The differential behavior of arbuscular mycorrhizal fungi in interaction with Astragalus sinicus L. under salt stress

Three arbuscular mycorrhizal (AM) fungi (Glomus mosseae, Glomus claroideum, and Glomus intraradices) were compared for their root colonizing ability and activity in the root of Astragalus sinicus L. under salt-stressed soil conditions. Mycorrhizal formation, activity of fungal succinate dehydrogenase, and alkaline phosphatase, as well as plant biomass, were evaluated after 7 weeks of plant growth. Increasing the concentration of NaCl in soil generally decreased the dry weight of shoots and roots. Inoculation with AM fungi significantly alleviated inhibitory effect of salt stress. G. intraradices was the most efficient AM fungus compared with the other two fungi in terms of root colonization and enzyme activity. Nested PCR revealed that in root system of plants inoculated with a mix of the three AM fungi and grown under salt stress, the majority of mycorrhizal root fragments were colonized by one or two AM fungi, and some roots were colonized by all the three. Compared to inoculation alone, the frequency of G. mosseae in roots increased in the presence of the other two fungal species and highest level of NaCl, suggesting a synergistic interaction between these fungi under salt stress.     

Response of the grapevine rootstock Richter 110 to inoculation with native and selected arbuscular mycorrhizal fungi and growth performance in a replant vineyard

Two indigenous arbuscular mycorrhizal (AM) fungi from the Mediterranean wine growing area in the Northeast of Spain were isolated and classified as Glomus intraradices Schenck & Smith. Both native fungi were found to increase the growth of the vine rootstock 110 Richter under greenhouse conditions compared with G. intraradices (BEG 72) and a phosphorus (P) fertilization treatment. The effectivity of field inoculation of Cabernet Sauvignon plants grafted on Richter 110 with the former native fungi and with G. intraradices BEG 72 in a replant vineyard severely infested by the root-rot fungus Armillaria mellea (Vahl ex Fr.) Kummer was assessed. The native fungi were not effective at enhancing plant development, and only G. intraradices BEG 72, resulted in a positive response. Field inoculation with this selected fungus increased plant shoot dry weight at the end of the first growing season.     

Growth enhancement of Citrus reshni after inoculation with Glomus intraradices and Trichoderma aureoviride and associated effects on microbial populations and enzyme activity in potting mixes

There have been some scientific reports suggesting that dual inoculations with arbuscular mycorrhizal (AM) and saprophytic soil fungi may cause an additive or synergistic growth enhancement of the inoculated host plant. Some Trichoderma spp. have shown antagonistic potential against pathogenic fungi and a beneficial effect on plant growth. Joint inoculations of the mycorrhizal fungus Glomus intraradices Schenck and Smith, isolated from a citrus nursery (Tarragona, Spain) and a strain of Trichoderma aureoviride Rifai, isolated from an organic compost, were tested on a citrus rootstock, Citrus reshni Hort. ex Tan. The interactions between both microorganisms and their influence on mycorrhizal root colonization and plant growth enhancement, the changes produced in the soil microbial activity, like esterase, trehalase, phosphatase and chitinase activities, and on microbial populations were evaluated in three organic substrates: (1) sphagnum peat and autoclaved sandy soil (1/1, v/v), (2) sphagnum peat, quartz sand and perlite (1/1/1, v/v) and (3) pine bark compost (BVU, Prodeasa Product). Substrate characteristics were more important than the AM inoculation treatment in the determination of enzyme activity. In bark compost, the number of bacterial colonies obtained on soil-dilution plates was significantly higher than in peat and sand mixtures. Inoculation with T. aureoviride alone produced no significant effect on growth enhancement of C. reshni. However, dual inoculation with both, T. aureoviride and G. intraradices significantly increased plant growth in two of the substrates used and was the best treatment in pine bark amended compost. The inoculation with T. aureoviride did not affect the development of mycorrhizal root colonization. These results show a synergistic effect of G. intraradices and T. aureoviride on the growth of C. reshni in organic substrates and indicate the potential benefits of using combined inoculations.     

