Microbial Biostimulants: From the Lab to the Field for a New Agriculture 3.0

A special issue of Microorganisms (ISSN 2076-2607). This special issue belongs to the section "Plant Microbe Interactions".

Deadline for manuscript submissions: closed (31 May 2024) | Viewed by 3525

Special Issue Editor


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Guest Editor
Plants and Pathogens Group, Research Institute Land Nature and Environment, Hepia, HES-SO University of Applied Sciences and Arts Western Switzerland, Jussy, 1200 Geneva, Switzerland
Interests: pathogens; plant genetic resources; plant pathogenic microorganisms; bioprospection; biostimulants; genomics; metagenomics
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Special Issue Information

Dear Colleagues,

This Special Issue is the continuation of our previous special issues "Microbial Biostimulants: From the Lab to the Field for a New Agriculture" and "Microbial Biostimulants: From the Lab to the Field for a New Agriculture 2.0".

Plant biostimulants have been named under different terminologies for the past 30 years as a function of their variable modes of action. The most consensual and recent definition states that biostimulants are biological substances, micro-organisms, and mineral compounds which can be directly applied to plants, seeds, and soil in order to improve plant growth, increase crop yield, and reduce plant stress. Mostly used in agriculture as preventive agents, they act as plant growth stimulators and enhancers of resistance to biotic and abiotic stress.

This Special Issue aims to bring together a sample of very recent developments in microbial biostimulants for agriculture, on their way to the biofertilizer market or recently available to diverse agricultural production sectors, whether it be in horticulture, environmental and fruit arboriculture, viticulture, silviculture, or vegetable or crop production. The development of these innovating products has been based on chemistry, biochemistry, biotechnology, and microbiology applied to agriculture, taking into account the physiological, agricultural, and ecological constraints of plants. Finally, these plant microbial biostimulants must be effective at very low doses, while being ecologically friendly. They especially must produce a positive and reproducible effect on crops. Whether bacteria or fungi, these microorganisms that can be used as plant biostimulants and plant health promoters are part of a wide unknown microbial diversity, constituting the rhizospheric, epiphytic, or endophytic microbiota which are on the way to being domesticated. Their activities are also sustained by genetic interactions between plant and microbe species, which have yet to be elucidated, alongside their impacts on human and animal health.

Prof. Dr. Francois Lefort
Guest Editor

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Keywords

  • microorganisms
  • plant biostimulants
  • plant health promoters
  • agricultural
  • production
  • biofertilizer

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Published Papers (3 papers)

