Article

Plant diversity improves protection against soil-borne pathogens by fostering antagonistic bacterial communities

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Abstract

1. Rhizosphere bacteria antagonistic to fungal pathogens improve plant performance by preventing infection. In temperate grasslands, primary productivity often increases with plant diversity, and we hypothesized that this effect may in part rely on the interactions between plants and antagonistic bacteria. 2. We investigated the impact of plant diversity and functional group composition on soil bacteria producing the antifungal compounds 2,4-diacetylphloroglucinol (DAPG) and pyrrolnitrin (PRN) in a long-term grassland biodiversity experiment, as well as their impact on soil suppressiveness. Soil suppressiveness was investigated in a model infection assay with Beta vulgaris and the pathogen Rhizoctonia solani. 3. The abundance of DAPG and PRN producers increased with plant diversity and that of PRN also increased in the presence of grasses. Moreover, legume species richness and coverage decreased the abundance of DAPG and PRN producers, respectively, contrary to beneficial effects of legumes on soil microorganisms reported previously. In turn, soil suppressiveness was at maximum when DAPG and PRN producer abundance was high. 4. Synthesis. Our results suggest that plant diversity contributes to plant community resistance against pathogens by fostering beneficial bacterial communities. This indirect soil feedback mechanism may contribute to the positive relationship between plant diversity and productivity and could also help the development of more sustainable and environmentally friendly agricultural management strategies.

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... High microbial diversity in the soil allows fewer pathogens to survive, and may also prevent the invasion of exogenous pathogens (Benizri et al. 2005). Several soil microorganisms confer benefits in nutrient acquisition (Berendsen et al. 2012;Chaparro et al. 2012) and protect host plants by preventing colonization from soil-borne pathogens (Cook and Baker 1983;Hadar and Papadopoulou 2012;Latz et al. 2012;Schlatter et al. 2017;Wellar et al. 2002). ...
... This concept of grassland as "preserver of microbial diversity" can be explored to identify more microbial taxa capable of disease suppression. The abundance of DAPG and PRN producers has been reported to increase with plant diversity but with greater spatial diversity (Latz et al. 2012). Therefore, a higher abundance of DAPG and PRN producers is detected in grassland soils than in cultivable soils (Garbeva et al. 2004). ...
... Therefore, a higher abundance of DAPG and PRN producers is detected in grassland soils than in cultivable soils (Garbeva et al. 2004). Grasses tend to increase the prnD gene abundance whereas legumes decrease DAPG and PRN producer abundance (Latz et al. 2012). ...
Article
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In the pursuit of higher food production and economic growth and increasing population, we have often jeopardized natural resources such as soil, water, vegetation, and biodiversity at an alarming rate. In this process, wider adoption of intensive farming practices, namely changes in land use, imbalanced fertilizer application, minimum addition of organic residue/manure, and non-adoption of site-specific conservation measures, has led to declining in soil health and land degradation in an irreversible manner. In addition, increasing use of pesticides, coupled with soil and water pollution, has led the researchers to search for an environmental-friendly and cost-effective alternatives to controlling soil-borne diseases that are difficult to control, and which significantly limit agricultural productivity. Since the 1960s, disease-suppressive soils (DSS) have been identified and studied around the world.Soil disease suppression is the reduction in the incidence of soil-borne diseases even in the presence of a host plant and inoculum in the soil. The disease-suppressive capacity is mainly attributed to diverse microbial communities present in the soil that could act against soil-borne pathogens in multifaceted ways. The beneficial microorganisms employ some specific functions such as antibiosis, parasitism, competition for resources, and predation. However, there has been increasing evidence on the role of soil abiotic factors that largely influence the disease suppression. The intricate interactions of the soil, plant, and environmental components in a disease triangle make this process complex yet crucial to study to reduce disease incidence. Increasing resistance of the pathogen to presently available chemicals has led to the shift from culturable microbes to unexplored and unculturable microbes. Agricultural management practices such as tillage, fertilization, manures, irrigation, and amendment applications significantly alter the soil physicochemical environment and influence the growth and behaviour of antagonistic microbes. Plant factors such as age, type of crop, and root behaviour of the plant could stimulate or limit the diversity and structure of soil microorganisms in the rhizosphere. Further, identification and in-depth of disease-suppressive soils could lead to the discovery of more beneficial microorganisms with novel anti-microbial and plant promoting traits. To date, several microbial species have been isolated and proposed as key contributors in disease suppression, but the complexities as well as the mechanisms of the microbial and abiotic interactions remain elusive for most of the disease-suppressive soils. Thus, this review critically explores disease-suppressive attributes in soils, mechanisms involved, and biotic and abiotic factors affecting DSS and also briefly reviewing soil microbiome for anti-microbial drugs, in fact, a consequence of DSS phenomenon.
... High biodiversity allows fewer resident pathogens to survive for long times and may also prevent the invasion of the exogenous ones. Several soil microorganisms can confer benefits in nutrient availability [82,83] and can protect the host plant by preventing colonization and invasion of pathogen [23,84]. There are two distinct models of disease suppressiveness differentiated by general and/or specific mechanisms. ...
... The concept of grassland as a "preserver of microbial diversity" can be explored in order to identify more microbial taxa inducing suppression. Abundance of C T E D 2,4-DAPG and PRN producers has been reported to increase with the plant diversity, and also with greater spatial diversity in grassland soil than in the cultivable ones [77,84]. Grasses tend to increase the prnD gene abundance, whereas legumes tend to decrease the 2,4-DAPG and PRN producers. ...
Article
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This review pays attention to the newest insights on the soil microbiome in plant disease suppressive soil (DSS) for sustainable plant health management from the perspective of a circular economy that provides beneficial microbiota by recycling agro-wastes into the soil. In order to increase suppression of soil-borne plant pathogens, the main goal of this paper is to critically discuss and compare the potential use of reshaped soil microbiomes by assembling different agricultural practices such as crop selection; land use and conservative agriculture; crop rotation, diversification, intercropping and cover cropping; compost and chitosan application; and soil pre-fumigation combined with organic amendments and bio-organic fertilizers. This review is seen mostly as a comprehensive understanding of the main findings regarding DSS, starting from the oldest concepts to the newest challenges, based on the assumption that sustainability for soil quality and plant health is increasingly viable and supported by microbiome-assisted strategies based on the next-generation sequencing (NGS) methods that characterize in depth the soil bacterial and fungal communities. This approach, together with the virtuous reuse of agro-wastes to produce in situ green composts and organic bio-fertilizers, is the best way to design new sustainable cropping systems in a circular economy system. The current knowledge on soil-borne pathogens and soil microbiota is summarized. How microbiota determine soil suppression and what NGS strategies are available to understand soil microbiomes in DSS are presented. Disturbance of soil microbiota based on combined agricultural practices is deeply considered. Sustainable soil microbiome management by recycling in situ agrowastes is presented. Afterwards, how the resulting new insights can drive the progress in sustainable microbiome-based disease management is discussed.
... Furthermore, in grassland environments, it seems that plant diversity favours the abundance of biocontrolrelated bacteria, i.e. Pseudomonas which can synthetize 2,4-diacetylphloroglucinol (DAPG) and pyrrolnitrin antibiotics, supporting the idea that mono-cropping is not a sustainable management for microflora diversity (Latz et al., 2012). ...
... Nevertheless, it should be considered that mono-cropping is particularly detrimental under no-tillage managements, because the accumulation of crop residues increases the pathogen load in soils (Lin, 2011). On the other hand, the induction of disease-suppressive soils through crop monoculture or specific cropping sequences demonstrates the plants' role in building a disease-suppressive soil microbiome (Weller et al., 2002;Peters et al., 2003;Latz et al., 2012). Notably, the suppressiveness of the soils described above is associated with the antagonistic potential of diverse Pseudomonas species (Stutz et al., 1986;Lemanceau and Alabouvette, 1993;Duijff et al., 1994;Mazzola, 2002;Mazzola et al., 2004;Landa et al., 2006;Mazzola, 2007;Weller, 2007;Weller et al., 2007;Mazurier et al., 2009;Hjort et al., 2010;Mendes et al., 2011;Michelsen et al., 2015) (Table 6.2). ...
Chapter
This book includes 25 contributions from vastly experienced, global experts in PGPR research in a comprehensive and influential manner, with the most recent facts and extended case studies. Also, the chapters address the current global issues in biopesticide research.
... • Les méthodes moléculaires. On séquence la totalité de l'ADN présent dans un sol, et on va chercher une famille de gènes dont on sait qu'ils sont liés à une fonction agronomique, par exemple les gènes nifH, amoA ou hao 60 qui codent la synthèse des enzymes du cycle de l'azote, ou les gènes phlD et prnD, impliqués dans la protection contre les champignons pathogènes 43 . On peut également s'intéresser au transcriptome (l'ARN), ce qui fournit une information a priori plus proche de ce qui a lieu dans le sol. ...
... • L'autre approche consiste à étudier les microorganismes présents dans les sols, leurs activités, leurs fonctions et leurs dynamiques pour éventuellement comprendre comment ces dynamiques peuvent être influencées. Des travaux ont par exemple montré que l'apport d'engrais, la pollution aux métaux lourds et le type de culture altéraient les microbiotes des sols, en matière de répartition d'espèces[38][39][40][41][42] , de potentiel à protéger contre les maladies des plantes (biocontrôle)43 ou d'activité solubilisatrice de phosphate 39,44 . Des équipes s'intéressent également à la répartition spatiale et temporelle de différentes activités enzymatiques dans le sol 45,46 . ...
