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Mechanism of Rhizosphere Microorganisms Promoting Crop Growth

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A special issue of Agronomy (ISSN 2073-4395). This special issue belongs to the section "Soil and Plant Nutrition".

Deadline for manuscript submissions: closed (10 June 2020) | Viewed by 26995

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Special Issue Editors

Prof. Dr. Ann M. Hirsch

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Guest Editor

Department of Molecular, Cell and Developmental Biology, University of California-Los Angeles, Los Angeles, CA 90095-1606, USA
Interests: biological nitrogen fixation; plant growth promoting bacteria; root and nodule microbiomes

Prof. Dr. Martha Hawes

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Guest Editor

Department of Soil, Water and Environmental Sciences, University of Arizona, Tucson, AZ 85721, USA
Interests: crop protection; plant root disease; soil; soil-borne bacteria; microbial populations; symbiotic and pathogenic bacteria and fungi; drought resistance mechanisms

Special Issue Information

Dear Colleagues,

We are preparing a Special Issue of Agronomy that will feature mechanisms used by rhizosphere microorganisms to promote plant growth with the goal of reducing dependence on synthetic herbicides, pesticides, and fertilizers. The world must quickly develop viable strategies involving not only plants but also microorganisms to ensure both plant and soil health and productivity. The need is urgent due to the growing human population, accelerated loss of soil fertility, and reduced availability of water. We are asking you to contribute to this issue not only because of your knowledge and expertise but also because we believe that you are concerned about our collective future and can offer a clear picture of our next steps to avoid the looming catastrophe. To help to focus your contribution, we ask you to consider: “If my part of the world were to become desertified with the next 30 years, how does my current research help to solve the problem?”

Prof. Ann M. Hirsch
Prof. Martha Hawes
Guest Editors

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 submissions that pass pre-check are 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 2600 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

rhizosphere microorganisms
crop protection
plant growth
soil health and productivity

Published Papers (4 papers)

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Research

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19 pages, 2879 KiB

Open AccessArticle

In-Vitro Plant Growth Promotion of Rhizobium Strains Isolated from Lentil Root Nodules under Abiotic Stresses

by Badreddine Sijilmassi, Abdelkarim Filali-Maltouf, Sara Fahde, Youness Ennahli, Said Boughribil, Shiv Kumar and Ahmed Amri

Agronomy 2020, 10(7), 1006; https://doi.org/10.3390/agronomy10071006 - 13 Jul 2020

Cited by 8 | Viewed by 3530

Abstract

Plant growth-promoting rhizobia are known to improve crop performance by multiple mechanisms. However, the interaction between host plants and Rhizobium strains is highly influenced by growing conditions, e.g., heat, cold, drought, soil salinity, nutrient scarcity, etc. The present study was undertaken to assess the use of Rhizobium as plant growth promoters under abiotic stress conditions. Fifteen Rhizobium strains isolated from lentil root nodules were tested for phosphate solubilization activity (PSA) and phytohormones production under salt and drought conditions. The results showed that 15 Rhizobium strains were significant phosphate solubilizers, and indole acedic acid (IAA) and gibberellic acid (GA3) producers based on least significant difference (LSD) analysis (p ≤ 0.05). The highest rate of PSA was attributed to three strains namely, 1145N5, 1159N11, and 1159N32 with a range of 144.6 to 205.6 P₂O₅ (µg/mL). The highest IAA production was recorded in the strain 686N5 with 57.68 ± 4.25 µg/mL as compared to 50.8667 ± 1.41 µg/mL and 37.32 ± 12.59 µg/mL for Rhizobium tropici CIAT 899 and Azospirillum brasilense DSM-1690, respectively. Strain 318N2111 produced 329.24 ± 7.84 µg/mL of GA3 as against 259.84 ± 25.55 µg/mL for A. brasilense DSM-1690. R. tropici CIAT 899 showed tolerance to salt (5% NaCl) and drought (ψ = −2.6 MPa) stress, whereas strain 686N5 showed an extremely high level of salt-tolerance (5% NaCl) and moderate level of drought tolerance (ψ = −0.75 MPa). These results indicate different pathways for drought and salt tolerance mechanisms. The assessment of plant growth promoting (PGP) activities of Rhizobium showed differences between bacterial viability and bacterial PGP activity in terms of abiotic stress tolerance where bacterial PGP activity is interrupted before reaching the bacterial tolerance threshold. These results integrate a new concept of PGPR screening based on PGP activity under abiotic stress. Full article

(This article belongs to the Special Issue Mechanism of Rhizosphere Microorganisms Promoting Crop Growth)

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16 pages, 1067 KiB

Open AccessArticle

Diversity and Effectivity of Indigenous Mesorhizobium Strains for Chickpea (Cicer arietinum L.) in Myanmar

by Khin Myat Soe, Aung Zaw Htwe, Kyi Moe, Abiko Tomomi and Takeo Yamakawa

Agronomy 2020, 10(2), 287; https://doi.org/10.3390/agronomy10020287 - 17 Feb 2020

