Contribution of Mycorrhizal Symbiosis to Plant Growth

A special issue of Plants (ISSN 2223-7747). This special issue belongs to the section "Plant Protection and Biotic Interactions".

Deadline for manuscript submissions: closed (30 November 2019) | Viewed by 32655

Special Issue Editors

Institute for Sustainable Plant Protection (IPSP), Italian National Research Council (CNR), Viale Mattioli 25, 10125 Torino, Italy
Interests: environmental microbiology: plants and soil microorganisms; root symbioses; plant–soil microbial interactions; nitrogen-fixing symbionts, arbuscular mycorrhizal fungi and their associated bacteria; metabarcoding analysis of soil microbial communities (fungi, bacteria, archaea) in natural (alpine, Mediterranean ecosystems) and agricultural environments (soils subjected to land-use gradient) and their impact on plant growth and development
Special Issues, Collections and Topics in MDPI journals
Institute for Sustainable Plant Protection (IPSP) Italian National Research Council (CNR) , Viale Mattioli 25, 10125 Torino, Italy
Interests: biology and biotechnology of plant-microorganisms interactions; biodiversity and impact of soil fungal communities in natural and agricultural ecosystems; biotechnological applications of mycorrhizal inoculants as biofertilizers and biostimulants in agriculture and in floriculture

Special Issue Information

Dear Colleagues,

The associations between soil mycorrhizal fungi and roots, referred to as mycorrhizae, are an essential feature of the biology of most terrestrial plants. The symbiotic nature of the interactions between plants roots and mycorrhizal fungi is based on nutritional exchanges. The extraradical mycorrhizal mycelium, which grows out from the roots in soil, has access to mineral nutrients that are delivered to the host plants in exchange for organic compounds. Mycorrhizal fungi play an important role in terrestrial ecosystems, as they regulate nutrient and carbon cycles, and influence various ecosystem processes (e.g., soil aggregation, litter decomposition, and seedling survival). Mycorrhizal symbioses influence plant growth and performance (including plant productivity), and increase their tolerance to biotic and abiotic stresses (e.g., water deficit). However, the effects are often variable between studies, and are related to the context (e.g., plant and fungal species, environmental conditions, and resources availability). The true magnitude of the fungal diversity has only recently been appreciated. The development of large-scale DNA sequence datasets, thanks to next-generation sequencing (NGS), and the development of several genome/transcriptome projects on soil fungi and plant allows for identifying new functions and verifying how different mycorrhizal fungi interact and communicate with their host plants.

The purpose of this Special Issue is to focus on some new aspects related to these widespread symbioses, highlighting some of their potentialities in agro-forest environments. Papers that describe single case studies, technical advances, and perspective views that depict the contribution of mycorrhizal symbiosis to plant growth are most welcome.

Dr. Erica Lumini
Dr. Valeria Bianciotto
Guest Editors

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Keywords

  • mycorrhizal fungi
  • root symbioses
  • plant growth promotion
  • mycorrhizal interaction with biotic and abiotic factors

Published Papers (8 papers)