Thesis
Les microbes des sols sont utiles à l’agriculture : ils aident les plantes à acquérir des nutriments, dégradent les déchets, protègent les plantations contre les pathogènes… Comprendre les interactions entre les microorganismes, les plantes et les autres éléments du sol pourrait permettre de gagner en productivité tout en préservant l’environnement. Dans cet optique, un des enjeux en agronomie est d’être capable de caractériser les communautés microbiennes des sols de manière fonctionnelle ; c’est-à-dire de quantifier les services qu’elles peuvent rendre à l’agriculture et à la société de manière générale. Par exemple, un « bon » microbiote d’un point de vue fonctionnel protégera les plantes des maladies et les aidera à acquérir des nutriments, il dégradera les éventuels polluants néfastes et limitera les efflux de gaz à effet de serre. Pour mener cette caractérisation, l’identification et l’analyse génétique des microbiotes ne suffisent pas ; des outils technologiques manquent.Nous avons choisi de nous occuper de ce problème en exploitant une technologie qui n’avait pas été employée jusqu’ici en agriculture : la millifluidique de gouttes, qui consiste à manipuler des gouttes de quelques centaines de nanolitres, séparées les unes des autres par une phase huileuse. En l’occurrence, nous avons utilisé l’automate de culture microbiologique en gouttes de la startup MilliDrop. Nous avons étudié une fonction : la capacité à solubiliser le phosphate du sol, un nutriment essentiel aux plantes. Nous avons adapté la recette d’un milieu de culture utilisé depuis plus de 70 ans : le milieu Pikovskaya. Il contient des particules de phosphate de calcium et nous avons dû mener un travail de formulation physico-chimique important pour transférer ces particules en gouttes et les y maintenir dispersées. Nous avons par ailleurs ajouté au milieu deux sondes fluorescentes qui nous ont permis de suivre à la fois le pH de nos gouttes et l’activité respiratoire. Ce protocole expérimental prêt, nous l’avons appliqué à une douzaine de sols agricoles.Grâce à la fluorescence de la résazurine, notre sonde d’activité respiratoire, nous avons estimé la concentration en cellules cultivables dans nos échantillons. Nous avons montré que l’on obtenait en tendance le même nombre de microorganismes avec notre méthode en gouttes qu’avec la méthode classique de dénombrement de colonies sur boîtes de Petri.En exploitant un bloc optique conçu pour notre projet, nous avons pu mener des mesures de néphélométrie (scattering) en gouttes et évaluer la capacité de nos microorganismes à faire baisser ce signal, ce que nous interprétons au moins partiellement comme la capacité des microorganismes à solubiliser le phosphate. Grâce à notre sonde pH, nous avons pu montrer que la baisse du signal de scattering était associée à une chute du pH sous 5,8 (qui correspond au pH théorique en-dessous duquel les particules se dissolvent par seul effet de l’acidité) dans environ 90% des gouttes. Il est possible que parmi les 10% des gouttes restantes, on trouve des microorganismes qui sécrètent de grandes quantités de chélatants, ce qui représente un intérêt agricole particulier. On trouve systématiquement plus de microorganismes solubilisateurs en gouttes qu’avec la méthode traditionnelle sur boîte de Petri, sans pour autant avoir de corrélation entre ces deux modes de mesure. Si différentes hypothèses pourraient être testées pour éclaircir ce phénomène, nos résultats remettent en question le test traditionnel sur boîtes.Notre protocole est rapide et simple : nos expériences ont pu être réalisées par une technicienne non spécialisée, le traitement de données est automatisable et une demi-heure de travail suffit à analyser quatre sols (plus avec de prochaines versions de la machine). Les résultats en gouttes sont obtenus sept fois plus vite que ceux sur boîtes de Petri. Cela fait de notre protocole un candidat pour devenir un test fonctionnel utilisé à grande échelle.
... Numerous studies have linked microbial diversity with a reduction in the incidence of disease (Keesing et al., 2010;Kopecky et al., 2019). A low potato common scab is observed, even in favorable conditions, when high bacterial diversity is present in the soil (Latz et al., 2012;van Elsas et al., 2012). Higher soil microbiome diversity offers better odds of finding a higher abundance of rare species able to bring specific protective functions against pathogens (Latz et al., 2012). ...
... A low potato common scab is observed, even in favorable conditions, when high bacterial diversity is present in the soil (Latz et al., 2012;van Elsas et al., 2012). Higher soil microbiome diversity offers better odds of finding a higher abundance of rare species able to bring specific protective functions against pathogens (Latz et al., 2012). As reported by Mendes et al. (2018), the exclusive and abundant presence of a bacterial taxon is a poorer indicator of disease suppression than the relative abundance of bacterial taxa. ...
Article
Full-text available
Plants have always grown and evolved surrounded by numerous microorganisms that inhabit their environment, later termed microbiota. To enhance food production, humankind has relied on various farming practices such as irrigation, tilling, fertilization, and pest and disease management. Over the past few years, studies have highlighted the impacts of such practices, not only in terms of plant health or yields but also on the microbial communities associated with plants, which have been investigated through microbiome studies. Because some microorganisms exert beneficial traits that improve plant growth and health, understanding how to modulate microbial communities will help in developing smart farming and favor plant growth-promoting (PGP) microorganisms. With tremendous cost cuts in NGS technologies, metagenomic approaches are now affordable and have been widely used to investigate crop-associated microbiomes. Being able to engineer microbial communities in ways that benefit crop health and growth will help decrease the number of chemical inputs required. Against this background, this review explores the impacts of agricultural practices on soil- and plant-associated microbiomes, focusing on plant growth-promoting microorganisms from a metagenomic perspective.
... Biomass production at the community level was slightly higher in the home soils relative to away soil conditioning but was signi cantly reduced in the sterile soils (Fig. 5a). Latz et al. 2012;Mommer et al. 2018;Teste et al. 2017). The presence of species representing multiple functional groups may enhance bene cial soil biota that promotes positive plant and soil biota interactions and potentially alleviating neighbouring plant drought stress (Baxendale et al. 2014;Latz et al. 2012). ...
... Latz et al. 2012;Mommer et al. 2018;Teste et al. 2017). The presence of species representing multiple functional groups may enhance bene cial soil biota that promotes positive plant and soil biota interactions and potentially alleviating neighbouring plant drought stress (Baxendale et al. 2014;Latz et al. 2012). However, the positive effect of soil biota appeared to be reduced in the soils with drought legacies, particularly when comparing home soils with sterile soils where PSFs shifted from being strongly positive to less positive. ...
Preprint
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Background Climate changes can shift plant-soil feedbacks (PSFs) causing unexpected knock-on effects on plant community dynamics. We test the hypothesis that prolonged drought legacies cause shifts in PSFs due to changes in plant-soil biotic interactions. Methods PSFs of twelve plant species representing four functional groups (C3 and C4 grasses, forbs, and legumes) were assessed in monocultures, and communities composed of one species from each of the four functional groups, in soils collected from plots with a five-year legacy of ambient rainfall or drought conditions under laboratory conditions. Plants were grown under well-watered conditions, with observed effects, therefore, being related to field drought legacies rather than experimental drought. Sterile soil conditioning was included to assess shifts in plant-soil biotic interactions associated with field rainfall legacies explicitly. Results C3 and C4 grasses displayed negative and positive PSFs, respectively, in both rainfall legacies treatments. PSFs of Plantago lanceolata shifted from positive to negative in drought legacies, while Cichorium intybus showed neutral PSFs in both soils. PSFs of Medicago sativa shifted from negative to positive, while Biserrula pelecinus and Trifolium repens showed neutral PSFs, in prolonged drought legacies. PSFs at the community level showed a trend to shift from near-positive to neutral PSFs in soils with a drought legacy, with significant negative PSFs observed when comparing home versus sterile soils, suggesting that drought may destabilise plant communities. Conclusion Our results provide evidence that prolonged drought legacies can modify plant community dynamics due to species-specific changes in PSFs that persist after droughts are alleviated.
... Due to the correlation of above-and below-below ground variety, a high microbial diversity can be expected [25]. Furthermore, natural habitats have a low number of pathogens, so the general rule of diversity versus pathogenicity would suggest a higher rate of biocontrol and plant growth promotion agents in such environments [26]. Agricultural systems, especially monocultures under intense management often have low microbial diversity with the exception of suppressive soils where the microbial community responds to mono-cultivation by enhancing biocontrol and plant growth promotion bacteria against a specific pathogen [27]. ...
... These suppressive soils are also an excellent source of new antagonists as already shown for wheat monocultures [28] and intense sugar beet cultivation [29]. Organically managed systems contain a high proportion of indigenous beneficial in comparison to conventional agriculture [26,30] such as the more exotic bioresource of lichens. These long-living symbiotic metaorganisms often adapt to extreme abiotic conditions and harbor a high proportion of antagonists to protect themselves against fungal parasites [31]. ...
Article
Full-text available
Trichoderma spp. is one of the most popular genus of fungi commercially available as a plant growth promoting fungus (PGPF) and biological control agent. More than 80 species of Trichoderma are reported in the literature. However T. asperellum, T. harzianum, T. viride, and T. virens are most commonly utilized as biocontrol agents. Studies were initiated to explore the potential of biocontrol agents in order to develop a cost effective and practical management strategy. Analysis of large number of soil samples collected from western parts of the region led to isolation of native biocontrol agents viz., Trichoderma harzianum, Aspergillus versicolor, and Bacillus firmus from different agricultural systems. These biocontrol agents have proved their antagonistic ability in laboratory tests and field trials. In India, two species of Trichoderma i.e., T. viride and T. harzianum are commercially registered for usage against soil borne plant pathogens mostly as a seed treatment or soil application. There are published scientific papers on the efficacy of T. asperellum and T. virens in India for suppressing pathogens but these are not yet registered under Central Insecticide Board and Registration Committee (CIB & RC). This review article focuses on the uses, commercialization and adoption issues of various fungal and bacterial consortium products in sustainable disease management.
... The effects of soil biotic communities as a whole may be positive, consistent with positive effects found in many experiments with soil inoculum (Andrews et al. 2010), an effect referred to as disease suppressive soils (Berendsen et al. 2012). Beneficial microbes, especially mutualists with plants, facilitate the efficiency of plant nutrient uptake, and potentially enhance plant disease resistance (Cook et al. 1995;Berendsen et al. 2012;Latz et al. 2012). The microbiota on plant roots and leaves can affect disease resistance through increased nutrient uptake by the plant host (Compant et al. 2005), by reducing pathogens through competition (Doornbos et al. 2012), or by releasing inhibitory allelochemicals (Sturz and Christie 2003;Berendsen et al. 2012). ...
... (1) Mutualists in the soil biotic community might improve plant growth, for example, by enhancing nutrient uptake, and offset the negative effects of disease infection (Cook et al. 1995, Berendsen et al. 2012Latz et al. 2012). ...
