Top PDF The network structure of plant-arbuscular mycorrhizal fungi

Alguacil MM, Roldán A, Torres MP. 2009. Assessing the diversity of AM fungi in arid gypsophilous plant communities. Environmental Microbiology 11: 2649-2659. Almeida-Neto M, Guimarães P, Guimarães Jr PR, Loyola RD, Ulrich W. 2008. A consistent metric for nestedness analysis in ecological systems: reconciling concept and measurement. Oikos 117: 1227-1239.

consensus tree produced was viewed using FigTree. The GMYC analysis was performed on the consensus tree in RStudio v.0.99 (https://www.rstudio.com) using the ‘splits’ package. As singletons can influence the analysis, if these were found in GMYC they were removed from the original alignment and the analysis was run again from the beginning [49]. The con- fidence of the species groupings produced by GMYC was also calculated using ‘splits’. Sequences were assigned to groups called epGT (early-diverging plant Glomeromycotina taxa) by comparing the results of mptp and GMYC. In cases where the analyses did not agree, the confidence levels were compared and the most confident grouping was selected. The reference DNA sequences previously acquired from GenBank were also included in the species delimitation analyses to allow compari- sons between AMF in the different plant groups. A species accumulation curve was produced using ‘vegan’ in RStudio and extrapolation was performed using the bootstrap method.

Few researchers have contributed to mycorrhizal distribution studies of the coastal Caspian forests (for example Vafadar and Zare-maivan, 2006; Baghvardani and Zare-maivan, 1999), but knowledge of the flora still lacks comprehensive ecological categorization and synthesis both for above ground plant species and their underground symbiotic fungal partners. Although, functional traits (Díaz et al., 2004) have been successfully used to describe ecosystem processes within the Iranian vegetation and studies investigating plant species distribution in relation to environmental factors are frequent, yet the knowledge on understory vegetation of Caspian forests and mycorrhaizal associations is not ideal for autecological and phytosociological mapping and even functional categorization based on climate or soil characteristics, for example, identifying a definite trait for assessing plant distribution with respect to soil pH (Cornelissen et al., 2003; Hodgson et al., 2011). Since, each plant population establishes its own niche and symbiotic partnership and functions within the ecosystem, identifying the diversity of mycorrhizal populations of the understory vegetation could provide knowledge on

Abstract : Pepper (Piper nigrum L.) is an important spice plant of Indonesia. In Bangka Belitung Province, the main pepper producer, pepper has been the most commonly cultivated commodity. However, the production has declined from time to time. One of the causes of the decline is Pepper Fot Rot, caused by Phytophthora capsici. The rapid spread and development of the disease is mainly due to utilization of diseased plant materials for pepper cuttings and infested or diseased plantation soil. The materials used in this research included the infected soil taken from the infected pepper plantation at Bangka Island with disease intensity of pepper foot rot 60%, inoculum of Arbuscular Mycorrhizal fungi in the zeolite medium, compost, and pepper seedling from Natar variety. This research was done by planting pepper seedling on infected soil and observing plant height, disease intensity, and infection of AM fungi on the roots. The results showed that soil from diseased pepper plants harbored high population of plant pathogens inoculum and caused the death of 9 week-old cuttings and retarded growth of the survivors. Sterilization of the infected soil with hot water vapor for 3 hours still could not control the pathogen. Good growth was observed on one node cutting planted in sterile soil amended with arbuscular mycorrhizal fungi.

consensus tree produced was viewed using FigTree. The GMYC analysis was performed on the consensus tree in RStudio v.0.99 (https://www.rstudio.com) using the ‘splits’ package. As singletons can influence the analysis, if these were found in GMYC they were removed from the original alignment and the analysis was run again from the beginning [49]. The con- fidence of the species groupings produced by GMYC was also calculated using ‘splits’. Sequences were assigned to groups called epGT (early-diverging plant Glomeromycotina taxa) by comparing the results of mptp and GMYC. In cases where the analyses did not agree, the confidence levels were compared and the most confident grouping was selected. The reference DNA sequences previously acquired from GenBank were also included in the species delimitation analyses to allow compari- sons between AMF in the different plant groups. A species accumulation curve was produced using ‘vegan’ in RStudio and extrapolation was performed using the bootstrap method.