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Research

18 pages, 1906 KiB  
Article
AM-Induced Alteration in the Expression of Genes, Encoding Phosphorus Transporters and Enzymes of Carbohydrate Metabolism in Medicago lupulina
Plants 2020, 9(4), 486; https://doi.org/10.3390/plants9040486 - 10 Apr 2020
Cited by 7 | Viewed by 2362
Abstract
Plant–microbe interactions, including those of arbuscular mycorrhiza (AM), have been investigated for a wide spectrum of model plants. The present study focuses on an analysis of gene expression that encodes phosphate and sugar transporters and carbohydrate metabolic enzymes in a new model plant, [...] Read more.
Plant–microbe interactions, including those of arbuscular mycorrhiza (AM), have been investigated for a wide spectrum of model plants. The present study focuses on an analysis of gene expression that encodes phosphate and sugar transporters and carbohydrate metabolic enzymes in a new model plant, the highly mycotrophic Medicago lupulina MLS-1 line under conditions of phosphorus deficiency and inoculation with Rhizophagus irregularis. Expression profiles were detected by RT-PCR at six plant stages of development (second leaf, third leaf, shooting, axillary shoot branching initiation, axillary shoot branching, flowering initiation). In comparison to control (without AM), the variant with AM inoculation exhibited a significant elevation of transcription levels of carbohydrate metabolic enzymes (MlSUS, MlHXK1) and sucrose transporters (MlSUC4) in M. lupulina leaves at the shooting stage. We suggest that this leads to a significant increase in the frequency of AM infection, an abundance of mycelium in roots and an increase in AM efficiency (which is calculated by the fresh weight of aerial parts and roots at the axillary shoot branching initiation stage). In roots, the specificity of MlPT4 and MlATP1 gene expressions were revealed for effective AM symbiosis. The level of MlPT4 transcripts in AM roots increased more than tenfold in comparison to that of non-specific MlPT1 and MlPT2. For the first time, MlPT1 expression was shown to increase sharply against MlPT2 in M. lupulina roots without AM at the shooting initiation stage. A significant increase in MlRUB expression was revealed at late stages in the host plant’s development, during axillary shoot branching and flowering initiation. The opposite changes characterized MlHXK1 expression. Alteration in MlHXK1 gene transcription was the same, but was more pronounced in roots. The obtained results indicate the importance of genes that encode phosphate transporters and the enzymes of carbohydrate metabolism for effective AM development at the shooting stage in the host plant. Full article
(This article belongs to the Special Issue Contribution of Mycorrhizal Symbiosis to Plant Growth)
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17 pages, 1190 KiB  
Article
Effect of Arbuscular Mycorrhizal Colonization on Cadmium-Mediated Oxidative Stress in Glycine max (L.) Merr.
Plants 2020, 9(1), 108; https://doi.org/10.3390/plants9010108 - 15 Jan 2020
Cited by 28 | Viewed by 3379
Abstract
Cadmium is a heavy metal (HM) that inhibits plant growth and leads to death, causing great losses in yields, especially in Cd hyperaccumulator crops such as Glycine max (L.) Merr. (soybean), a worldwide economically important legume. Furthermore, Cd incorporation into the food chain [...] Read more.
Cadmium is a heavy metal (HM) that inhibits plant growth and leads to death, causing great losses in yields, especially in Cd hyperaccumulator crops such as Glycine max (L.) Merr. (soybean), a worldwide economically important legume. Furthermore, Cd incorporation into the food chain is a health hazard. Oxidative stress (OS) is a plant response to abiotic and biotic stresses with an intracellular burst of reactive oxygen species (ROS) that causes damage to lipids, proteins, and DNA. The arbuscular mycorrhizal fungal (AMF) association is a plant strategy to cope with HM and to alleviate OS. Our aim was to evaluate the mitigation effects of mycorrhization with AMF Rhizophagus intraradices on soybean growth, nutrients, Cd accumulation, lipid peroxidation, and the activity of different antioxidant agents under Cd (0.7–1.2 mg kg−1 bioavailable Cd) induced OS. Our results suggest that glutathione may act as a signal molecule in a defense response to Cd-induced OS, and mycorrhization may avoid Cd-induced growth inhibition and reduce Cd accumulation in roots. It is discussed that R. intraradices mycorrhization would act as a signal, promoting the generation of a soybean cross tolerance response to Cd pollution, therefore evidencing the potential of this AMF association for bioremediation and encouragement of crop development, particularly because it is an interaction between a worldwide cultivated Cd hyperaccumulator plant and an AMF–HM–accumulator commonly present in soils. Full article