Article
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The effects of whole soil biotic communities on plants is a result of positive and negative interactions from a complex suite of mutualists and pathogens. However, few experiments have evaluated the composite effects of whole soil biotic communities on plant growth and disease resistance. We conducted a factorial greenhouse experiment with 14 Rhododendron species grown with and without live conspecific soil biota and with and without the disease, Phytophthora cinnamomi. We tested the prediction that the presence of whole soil biotic communities influences survival in the presence of disease. We also explored functional trait correlations with disease susceptibility across the phylogeny. The presence of live soil biota led to higher survival in the presence of disease compared with sterilized soils, and the direction of this effect was consistent for seven species across four clades. The presence of live soil biota also significantly reduced plant growth rate and decreased shoot biomass, relative to plants grown in sterilized soil, indicating that live soil biota might influence plant allocation strategies. We found that Rhododendron species with higher Root Shoot Ratios were less susceptible to Phytophthora, suggesting that water relations influence disease susceptibility. Our findings that disease resistance and susceptibility occur independently across multiple clades and that whole soil biotic communities consistently enhance disease resistance across clades, suggest that soil biota may play an important role in disease resistance and can moderate disease-induced mortality.
... Biomass production at the community level was slightly higher in the home soils relative to away soil conditioning but was significantly reduced in the sterile soils (Figure 4a). It is possible that the presence of species of different functional groups promotes beneficial soil microbes while diluting the effect of soil-borne pathogens resulting in soil biological communities that induce positive PSFs (Bartelt-Ryser et al., 2005;Latz et al., 2012;Baxendale et al., 2014;Mommer et al., 2018). For example, it has been proposed that the presence of species representing multiple functional groups may increase the diversity of beneficial soil biota that promotes positive plant-and soil-biota interactions that can alleviate neighbouring-plant drought stress (Latz et al., 2012;Baxendale et al., 2014). ...
... It is possible that the presence of species of different functional groups promotes beneficial soil microbes while diluting the effect of soil-borne pathogens resulting in soil biological communities that induce positive PSFs (Bartelt-Ryser et al., 2005;Latz et al., 2012;Baxendale et al., 2014;Mommer et al., 2018). For example, it has been proposed that the presence of species representing multiple functional groups may increase the diversity of beneficial soil biota that promotes positive plant-and soil-biota interactions that can alleviate neighbouring-plant drought stress (Latz et al., 2012;Baxendale et al., 2014). Indeed, the positive effect of soil biota appeared to be reduced in the soils with drought legacies, particularly when comparing home soils with sterile soils ...
Article
Question Climate change has been shown to cause shifts in plant-soil feedbacks (PSFs) that may affect plant community dynamics, but the effect of prolonged drought is uncertain. We asked whether prolonged drought legacies cause shifts in PSFs due to changes in plant-soil biotic interactions. Location Richmond, New South Wales, Australia. Methods We collected soils from a five-year field-based rainfall manipulation experiment simulating ambient rainfall and drought (50% reduction) in a mesic temperate grassland. PSFs of twelve plant species representing four functional groups (C3 and C4 grasses, forbs, and legumes) were assessed when grown alone and in mixed cultures (one species from each of the four functional groups) under laboratory conditions following a standard PSF protocol in soils with ambient rainfall and drought legacies. All soils were sterilized and then re-inoculated to create the respective treatments including a non-inoculated control for biota mediated PSFs. Results PSFs varied considerably among species and functional types in both legacy treatments. Overall, C3 grasses displayed less negative and C4 grasses less positive PSFs in soils with a legacy of prolonged drought compared with soil with ambient rainfall legacies, while PSFs for forbs and legumes were not significantly different from zero in either rainfall treatment. However, PSFs differed between species within functional groups. For example, Plantago showed positive PSFs in soils with ambient rainfall legacies but negative PSFs in soils with drought legacies while the opposite was observed for Medicago. PSFs of the mixed communities showed a trend to shift from positive to neutral in soils with drought legacies, with significant differences in PSFs observed when comparing home versus sterile soils, suggesting that drought may destabilise plant communities. Conclusions Our results provide evidence that prolonged drought legacies can modify plant community dynamics due to species-specific changes in PSFs that persist after droughts are alleviated.
... In W&F and M&F systems, the differentiation of potential fungal pathogens could play a more important role in mediating crop growth performance, while in W&M system, the consequence might be driven by the interplay among pathogens, symbionts and saprotrophs ( Figure S5). The weaker bacterial effect may be due to convergence induced by abiotic factors after crop harvesting (Bainard et al., 2016); however, the roles of bacteria should not be neglected, as they directly participate the PSF process and also are involved in other processes that could indirectly affect PSF, like nutrient mineralization (Weidner et al., 2015) and pathogen suppression (Latz et al., 2012). ...
Article
Although the importance of the soil microbiome in mediating plant community structures and functions has been increasingly emphasized in ecological studies, the biological processes driving crop diversity overyielding remain unexplained in agriculture. Based on the plant–soil feedback (PSF) theory and method, we quantified to what extent and how soil microbes contributed to intercropping overyielding. Soils were collected as inocula and sequenced from a unique 10‐year field experiment, consisting of monoculture, intercropping and rotation planted with wheat (Triticum aestivum), maize (Zea mays) or faba bean (Vicia faba). A PSF greenhouse study was conducted to test microbial effects on three crops' growth in monoculture or intercropping. In wheat & faba bean (W&F) and maize & faba bean (M&F) systems, soil microbes drove intercropping overyielding compared to monoculture, with 28%–51% of the overyielding contributed by microbial legacies. The overyielding effects resulted from negative PSFs in both systems, as crops, in particular faba bean grew better in soils conditioned by other crops than itself. Moreover, faba bean grew better in soils from intercropping or rotation than from the average of monocultures, indicating a strong positive legacy effect of multispecies cropping systems. However, with positive PSF and negative legacy benefit effect of intercropping/rotation, we did not observe significant overyielding in the W&M system. With more bacterial and fungal dissimilarities by metabarcoding in heterospecific than its own soil, the better it improved faba bean growth. More detailed analysis showed faba bean monoculture soil accumulated more putative pathogens with higher Fusarium relative abundance and more Fusarium oxysporum gene copies by qPCR, while in heterospecific soils, there were less pathogenic effects when cereals were engaged. Further analysis in maize/faba bean intercropping also showed an increase of rhizobia relative abundance. Synthesis and applications. Our results demonstrate a soil microbiome‐mediated advantage in intercropping through suppression of the negative PSF of pathogens and increasing beneficial microbes. As microbial mediation of overyielding is context‐dependent, we conclude that the dynamics of both beneficial and pathogenic microbes should be considered in designing cropping systems for sustainable agriculture, particularly including combinations of legumes and cereals. Our results demonstrate a soil microbiome‐mediated advantage in intercropping through suppression of the negative PSF of pathogens and increasing beneficial microbes. As microbial mediation of overyielding is context‐dependent, we conclude that the dynamics of both beneficial and pathogenic microbes should be considered in designing cropping systems for sustainable agriculture, particularly including combinations of legumes and cereals.
... This may have resulted in a more monoculture-like selective environment for the associated microbes. Plant functional groups have been shown to influence bacterial abundance(Stephan et al., 2000;Bartelt-Ryser et al., 2005;Latz et al., 2012;Latz et al., 2016;Lange et al., 2014) and richness(Dassen et al., 2017;Stephan et al., 2000) in soil.Dassen et al. (2017) suggested that plant functional groups are more important determinants of bacterial richness than plant species. Together, our results suggest that individual OTU abundances and overall bacterial richness in the rhizosphere generally increase with increasing plant species diversity to the extent that this feeds back to newly establishing plants, but that they are also positively influenced by plant functional diversity. ...
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Soil microbes are known to be involved in a number of essential ecosystem processes such as nutrient cycling, plant productivity and the maintenance of plant species diversity. However, how plant species diversity and identity affect soil microbial diversity and community composition is largely unknown. We tested whether, over the course of 11 years, distinct soil bacterial communities developed under plant monocultures and mixtures, and if over this timeframe plants with a monoculture or mixture history changed in the microbial communities they associated with. For eight species, we grew offspring of plants that had been grown for 11 years in the same monocultures or mixtures (monoculture- or mixture-type plants) in pots inoculated with microbes extracted from the monoculture and mixture soils. After five months of growth in the glasshouse, we collected rhizosphere soil from each plant and used 16S-rRNA gene sequencing to determine the community composition and diversity of the bacterial communities. Microbial community structure in the plant rhizosphere was primarily determined by soil legacy (monoculture vs. mixture soil) and by plant species identity, but not by plant legacy (monoculture- vs. mixture-type plants). In seven out of the eight plant species bacterial abundance was larger when inoculated with microbes from mixture soil. We conclude that plant diversity can strongly affect belowground community composition and diversity, feeding back to the assemblage of rhizosphere microbial communities in newly establishing plants. Thereby our work demonstrates that concerns for plant biodiversity loss are also concerns for soil biodiversity loss.
... In addition, previous studies demonstrated that the occurrence of soil-borne diseases was responsible for either a decrease in soil microbial diversity or an increase in population size of antagonistic bacteria (Latz et al., 2012;Shen et al., 2014). However, our research found that in rhizosphere soil, beneficial groups conferring "biocontrol" effects on plant growth increased with increasing years of A. bidentata planting. ...
Article
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The complex composition and interaction of root-associated microbes are critical to plant health and performance. In this study, we presented a detailed characterization of three rhizocompartment (rhizosphere, rhizoplane, and root) microbiomes of Achyranthes bidentata under different years of consecutive monoculture by deep sequencing in order to determine keystone microorganisms via co-occurrence network analysis. The network analysis showed that multiple consecutive monoculture (MCM, represented 5Y and 10Y) soils generated some distinct beneficial bacterial taxa such as Bacillus, Fictibacillus, Bradyrhizobium, Shinella, and Herbaspirillum. For fungi, Mortierella substituted for Fusarium in occupying an important position in different rhizocompartments under A. bidentate monoculture. Quantitative PCR analysis confirmed a significant increase in Bacillus, Pseudomonas, and Burkholderia spp. The results of the inoculation assay showed that addition of beneficial bacteria Bacillus subtilis 74 and Bacillus halodurans 75 significantly increased the root length and fresh weight of A. bidentata. Furthermore, three types of phytosterones, as the main allochemicals, were identified both in the rhizosphere soil and in culture medium under sterile conditions by LC-MS/MS. When looking at in vitro interactions, it was found that phytosterones displayed a positive interaction with dominant beneficial species (Bacillus amyloliquefaciens 4 and B. halodurans 75) and had a negative effect on the presence of the pathogenic fungi Fusarium solani and Fusarium oxysporum. Overall, this study demonstrated that consecutive monoculture of A. bidentata can alter the bacterial and fungal community by secreting root exudates, leading to recruitment of beneficial microbes and replacement of plant-specific pathogenic fungi with plant beneficial fungi.