Black soils, referred to as Mollisols, are one of the most crucial soil resources for crop production (Liu et al. 2012a), due to their key roles in the supply of national staple food (Han et al. 2013). However, excessive cultiva- tion and intensive fertilization have caused serious soil degeneration and substantial losses of soil productivity since the middle of the last century (Singh et  al. 2014; Liu et al. 2015a). Intensive inorganic input leads to a shift from fungal-based to more bacterial-based soil food webs (Thiele-Bruhn et  al. 2012). Moreover, repeated applica- tion of inorganic fertilizer decreases soil pH (Liu et  al. 2012b), which in turn can reduce nutrient availability and microbial biomass (Bardgett 2005). Application of organic manure can reduce use of inorganic fertilizers and benefit soil quality by alleviating soil acidification, accumulating soil organic matter (OM), improving soil microbial community structure and reinforcing the self- regulating status of soil systems (Hammesfahr et al. 2011; Insam et  al. 2015). The responses of soil bacterial and fungal communities to inorganic fertilizer and manure in black soils were well reported in previous stud- ies (Zhou et al. 2015, 2016; Ding et al. 2016, 2017), but we know less about the effects on AMF, which work as good indicators of the soil ecosystem and affect the soil nutrition cycle and plant health. With chronic fertilizer input, the changes in soil properties no doubt influence AMF microbial communities and shift the plant–AMF symbiosis towards reduced mutualism or parasitism along a continuum (Verbruggen and Kiers 2010), as they could reduce the benefits provided by these symbionts. Understanding the shift of AMF community composi- tion is critical to assessing the impact of fertilization for determining a more effective strategy in sustainable soil fertility. As previously documented, several mycorrhizal fungi are closely associated with the soil P cycle (Smith et  al. 2011), and provide the plant hosts with P in the typically available form of phosphate. Given the relation- ship between AMF and soil available P (AP), and that soil AP, OM and pH are important contributors to the fun- gal community (Ding et  al. 2017), they may also shape the AMF community. In this study, we investigated the chronic (37-year) effects of fertilization regimes on soil properties and the AMF community, and determined the primary factors driving the shifts in the AMF community. We hypothesized the following: (1) chronic inorganic fer- tilization would significantly decrease AMF diversity; (2)

that improved plant nutrition by AM symbiosis allows cells to regulate and separate flowing ions more effect- ively (Giri et al . 2007). The nutrient imbalance due to salt stress results from the effects of salinity on nutrient availability, competitive uptake, transport, or partitioning within the plants (Grattan and Grieve 1993). The results here that mycorrhizal roots kept a higher K + /Na + ratio confirmed that K + competed for the site of Na + on the cell membrane. The conclusion was also reported by Hu and Schmidhalter (2005) Maintenance of a high cytosolic K + /Na + ratio is a key feature of plant salt tolerance (Cuin et al . 2008). The competition of K + due to mycorrhiza- tion may induce the decrease of Na + , thus enhancing salt tolerance of mycorrhizal apple plants.

The clover root weevil Sitona lepidus Gyllenhal (Coleoptera: Cur- culionidae) exhibits a preference for Trifolium spp. (Murray and Clements, 1994) and in the field feeds on white clover (Trifolium repens L.) which is the dominant legume in grazed pastures in the UK. The adults feed on the foliage, first instar larvae on the nodules, and later instars on progressively larger roots (Gerard, 2001). Consequently root (Murray and Clements, 1992) and foliar biomass (Murray et al., 1996) are reduced, as well as the func- tioning of the nitrogen-fixing nodules (Murray et al., 2002), and there is increased risk of pathogenic fungal attack at feeding sites (Kilpatrick, 1961). As a result, species of Sitona have long been regarded as pests of legumes in the UK and elsewhere (e.g. Jackson, 1920; Morrison et al., 1974; Goldson et al., 1988). Clements and Murray (1993) found that up to 30% of the photosynthetic area of a clover plant could be removed by adult weevils especially in late winter when a temporary rise in ambient temperature allowed the weevils to feed on the clover plants when they were either growing slowly or not at all. Consequently, the competitive abil- ity of clover in a mixed grass/clover sward may be weakened leading to reduced clover content in the sward. It is desirable to have T. repens in the sward due to its nitrogen-fixing capa- bilities (Newbould, 1982) and its feeding value for livestock (Bax and Schills, 1993). AMF are known to increase nodulation of T. repens (Crush, 1974; Barea et al., 1989) and thus the question addressed in this paper is whether these fungi also affect the growth and survival of S. lepidus, thus presenting the first study of the responses of a specialist root-feeding insect to these fungi. We hypothesised that extra availability of root nodules, mediated by AMF, might increase larval survival and growth, as the lar- vae are highly dependent on this crucial resource (Johnson et al., 2004).