(This article belongs to the Special Issue Contribution of Mycorrhizal Symbiosis to Plant Growth)
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17 pages, 2906 KiB  
Article
Symbionts as Filters of Plant Colonization of Islands: Tests of Expected Patterns and Environmental Consequences in the Galapagos
Plants 2020, 9(1), 74; https://doi.org/10.3390/plants9010074 - 07 Jan 2020
Cited by 7 | Viewed by 3174
Abstract
The establishments of new organisms that arrive naturally or with anthropogenic assistance depend primarily on local conditions, including biotic interactions. We hypothesized that plants that rely on fungal symbionts are less likely to successfully colonize remote environments such as oceanic islands, and this [...] Read more.
The establishments of new organisms that arrive naturally or with anthropogenic assistance depend primarily on local conditions, including biotic interactions. We hypothesized that plants that rely on fungal symbionts are less likely to successfully colonize remote environments such as oceanic islands, and this can shape subsequent island ecology. We analyzed the mycorrhizal status of Santa Cruz Island, Galapagos flora compared with the mainland Ecuador flora of origin. We experimentally determined plant responsiveness and plant–soil feedback of the island flora and assessed mycorrhizal density and soil aggregate stability of island sites. We found that a greater proportion of the native island flora species belongs to families that typically do not associate with mycorrhizal fungi than expected based upon the mainland flora of origin and the naturalized flora of the island. Native plants benefited significantly less from soil fungi and had weaker negative soil feedbacks than introduced species. This is consistent with the observation that field sites dominated by native plant species had lower arbuscular mycorrhizal (AM) fungal density and lower soil aggregate stability than invaded field sites at the island. We found support for a mycorrhizal filter to the initial colonization of the Galapagos. Full article
(This article belongs to the Special Issue Contribution of Mycorrhizal Symbiosis to Plant Growth)
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16 pages, 2488 KiB  
Article
Changes in an Arbuscular Mycorrhizal Fungi Community Along an Environmental Gradient
Plants 2020, 9(1), 52; https://doi.org/10.3390/plants9010052 - 01 Jan 2020
Cited by 33 | Viewed by 4344
Abstract
Gradual environmental changes are determining factors in the disposition of plants and associated organisms, such as arbuscular mycorrhizal fungi (AMF). The objective of this study was to evaluate the AMF species communities in a tropical semi-arid region of NE Brazil under decreasing clay [...] Read more.
Gradual environmental changes are determining factors in the disposition of plants and associated organisms, such as arbuscular mycorrhizal fungi (AMF). The objective of this study was to evaluate the AMF species communities in a tropical semi-arid region of NE Brazil under decreasing clay content at a mountain top area forming a vegetative mosaic of dry forests, savanna-like shrubland and humid montane forests. Through field and trap culture samples, 80 species of AMF were identified belonging to 25 genera, of which Acaulospora and Glomus were the most representative. In general, representatives of the order Gigasporales were indicators of sites with lower clay content and showed greater abundance in these sites. As expected, less richness was found in the site with higher clay content, but there was no variation in the Shannon-Weaver index in the gradient studied. The areas showed different assemblies of AMF among the sites with higher and lower clay content, and the main factors structuring the species were carbon, clay and potential acidity. In addition, field samples and trap cultures showed different assemblies; through the use of cultures it was possible to detect additional species. Soil properties have been found to be determinants for the distribution of these microorganisms and further studies in different vegetation types can help to understand the ecological preferences of AMF species. Full article