... Primarily, phytopathogens impact plant fitness by upsetting the growth and competitive ability of the plants. These significant effects change the plant population and community structure (Latz et al., 2012). ...
... The decrease of plant pathogens and increase of abundance of beneficial fungi and bacteria in soil contributed to positive interactions between plant and microorganisms (Latz et al., 2012;Zhou et al., 2017). The study showed that the PF mixture increased the relative abundances of Metarhizium (Moorhouse et al., 1992), Lecanicillium (Cabanillas and Jones, 2009), Cryptococcus (Köhl et al., 2015), Beauveria (Cabrera-Mora et al., 2019), Chryseolinea (Jatoi et al., 2019), and Lysobacter spp. ...
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Continuous monoculture of cool-season turfgrass causes soil degradation, and visual turf quality decline is a major concern in black soil regions of Northeast China. Turf mixtures can enhance turfgrass resistance to biotic and abiotic stresses and increase soil microbial diversity. Understanding mechanism by plant-soil interactions and changes of black soil microbial communities in turf mixture is beneficial to restoring the degradation of urbanized black soils and maintaining sustainable development of urban landscape ecology. In this study, based on the previous research of different sowing models, two schemes of turf monoculture and mixture were conducted in field plots during 2016–2018 in a black soil of Heilongjiang province of Northeast China. The mixture turf was established by mixing 50% Kentucky bluegrass “Midnight” (Poa pratensis L.) with 50% Red fescue “Frigg” (Festuca rubra L.); and the monoculture turf was established by sowing with pure Kentucky bluegrass. Turf performance, soil physiochemical properties, and microbial composition from rhizosphere were investigated. Soil microbial communities and abundance were analyzed by Illumina MiSeq sequencing and quantitative PCR methods. Results showed that turfgrass quality, turfgrass biomass, soil organic matter (SOM), urease, alkaline phosphatase, invertase, and catalase activities increased in PF mixture, but disease percentage and soil pH decreased. The microbial diversity was also significantly enhanced under turf mixture model. The microbial community compositions were significantly different between the two schemes. Turf mixtures obviously increased the abundances of Beauveria, Lysobacter, Chryseolinea, and Gemmatimonas spp., while remarkably reduced the abundances of Myrothecium and Epicoccum spp. Redundancy analysis showed that the compositions of bacteria and fungi were related to edaphic parameters, such as SOM, pH, and enzyme activities. Since the increasing of turf quality, biomass, and disease resistance were highly correlated with the changes of soil physiochemical parameters and microbial communities in turf mixture, which suggested that turf mixture with two species (i.e., Kentucky blue grass and Red fescue) changed soil microbial communities and enhanced visual turfgrass qualities through positive plant-soil interactions by soil biota.
... One of the rhizobacteria with the innate ability to produce these chemicals is Pseudomonas fluorescence (Raaijmakers and Mazzola, 2012) who found the bacterium capable of suppressing the fungal pathogens belonging to Fusarium. 2,4-diacetylphloroglucinol, as well as, pyrrolnitrin have been implicated also in Rhizoctonia solani suppression, while phenazines and Pyoluteorin contribute to suppression of Thielaviopsis basicola (Latz et al., 2012;Mazurier et al., 2009). In fact, volatile organic compounds synthesized by rhizosphere microbes such as hydrogen cyanide/cyanic acid (Abd El-Rahman et al., 2019), ammonia (Kumar and Dubey, 2020), 2,5 dimethyl pyrazine and 1-octen-3-ol (Haidar et al., 2016) participate in suppression of soil-borne pathogens by directly interrupting biological activities of pathogenic microbes. ...
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The majority of plant infections caused by pathogens takes place beneath the soil surface. Soil borne pathogens’ attack on food crops could result in shortage of food supply and increase in economic losses. Every soil harbors certain peculiar microbial communities comprising bacteria, fungi, archaea, viruses and others that could participate in plants’ defense. Plants and its holobiont interact to enhance plant tolerance to biotic stress. The basic lines of defense are the rhizosphere (first defense line), plants immunity (second) and endophytic roots microbiome (third defense line). Understanding of the biotic lines of defense in the soil environment is crucial for soil and plant microbiome engineering, so as to improve disease suppression in the soil. This review focuses on understanding the basic lines of defense which are the rhizosphere, plant immune system and the endophytic roots microbiome against invasive soil borne pathogens of plant.
... Since then a number of other studies have connected these kinds of soil biota-driven indirect facilitative effects to interspecific BEF (e.g. Bennett et al., 2017;Hendriks et al., 2013;Latz et al., 2012;Teste et al., 2017;Yang et al., 2015) and intraspecific BEF (Luo et al., 2016). ...
Article
After 25 years of biodiversity experiments, it is clear that higher biodiversity (B) plant communities are usually more productive and often have greater ecosystem functioning (EF) than lower diversity communities. However, the mechanisms underlying this positive biodiversity–ecosystem functioning (BEF) relationship are still poorly understood. The vast majority of past work in BEF research has focused on the roles of mathematically partitioned complementarity and selection effects. While these mathematical approaches have provided insights into underlying mechanisms, they have focused strongly on competition and resource partitioning. Importantly, mathematically partitioned complementarity effects include multiple facilitative mechanisms, including dilution of species-specific pathogens, positive changes in soil nutrient cycling, associational defence and microclimate amelioration. Synthesis. This Special Feature takes an experimental and mechanistic approach to teasing out the facilitative mechanisms that underlie positive BEF relationships. As an example, we demonstrate diversity-driven changes in microclimate amelioration. Articles in this Special Feature explore photoinhibition, experimental manipulations of microclimate, lidar examinations of plant canopy effects and higher-order trophic interactions as facilitative mechanisms behind classic BEF processes. We emphasize the need for future BEF experiments to disentangle the facilitative mechanisms that are interlinked with niche complementarity to better understand the fundamental processes by which diversity regulates life on Earth.
... For example, a plant that accumulates species-specific symbionts can be expected to benefit more from those symbionts in a dense monoculture than in a diverse community (Kulmatiski et al., 2012). The role of plant mutualists in soil has been reported to affect plant community performance (Latz et al., 2012;Wagg et al., 2011) and suggested to codetermine selection and complementarity effects (Eisenhauer, 2011;. However, positive PSF can also occur when a species' growth is suppressed by soils cultivated by a different species (e.g., allelopathy; van der Putten et al., 2016). ...
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1. Plant-soil feedback (PSF) has gained attention as a mechanism promoting plant growth and coexistence. However, because most PSF research has measured monoculture growth in greenhouse conditions, field-based PSF experiments remain an important frontier for PSF research. 2. Using a four-year, factorial field experiment in Jena, Germany, we measured the growth of nine grassland species on soils conditioned by each of the target species (i.e., PSF). Plant community models were parameterized with or without these PSF effects, and model predictions were compared to plant biomass production in new and existing diversity-productivity experiments. 3. Plants created soils that changed subsequent plant biomass by 36%. However, because they were both positive and negative, the net PSF effect was 14% less growth on ‘home’ than ‘away’ soils. At the species level, seven of nine species realized non-neutral PSFs, but the two dominant species grew only 2% less on home than away soils. At the species*soil type level, 31 of 72 PSFs differed from zero. 4. In current and pre-existing diversity-productivity experiments, nine-species plant communities produced 37 to 29% more biomass than monocultures due primarily to selection effects. Null and PSF models predicted 29 to 28% more biomass for polycultures than monocultures, again due primarily to selection effects. 5. Synthesis: In field conditions, PSFs were large enough to be expected to cause roughly 14% overyielding due to complementarity, however, in plant communities overyielding was caused by selections effects, not complementarity effects. Further, large positive and large negative PSFs were associated with subdominant species, suggesting there may be selective pressure for plants to create neutral PSF. Broadly, results highlighted the importance of testing PSF effects in communities because there are several ways in which PSFs may be more or less important to plant growth in communities than suggested from simple PSF values.
... The general notion is that pathogen specialization on a given host plant is constrained in a multiplant environment [15,64]. Trophic control of fungal or other plant pathogens in the soil is another mechanism underlying pathogen dilution, because diverse plant communities can sustain a greater density and diversity of microbial predators compared with plant monocultures [30,65,66]. ...
Article
Plant–soil feedback (PSF) and diversity–productivity relationships are important research fields to study drivers and consequences of changes in plant biodiversity. While studies suggest that positive plant diversity–productivity relationships can be explained by variation in PSF in diverse plant communities, key questions on their temporal relationships remain. Here, we discuss three processes that change PSF over time in diverse plant communities, and their effects on temporal dynamics of diversity–productivity relationships: spatial redistribution and changes in dominance of plant species; phenotypic shifts in plant traits; and dilution of soil pathogens and increase in soil mutualists. Disentangling these processes in plant diversity experiments will yield new insights into how plant diversity–productivity relationships change over time.
... Studies from grassland also demonstrate that the species richness of N-fixing plants is a reasonable surrogate for N-fixer abundance (Jin et al., 2013;Latz et al., 2012). ...
Article
Abstract Aim Plants that host root‐symbiotic nitrogen‐fixing bacteria have an important role in driving terrestrial ecosystem processes, but N‐fixing ability is unequally distributed among plant taxa and ecosystems. Here we explore the large‐scale distribution of N‐fixing plant species worldwide. Location Global. Time period Present. Major taxa studied Vascular plants. Methods We estimated root‐symbiotic N‐fixing plant species diversity (as Shannon entropy) and relative richness (log‐ratio of N‐fixing to non‐fixing plant species) for c. 7,800 km2 hexagonal grid cells using the NodDB and Global Biodiversity Information Facility (GBIF) databases. Additionally, we explored the distributions of plant species associated with rhizobia, actinobacteria or cyanobacteria (relative to other plant species), and the relative richness of N‐fixing trees (log‐ratio of N‐fixing to non‐fixing trees). We related N‐fixing plant species distribution to environmental (climate, soil) and biogeographical (biome, realm) variables using multiple linear regression. Results N‐fixing plant diversity and relative richness showed unimodal relationships with latitude. Diversity of N‐fixing plants was highest in warm and wet climates, but in dry biomes and in Australasia. The relative richness of N‐fixing plants was highest in warm and dry climates, in tropical and temperate grasslands and in Eurasia. Plants associated with cyanobacteria were more widely distributed near the equator, while those associated with rhizobia were more prevalent at the edge of the tropics, and those associated with actinobacteria at higher latitudes (especially in boreal forests). The relative richness of N‐fixing tree species was highest in cold and dry areas and in boreal forests, with contrasting peaks in the Northern and Southern Hemispheres. Main conclusions The distribution of N‐fixing plant species exhibits regional hotspots and coldspots related to both environmental conditions and biogeographical history. Global N‐fixing plant distributions are different for the key root‐symbiotic bacterial groups. Information about N‐fixing plant distribution can improve global models of ecosystem functions and contribute to understanding how plants respond to global change.