Responses of soil microbial catabolic diversity to arbuscular mycorrhizal inoculation and soil disinfection

Although it is usually admitted that arbuscular mycorrhizal (AM) fungi are key components in soil bio-functioning, little is known on the response of microbial functional diversity to AM inoculation. The aims of the present study were to determine the influence of Glomus intraradices inoculum densities on plant growth and soil microflora functional diversity in autoclaved soil or non-disinfected soil. Microbial diversity of soil treatments was assessed by measuring the patterns of in situ catabolic potential of microbial communities. The soil disinfection increased sorghum growth, but lowered catabolic evenness (4.8) compared to that recorded in the non-disinfected soil (6.5). G. intraradices inoculation induced a higher plant growth in the autoclaved soil than in the non-disinfected soil. This AM effect was positively related to inoculum density. Catabolic evenness and richness were positively correlated with the number of inoculated AM propagules in the autoclaved soil, but negatively correlated in the non-disinfected soil. In addition, after soil disinfection and AM inoculation, these microbial functionality indicators had higher values than in the autoclaved or in the non-disinfected soil without AM inoculation. These results are discussed in relation to the ecological influence of AM inoculation, with selected fungal strains and their associated microflora on native soil microbial activity.     

Effect of Tilemsi phosphate rock-solubilizing microorganisms on phosphorus uptake and yield of field-grown wheat (Triticum aestivum L.) in Mali

With the broad aim of biologically improving P uptake by wheat fertilized with Tilemsi phosphate rock (TPR), we investigated the effect of inoculation with TPR-solubilizing microorganisms isolated from Malian soils and with a commercial isolate of the arbuscular mycorrhizal (AM) fungus Glomus intraradices (Gi). AM root length colonization, and growth yield and P concentration of the cultivar Tetra of wheat were measured under field conditions in Mali. Experimental plots were established in Koygour (Diré) during the 2001–2002 cropping season. Inoculation treatments included two fungal isolates, Aspergillus awamori (C1) and Penicillium chrysogenum (C13), and an isolate of Pseudomonas sp. (BR2), used alone or in fungus-bacterium combinations in the presence or absence of the AM fungus Gi. In fertilized treatments, 0 or 30 kg P ha⁻¹ was applied as TPR or diammonium phosphate (DAP). In 45-day-old wheat plants, the highest root length AM colonization (62%) was observed with TPR fertilized wheat inoculated with Gi and BR2. Our results suggest that BR2 is a mycorrhizal-helper bacteria and a good plant growth-promoting rhizobacteria. In fact, inoculation of wheat Tetra fertilized with TPR with a combination of Gi, BR2 and C1 produced the best grain yield with the highest P concentration. This work shows that by inoculating seeds with TPR-solubilizing microorganisms and AM fungi under field conditions in Mali it is possible to obtain wheat grain yields comparable to those produced by using the expensive DAP fertilizer.     

Displacement of an herbaceous plant species community by mycorrhizal and non-mycorrhizal Gmelina arborea, an exotic tree, grown in a microcosm experiment

Gmelina arborea Roxb. (Gmelina, Yemane) is a fast growing tree, native from India and considered as a potentially invasive woody plant in West Africa. Mycorrhizal inoculation of seedlings with Glomus intraradices was performed to study (1) the effect on the growth of G. arborea, (2) the impact on the catabolic diversity of soil microbial communities and (3) the influence on the structure of herbaceous plant species communities in microcosms. Treatments consisted of control plants, pre-planting fertilizer application and arbuscular mycorrhizal (AM) inoculation. After 4 months’ culture in autoclaved soil, G. arborea seedlings were either harvested for growth measurement or transferred into containers filled with the same soil but not sterilized. Other containers were kept without G. arborea seedlings. After 12 months’ further culture, effects of fertilizer amendment and AM inoculation on the growth of G. arborea seedlings were recorded. AM colonization was significantly and positively correlated with plant diversity. The substrate-induced respiration response to carboxylic acids was significantly higher in the absence of G. arborea and in the presence of G. intraradices as compared to the other treatments. The influence of AM symbiosis on plant coexistence and on allelopathic processes of invasive plants are discussed.     

