The Hidden World within Plants 2.0

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

Deadline for manuscript submissions: closed (31 July 2023) | Viewed by 9597

Special Issue Editors

Research Unit Induced Resistance and Plant Bioprotection, University of Reims, EA 4707 USC INRAe 1488, SFR Condorcet FR CNRS 3417, 51100 Reims, France
Interests: plant-microbe interaction; stress physiology plants responses to biotic and abiotic stress; crop protection; biological control
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

This Special Issue is the continuation of our previous special issue "The Hidden World within Plants".

Plants offer an exceptional ecosystem for microorganisms, including members of phyla as diverse as viruses, bacteria, oomycetes, fungi, and eukaryotic protozoans, which intimately interact with plant cells and tissues with different levels of dependence ranging from mutualism to pathogenicity.

Some of these microorganisms cause harm by employing diverse strategies to attack plants and impair plant growth and reproduction, others improve the plant growth through different physiological activities that may have profound effects on the growth and/or health of plants. On the other hand, beneficial microorganisms are able to improve the plant fitness through different physiological activities that may have a profound effect on their growth and/or health. They are also able to compete with pathogens for nutrients and niches or exert antagonism through antimicrobial compounds. These beneficial microbes are also able to interfere with pathogen signals or trigger the plant host immunity.

Why do some microbes attack only certain plants? Is it because those plants are genetically less well-armed to repel pathogen attacks, or because the pathogens have the required arsenals to invade plant tissues? Why are some microbes pathogenic, and others not? How are beneficial microorganisms able to modulate the plant’s signaling to trigger the plant immunity?

These are some questions that will be targeted in this Issue. We encourage the contribution of high-quality and review articles related to different aspects of plant-microbe interactions.

Prof. Dr. Philippe Jeandet
Prof. Dr. Essaid Ait Barka
Prof. Dr. Rachid Lahlali
Guest Editors

Manuscript Submission Information

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Keywords

  • beneficial microorganisms
  • pathogens
  • plant immunity
  • plant-microbe interaction
  • virulence factors

Published Papers (6 papers)

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Editorial

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5 pages, 210 KiB  
Editorial
The Hidden World within Plants 2.0
Microorganisms 2023, 11(12), 2903; https://doi.org/10.3390/microorganisms11122903 - 01 Dec 2023
Viewed by 562
Abstract
Interactions between plants and microorganisms are complex, with some microorganisms causing damage by employing strategies that hinder plant growth and reproduction, while others positively influence plant growth through various physiological activities [...] Full article
(This article belongs to the Special Issue The Hidden World within Plants 2.0)