... Primarily, phytopathogens impact plant fitness by upsetting the growth and competitive ability of the plants. These significant effects change the plant population and community structure (Latz et al., 2012). ...
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Plant diseases become one of the significant threats in crop production worldwide which causes billion-dollar yield losses directly. Many approaches found to suppress various disease effects on crops. Among all the options available, biotic control of crop diseases promises one and in which Mycorrhizal Fungi (MF), especially endo mycorrhizae would play a significant role. Many reviews have reported on the interface mechanisms among Arbuscular Mycorrhizal Fungi (AMF) and plant pathogens. It includes improvements in plant nutrition, competition for nutrient and photosynthates and antibiosis. Depending on the infections and the ecological conditions, all mechanisms may be involved. Studies revealed that AMF, Glomus sp and Gigaspora sp. are the best models used to control plant fungal and bacterial diseases. Further, Rhizophagus sp, Funneliformis sp and Claroideoglomus sp. are few of the excellent applicants of AMF shows better potential to oversee viral infections in plants. However, sufficient researches are not done so far to focus on exact stages of infection side effects of AMF when it incorporates with the crops to control pathogens. Future research on the AMF-mediated promotion of crop quality and productivity is therefore required with exploring the adverse effects of AMF, with emphasis on plant disease management. It can conclude that when biological management techniques are paired with effective AMF tactics while considering the environmental protection measures, a sustainable way of plant disease management is possible.
... This inhibition effect on the Streptomyces sp. is due to the antimicrobial substance (Phenazine-1-carboxylic acid) produced by P. fluorescens LBUM223, which interferes with the proper cellular function of the pathogen and so results in its inhibition [14]. Antimicrobial substances like 2,4-diacetylphloroglucinol, hydrogen cyanide, chitinase, phenazines, organic acids, as well as iron-chelating substances (siderophores) are responsible for the induction and maintenance of a disease suppressive soil [15][16][17][18]. In this study, we evaluated the functional genes profile abundance involved in chemotaxis and antimicrobial and siderophore producing substances from the maize rhizosphere under organic, inorganic, and untreated control using shotgun metagenomics study. ...
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Soil fertility is a function of the level of organic and inorganic substances present in the soil, and it influences the activities of soil-borne microbes, plant growth performance and a host of other beneficial ecological functions. In this metagenomics study, we evaluated the response of maize microbial functional gene diversity involved in chemotaxis, antibiotics, siderophores, and antifungals producing genes within the rhizosphere of maize plants under compost, inorganic fertilizer, and unfertilized conditions. The results show that fertilization treatments at higher compost manure and lower inorganic fertilizer doses as well as maize plants itself in the unfertilized soil through rhizosphere effects share similar influences on the abundance of chemotaxis, siderophores, antifungal, and antibiotics synthesizing genes present in the samples, while higher doses of inorganic fertilizer and lower compost manure treatments significantly repress these genes. The implication is for a disease suppressive soil to be achieved, soil fertilization with high doses of compost manure fertilizer treatments as well as lower inorganic fertilizer should be used to enrich soil fertility and boost the abundance of chemotaxis and disease suppressive genes. Maize crops also should be planted sole or intercropped with other crops to enhance the rhizosphere effect of these plants in promoting the expression and abundance of these beneficial genes in the soil.
... Several Pseudomonas species produced DAPG and PHZ in soils, which suppressed Fusarium wilt of flax or wheat [146]. Moreover, DAPG and pyrrolnitrin suppressed the growth of R. solani [147], while PHZ and pyoluteorin were widely distributed in soils and are involved in the suppression of Thielaviopsis basicola [148]. A rice seed endophyte, Sphingomonas melonis, promoted the rice panicle rot disease suppression in rice seedlings by producing anthranilic acid against Burkholderia plantarii [149]. ...
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Plants host diverse but taxonomically structured communities of microorganisms, called microbiome, which colonize various parts of host plants. Plant-associated microbial communities have been shown to confer multiple beneficial advantages to their host plants, such as nutrient acquisition, growth promotion, pathogen resistance, and environmental stress tolerance. Systematic studies have provided new insights into the economically and ecologically important microbial communities as hubs of core microbiota and revealed their beneficial impacts on the host plants. Microbiome engineering, which can improve the functional capabilities of native microbial species under challenging agricultural ambiance, is an emerging biotechnological strategy to improve crop yield and resilience against variety of environmental constraints of both biotic and abiotic nature. This review highlights the importance of indigenous microbial communities in improving plant health under pathogen-induced stress. Moreover, the potential solutions leading towards commercialization of proficient bioformulations for sustainable and improved crop production are also described.
... There is growing evidence that the deterioration of plant communities at low diversity is related to the accumulation of specific plant antagonists generating negative feedback effects (de Kroon et al., 2012;Hendriks et al., 2013;Kulmatiski et al., 2012;Maron et al., 2011;Schnitzer et al., 2011). On the other hand, positive feedback effects, (e.g. by mycorrhizal fungi, biocontrol bacteria) might increase plant performance at high diversity (Eisenhauer, 2012;Latz et al., 2012;Wagg et al., 2011). ...
Article
Biodiversity often enhances ecosystem functioning likely due to multiple, often temporarily separated drivers. Yet, most studies are based on one or two snapshot measurements per year. We estimated productivity using bi-weekly estimates of high-resolution canopy height in 2 years with terrestrial laser scanning (TLS) in a grassland diversity experiment. We measured how different facets of plant diversity (functional dispersion [FDis], functional identity [PCA species scores], and species richness [SR]) predict aboveground biomass over time. We found strong intra- and inter-annual variability in the relative importance of different mechanisms underlying the diversity effects on mean canopy height, i.e., resource partitioning (via FDis) and identity effects (via species scores), respectively. TLS is a promising tool to quantify community development non-destructively and to unravel the temporal dynamics of biodiversity-ecosystem functioning mechanisms. Our results show that harvesting at estimated peak biomass—as done in most grassland experiments—may miss important variation in underlying mechanisms driving cumulative biomass production.
... The casing soil microbiome of the peat and alternatives, not only supplies beneficial microorganisms to induce fructification of the mushrooms, but it also determines the invasion resistance of the community in the event of a pathogen introduction. This invasion resistance is often determined by the diversity of the resident community and the complexity and stability of its interaction network (Latz et al., 2012;. Resistant microbial communities are known to show high modularity and complexity instead of a compact interaction network (Mendes et al., 2018). ...
... The past two decades have also seen an increased interest in apparent competition mediated by soil microorganisms. More and more studies reveal that plants modify soil microorganisms, with consequences for their own development and for plants that grow subsequently on the soil [31][32][33][34][35] (a mechanism that we hereafter refer to as a soil-legacy effect). ...
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While most alien species fail to establish, some invade native communities and become widespread. Our understanding of invasion success is derived mainly from pairwise interactions between aliens and natives, while interactions among more than two species remain largely unexplored. Here, we experimentally tested whether and how a third plant species, either native or alien, affected the competitive outcomes between alien and native plants through its soil legacy. We first conditioned soil with one of ten species (six natives and four aliens) or without plants. We then grew on these 11 soils five aliens and five natives without competition, or with intra- or interspecific competition. We found that aliens were not more competitive than natives when grown on soil conditioned by other natives or on non-conditioned soil. However, aliens were more competitive than natives on soil conditioned by other aliens (that is, invasional meltdown). Soil conditioning did not change competitive outcomes by affecting the strength of competition between later plants. Instead, soil conditioned by aliens pushed competitive outcomes towards later aliens by affecting the growth of aliens less negatively than that of natives. Microbiome analysis verified this finding, as we showed that the soil-legacy effects of a species on later species were less negative when their fungal endophyte communities were less similar, and that fungal endophyte communities were less similar between two aliens than between aliens and natives. Our study reveals invasional meltdown in multispecies communities and identifies soil microorganisms as a driver of the invasion success of alien plants.
... Previous reports have shown that a fungal-dominant microbial community can aggravate the root rot of P. notoginseng (Wei et al. 2018;Luo et al. 2019). In contrast, many researchers have reported that an increase in the relative abundance of bacteria, especially antagonistic bacteria, can significantly reduce the harm of pathogens (Latz et al. 2012;Mendes et al. 2018;Wei et al. 2019), even forming disease-suppressive soil to protect plant health (Mendes et al. 2011;Cha et al. 2016;Siegel-Hertz et al. 2018). Likewise, a bacteria-dominant microbial community has advantages for microbial interactions and may favor bacteria-driven soil nutrient cycling (Bahram et al. 2018). ...
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The accumulation of soil-borne pathogens is the main driving factor of negative plant-soil feedbacks (NPSFs), which seriously restricts the sustainable development of agriculture. Using natural volatile organic compounds (VOCs) from plants or microorganisms as biofumigants is an emerging strategy to alleviate NPSFs in an environmentally-friendly way. Here, we identified α-terpineol from the VOCs of pine needles, confirmed the ability of α-terpineol fumigation in alleviating the NPSF of Panax notoginseng via significantly reducing seed decay rate, and also deciphered the underlying mechanism by which the soil microbial community is modified. α-Terpineol fumigation could suppress culturable fungi but enrich bacteria in a dose-dependent manner. Network analysis with high-throughput sequencing data revealed that α-terpineol could distinctly modify both fungal and bacterial communities. In detail, α-terpineol significantly suppressed the relative abundance of Ascomycota from 64.04 to 32.26%, but enriched the relative abundance of Proteobacteria, Acidobacteria and Actinobacteria. Subnetwork analysis further demonstrated that α-terpineol could directly or indirectly suppress fungal pathogens and enrich plant growth-promoting rhizobacteria (PGPRs). In vitro fumigation and co-culture experiments with culturable isolates validated these findings. The antagonism between beneficial bacteria and pathogens, and the synergistic growth promotion among α-terpineol-enriched bacteria might be involved in soil microbial community assembly. In summary, α-terpineol fumigation could directly or indirectly modify the soil microbial community to alleviate NPSFs, especially by suppressing fungal pathogens and enriching beneficial bacteria. This study suggests that VOCs from natural products are worth developing as biofumigants due to their multiple functions in modifying the soil microbial community.