Cited by 9 | Viewed by 3221

Abstract

Chickpea (Cicer arietinum L.) is one of the world’s main leguminous crops that provide chief source of food for humans. In the present study, we characterized thirty isolates of indigenous chickpea rhizobia from Myanmar based on the sequence analysis of the bacterial 16S rRNA gene. The sequence analysis confirmed that all isolates were categorized and identified as the genus Mesorhizobium and they were conspecific with M. plurifarium, M. muliense, M. tianshanense, and M. sp. This is the first report describing M. muliense, M. tianshanense, and M. plurifurium from different geographical distribution of indigenous mesorhizobia of chickpea in Myanmar. In order to substitute the use of chemical fertilizers in legume production, there is a need for the production of Biofertilizers with rhizobial inoculants. The effectiveness of Myanmar Mesorhizobim strains isolated from soil samples of major chickpea growing areas of Myanmar for plant growth and nitrogen fixation were studied in pot experiments. The nodule dry weight and acetylene reduction activity of the plant inoculated with Mesorhizobium tianshanense SalCP19 was significantly higher than the other tested isolates in Yezin-4 chickpea variety. But, Mesorhizobium sp. SalCP17 was showed high level of acetylene reduction activity per plant in Yezin-6 chickpea variety. Full article

(This article belongs to the Special Issue Mechanism of Rhizosphere Microorganisms Promoting Crop Growth)

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9 pages, 236 KiB

Open AccessArticle

Potential of Rhizobium sullae–Sulla coronaria Symbiotic Biological Nitrogen Fixation to Supplement Synthetic Mineral Nitrogen in Olive Tree Fertilization

by Biagi Angelo Zullo and Gino Ciafardini

Agronomy 2020, 10(2), 270; https://doi.org/10.3390/agronomy10020270 - 14 Feb 2020

Cited by 3 | Viewed by 2282

Abstract

The aim of the present work is to compare olive tree nitrogen fertilization over two years of trials, using synthetic chemical fertilizers along with organic fertilizers composed of the green manure of sulla (Sulla coronaria) inoculated with the symbiont Rhizobium sullae or left uninoculated. The tests indicated that symbiotic nitrogen fixation promoted by the sulla–R. sullae symbiosis represents an important source of nitrogen that can replace or supplement synthetic nitrogen fertilizers for olive tree cultivation when sulla is inoculated with R. sullae in a soil already populated by the symbiont. Integration of the indigenous population of R. sullae via sulla inoculation with a selected strain yielded nodule formation in 100% of plants and produced a sufficient amount of biomass rich in nitrogen with a low C/N ratio. On the contrary, olive tree fertilization using the green manure of sulla that was not inoculated with the symbiont supplied significantly less organic nitrogen in 2017 and 2018, respectively, compared to the control. Optimal management of the multi-factorial approaches involved in green manure olive fertilization are also reported. Full article

(This article belongs to the Special Issue Mechanism of Rhizosphere Microorganisms Promoting Crop Growth)

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Review

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29 pages, 2085 KiB

Open AccessReview

Plant Growth Promoting Rhizobacterial Mitigation of Drought Stress in Crop Plants: Implications for Sustainable Agriculture

by Omena Bernard Ojuederie, Oluwaseyi Samuel Olanrewaju and Olubukola Oluranti Babalola

Agronomy 2019, 9(11), 712; https://doi.org/10.3390/agronomy9110712 - 4 Nov 2019

Cited by 130 | Viewed by 17506

Abstract

Abiotic stresses arising from climate change negates crop growth and yield, leading to food insecurity. Drought causes oxidative stress on plants, arising from excessive production of reactive oxygen species (ROS) due to inadequate CO₂, which disrupts the photosynthetic machinery of plants. The use of conventional methods for the development of drought-tolerant crops is time-consuming, and the full adoption of modern biotechnology for crop enhancement is still regarded with prudence. Plant growth-promoting rhizobacteria (PGPR) could be used as an inexpensive and environmentally friendly approach for enhancing crop growth under environmental stress. The various direct and indirect mechanisms used for plant growth enhancement by PGPR were discussed. Synthesis of 1-aminocyclopropane−1-carboxylate (ACC) deaminase enhances plant nutrient uptake by breaking down plant ACC, thereby preventing ethylene accumulation, and enable plants to tolerate water stress. The exopolysaccharides produced also improves the ability of the soil to withhold water. PGPR enhances osmolyte production, which is effective in reducing the detrimental effects of ROS. Multifaceted PGPRs are potential candidates for biofertilizer production to lessen the detrimental effects of drought stress on crops cultivated in arid regions. This review proffered ways of augmenting their efficacy as bio-inoculants under field conditions and highlighted future prospects for sustainable agricultural productivity. Full article

(This article belongs to the Special Issue Mechanism of Rhizosphere Microorganisms Promoting Crop Growth)

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