(This article belongs to the Special Issue Contribution of Mycorrhizal Symbiosis to Plant Growth)
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15 pages, 6836 KiB  
Article
Effect of Indigenous and Introduced Arbuscular Mycorrhizal Fungi on Growth and Phytochemical Content of Vegetatively Propagated Prunus africana (Hook. f.) Kalkman Provenances
Plants 2020, 9(1), 37; https://doi.org/10.3390/plants9010037 - 25 Dec 2019
Cited by 6 | Viewed by 3539
Abstract
Prunus africana bark contains phytochemical compounds used in the treatment of benign prostatic hyperplasia and prostate cancer. It has been shown that this plant establishes association with arbuscular mycorrhizal fungi (AMF). AMF are involved in nutrient uptake, which may also affect plant growth [...] Read more.
Prunus africana bark contains phytochemical compounds used in the treatment of benign prostatic hyperplasia and prostate cancer. It has been shown that this plant establishes association with arbuscular mycorrhizal fungi (AMF). AMF are involved in nutrient uptake, which may also affect plant growth and secondary metabolites composition. However, there is no information regarding the role of AMF in the growth and phytochemical content of P. africana. A pot experiment was carried out to assess the response of 8 months old vegetatively propagated P. africana seedlings inoculated with indigenous AMF collected from Mount Cameroon (MC) and Mount Manengumba (MM) in Cameroon, Malava near Kakamega (MK) and Chuka Tharaka-Nithi (CT) in Kenya. Mycorrhizal (frequency, abundance and intensity), growth (height, shoot weight, total weight, number of leaf, leaf surface) and phytochemical (total phenol, tannin and flavonoids) parameters were measured three months after growth of seedlings from two provenances (Muguga and Chuka) with the following inoculation treatments: MK, CT, MC, MM, non-sterilized soil (NS) and sterilized sand as non-inoculated control. Results showed that seedling heights were significantly increased by inoculation and associated with high root colonization (>80%) compared to non-inoculated seedlings. We also found that AMF promoted leaf formation, whereas inoculation did not have any effect on the seedling total weight. AMF inoculum from MM had a higher tannin content, while no significant difference was observed on the total phenol and flavonoid contents due to AMF inoculation. Pearson’s correlation was positive between mycorrhizal parameters and the growth parameters, and negative with phytochemical parameters. This study is the first report on the effect of AMF on the growth and phytochemical in P. africana. Further investigations are necessary to determine the effect of single AMF strains to provide better understanding of the role of AMF on the growth performance and physiology of this important medicinal plant species. Full article
(This article belongs to the Special Issue Contribution of Mycorrhizal Symbiosis to Plant Growth)
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15 pages, 5099 KiB  
Article
Arbuscular Mycorrhizal Fungi Colonization Promotes Changes in the Volatile Compounds and Enzymatic Activity of Lipoxygenase and Phenylalanine Ammonia Lyase in Piper nigrum L. ‘Bragantina’
Plants 2019, 8(11), 442; https://doi.org/10.3390/plants8110442 - 23 Oct 2019
Cited by 19 | Viewed by 4015
Abstract
Arbuscular mycorrhizal fungi (AMF) have been used to promote numerous benefits to plants. In this study, we evaluated the symbiosis between AMF species (Rhizophagus clarus, Claroideoglomus etunicatum) and Piper nigrum L. ‘Bragantina’. Volatile compounds, lipoxygenase (LOX) and phenylalanine ammonia-lyase (PAL) [...] Read more.
Arbuscular mycorrhizal fungi (AMF) have been used to promote numerous benefits to plants. In this study, we evaluated the symbiosis between AMF species (Rhizophagus clarus, Claroideoglomus etunicatum) and Piper nigrum L. ‘Bragantina’. Volatile compounds, lipoxygenase (LOX) and phenylalanine ammonia-lyase (PAL) activities, and total phenolic content were monitored from 1 to 60 days post-inoculation (dpi). Hyphae, arbuscles, and vesicles were observed during the root colonization. In the leaves, AMF induced an increase of sesquiterpene hydrocarbons (54.0%–79.0%) and a decrease of oxygenated sesquiterpenes (41.3%–14.5%) at 7 dpi and 60 dpi (41.8%–21.5%), respectively. Cubenol, the main volatile compound of leaves, showed a significant decrease at 7 dpi (21.5%–0.28%) and 45 dpi (20.4%–18.42%). β-caryophyllene, the major volatile compound of the roots, displayed a significant reduction at 45 dpi (30.0%–20.0%). LOX increased in the roots at 21, 30, and 60 dpi. PAL was higher in leaves during all periods, except at 60 dpi, and increased at 21 and 45 dpi in the roots. The total phenolic content showed a significant increase only in the roots at 30 dpi. The results suggested that AMF provided changes in the secondary metabolism of P. nigrum, inducing its resistance. Full article
