Special Issue "Beneficial Microbes for Sustainable Agriculture: Understanding the Functional Relationship between Plants and Their Microbiota"

A special issue of Agronomy (ISSN 2073-4395). This special issue belongs to the section "Farming Sustainability".

Deadline for manuscript submissions: 25 October 2020.

Special Issue Editor

Dr. Lambert Brau
Website
Guest Editor
School of Life & Environmental Sciences, Faculty of Science Engineering & Built Environment, Melbourne Burwood Campus, Deakin University, Burwood, VIC 3125, Australia
Interests: plant microbe interactions; molecular microbiology; microbial ecology; biological nitrogen fixation; agro-ecology; sustainable agriculture; soil microbiology; plant growth promoting rhizobacteria; microbial molecular biology; environmental microbiology

Special Issue Information

Dear Colleagues,

Globally, agriculture relies on supplementing cropped soils with macro and micronutrients sourced from mined ores or industrially produced through energy intensive processes. The major outcome of supplementing crops with these fertilizers is a consistent yield, however, as global demand for fertilizers increases, the costs associated with the production for each of these major nutrients increase. There are also numerous, well-characterized, negative impacts of chemical fertilizer use, including pollution, eutrophication and soil depletion.

Plant growth promoting bacteria (PGPB), which naturally occur in soils and aggressively colonize around plant roots, have been shown to promote plant growth by various direct and indirect mechanisms. The potential of PGPB to reduce dependence on high levels of fertilizer inputs has gained significant increase in interest over recent years.

Sustainably improving agricultural production by plant growth-promoting microorganisms is a promising field of research; however, there still exist significant gaps in the understanding of the actual mechanism of plant growth promotion. This Special Issue of Agronomy is dedicated to PGPB with a particular focus on their mode of action, examples of innovative methodologies for their characterization of the mode of action and analysis of their interaction with the host plant.

Dr. Lambert Brau
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Agronomy is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • plant growth promoting bacteria (PGPB)
  • plant-microbe interactions
  • PGPB method of action
  • plant-microbe signalling
  • secondary metabolites
  • rhizosphere interactions
  • plant microbiome
  • siderophores
  • micorbial genomics
  • agroecosystems

Published Papers (4 papers)

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Research

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Open AccessArticle
Assessment of the Capacity of Beneficial Bacterial Inoculants to Enhance Canola (Brassica napus L.) Growth under Low Water Activity
Agronomy 2020, 10(9), 1449; https://doi.org/10.3390/agronomy10091449 - 22 Sep 2020
Abstract
Canola (Brassica napus L.) is the third largest crop produced in Australia after wheat and barley. For such crops, the variability of water access, reduced long-term annual rainfall and increasing water prices, higher overall production costs, and variability in production quantity and [...] Read more.
Canola (Brassica napus L.) is the third largest crop produced in Australia after wheat and barley. For such crops, the variability of water access, reduced long-term annual rainfall and increasing water prices, higher overall production costs, and variability in production quantity and quality are driving the exploration of new tools to maintain production in an economical and environmentally sustainable way. Microorganisms associated with the rhizosphere have been shown to enhance plant growth and offer a potential way to maintain or even increase crop production quality and yield in an environmentally sustainable way. Here, seven bacterial isolates from canola rhizosphere samples are shown to enhance canola growth, particularly in low water activity systems. The seven strains all possessed commonly described plant growth promoting traits, including the ability to produce indole-3-acetic acid and 1-aminocyclopropane-1-carboxylate deaminase, and the capacity to solubilise nutrients (Fe2+/3+ and PO43−). When the isolates were inoculated at the time of sowing in pot-based systems with either sand or clay loam media, and in field trials, a significant increase in dry root and shoot biomass was recorded compared to uninoculated controls. It is likely that the strains’ plant growth promoting capacity under water stress is due to the combined effects of the bacterial phenotypes examined here. Full article
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Open AccessArticle
Effect of Co-Inoculation of Bradyrhizobium and Trichoderma on Growth, Development, and Yield of Arachis hypogaea L. (Peanut)
Agronomy 2020, 10(9), 1415; https://doi.org/10.3390/agronomy10091415 - 17 Sep 2020
Abstract
Cultivation of the peanut (Arachis hypogaea L.) on the same land contributes to the accumulation of root exudates, leading to increased soil pathogens and decreased yield. Trichoderma harzianum is a naturally occurring endophytic biocontrol fungus that can enhance plant growth, nutrient uptake, [...] Read more.
Cultivation of the peanut (Arachis hypogaea L.) on the same land contributes to the accumulation of root exudates, leading to increased soil pathogens and decreased yield. Trichoderma harzianum is a naturally occurring endophytic biocontrol fungus that can enhance plant growth, nutrient uptake, and tolerance to biotic and abiotic stresses. Separately, Bradyrhizobium spp. is a biological nitrogen-fixing (BNF) bacterium favoring nodule formation in peanut roots which promotes nitrogen fixation. The dynamics of the symbiotic association between these two organisms were evaluated in the laboratory and greenhouse conditions. Peanuts were cultivated in pots inoculated with either Bradyrhizobium or Trichoderma or both to evaluate growth, development, and yield. The in vitro study results showed that seeds treated with Trichoderma had better germination and seedling biomass (p = 0.0008) compared to the other treatments. On the other hand, the results of greenhouse studies showed that seeds inoculated with both microbes, and those inoculated with Bradyrhizobium alone had higher dry biomass (p < 0.0001) as well as higher chlorophyll content (p < 0.0001) compared to the other treatments. Understanding of the interactive effects of fungal endophytes and rhizobial bacteria on plant growth and development will help in both the nutrient and disease management of Arachis hypogaea L. Full article
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Open AccessArticle
Arbuscular Mycorrhizas Traits and Yield of Winter Wheat Profiled by Mineral Fertilization
Agronomy 2020, 10(6), 846; https://doi.org/10.3390/agronomy10060846 - 13 Jun 2020
Abstract
Our aim is to evaluate the changes in arbuscular mycorrhiza characteristics of winter wheat in a three-year experiment. Study results show that fertilizers produce strong variations in arbuscular mycorrhiza extension, with colonization frequency values within 76–98%. The intensity of colonization is only 12% [...] Read more.
Our aim is to evaluate the changes in arbuscular mycorrhiza characteristics of winter wheat in a three-year experiment. Study results show that fertilizers produce strong variations in arbuscular mycorrhiza extension, with colonization frequency values within 76–98%. The intensity of colonization is only 12% when phosphorus (P) exceeds nitrogen (N) in autumn, but reaches 38% when the N:P ratio is equal. Root colonization shows no consistency from one experimental year to another, with the largest fluctuations recorded in colonization intensity (22–65%) and arbuscules abundance (0–5%). Arbuscules are maintained below 1% by fertilizer with more P than N. Colonization forecasting models indicate P as a factor for the reduction of symbiosis. Each kg of applied P can reduce the colonization frequency by 0.28% and intensity by 0.37%. The maximum of the colonization degree is 61% due to the synergy of equal N and P doses in autumn and ammonium nitrate applied in spring. The application of multiple moderate doses acts as a stimulant for the development of a large root-fungal interface. Full article
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Review