to show any resistance when the experiment was switched to single NaCl salt addition. Several studies have also reported the detrimental effect of NaCl on individual AM fungal species (Giri et al., 2007; Juniper & Abbott 2006; Sheng et al., 2008). Despite the documented negative effects of salinity on mycorrhizal spore germination and root colonisation (Juniper & Abbott 2006; Evelin et al., 2009), many reports indicate that mycorrhizas can still be symbiotically effective under saline conditions depending on the identity of the AM species (Giri & Mukerji 2004; Daei et al., 2009; Evelin et al., 2012; Talaat & Shawky 2014). Multi-factorial meta-analyses conducted by Hoeksema and colleagues (2010) proved that the identity and diversity of mycorrhizal fungi as well as the host plant identity are critical factors in determining the variation in plant response to mycorrhizal inoculation. These authors also suggested that the experimental site (laboratory vs. field) per se is a relatively less important factor than the plant and fungal characteristics in the symbiosis (Hoeksema et al., 2010). Meanwhile, another meta-analysis emphasized, in sharp contrast, the importance of the location and showed a greater plant response to AM in the glasshouse than in the field (Lekberg & Koide 2005). This might explain the improved outcome with the commercial AM fungal mix observed in the glasshouse experiment in Chapter 6, which should be taken into consideration for future experiments.

AA has a great importance for animal and vegetal organisms and its biosynthesis was clarified in 1998, when Wheeler Jones and Smornoff demonstrated in Arabidopsis leaves that L-galactose (L-GAL) and L-galactone- 1,4-lactone (L-GL) are key precursors of this bioactive compound (Soares et al., 2004). In their study with several vegetables, aiming to investigate ascorbic acid precursors, Soares et al. (2004) confirmed that L-GAL and L-GL are very efficient AA precursors. These precursors are formed from D-glicose, D-frutose, D-manose (D-MAN) in the studied vegetables, phosphorylation being needed so that D-MAN is converted into L-GAL, with a high energetic demand, which, if not supplied, diverts D-MAN to other pathways. This may be why response to AMF inoculation in the fruits AA degree can vary so much, as it depends, among other factors, on the existing availability of P in different substrata, on the presence of a native AMF community and other stressing conditions that may act on the plant.

hickpea (Cicer arietinum L.) is an important source of human food and animal feed that also helps in the management of soil fertility, particularly in dry lands [1]. Fusarium wilt, caused by Fusarium oxysporum Schlechtend.: Fr. f. sp. ciceris (Padwick) Matuo & K. Sato, is one of the most important limiting factors of chickpea production in the Mediterranean Basin and Indian Subcontinent [2]. Fusarium wilt epidemics cause significant annual losses of chickpea yields [2,3] that may reach 100 % under conditions favourable for disease [3,4]. Fusarium oxysporum f. sp. ciceris is a soil-borne fungus pathogenically specialized on Cicer spp. that causes wilt. Interest in biological control has increased recently fuelled by public concerns over the use of chemicals in the environment in general, and the need to find alternatives to the use of chemicals for disease control in particular. The key to achieving successful, reproducible biological control is the gradual appreciation that knowledge of the ecological interactions taking place in the soil and root environments is required to predict the conditions under which biocontrol can be achieved [5,6]. The major feature involves improving plant nutritional status, perhaps water balance and thus plant growth, biocontrol of plant pathogens is generally viewed as a secondary role [7].