An Indigenous Drought-Tolerant Strain of Glomus intraradices Associated with a Native Bacterium Improves Water Transport and Root Development in Retama sphaerocarpa

The effects of interactions between Bacillus thuringiensis, a drought-adapted bacterium, and two isolates of Glomus intraradices, an arbuscular mycorrhizal (AM) fungus, on Retama sphaerocarpa, a drought-adapted legume, were investigated. The fungal isolates were an indigenous drought-tolerant and a nonindigenous drought-sensitive isolate. Shoot length and root growth, symbiotic parameters, water transport (in terms of percent relative plant water uptake), and volumetric soil moisture and soil enzymatic activities in response to microbial inoculations were evaluated. Retama plants colonized by G. intraradices plus Bacillus possessed similar shoot length after 30 days from sowing compared with noninoculated Retama plants after 150 days. Inoculation with drought-adapted bacterium increased root growth by 201%, but maximum root development was obtained by co-inoculation of B. thuringiensis and the indigenous G. intraradices. Nodules were formed only in plants colonized by autochthonous AM fungi. Relative water uptake was higher in inoculated than in noninoculated Retama plants, and these inoculants depleted soil water content concomitantly. G. intraradices-colonized Retama reached similar shoot length irrespective of the fungal origin, but there were strong differences in relative water uptake by plants colonized by each one of the fungi. Indigenous G. intraradices-colonized roots (evaluated as functional alkaline phosphatase staining) showed the highest intensity and arbuscule richness when associated with B. thuringiensis. The interactive microbial effects on Retama plants were more relevant when indigenous microorganisms were involved. Co-inoculation of autochthonous microorganisms reduced by 42% the water required to produce 1 mg of shoot biomass. This is the first evidence of the effectiveness of rhizosphere bacterium, singly or associated with AM fungus, in increasing plant water uptake, which represents a positive microbial effect on plants grown under drought environments.     

Alleviation of salt stress in Lotus glaber by Glomus intraradices

Lotus glaber is a glycophytic, perennial legume from Europe that occurs widely in saline habitats. We evaluated the effect of mycorrhizal fungus colonization on the response to salt stress of two genotypes of L. glaber differing in their tolerance to salinity. The experiment consisted of a randomized block design with two factors: (1) mycorrhizal fungus treatments (with or without AM fungus) and (2) two salinity levels of 0 and 200 mM NaCl. Our results indicated that Glomus intraradices established a more efficient symbiosis with the tolerant than with the sensitive genotype. G. intraradices improved growth of L. glaber plants under saline conditions. They showed higher values of net growth, shoot/root and K⁺/Na⁺ ratios, and protein concentrations than controls. Tolerant AM plants also showed higher chlorophyll levels than non-AM ones. Prevention of Na⁺ accumulation in the plant and enhancement of K⁺ concentrations in roots observed in this work could be part of the general mechanism of salt stress alleviation of L. glaber by G. intraradices.     

Effects of preplant inoculation of apple (Malus domestica Borkh.) with arbuscular mycorrhizal fungi on population growth of the root-lesion nematode,Pratylenchus penetrans

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.     

Induction of antioxidant enzymes is involved in the greater effectiveness of a PGPR versus AM fungi with respect to increasing the tolerance of lettuce to severe salt stress

This study investigated the influence of inoculation with a plant growth-promoting rhizobacterium, Pseudomonas mendocina Palleroni, alone or in combination with an arbuscular mycorrhizal (AM) fungus, Glomus intraradices (Schenk & Smith) or Glomus mosseae (Nicol & Gerd.) Gerd. & Trappe, on antioxidant enzyme activities (catalase and total peroxidase), phosphatase activity, solute accumulation, growth and mineral nutrient uptake in leaves of Lactuca sativa L. cv. Tafalla affected by three different levels of salt stress. Salinity decreased lettuce growth, regardless of the biological treatment and of the salt stress level. The plants inoculated with P. mendocina had significantly greater shoot biomass than the control plants at both salinity levels, whereas the mycorrhizal inoculation treatments only were effective in increasing shoot biomass at the medium salinity level. At the highest salinity level, the water content was greater in leaves of plants treated with P. mendocina or G. mosseae. At the medium salinity level, G. intraradices- or G. mosseae-colonised plants showed the highest concentrations of foliar P. The P. mendocina- and G. mosseae-colonised plants presented higher concentrations of foliar K and lower concentrations of foliar Na under high salt conditions. Salt stress decreased sugar accumulation and increased foliar proline concentration, particularly in plants inoculated with the PGPR. Increasing salinity stress raised significantly the antioxidant enzyme activities, including those of total peroxidase and catalase, of lettuce leaves compared to their respective non-stressed controls. The PGPR strain induced a higher increase in these antioxidant enzymes in response to severe salinity. Inoculation with selected PGPR could serve as a useful tool for alleviating salinity stress in salt-sensitive plants.     