(This article belongs to the Special Issue Contribution of Mycorrhizal Symbiosis to Plant Growth)
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11 pages, 3193 KiB  
Article
Bletilla striata (Orchidaceae) Seed Coat Restricts the Invasion of Fungal Hyphae at the Initial Stage of Fungal Colonization
Plants 2019, 8(8), 280; https://doi.org/10.3390/plants8080280 - 11 Aug 2019
Cited by 7 | Viewed by 5228
Abstract
Orchids produce minute seeds that contain limited or no endosperm, and they must form an association with symbiotic fungi to obtain nutrients during germination and subsequent seedling growth under natural conditions. Orchids need to select an appropriate fungus among diverse soil fungi at [...] Read more.
Orchids produce minute seeds that contain limited or no endosperm, and they must form an association with symbiotic fungi to obtain nutrients during germination and subsequent seedling growth under natural conditions. Orchids need to select an appropriate fungus among diverse soil fungi at the germination stage. However, there is limited understanding of the process by which orchids recruit fungal associates and initiate the symbiotic interaction. This study aimed to better understand this process by focusing on the seed coat, the first point of fungal attachment. Bletilla striata seeds, some with the seed coat removed, were prepared and sown with symbiotic fungi or with pathogenic fungi. The seed coat-stripped seeds inoculated with the symbiotic fungi showed a lower germination rate than the intact seeds, and proliferated fungal hyphae were observed inside and around the stripped seeds. Inoculation with the pathogenic fungi increased the infection rate in the seed coat-stripped seeds. The pathogenic fungal hyphae were arrested at the suspensor side of the intact seeds, whereas the seed coat-stripped seeds were subjected to severe infestation. These results suggest that the seed coat restricts the invasion of fungal hyphae and protects the embryo against the attack of non-symbiotic fungi. Full article
(This article belongs to the Special Issue Contribution of Mycorrhizal Symbiosis to Plant Growth)
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13 pages, 1753 KiB  
Article
Isolation of Native Arbuscular Mycorrhizal Fungi within Young Thalli of the Liverwort Marchantia paleacea
Plants 2019, 8(6), 142; https://doi.org/10.3390/plants8060142 - 30 May 2019
Cited by 4 | Viewed by 5550
Abstract
Arbuscular mycorrhizal fungi (AMF) are a group of soil microorganisms that establish symbioses with most land plant species. “Root trap culture” generally has been used for isolating a single regenerated spore in order to establish a monospecific, native AMF line. Roots may be [...] Read more.
Arbuscular mycorrhizal fungi (AMF) are a group of soil microorganisms that establish symbioses with most land plant species. “Root trap culture” generally has been used for isolating a single regenerated spore in order to establish a monospecific, native AMF line. Roots may be co-colonized with multiple AMF species; however, only a small portion of AMF within roots sporulate, and do so only under certain conditions. In this study, we tested whether young thalli (<2 mm) of the liverwort Marchantia paleacea harbour monospecific AMF, and can be used as a vegetative inoculant line. When M. paleacea gemmae were co-cultivated with roots obtained from the field, the young thalli were infected by AMF via rhizoids and formed arbuscules after 18 days post-sowing. Ribosomal DNA sequencing of the AMF-colonized thalli (mycothalli) revealed that they harboured phylogenetically diverse AMF; however, new gemmae sown around transplanted mycothalli showed evidence of colonization from phylogenetically uniform Rhizophagus species. Of note, mycothalli can also be used as an inoculum. These results suggest that the young thalli of M. paleacea can potentially isolate monospecific AMF from field soil in a spore-independent manner. Full article
(This article belongs to the Special Issue Contribution of Mycorrhizal Symbiosis to Plant Growth)
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