... Crop rotation is a traditional agronomic method that has been used to regulate nutrition and reduce soilborne diseases by increasing plant diversity and reshaping the soil microbiome [35][36][37][38]. A recent study reported that under cotton-maize rotation, the diversity of the soil bacterial community increased, while the fungal community decreased [39], which is concordant to our findings on the two cropping patterns of L. brownii-rice rotation and consecutive monoculture L. brownii. ...
Article
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Replant disease caused by continuous cropping obstacles commonly occurs in a Lilium brownii consecutive monoculture. To reveal the mechanisms contributing to the continuous cropping obstacles of L. brownii, four cropping patterns (fallow, L. brownii-rice rotation, newly planted L. brownii, and 2-year L. brownii consecutive monoculture) were designed, and Illumina MiSeq (16S rDNA and ITS) was utilized to detect shifts in the microbial community in the rhizosphere. Our result showed that planting of L. brownii significantly reduced soil pH. Consecutive monoculture of L. brownii can significantly decrease the diversity and abundance of soil bacteria, but markedly increase the diversity and abundance of soil fungi. Under the four planting pattern treatments, the changes in soil pH were consistent with the changes in the Shannon diversity index of soil bacterial communities, whereas we observed a negative correlation between soil pH and Shannon diversity index for fungi. The relative abundance of Lactobacillales significantly increased in soils of L. brownii consecutive monoculture, while Acidobacteriales, Solibacterales, and Xanthomonadales increased in soils of L. brownii-rice rotation and newly planted L. brownii. Collectively, this work aimed to elucidate the relationship between the L. brownii planting patterns and soil microbiome, thereby providing a theoretical basis for screening new biological agents that may contribute to resolving continuous cropping obstacles of L. brownii.
... The casing soil microbiome of the peat and alternatives, not only supplies beneficial microorganisms to induce fructification of the mushrooms, but it also determines the invasion resistance of the community in the event of a pathogen introduction. This invasion resistance is often determined by the diversity of the resident community and the complexity and stability of its interaction network (Mallon et al., 2015;Latz et al., 2012). Resistant microbial communities are known to show high modularity and complexity instead of a compact interaction network (Mendes et al., 2018). ...
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Peat use in horticulture is associated with a large ecological footprint. Peat is the predominant growing media in Europe. Modern cropping systems rely heavily on dynamic interactions of the crop with the microorganisms in the growing media and yet, in the search for sustainable peat-alternatives, the microbiome of the growing media has often been ignored. In mushroom cultivation, peat is a prime determinant of productivity, in the form of a casing soil which supplies beneficial microbes. In this study we describe the microbial composition, interactions, and activity of four circular substrates used to proportionally replace peat in mushroom growing media. We also evaluate various physico-chemical characteristics of the peat-alternatives. We characterize the impact of sanitary pre-treatments such as steaming and acidification on the microbiome as well as the agronomical performance of the peat-reduced growing media. We found that grass fibres from agricultural residue streams, peat-moss farmed in degraded peatlands, and spent casing soil recycled from previous cultivation cycles can be used to successfully replace peat in mushroom growing media. Peat moss and spent casing were expectedly similar to peat in physical, chemical, and microbiological properties. However, the grass fibres had unique characteristics, such as high organic matter content, low water holding capacity and a diverse and competitive microbiome. Pre-treatment of the substrates by acidification and steaming significantly affected the microbiome, and reduced the presence of pests, pathogens and competitive fungi in the peat-reduced media. Strong trade-offs existed between the productivity and disease pressure in the circular cropping system, which are also governed by the microbial composition of the growing media. Knowledge on the accessibility, sustainability, and economic viability of these peat-alternatives will further determine the transition away from peat use and towards sustainable growing media.
... The wealth of understanding correlated with the well-characterized models of soil suppressiveness in arable systems (Cha et al. 2016;Carrión et al. 2018) provides opportunities to explore and exploit mechanisms in pastoral agricultural systems. The latter improves our understanding of the processes that underlie release from pathogen pressure in natural grassland systems (Maron et al. 2011;Schnitzer et al. 2011;Latz et al. 2012Latz et al. , 2016Mommer et al. 2018). Surprisingly, only a few studies have focused on the distribution of diseasesuppressive microbiota in agricultural grasslands and the mechanisms by which these communities relate or respond to soil management practices (Dignam et al. 2016;Wakelin 2018). ...
... This is particularly associated with the activities of biocontrol agents, including fluorescent Pseudomonad (Dawadi et al. 2019;Panth et al. 2020). Fluorescent Pseudomonas species are fast-growing gram-negative bacteria (Weller 2007), which can play the suppressive role against soil pathogens by producing a metabolite 2,4-diacetylphloroglucinol (Mazzola 2002;Weller et al. 2002;Latz et al. 2012). The effective suppressive potential of Pseudomonad has already been well documented against R. solani and some species of Phytophthora and Phytopythium (Lucas et al. 1993;Weller et al. 2002;Panth et al. 2020). ...
Article
Cover crops represent a potential tool for suppression of soilborne diseases in woody ornamental nursery production, which can cause significant economic losses. Field experiments were conducted in 2019 and 2020 to explore the effects of a cover crop and the timing of cover crop disturbance on soilborne disease suppression. Soils from red maple (Acer rubrum ‘October Glory’) plantations grown with or without a cover crop [crimson clover (Trifolium incarnatum)] were sampled following senescence of the cover crop. Greenhouse bioassays were conducted using red maple cuttings on inoculated (with Rhizoctonia solani, Phytopythium vexans or Phytophthora nicotianae) and non-inoculated field soils. Plant height, total and root fresh weight were measured, and the roots were assessed for disease severity on a 0 to 100% root damage scale. Pathogen recovery was assessed by culturing root pieces (~1 cm length) on oomycetes or Rhizoctonia semi-selective media. Soil samples were analyzed for organic matter, nitrogen, phosphorus, potassium, pH and Pseudomonad population count. A minimal effect of cover crop disturbance timing (late fall or early spring) was found on disease suppression. Cover crop usage reduced disease severity and pathogen recovery in red maple field soils. Plants grown in cover cropped soil had greater total, root and aboveground fresh weight compared with those from non-cover cropped soil, but plant height was not affected. Cover crops increased soil organic matter and total nitrogen in 2020. Pseudomonad populations were higher when cover crops were used. The results suggest that cover crops can reduce soilborne disease in woody ornamentals.
... Phytopathogens change these connections by hampering the health of plants and decreasing their development. This competitiveness of diseased plants can stimulate a direct force on the population and community organization of the plants (Burdon et al., 2006;Bradley et al., 2008;Maron et al., 2011;Latz et al., 2012). Studies examining the effects of biodiversity on the capacity of the environment to protect against disease are still in their experimental phase. ...
Article
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The two most commonly used disease management methods prevalent in agricultural package of practices are: the application of chemicals and the selection of disease-resistant cultivars through the introduction of resistance genes. Each of these preventive measures are equally susceptible to the adaptations of phytopathogens in due course of time. There are numerous records of several phytopathogens overcomimg the resistance provided by the main resistance gene through continuous evolution. In a similar fashion, the development and fixation of pesticides resistance mutations in the phytopathogens has made many pesticides to lose their effectiveness. The existingdisease management practices are presumably deficient in supporting the sustainable intensification of crop productivity due to its inadequacy of minimizing the phytopathogen evolution. Thus, comes the role of cultivar mixture which is based on the principle of supressing the evolution of phytopathogen against a specific gene or pesticide. Combinations of cultivars having several different characteristics but sufficient morphological and physiological similarities can be cultivated collectively.These cultivar mixtures do not cause any significant changes in crop production system, yet improve the yield accuracy, and decrease the use of pesticides in many cases. They are also faster and cheaper to develop and are distinctive to "multiline" which are identified as combinations of genetically identical lines of a crop species varying mostly in disease resistance gene. The use of cultivar mixtures can improve the effectiveness of disease management practices as their level of resistance vary in the same region.
... Previous studies have shown that complex belowground microbial networks (networks with a high number of nodes, links, and average connectivity) are more conducive to plant growth and health than simple networks Tao et al. 2018). Furthermore, in terms of soil disease resistance, a highly diverse microbial community may also be more conducive to resisting pathogen infection than other microbial communities (Latz et al. 2012;Mallon et al. 2015), based on the assumption that more diverse communities exhibit a higher number of species interactions and fiercer niche competition (van Elsas et al. 2012). ...
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The microbial community within the root system, the rhizosphere closely connected to the root, and their symbiotic relationship with the host are increasingly seen as possible drivers of natural pathogen resistance. Resistant cultivars have the most effective strategy in controlling the Chinese wheat yellow mosaic disease, but the roles of the root and rhizosphere microbial interactions among different taxonomic levels of resistant cultivars are still unknown. Thus, we aimed to investigate whether these microbial community composition and network characteristics are related to disease resistance and to analyze the belowground plant-associated microflora. Relatively high microbial diversity and stable community structure for the resistant cultivars were detected. Comparison analysis showed that some bacterial phyla were significantly enriched in the wheat root or rhizosphere of the resistant wheat cultivar. Furthermore, the root and rhizosphere of the resistant cultivars greatly recruited many known beneficial bacterial and fungal taxa. In contrast, the relative abundance of potential pathogens was higher for the susceptible cultivar than for the resistant cultivar. Network co-occurrence analysis revealed that a much more complex, more mutually beneficial, and a higher number of bacterial keystone taxa in belowground microbial networks were displayed in the resistant cultivar, which may have been responsible for maintaining the stability and ecological balance of the microbial community. Overall, compared with the susceptible cultivar, the resistant cultivar tends to recruit more potential beneficial microbial groups for plant and rhizosphere microbial community interactions. These findings indicate that beneficial rhizosphere microbiomes for cultivars should be targeted and evaluated using community compositional profiles. Key points • Different resistance levels in cultivars affect the rhizosphere microbiome.. • Resistant cultivars tend to recruit more potential beneficial microbial groups. • Bacteria occupy a high proportion and core position in the microflora network.