Differential Effects of Pseudomonas mendocina and Glomus intraradices on Lettuce Plants Physiological Response and Aquaporin PIP2 Gene Expression Under Elevated Atmospheric CO2 and Drought

Arbuscular mycorrhizal (AM) symbiosis and plant-growth-promoting rhizobacterium (PGPR) can alleviate the effects of water stress in plants, but it is unknown whether these benefits can be maintained at elevated CO₂. Therefore, we carried out a study where seedlings of Lactuca sativa were inoculated with the AM fungus (AMF) Glomus intraradices N.C. Schenk & G.S. Sm. or the PGPR Pseudomonas mendocina Palleroni and subjected to two levels of watering and two levels of atmospheric CO₂ to ascertain their effects on plant physiological parameters and gene expression of one PIP aquaporin in roots. The inoculation with PGPR produced the greatest growth in lettuce plants under all assayed treatments as well as the highest foliar potassium concentration and leaf relative water content under elevated [CO₂] and drought. However, under such conditions, the PIP2 gene expression remained almost unchanged. G. intraradices increased significantly the AMF colonization, foliar phosphorus concentration and leaf relative water content in plants grown under drought and elevated [CO₂]. Under drought and elevated [CO₂], the plants inoculated with G. intraradices showed enhanced expression of the PIP2 gene as compared to P. mendocina or control plants. Our results suggest that both microbial inoculation treatments could help to alleviate drought at elevated [CO₂]. However, the PIP2 gene expression was increased only by the AMF but not by the PGPR under these conditions.     

Effect of <Emphasis Type="Italic">Glomus</Emphasis> species on physiology and biochemistry of <Emphasis Type="Italic">Catharanthus roseus</Emphasis>

The present study on efficacy of different Glomus species, an arbuscular mycorrhizal (AM) fungus (G. aggregatum, G. fasciculatum, G. mosseae, G. intraradices) on various growth parameters such as biomass, macro and micronutrients, chlorophyll, protein, cytokinin and alkaloid content and phosphatase activity of pink flowered Catharanthus roseus plants showed that all Glomus species except G. intraradices enhanced the chlorophyll, protein, crude alkaloid, phosphorus, sulphur, manganese and copper contents of C. roseus plants along with phosphatase activity significantly over uninoculated plants. However only G. mosseae and G. fasciculatum exhibited superior symbiotic relationship with the plant. G. mosseae was found to be the best for increasing the crude alkaloid content (8.19%) in leaf and also in increasing the quantity of important alkaloids vincristine and vinblastine.     

Synergistic effects of inoculating arbuscular mycorrhizal fungi and Methylobacterium oryzae strains on growth and nutrient uptake of red pepper (Capsicum annuum L.)

A greenhouse experiment was conducted to examine the effects of inoculation with two Methylobacterium oryzae strains (CBMB20 and CBMB110) and a consortium of three arbuscular mycorrhizal (AM) fungi on the growth of red pepper (Capsicum annum L.). Inoculation of red pepper plants with the M. oryzae strains resulted in a significant increase in root length and root fresh weight compared to untreated control plants. The combined inoculation of M. oryzae strains and AM fungi significantly increased various plant growth parameters and chlorophyll content compared to uninoculated controls. Mycorrhizal colonisation and the number of AM fungal spores were higher in co-inoculation treatments. In addition, the combined inoculation of M. oryzae strains and AM fungi resulted in significantly higher nitrogen (N) accumulation in the roots and shoots of red pepper plants compared to uninoculated controls. The combined inoculation of M. oryzae strain CBMB110 and AM fungi increased the phosphorus (P) content by 23.3% compared to untreated controls. The micronutrient content of the red pepper plants also increased in most of the inoculation treatments. A perfect mutualism among CBMB100-AMF was found which was attributed to the improved macro- and micronutrient uptake along with higher chlorophyll content in red pepper. Further research on in-depth understanding of the co-operative microbial interactions will facilitate the successful application of Methylobacterium-AM fungi products in biotechnology.     

Effect of aromatic plant species on vesicular-arbuscular mycorrhizal establishment in Pistacia terebinthus

The inoculation of Pistacia terebinthus with vesicular-arbuscular mycorrhizal (VAM) fungi and the spread of the infection were studied using a mixed cropping system, under glasshouse conditions, with Salvia officinalis, Lavandula officinalis and Thymus vulgaris colonized by Glomus mosseae as an inoculation method. This method was compared with soil inoculum placed under the seed or distributed evenly in the soil. Indirect inoculation with all the aromatic plants tested significantly increased VAM root colonization of P. terebinthus compared with the use of soil inoculum, although the effect on plant growth was different for each one of the aromatic species used as inoculum source. Inoculation with L. officinalis and T. vulgaris were the best treatments resulting in high VAM colonization and growth enhancement of P. terebinthus.     