equivalent. The fungal taxa least affected by the fungicide were widespread taxa that have been recorded with many other plant genera, not only at this field site but elsewhere (Öpik et al. 2006). The rare and specific taxa, some of which have not been recorded from field samples previously, may therefore have been principally responsible for promoting P uptake in A. reptans. Cultures of Glomus sp. UY1225 (Glo3) and G. hoi, two of the widespread taxa identified in A. reptans roots in this study (Fig 2b), have been used as symbionts in a previous laboratory experiment with A. reptans and several other co-occurring plant species from the same field site. Both fungal taxa were successful colonisers, and both resulted in only a small increase in P uptake by A. reptans relative to uncolonised controls (Helgason et al. 2002). The same effect was seen with most other plant-fungus pairs in the experiment. G.mosseae and G. intraradices, two commonly cultured taxa, are also among the most commonly identified sequence types in field studies. G. mosseae increased in frequency, and G. intraradices remained the most abundant AM type after benomyl treatment, at the expense of Acaulospora spp. That result is consistent with Fig 2b (open symbols) and reinforces the view that these fungi are indeed generalists. This interpretation of course depends on demonstrating that the generalist taxa are less able to promote uptake of P, something this study was not able to do. It is possible that this response is due to a differential effect of benomyl on the AM fungi that may not necessarily reflect a difference in function. Clearly, the next step is to determine whether or not there is any functional diversity among taxa in the field. Diversity in P-uptake has been demonstrated even within a single species in laboratory experiments (Munkvold et al. 2004), so it would be reasonable to predict such diversity in a field community.

artificial native grassland community. As the chosen site was formerly used as an arable plot, we expected low AM fungal diversity (Giovannetti & Gianinazzi- Pearson, 1994; Helgason et al., 1998). This would make it easier to detect any seasonal or treatment effects and also impacts on key species. So far only around 150 species, all belonging to the order Glomales (Glomeromycota), have been described by spore mor- phology. Attempts to distinguish AM species based entirely on intra-radical hyphal structures (Abbott & Robson 1984; Merryweather & Fitter, 1998a) are system- specific and time consuming. More recently, fungal taxa have been recognized from differences in their small sub-unit (SSU) rRNA (Giovannetti & Gianinazzi-Pear- son, 1994; Helgason et al., 1999), amplified directly from spores or from host plant roots using AM fungal- specific primers. A combination of molecular analysis with assessment of colonization of paired root samples over time enabled us to characterize both the structure and dynamics of the AM fungal community and also its interaction with other root-colonizing fungi. We tested four hypotheses: (i) light has a greater influence on root colonization by AM fungi than temperature within the range likely to be experienced following climate warming; (ii) seasonal light changes will be more important than shading; (iii) soil warming is most influential during cooler periods either by increasing colonization or by prolonging the production of young roots; (iv) there will be differences in the responses of native AM fungal species to temperature and shading treatments.

1859 | Page between AM fungi and host plant genotype (Ahiabor and Hirata, 1995; Marschner, 1995). Mycorrhizae have also been reported in plants growing on heavy metal contaminated sites (Chaudhry et al., 1998; Shetty et al., 1995) indicating that these fungi have evolved a HM- tolerance and that they may play a role in the phytoremediation of the site. Noyd et al. (1996) reported that AM fungal infectivity of native prairie grasses increased over three seasons on a coarse taconite iron ore tailing plots which helped to establish a sustainable native grass community that will meet reclamation goals. The reported symbiotic associations in the plants colonizing heavy metal contaminated soils further suggests a selective advantage for these plants as pioneering species on such sites and that they may be largely responsible for the successful colonization of such habitats. Also, Gali et al. (1994) suggested that mycorrhizae can play a crucial role in protecting plant roots from heavy metals. The efficiency of protection, however, differs between distinct isolates of mycorrhizal fungi and different heavy metals.