... Therefore, we suggest there are clear trade-offs of managing cultivated perennial grasslands dominated by a single or few grass species, as grassland intensification may enable pest infestation by affecting plant community stability and self-regulation (Power 2010). Native grasslands also support abundant beneficial soil microbes that are antagonistic to many soil-borne pathogens (Latz et al. 2012). Hence, maintenance of native or relatively diverse grasslands can potentially save billions of dollars while controlling pests (Power 2010). ...
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... Several Pseudomonas species produced DAPG and PHZ in soils, which suppressed Fusarium wilt of flax or wheat [146]. Moreover, DAPG and pyrrolnitrin suppressed the growth of R. solani [147], while PHZ and pyoluteorin were widely distributed in soils and are involved in the suppression of Thielaviopsis basicola [148]. A rice seed endophyte, Sphingomonas melonis, promoted the rice panicle rot disease suppression in rice seedlings by producing anthranilic acid against Burkholderia plantarii [149]. ...
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Plants host diverse but taxonomically structured communities of microorganisms, called microbiome, which colonize various parts of host plants. Plant-associated microbial communities have been shown to confer multiple beneficial advantages to their host plants, such as nutrient acquisition, growth promotion, pathogen resistance, and environmental stress tolerance. Systematic studies have provided new insights into the economically and ecologically important microbial communities as hubs of core microbiota and revealed their beneficial impacts on the host plants. Microbiome engineering, which can improve the functional capabilities of native microbial species under challenging agricultural ambiance, is an emerging biotechnological strategy to improve crop yield and resilience against variety of environmental constraints of both biotic and abiotic nature. This review highlights the importance of indigenous microbial communities in improving plant health under pathogen-induced stress. Moreover, the potential solutions leading towards commercialization of proficient bioformulations for sustainable and improved crop production are also described.
... Primarily, phytopathogens impact plant fitness by upsetting the growth and competitive ability of the plants. These significant effects change the plant population and community structure (Latz et al., 2012). ...
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... Two Year 2 disease-suppressive soils were from fields with diverse vegetable-arable rotations. Although previous studies have reported that diverse crop rotations can enhance protection against particular soilborne pathogens by fostering antagonistic soil bacterial communities (Latz et al. 2012;Peralta et al. 2018), this is inconclusive in present study, and further research is required to robustly confirm that that crop rotations play major roles in powdery scab suppression. ...
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... For example, a plant that accumulates species-specific symbionts can be expected to benefit more from those symbionts in a dense monoculture than in a diverse community (Kulmatiski et al., 2012). The role of plant mutualists in soil has been reported to affect plant community performance (Latz et al., 2012;Wagg et al., 2011) and suggested to codetermine selection and complementarity effects (Eisenhauer, 2011;. However, positive PSF can also occur when a species' growth is suppressed by soils cultivated by a different species (e.g., allelopathy; van der Putten et al., 2016). ...
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Plant–soil feedback (PSF) has gained attention as a mechanism promoting plant growth and coexistence. However, most PSF research has measured monoculture growth in greenhouse conditions. Translating PSFs into effects on plant growth in field communities remains an important frontier for PSF research. Using a 4-year, factorial field experiment in Jena, Germany, we measured the growth of nine grassland species on soils conditioned by each of the target species (i.e., 72 PSFs). Plant community models were parameterized with or without these PSF effects, and model predictions were compared to plant biomass production in diversity–productivity experiments. Plants created soils that changed subsequent plant biomass by 40%. However, because they were both positive and negative, the average PSF effect was 14% less growth on “home” than on “away” soils. Nine-species plant communities produced 29 to 37% more biomass for polycultures than for monocultures due primarily to selection effects. With or without PSF, plant community models predicted 28%–29% more biomass for polycultures than for monocultures, again due primarily to selection effects. Synthesis: Despite causing 40% changes in plant biomass, PSFs had little effect on model predictions of plant community biomass across a range of species richness. While somewhat surprising, a lack of a PSF effect was appropriate in this site because species richness effects in this study were caused by selection effects and not complementarity effects (PSFs are a complementarity mechanism). Our plant community models helped us describe several reasons that even large PSF may not affect plant productivity. Notably, we found that dominant species demonstrated small PSF, suggesting there may be selective pressure for plants to create neutral PSF. Broadly, testing PSFs in plant communities in field conditions provided a more realistic understanding of how PSFs affect plant growth in communities in the context of other species traits.
... Primarily, phytopathogens impact plant fitness by upsetting the growth and competitive ability of the plants. These significant effects change the plant population and community structure (Latz et al., 2012). ...
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—Plant diseases become one of the significant threats in crop production worldwide which causes billion-dollar yield losses directly. Many approaches found to suppress various disease effects on crops. Among all the options available, biotic control of crop diseases promises one and in which Mycorrhizal Fungi (MF), especially endo mycorrhizae would play a significant role. Many reviews have reported on the interface mechanisms among Arbuscular Mycorrhizal Fungi (AMF) and plant pathogens. It includes improvements in plant nutrition, competition for nutrient and photosynthates and antibiosis. Depending on the infections and the ecological conditions, all mechanisms may be involved. Studies revealed that AMF, Glomus sp and Gigaspora sp. are the best models used to control plant fungal and bacterial diseases. Further, Rhizophagus sp, Funneliformis sp and Claroideoglomus sp. are few of the excellent applicants of AMF shows better potential to oversee viral infections in plants. However, sufficient researches are not done so far to focus on exact stages of infection side effects of AMF when it incorporates with the crops to control pathogens. Future research on the AMF-mediated promotion of crop quality and productivity is therefore required with exploring the adverse effects of AMF, with emphasis on plant disease management. It can conclude that when biological management techniques are paired with effective AMF tactics while considering the environmental protection measures, a sustainable way of plant disease management is possible. Keywords—Arbuscular mycorrhizal fungi, Association, Mycorrhizal fungi, Pathogen, Plant disease
... While there was no connection made to plant-mediated microbiome shifts at the time, subsequent work made this link more apparent. For instance, Latz et al. (2012) found that legumes from a long-term field experiment promoted antifungal gene abundance among soil bacteria. Similarly, long term soybean cropping systems are known to reduce the diversity, abundance, and pathogenicity of the root rot-causing fungal pathogen Fusarium within the rhizosphere (Wei et al., 2014). ...
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Pyrrolnitrin (PRN) from rhizobacteria displays a key role in biocontrol of phytopathogenic fungi in rhizospheric soil. Therefore, different rhizospheric soils were investigated for the prevalence of PRN producer in minimal salt (MS) medium containing tryptophan (0.2 M NaCl; pH 8) using three successive enrichments. Of 12% isolates, only five bacterial strains had shown PRN secretion, screened with Thin Layer Chromatography ( R f 0.8) and antifungal activity (27 mm) against phytopathogen. The phenetic and 16S rRNA sequence revealed the close affiliation of isolates (KMB, M-2, M-11, TW3, and TO2) to Stenotrophomonas rhizophila (KY800458) , Enterobacter spp. (KY800455), Brevibacillus parabrevis (KY800454), Serratia marcescens (KY800456) and Serratia nemtodiphila (KY800457). Purified compound from isolates was characterised using UV, IR, HPLC, LCMS and GCMS as PRN. However, BLASTn hit of prn gene sequences from both Serratia species showed 99% similarity with NADPH dependent FMN reductase component ( prnF ). The homology protein model of prnF was developed from translated sequence of S. marcescens TW3 with chromate reductase of Escherichia coli K-12. Docking with FMN and NADPH was performed. The study demonstrated the possible role of prnF NADPH dependent FMN reductases in prnD for supply of reduced flavin in rhizobacterial strain of Serratia spp . which may pave a way to understand PRN production.
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O livro, com 21 capítulos reunindo inúmeros autores de renomada experiência, traz uma infinidade de informações, fruto de extensas revisões e principalmente obtidas através de densos projetos de pesquisa desenvolvidos pelas principais instituições públicas, capitaneada pela UDESC, em parceria com produtores individuais ou associados, localizados na Região de Altitude mais tradicional na produção de uvas de Santa Catarina. A identificação das melhores cultivares e as possíveis combinações de porta-enxertos, a definição do manejo do dossel, a carga de gemas, o manejo da poda e os sistemas de condução para cada situação, aliados a todas as questões relativas ao manejo o solo, da nutrição e adubação e a delicada e complexa questão da fitossanidade, chegando na colheita e processamento, entre outros, exemplifica a importância de todos capítulos desse grande livro.
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A large number of studies have now explicitly examined the relationship between species loss and ecosystem functions. The results from such “biodiversity experiments” have previously been collated and analyzed by two independent groups of authors. Both data sets show that reductions in species diversity generally result in reduced ecosystem functioning, even though the studies cover a wide range of ecosystems, diversity manipulations, and response variables. In this chapter, we analyze the two data sets in parallel to explain variation in the observed functional effects of biodiversity. The main conclusions are: 1) the functional effects of biodiversity differ among ecosystem types (but not between terrestrial and aquatic systems), 2) increases in species richness enhance community responses but negatively affect population responses, 3) stocks are more responsive than rates to biodiversity manipulations, 4) when diversity reductions at one trophic level affect a function at an adjacent trophic level (higher or lower), the function is often reduced 5) increased biodiversity results in increased invasion resistance. We also analyze the shape of the relationship between biodiversity and response variables, and discuss some consequences of different relationships.
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The loss of plant species from terrestrial ecosystems may cause changes in soil decomposer communities and in decomposition of organic material with potential further consequences for other ecosystem processes. This was tested in experimental communities of 1, 2, 4, 8, 32 plant species and of 1, 2 or 3 functional groups (grasses, legumes and non-leguminous forbs). As plant species richness was reduced from the highest species richness to monocultures, mean aboveground plant biomass decreased by 150%, but microbial biomass (measured by substrate induced respiration) decreased by only 15% (P = 0.05). Irrespective of plant species richness, the absence of legumes (across diversity levels) caused microbial biomass to decrease by 15% (P = 0.02). No effect of plant species richness or composition was detected on the microbial metabolic quotient (qCO 2) and no plant species richness effect was found on feeding activity of the mesofauna (assessed with a bait-lamina-test). Decomposition of cellulose and birchwood sticks was also not affected by plant species richness, but when legumes were absent, cellulose samples were decomposed more slowly (16% in 1996, 27% in 1997, P = 0.006). A significant decrease in earthworm population density of 63% and in total earthworm biomass by 84% was the single most prominent response to the reduction of plant species richness, largely due to a 50% reduction in biomass of the dominant 'anecic' earthworms. Voles (Arvicola terrestris L.) also had a clear preference for high-diversity plots. Soil moisture during the growing season was unaffected by plant species richness or the number of functional groups present. In contrast, soil temperature was 2 K higher in monocultures compared with the most diverse mixtures on a bright day at peak season. We conclude that the lower abundance and activity of decomposers with reduced plant species richness was related to altered substrate quantity, a signal which is not reflected in rates of decomposition of standard test material. The presence of nitrogen fixers seemed to be the most important component of the plant diversity manipulation for soil heterotrophs. The reduction in plant biomass due to the simulated loss of plant species had more pronounced effects on voles and earthworms than on microbes, suggesting that higher trophic levels are more strongly affected than lower trophic levels.