Overlapping expression patterns and differential transcript levels of phosphate transporter genes in arbuscular mycorrhizal,P<Subscript>i</Subscript>-fertilised and phytohormone-treated <Emphasis Type="Italic">Medicago truncatula</Emphasis> roots

A microarray carrying 5,648 probes of Medicago truncatula root-expressed genes was screened in order to identify those that are specifically regulated by the arbuscular mycorrhizal (AM) fungus Gigaspora rosea, by P_i fertilisation or by the phytohormones abscisic acid and jasmonic acid. Amongst the identified genes, 21% showed a common induction and 31% a common repression between roots fertilised with P_i or inoculated with the AM fungus G. rosea, while there was no obvious overlap in the expression patterns between mycorrhizal and phytohormone-treated roots. Expression patterns were further studied by comparing the results with published data obtained from roots colonised by the AM fungi Glomus mosseae and Glomus intraradices, but only very few genes were identified as being commonly regulated by all three AM fungi. Analysis of P_i concentrations in plants colonised by either of the three AM fungi revealed that this could be due to the higher P_i levels in plants inoculated by G. rosea compared with the other two fungi, explaining that numerous genes are commonly regulated by the interaction with G. rosea and by phosphate. Differential gene expression in roots inoculated with the three AM fungi was further studied by expression analyses of six genes from the phosphate transporter gene family in M. truncatula. While MtPT4 was induced by all three fungi, the other five genes showed different degrees of repression mirroring the functional differences in phosphate nutrition by G. rosea, G. mosseae and G. intraradices. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Beyond the rhizosphere: growth and function of arbuscular mycorrhizal external hyphae in sands of varying pore sizes

Research on nutrient acquisition by symbiotic arbuscular mycorrhizal (AM) fungi has mainly focused on the root–fungus interface and less attention has been given to the growth and functioning of external hyphae in the bulk soil. The growth and function of external hyphae may be affected by unfavourable soil environments, such as compacted soils in which pores may be narrow. The effects of pore size on the growth of two AM fungi (Glomus intraradices and G. mosseae) and their ability to transport ³³P from the bulk soil to the host were investigated. Trifolium subterraneum L. plants were grown individually in `single arm cross-pots' with and without AM fungi. The side arm was separated from the main compartment by nylon mesh to prevent root penetration. It contained three zones: 5 mm of soil:sand mix (HC1); 25 mm of media treatment (HC2); and 20 mm of ³³P-labelled soil (HC3). There were four media treatments; soil and three types of quartz sand with most common continuous pore diameters of 100, 38 and 26 m. AM plants had similar growth and total P uptake in all treatments. However, plants grown with G. intraradices contained almost three times more ³³P than those grown with G. mosseae, indicating G. intraradices obtained a greater proportion of P at a distance from the host roots. Differences in P acquisition were not correlated with production of external hyphae in the four media zones and changes in sand pore size did not affect the ability of the fungi studied to acquire P at a distance from the host roots. Production of external hyphae in HC2 was influenced by fungal species and media treatment. Both fungi produced maximum amounts of external hyphae in the soil medium. Sand pore size affected growth of G. intraradices (but not G. mosseae) and hyphal diameter distributions of both fungi. The results suggest that not only are G. mosseae and G. intraradices functionally complementary in terms of spatial phosphorus acquisition, they are also capable of altering their morphology in response to the soil environment.     

Differential effects of AM fungal isolates on Medicago truncatula growth and metal uptake in a multimetallic (Cd, Zn, Pb) contaminated agricultural soil

Toxic metal accumulation in soils of agricultural interest is a serious problem needing more attention, and investigations on soil–plant metal transfer must be pursued to better understand the processes involved in metal uptake. Arbuscular mycorrhizal (AM) fungi are known to influence metal transfer in plants by increasing plant biomass and reducing metal toxicity to plants even if diverging results were reported. The effects of five AM fungi isolated from metal contaminated or non-contaminated soils on metal (Cd, Zn) uptake by plant and transfer to leachates was assessed with Medicago truncatula grown in a multimetallic contaminated agricultural soil. Fungi isolated from metal-contaminated soils were more effective to reduce shoot Cd concentration. Metal uptake capacity differed between AM fungi and depended on the origin of the isolate. Not only fungal tolerance and ability to reduce metal concentrations in plant but also interactions with rhizobacteria affected heavy metal transfer and plant growth. Indeed, thanks to association with nodulating rhizobacteria, one Glomus intraradices inoculum increased particularly plant biomass which allowed exporting twofold more Cd and Zn in shoots as compared to non-mycorrhizal treatment. Cd concentrations in leachates were variable among fungal treatments, but can be significantly influenced by AM inoculation. The differential strategies of AM fungal colonisation in metal stress conditions are also discussed.     