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Research

15 pages, 2343 KiB  
Article
Synergistic Effects of Microbial Biostimulants and Calcium in Alleviating Drought Stress in Oilseed Rape
by Virgilija Gavelienė, Rima Mockevičiūtė, Elžbieta Jankovska-Bortkevič, Vaidevutis Šveikauskas, Mariam Zareyan, Tautvydas Žalnierius, Jurga Jankauskienė and Sigita Jurkonienė
Microorganisms 2025, 13(3), 530; https://doi.org/10.3390/microorganisms13030530 - 27 Feb 2025
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Abstract
The study aimed to examine the changes in winter oilseed rape (Brassica napus L.) under simulated prolonged drought and to assess the effects of a microbial biostimulant ProbioHumus and calcium, individually and in combination, in order to improve the plant’s drought resistance [...] Read more.
The study aimed to examine the changes in winter oilseed rape (Brassica napus L.) under simulated prolonged drought and to assess the effects of a microbial biostimulant ProbioHumus and calcium, individually and in combination, in order to improve the plant’s drought resistance and to identify the biochemical processes occurring in the plant tissues. The oilseed rape cv. ‘Visby’ was grown under controlled laboratory conditions. CaCO3 (hereafter, Ca) (3.71 g) was added to the soil of one pot at 70 g m−2. Seedlings at the 3–4 leaf stage were sprayed with ProbioHumus 2 mL 100 mL−1 and exposed to drought for 8 days to achieve a high water deficit. Irrigation was then resumed, and recovery was assessed after 4 days. The data showed that the microbial biostimulant alleviated the physiological and biochemical response of oilseed rape to drought stress. ProbioHumus + Ca reduced plant wilting by increasing leaf relative water content (RWC) by 87% and induced drought tolerance by increasing endogenous proline content 4-fold, increasing photosynthetic pigment content in leaves by 10–28%, reducing H2O2 by 53% and malondialdehyde (MDA) by 45%, and stimulating stomata opening (by 2-fold on the upper and 1.4-fold in the lower leaf surface), vs. drought control. The most effective measure to increase plant survival and/or resume growth after drought was the application of a microbial biostimulant with additional calcium to the soil. The practical implications of this research point to the potential benefits of applying these ecological measures under field conditions. Full article
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35 pages, 14424 KiB  
Article
Quick In Vitro Screening of PGPMs for Salt Tolerance and Evaluation of Induced Tolerance to Saline Stress in Tomato Culture
by Lucas Arminjon and François Lefort
Microorganisms 2025, 13(2), 246; https://doi.org/10.3390/microorganisms13020246 - 23 Jan 2025
Viewed by 1213
Abstract
Soil salinity, affecting 20–50% of irrigated farmland globally, poses a significant threat to agriculture and food security, worsened by climate change and increasing droughts. Traditional methods for managing saline soils—such as leaching, gypsum addition, and soil excavation—are costly and often unsustainable. An alternative [...] Read more.
Soil salinity, affecting 20–50% of irrigated farmland globally, poses a significant threat to agriculture and food security, worsened by climate change and increasing droughts. Traditional methods for managing saline soils—such as leaching, gypsum addition, and soil excavation—are costly and often unsustainable. An alternative approach using plant growth-promoting microorganisms (PGPMs) offers promise for improving crop productivity in saline conditions. This study tested twenty-three bacterial strains, one yeast, and one fungal strain, isolated from diverse sources including salicornia plants, sandy soils, tomato stems or seeds, tree leaves, stems, and flowers. They were initially submitted to in vitro selection tests to assess their ability to promote plant growth under salt stress. In vitro tests included auxin production, phosphate solubilization, and co-culture of microorganisms and tomato seedlings in salt-supplemented media. The Bacillus sp. strain 44 showed the highest auxin production, while Bacillus megaterium MJ had the strongest phosphate solubilization ability. Cryptococcus sp. STSD 4 and Gliomastix murorum (4)10-1(iso1) promoted germination and the growth of tomato seedlings in an in vitro co-culture test performed on a salt-enriched medium. This innovative test proved particularly effective in selecting relevant strains for in planta trials. The microorganisms that performed best in the various in vitro tests were then evaluated in vivo on tomato plants grown in greenhouses. The results showed significant improvements in growth, including increases in fresh and dry biomass and stem size. Among the strains tested, Gliomastix murorum (4)10-1(iso1) stood out, delivering an increase in fresh biomass of 94% in comparison to the negative control of the salt modality. These findings highlight the potential of specific PGPM strains to enhance crop resilience and productivity in saline soils, supporting sustainable agricultural practices. Full article
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21 pages, 3836 KiB  
Article
A Comprehensive Approach Combining Short-Chain Polyphosphate and Bacterial Biostimulants for Effective Nutrient Solubilization and Enhanced Wheat Growth
by Kaoutar Bourak, Fatima Ezzahra Oulkhir, Fatima Zahra Maghnia, Sebastien Massart, Latefa Biskri, M. Haissam Jijakli and Abdelmounaaim Allaoui
Microorganisms 2024, 12(7), 1423; https://doi.org/10.3390/microorganisms12071423 - 13 Jul 2024
Cited by 3 | Viewed by 1481
Abstract
Phosphorus constitutes a crucial macronutrient for crop growth, yet its availability often limits food production. Efficient phosphorus management is crucial for enhancing crop yields and ensuring food security. This study aimed to enhance the efficiency of a short-chain polyphosphate (PolyP) fertilizer by integrating [...] Read more.
Phosphorus constitutes a crucial macronutrient for crop growth, yet its availability often limits food production. Efficient phosphorus management is crucial for enhancing crop yields and ensuring food security. This study aimed to enhance the efficiency of a short-chain polyphosphate (PolyP) fertilizer by integrating it with plant growth-promoting bacteria (PGPB) to improve nutrient solubilization and wheat growth. Specifically, the study investigated the effects of various bacterial strains on wheat germination and growth when used in conjunction with PolyP. To achieve this, a greenhouse experiment was conducted in which the wheat rhizosphere was amended with a short-chain PolyP fertilizer. Based on the morphological aspect, eight bacteria, designated P1 to P8, were isolated and further characterized. Plant growth-promoting traits were observed in all bacterial strains, as they presented the ability to produce Indole Acetic Acid (IAA) in significant amounts ranging from 7.5 ± 0.3 µg/mL to 44.1 ± 2 µg/mL, expressed by B. tropicus P4 and P. soyae P1, respectively. They also produced ammonia, hydrogen cyanide (HCN), and siderophores. Their effect against the plant pathogen Fusarium culmorum was also assessed, with P. reinekei P2 demonstrating the highest biocontrol activity as it presented a total inhibitory effect. Additionally, some strains exhibited the ability to solubilize/hydrolyze phosphorus, potassium, and zinc. In vivo, the initial growth potential of wheat seeds indicated that those inoculated with the isolated strains exhibited elevated germination rates and enhanced root growth. Based on their plant growth-promoting traits and performance in the germination assay, three strains were selected for producing the best results, specifically phosphorus hydrolyzation/solubilization, zinc solubilization, IAA production, HCN, and siderophores production. Wheat seeds were inoculated by drenching in a bacterial suspension containing 1010 CFU/mL of log phase culture, and an in planta bioassay was conducted in a growth chamber using three selected strains (Pseudomonas soyae P1, Pseudomonas reinekei P2, and Bacillus tropicus P4), applied either individually or with PolyP on a P-deficient soil (28 mg/kg of P Olsen). Our findings demonstrated that the combination of Pseudomonas soyae P1 and PolyP achieved the highest shoot biomass, averaging 41.99 ± 0.87 g. Notably, applying P. soyae P1 or Bacillus tropicus P4 alone yielded similar results to the use of PolyP alone. At the heading growth stage, the combination of Bacillus tropicus P4 and PolyP significantly increased the Chlorophyll Content Index (CCI) to 37.02 µmol/m2, outperforming both PolyP alone (24.07 µmol/m2) and the control (23.06 µmol/m2). This study presents an innovative approach combining short-chain PolyP with bacterial biostimulants to enhance nutrient availability and plant growth. By identifying and characterizing effective bacterial strains, it offers a sustainable alternative to conventional fertilizers. Full article
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