in the abandoned parts, when compared to the managed parts, whereas there was little correlation of the colonisation parameters with physicochemical parameters of rhizospheric soil properties. Molecular analysis by temporal temperature gradient gel electrophoresis (TTGE) of roots of halophytic plant species with confirmed AMF colonisation (arbuscules present) revealed the occurrence of at least six different AMF species, related to Glomus geosporum, Glomus caledonium and Glomus intraradices, and to different Glomus sp. clades and the Diversispora clade. This is to the best of our knowledge the first report of AMF and DSE mycorrhizal status of most of the halophyte plant species examined and of the brother scale identification of AMF species based on molecular analyses of roots of diverse halophytes from high saline environments. [Copyright &y& Elsevier]

Abstract: Several plant species with amphibious characteristics from intermittent aquatic habitats were examined for colonisation with arbuscular mycorrhizal fungi (AM), dark septate endophytes (DSE) and the ratio of aerenchyma in root tissue. We studied submerged specimens of Alisma plantago-aquatica, Mentha aquatica, Myosotis scorpioides, Oenanthe fistulosa, Gratiola officinalis, Glyceria fluitans, Sium latifolium and Teucrium scordium. In the first four, we also examined the emerged growth forms, which were grown under experimental conditions. Roots of all species were mycorrhizal and showed AM and DSE colonisation. The results suggest that AM colonisation may also be abundant in plants of aquatic environment. Arbuscules were not found in submerged specimens of M. aquatica, O. fistulosa and S. latifolium. The AM colonisation was generally higher in emerged specimens as compared to submerged ones. The aerenchyma ratio in root cross-sections ranged from 10 to 50% and in most cases did not differ between submerged and emerged specimens. No clear relationship between AM colonisation and aerenchyma ratio was recognized, while a positive correlation between AM and plant available phosphorous was established. [Copyright &y& Elsevier]