AM 真菌影响三叶草根系抗氧化酶活性的系统效应

本文对三叶草接种AM 真菌根内球囊霉, 用盆栽试验和分根试验测定根系的菌根侵染率和抗氧化酶活性, 研究AM 真菌对根系抗氧化酶活性的影响以及该影响的系统性。结果表明, 盆栽试验中接种根内球囊霉显著提高了根系中SOD、POD、CAT 的活性, 表明AM 真菌可以促进根系的抗氧化酶活性; 分根试验中一半根系接种了根内球囊霉的植株, 其另一半未接种的根系SOD、POD 活性也增加, 表明AM 真菌对根系抗氧化酶系统的促进具有系统效应。由于抗氧化酶系统是植物产生抗逆性的生理生化基础, 可以推测, AM 真菌对根系抗氧化酶活性的系统性提高有助于保护根系整体, 而非仅仅保护受侵染根段。     

Development and activity of Glomus intraradices as affected by co-existence with Glomus claroideum in one root system

The co-existence of two arbuscular mycorrhizal fungal (AMF) species, Glomus intraradices and Glomus claroideum, in the root systems of plants was investigated in a greenhouse experiment aimed at reconstructing interactions during an early stage of primary succession on a coal-mine spoil bank in Central Europe. Two plant species, Tripleurospermum inodorum and Calamagrostis epigejos, were inoculated either with one or both AMF species. Fungal development, determined by trypan blue and alkaline phosphatase staining as well as by PCR amplification of rRNA genes with species-specific primers, and the expression of five genes with different metabolic functions in the intraradical structures of G. intraradices were followed after 6 and 9 weeks of cultivation. The two AMF closely co-existed in the root systems of both plants possibly through similar colonisation rates and competitivity. Inoculation with the two fungi, however, did not bring any additional benefit to the host plants in comparison with single inoculation; moreover, plant growth depression observed after inoculation with G. claroideum persisted also in mixed inoculation. The expression of all the assayed G. intraradices genes was affected either by host plant or by co-inoculation with G. claroideum. The effects of both factors depended on the time of sampling, which underlines the importance of addressing this topic in time-course studies.     

Changes of antioxidative enzymes,lipid peroxidation and chlorophyll content in chickpea types colonized by different <Emphasis Type="Italic">Glomus</Emphasis> species under drought stress

In order to investigate the effects of Glomus species on some physiological characteristics of two chickpea types (Pirouz cultivar of Desi type and ILC-482 of Kabuli type) under non-stress (NS) and drought stress, an experiment was conducted using a factorial arrangement based on completely randomized design with three replications. Drought stress decreased shoot and total dry weight in plants. However inoculation of plants with mycorrhiza improved these traits. Leaf chlorophyll content was decreased, but leaf proline content and guaiacol peroxidases (EC 1.11.1.7) (POD), catalase (EC 1.11.1.6) (CAT), and ascorbate peroxidase (EC 1.11.1.11) (APX) activities were increased as a result of drought stress. Drought stress had no significant effect on soluble protein content and polyphenol oxidase (EC 1.10.3.1) (PPO) enzymatic activity in chickpea plants. In general, drought stress and especially severe drought stress increased membrane lipid peroxidation (MDA) in chickpea plants, which was more evident in non-inoculated than in inoculated plants. Inoculation of chickpea by AM significantly increased POD and PPO activities compared with non-inoculated chickpea, but had no effect on CAT activity and proline content of leaves. The reaction of chickpea cultivars to inoculation by AM species and irrigation levels were different. ILC-482 showed that antioxidant enzymes activities were more and thus less MDA compared with Pirouz cultivar. In general, the most POD and PPO activities were recorded for inoculated plants with G. etunicatum and G. versiform species, and the most APX activity was observed in plants inoculated with G. intraradices.