The positive interaction between Azospirillum and VAM fungi in the rhizosphere could be due to direct interaction between microorganisms or indirectly by their effect on the host plant physiology. The presence of VAM fungi causes increase in number and diversity of microorganisms in rhizosphere. Colonization of roots with VAM fungi stimulates inflow of sugars from shoot to root, that may alter C availability to the rhizosphere microorganisms. Rhizosphere interactions occur between AM fungi and other soil microorganisms with effects on plant nutrient balances, such as nitrogen-fixing bacteria and plant growth-promoting rhizobacteria (Paula et al., 1993). Microbial interactions involving AMF appear to play a key role in ecological and biotechnological approaches to improving sustainability of soil-plant systems. Rhizosphere microorganisms can affect AM formation by acting on AM propagule germination and/or the establishment of entry points of the AM fungi in the roots. Conversely, by altering the quality and quantity of root exudates, AM symbiosis can modulate the activity and/or number of the microbial components in the soil surrounding the mycorrhizal root system, giving way to the so-called mycorrhizosphere (Azcon et al., 1992). Specific types of organisms are able to establish relationships with mycorrhizal fungi which affect plant growth and health and also soil quality. AM have the potential to alter bacterial species composition in rhizosphere soil (Meyer and Linderman, 1986) and some bacteria can positively stimulate certain aspects of the symbiosis (Azcon and Barea, 1985). However, it is unknown whether microbial effects can be exerted directly on AM fungal hyphae. The length of AM hyphae may increase in response to a high content of soil organic matter and that in response to AM colonization the activity of acid phosphatase in soil may decrease. Increased alkaline phosphatase activity

more the establishment of this mutualistic association can stimulate, via activation of antioxidant, phenylpropanoid and carotenoid pathways [7], the synthesis of plant sec- ondary metabolites which are important for increased plant tolerance to abiotic and biotic stresses [8,9] or beneficial to human health through their antioxidant ac- tivity [10,11]. In recent years, much effort has been paid to obtain suitable formulations for AM fungal inocula and appropriate ways for their application to the field [12]. The development of inocula based on AM fungi has to take in account the adaptation ability in a contest of indigenous AMF populations. The native communities in fact show generally a better fitness in the environmental conditions of their eco/agro-system in comparison to foreign species [13] and this could compromise the effi- ciency on AMF inocula application. In addition, as AM fungal inoculants are most often of foreign origin, atten- tion has to be paid about the possibility of invasive spreading after release to the field and further negative ecological consequences [14]. The study and selection of isolates from endemic AMF communities could represent an alternative to the use of not native organisms, also in the aim of restocking those soils with a microflora de- pleted by intensive agricultural practices.

Ocimum sanctum L., is an under shrub with enormous medicinal value. It is commonly known as tulasi. It is used as stimulant, diaphoretic and expectorant. Used in catarrh, bronchitis, ringworm, cutaneous disease, stomach aches, malarial fevers, genital urinary disorders and asthma etc. Plant extracts showed antifungal, antibacterial properties against Aspergillus flavus, A. parasitica, Mycobacterium tuberculosis, Salmonella typhosa, Escherichia coli and Micrococcus pyrogens. So far no studies were carried out with AM fungal inoculation on Ocimum sanctum L. Hence the present study was undertaken with aim for selecting efficient AM fungus to improve plant growth and biomass production under experimental condition. Abstract: Screening of four indigenous AM fungi for improvement of plant growth, biomass production and nutrient uptake was undertaken on Ocimum sanctum L. the results revealed that, plants inoculated with Rhizophagus fasciculatus was found to be the most significant. After 30 days increased shoot length, dry weight of root and shoot, mycorrhizal colonization and spore number were recorded. Plants inoculated with AM fungus R. fasciculatus showed significantly more number of flowers, compared to other AM fungi treated plants. The indigenous species, Rhizophagus fasciculatus was the best species among four species tested. Hence, it can be concluded that experimental plant showed varied response to different AM fungi and Rhizophagus fasciculatus confers maximum growth benefits compared to all other fungi used in this study.