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Declining biodiversity represents one of the most dramatic and irreversible aspects of anthropogenic global change, yet the ecological implications of this change are poorly understood. Recent studies have shown that biodiversity loss of basal species, such as autotrophs or plants, affects fundamental ecosystem processes such as nutrient dynamics and autotrophic production. Ecological theory predicts that changes induced by the loss of biodiversity at the base of an ecosystem should impact the entire system. Here we show that experimental reductions in grassland plant richness increase ecosystem vulnerability to invasions by plant species, enhance the spread of plant fungal diseases, and alter the richness and structure of insect communities. These results suggest that the loss of basal species may have profound effects on the integrity and functioning of ecosystems.
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Summary1 Utilization of carbon sources by culturable soil bacteria can be assessed with BIOLOG microtiter plates (contain 31 C sources). We used this technique to investigate bacterial community structure at various levels of plant diversity. Plant diversity levels were replicated and we investigated the influence of three plant functional groups, grasses, legumes and non-leguminous herbs, as well as the influence of individual plant species.2 Catabolic activity and catabolic diversity of culturable soil bacteria were used to estimate their density (abundance) and functional diversity, respectively. Both increased linearly with the logarithm of plant species number and with the number of plant functional groups in experimental grassland ecosystems. These effects may have been caused by an increased diversity and quantity of material and energy flows to the soil. They may also have been mediated by increased diversity of soil microhabitats via a stimulation of the soil fauna.3 The presence of particular plant species or functional groups in the different experimental communities stimulated the activity and functional diversity of the culturable soil bacteria in addition to their contribution via plant diversity. The legume Trifolium repens had the strongest effect and may be regarded as a keystone species with regard to plant–microbial interactions in the systems studied.
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Numerous experiments have been established to examine the effect of plant diversity on the soil microbial community. However, the relationship between plant diversity and microbial functional diversity along broad spatial gradients at a large scale is still unexplored. In this paper, we examined the relationship of plant species diversity with soil microbial biomass C, microbial catabolic activity, catabolic diversity and catabolic richness along a longitudinal gradient in temperate grasslands of Hulunbeir, Inner Mongolia, China. Preliminary detrended correspondence analysis (DCA) indicated that plant composition showed a significant separation along the axis 1, and axis 1 explained the main portion of variability in the data set. Moreover, DCA-axis 1 was significantly correlated with soil microbial biomass C (r=0.735, P=0.001), microbial catabolic activity (average well color development; r=0.775, P<0.001) and microbial functional diversity (catabolic diversity: r=0.791, P<0.001 and catabolic richness: r=0.812, P<0.001), which suggested thatsome relationship existed between plant composition and the soil microbial community along the spatial gradient at a large scale. Soil microbial biomass C, microbial catabolic activity, catabolic diversity and catabolic richness showed a significant, linear increase with greater plant species richness. However, many responses that we observed could be explained by greater aboveground plant biomass associated with higher levels of plant diversity, which suggested that plant diversity impacted the soil microbial community mainly through increases in plant production.
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The focus of a new experiment, set up in Jena in spring 2002, are the effects of biodiversity on element cycles and the interaction of plant diversity with herbivores and soil fauna. The experimental design explicitly addresses criticisms provoked by previous biodiversity experiments. In particular, the choice of functional groups, the statistical separation of sampling versus complementarity effects, and testing for the effects of particular functional groups differ from previous experiments. Based on a species pool of 60 plant species common to the Central European Arrhenatherion grasslands, mixtures of one to 16 (60) species and of one to four plant functional groups were established on 90 plots (20 m x 20 m) with nested experiments. In order to test specific hypotheses 390 additional small-area plots (3.5 m x 3.5 m) were set-up. Exact replicates of all species mixtures serve to assess the variability in ecosystem responses. In a dominance experiment, the effects of interactions among nine selected highly productive species are studied. Each species is grown as monoculture replicated once.
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Ecosystem productivity commonly increases asymptotically with plant species diversity, and determining the mechanisms responsible for this well-known pattern is essential to predict potential changes in ecosystem productivity with ongoing species loss. Previous studies attributed the asymptotic diversity-productivity pattern to plant competition and differential resource use (e.g., niche complementarity). Using an analytical model and a series of experiments, we demonstrate theoretically and empirically that host-specific soil microbes can be major determinants of the diversity-productivity relationship in grasslands. In the presence of soil microbes, plant disease decreased with increasing diversity, and productivity increased nearly 500%, primarily because of the strong effect of density-dependent disease on productivity at low diversity. Correspondingly, disease was higher in plants grown in conspecific-trained soils than heterospecific-trained soils (demonstrating host-specificity), and productivity increased and host-specific disease decreased with increasing community diversity, suggesting that disease was the primary cause of reduced productivity in species-poor treatments. In sterilized, microbe-free soils, the increase in productivity with increasing plant species number was markedly lower than the increase measured in the presence of soil microbes, suggesting that niche complementarity was a weaker determinant of the diversity-productivity relationship. Our results demonstrate that soil microbes play an integral role as determinants of the diversity-productivity relationship.
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One of the most significant consequences of contemporary global change is the rapid decline of biodiversity in many ecosystems. Knowledge of the consequences of biodiversity loss in terrestrial ecosystems is largely restricted to single ecosystem functions. Impacts of key plant functional groups on soil biota are considered to be more important than those of plant diversity; however, current knowledge mainly relies on short-term experiments. We studied changes in the impacts of plant diversity and presence of key functional groups on soil biota by investigating the performance of soil microorganisms and soil fauna two, four and six years after the establishment of model grasslands. The results indicate that temporal changes of plant community effects depend on the trophic affiliation of soil animals: plant diversity effects on decomposers only occurred after six years, changed little in herbivores, but occurred in predators after two years. The results suggest that plant diversity, in terms of species and functional group richness, is the most important plant community property affecting soil biota, exceeding the relevance of plant above- and belowground productivity and the presence of key plant functional groups, i.e. grasses and legumes, with the relevance of the latter decreasing in time. Plant diversity effects on biota are not only due to the presence of key plant functional groups or plant productivity highlighting the importance of diverse and high-quality plant derived resources, and supporting the validity of the singular hypothesis for soil biota. Our results demonstrate that in the long term plant diversity essentially drives the performance of soil biota questioning the paradigm that belowground communities are not affected by plant diversity and reinforcing the importance of biodiversity for ecosystem functioning.
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Predominant frameworks for understanding plant ecology have an aboveground bias that neglects soil micro-organisms. This is inconsistent with recent work illustrating the importance of soil microbes in terrestrial ecology. Microbial effects have been incorporated into plant community dynamics using ideas of niche modification and plant-soil community feedbacks. Here, we expand and integrate qualitative conceptual models of plant niche and feedback to explore implications of microbial interactions for understanding plant community ecology. At the same time we review the empirical evidence for these processes. We also consider common mycorrhizal networks, and propose that these are best interpreted within the feedback framework. Finally, we apply our integrated model of niche and feedback to understanding plant coexistence, monodominance and invasion ecology.
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Traditional farming practices suggest that cultivation of a mixture of crop species in the same field through temporal and spatial management may be advantageous in boosting yields and preventing disease, but evidence from large-scale field testing is limited. Increasing crop diversity through intercropping addresses the problem of increasing land utilization and crop productivity. In collaboration with farmers and extension personnel, we tested intercropping of tobacco, maize, sugarcane, potato, wheat and broad bean--either by relay cropping or by mixing crop species based on differences in their heights, and practiced these patterns on 15,302 hectares in ten counties in Yunnan Province, China. The results of observation plots within these areas showed that some combinations increased crop yields for the same season between 33.2 and 84.7% and reached a land equivalent ratio (LER) of between 1.31 and 1.84. This approach can be easily applied in developing countries, which is crucial in face of dwindling arable land and increasing food demand.
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The population dynamics, genotypic diversity and activity of naturally-occurring 2,4-diacetylphloroglucinol (DAPG)-producing Pseudomonas spp. was investigated for four plant species (wheat, sugar beet, potato, lily) grown in two different soils. All four plant species tested, except lily and in some cases wheat, supported relatively high rhizosphere populations (5 × 104 to 1 × 106 CFU/g root) of indigenous DAPG-producing Pseudomonas spp. during successive cultivation in both a take-all suppressive and a take-all conducive soil. Although lily supported on average the highest population densities of fluorescent Pseudomonas spp., it was the least supportive of DAPG-producing Pseudomonas spp. of all four plant species. The genotypic diversity of 492 DAPG-producing Pseudomonas isolates, assessed by Denaturing Gradient Gel Electrophoresis (DGGE) analysis of the phlD gene, revealed a total of 7 genotypes. Some of the genotypes were found only in the rhizosphere of a specific plant, whereas the predominant genotypes were found at significantly higher frequencies in the rhizosphere of three plant species (wheat, sugar beet and potato). Statistical analysis of the phlD+ genotype frequencies showed that the diversity of the phlD+ isolates from lily was significantly lower than the diversity of phlD+ isolates found on wheat, sugar beet or potato. Additionally, soil type had a significant effect on both the phlD+ population density and the phlD+ genotype frequencies, with the take-all suppressive soil being the most supportive. HPLC analysis further showed that the plant species had a significant effect on DAPG-production by the indigenous phlD+ population: the wheat and potato rhizospheres supported significantly higher amounts of DAPG produced per cell basis than the rhizospheres of sugar beet and lily. Collectively, the results of this study showed that the host plant species has a significant influence on the dynamics, composition and activity of specific indigenous antagonistic Pseudomonas spp.
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