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Open AccessReview
Facing Climate Change: Application of Microbial Biostimulants to Mitigate Stress in Horticultural Crops
Agronomy 2020, 10(6), 794; https://doi.org/10.3390/agronomy10060794 - 03 Jun 2020
Cited by 1
Abstract
In the current scenario of rapidly evolving climate change, crop plants are more frequently subjected to stresses of both abiotic and biotic origin, including exposure to unpredictable and extreme climatic events, changes in plant physiology, growing season and phytosanitary hazard, and increased losses [...] Read more.
In the current scenario of rapidly evolving climate change, crop plants are more frequently subjected to stresses of both abiotic and biotic origin, including exposure to unpredictable and extreme climatic events, changes in plant physiology, growing season and phytosanitary hazard, and increased losses up to 30% and 50% in global agricultural productions. Plants coevolved with microbial symbionts, which are involved in major functions both at the ecosystem and plant level. The use of microbial biostimulants, by exploiting this symbiotic interaction, represents a sustainable strategy to increase plant performances and productivity, even under stresses due to climate changes. Microbial biostimulants include beneficial fungi, yeasts and eubacteria sharing the ability to improve plant nutrition, growth, productivity and stress tolerance. This work reports the current knowledge on microbial biostimulants and provides a critical review on their possible use to mitigate the biotic and abiotic stresses caused by climate changes. Currently, available products often provide a general amelioration of cultural conditions, but their action mechanisms are largely undetermined and their effects often unreliable. Future research may lead to more specifically targeted products, based on the characterization of plant-microbe and microbial community interactions. Full article
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

The Rhizosphere Talk Show: the rhizobia on stage (Running title: Rhizobia in the rhizosphere)

Alice Checcucci1,2, Marta Marchetti3,4

1   Department of Agricultural and Food Science , University of Bologna, Italy;

2   Department of Biology, University of Florence, Italy; 3INRA, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR441, Castanet-Tolosan, France; 4CNRS, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR2594, Castanet-Tolosan, France.

*   Correspondence:orresponding author: [email protected]; +39 051 20 9 6263

AbstractBackground From bacterial quorum sensing to bees’ signals, communication is the basis of biotic interactions. Frequently, more than two organisms can take part in the speeches, resulting in a complex network of cross-talks. Recent advances in plant-microbe interactions research have shown that communication, both inter-kingdom and intra-kingdom, is shaped by a broad spectrum of factors. In this context, the rhizosphere (i.e., the soil close to the root surface) provides a specific microhabitat where complex interactions occur. Scop: The aim of this review is to explore the components of such rhizospheric Talk Show in the frame of the rhizobium-legume interactions. This symbiosis is a complex process that involves several signals that can be shaped by plant rhizospheric exudates and microbiome composition. Here, we synthesize research that accounts for strategies, molecules, and organisms that influence the place of rhizobia in the rhizosphere, accounting for the most recent approaches for the study and the subsequent exploitation of organism’s diversity. Conclusion The complex environment that makes up the rhizosphere can select for certain microbial populations, which are adapted to this unique niche. Among them, rhizobia are coming out as an important component of the rhizospheric microbiome. We argue the relationship that rhizobia can entertain with other rhizospheric organisms including the impact of abiotic environmental and host factors, pointing out the beneficial role that these bacteria can play on plant health. The study of plant-microbes communication and of its evolution is fundamental for exploitation of such interactions to develop highly efficient inoculants to reduce the use of fertilizers in agriculture.

Keywords: Rhizosphere; rhizobia; communication; interaction; microbial communities.  

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