ecosystems; functioning of indigenus mycorrhizal symbiosis (IMS) and related environmental factors at coastal Caribbean ecosystems remains still scarce. In order to determine functionality of IMS under contrasting land uses and wet seasons from Cuba, the influence of the water stress on some AMF functionality parameters from a semi-natural savannah (NS), a recovered savannah (RS) and an agro-ecosystem (AG) from the Managed Floristic Reserve San Ubaldo-Sabanalamar, Pinar del Rio, Cuba were assessed during two-years. Soil and root samples were collected in April and October, during the dry and wet seasons, respectively, in 2008 and 2010. Four plots in each ecosystem were selected, and five soil sub-samples were randomly collected, bulked, mixed homogeneously and used as the composite sample per plot. The host plant root biomass, arbuscular mycorrhi- zal colonization of the host plant, density of the intraradical and extraradical AMF mycelia, fungal endophyte biomass and AMF spore density were assessed. The host plant root biomass increased in the NS environment during the dry season, and approximately 12.85g root/dm 3 dry soil was recorded. The colonization degree were significantly higher in all environments during the wet season of the second year, with means ranging from 79% to 89%. The extraradical mycelia were significantly more abundant in the dry season of the second year in all environments, with a maximum of 279mg/dm 3 in the RS ecosystem. The density of AMF spores was highest in the dry season of the second year for the three studied ecosystems. The RS ecosystem hosted 5 670 spores/100g dry soil. In general, the influence of rainfall seasonality on the function of AMF was stronger than the influence of ecosystem management. The root biomass and extraradical mycelia were high in the dry seasons, suggesting strategies to increase the volume of soil for the mutual benefit of the symbionts. The increase in spore density during the dry seasons appears as an adaptation allowing AMF to survive period of water shortage. This study improves our understanding of the adaptative responses of arbuscular mycorrhizal symbiosis to seasonal varia- tions in soil water availability. Rev. Biol. Trop. 63 (2): 341-356. Epub 2015 June 01.

Research on arbuscular mycorrhizal fungi (AMF), presently, is at the crossroads. Some aspects like their beneficial role in overall plant growth under diverse edaphic conditions, have been thoroughly investigated and further, there is no second opinion to the advocacy of their development as bioinoculants. However, the biosystematics, culturability and field performance evaluation of this group of fungi are still some areas lagging behind for want of suitable techniques, which have become hurdles for further progress of research. Having exhausted all the options to resolve the issues, the mycorrhizologists are looking towards molecular aspects of this group of organisms. rDNA region of the genome, with its variable and conserved regions, has been found to be an ideal location to offer solution to the issues. PCR-based techniques have become mandatory to obtain sufficient quantities of DNA, as these organisms are nonculturable and thus only a small quantity of DNA could be isolated from spores and infected roots. Employing DNA-based molecular markers, some ad- vancements and success have already been achieved in areas like phylogeny, taxonomy and functional sym- biosis. The next one or two decades are going to witness tremendous increases in molecular level research on this group of organisms, which hopefully will help re- solve many issues being confronted today. This article reviews the molecular investigations carried out during the last two decades all over the world and also project areas for future research in India.

This study provides the first baseline for the diversity of AMF in Ontario TGPs, and improved depth and resolution over previous studies of AMF in TGPs of Walpole Island First Nation (Chokroborty Hoque 2011, Stover et al. 2012). Nonetheless, it should still be considered a preliminary assessment, for various reasons. The primer pair used amplified a section of the SSU approximately 250 bp long, and when looking at species differences between AMF that may not be a sufficient length. Thiéry et al. (2012) sequenced a 4960 bp segment of SSU, ITS and part of the LSU, and suggested there is low intra- and interspecific variation of the small subunit regions typically studied. This suggests that a larger section of the ribosomal operon may be needed when studying AM fungal communities. Secondly, this study did not consider the plant populations or soil characteristics of the TGPs, which have been shown to influence AMF communities (Egerton-Warburton and Allen 2000, Eom et al. 2000, Bever et al. 2001, Helgason et al. 2002, Husband et al. 2002, Vandenkoornhuyse et al. 2002). The study was small-scale with only one replication for each season, which decreases the information that could have been obtained. Ideally, multiple replications over multiple years would have provided a more thorough characterization of the AMF communities of Ontario TGPs. However, in this preliminary assessment, the number of OTUs of Glomeromycota obtained was greater than what was found in most studies that used the AMV4.5NF/AMDG-R with 454 pyrosequencing (Lumini et al. 2010, Dai et al. 2013, Bainard et al. 2015), and much greater than earlier studies of the same sites using culture-based or cloning and sequencing methods (Chokroborty Hoque 2011, Stover et al. 2012).