Research

Jump to: Editorial

13 pages, 986 KiB  
Article
Endophytic Seed-Associated Bacteria as Plant Growth Promoters of Cuban Rice (Oryza sativa L.)
Microorganisms 2023, 11(9), 2317; https://doi.org/10.3390/microorganisms11092317 - 14 Sep 2023
Cited by 4 | Viewed by 1011
Abstract
Cuban rice cultivars INCA LP-5 and INCA LP-7 are widely distributed in Cuba and Caribbean countries. Although there are studies about rhizospheric bacteria associated with these cultivars, there are no reports about their seed-associated bacteria. This study aimed to isolate endophytic bacteria from [...] Read more.
Cuban rice cultivars INCA LP-5 and INCA LP-7 are widely distributed in Cuba and Caribbean countries. Although there are studies about rhizospheric bacteria associated with these cultivars, there are no reports about their seed-associated bacteria. This study aimed to isolate endophytic bacteria from rice seeds and select those with the greatest plant growth-promoting traits. A total of nineteen bacterial strains from the genera Pantoea, Bacillus, Paenibacillus, and Pseudomonas were isolated from the husk and endosperm of rice seeds. The strains Pantoea sp. S5-1, Pseudomonas sp. S5-38, and Pseudomonas sp. S7-1 were classified as the most promissory to increase rice growth as they demonstrated the presence of multiple plant growth-promoting traits such as the production of auxins, phosphate, and potassium solubilization, the production of siderophores, and the inhibition of the phytopathogen Pyricularia oryzae. The inoculation of strains of Pantoea sp. and Pseudomonas spp. in rice improves the height, root length, fresh weight, and dry weight of the shoot and root after 21 days post-inoculation in hydroponic assays. This study constitutes the first report on Cuban rice cultivars about the presence of endophytes in seeds and their potential to promote seedling growth. Pantoea sp. S5-1, Pseudomonas sp. S5-38, and Pseudomonas sp. S7-1 were selected as the more promising strains for the development of bio-stimulators or bio-inoculants for Cuban rice crops. Full article
(This article belongs to the Special Issue The Hidden World within Plants 2.0)
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16 pages, 2810 KiB  
Article
Studies Using Mutant Strains of Azospirillum brasilense Reveal That Atmospheric Nitrogen Fixation and Auxin Production Are Light Dependent Processes
Microorganisms 2023, 11(7), 1727; https://doi.org/10.3390/microorganisms11071727 - 30 Jun 2023
Cited by 2 | Viewed by 1019
Abstract
As the use of microbial inoculants in agriculture rises, it becomes important to understand how the environment may influence microbial ability to promote plant growth. This work examines whether there are light dependencies in the biological functions of Azospirillum brasilense, a commercialized [...] Read more.
As the use of microbial inoculants in agriculture rises, it becomes important to understand how the environment may influence microbial ability to promote plant growth. This work examines whether there are light dependencies in the biological functions of Azospirillum brasilense, a commercialized prolific grass-root colonizer. Though classically defined as non-phototrophic, A. brasilense possesses photoreceptors that could perceive light conducted through its host’s roots. Here, we examined the light dependency of atmospheric biological nitrogen fixation (BNF) and auxin biosynthesis along with supporting processes including ATP biosynthesis, and iron and manganese uptake. Functional mutants of A. brasilense were studied in light and dark environments: HM053 (high BNF and auxin production), ipdC (capable of BNF, deficient in auxin production), and FP10 (capable of auxin production, deficient in BNF). HM053 exhibited the highest rate of nitrogenase activity with the greatest light dependency comparing iterations in light and dark environments. The ipdC mutant showed similar behavior with relatively lower nitrogenase activity observed, while FP10 did not show a light dependency. Auxin biosynthesis showed strong light dependencies in HM053 and FP10 strains, but not for ipdC. Ferrous iron is involved in BNF, and a light dependency was observed for microbial 59Fe2+ uptake in HM053 and ipdC, but not FP10. Surprisingly, a light dependency for 52Mn2+ uptake was only observed in ipdC. Finally, ATP biosynthesis was sensitive to light across all three mutants favoring blue light over red light compared to darkness with observed ATP levels in descending order for HM053 > ipdC > FP10. Full article
(This article belongs to the Special Issue The Hidden World within Plants 2.0)
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15 pages, 6595 KiB  
Article
Evaluation of the Antifungal Activity of Endophytic and Rhizospheric Bacteria against Grapevine Trunk Pathogens
Microorganisms 2022, 10(10), 2035; https://doi.org/10.3390/microorganisms10102035 - 14 Oct 2022
Cited by 13 | Viewed by 1927
Abstract
Grapevine trunk diseases (GTDs) are caused by multiple unrelated fungal pathogens, and their management remains difficult worldwide. Biocontrol is an attractive and sustainable strategy given the current need for a cleaner viticulture. In this study, twenty commercial vineyards were sampled across California to [...] Read more.
Grapevine trunk diseases (GTDs) are caused by multiple unrelated fungal pathogens, and their management remains difficult worldwide. Biocontrol is an attractive and sustainable strategy given the current need for a cleaner viticulture. In this study, twenty commercial vineyards were sampled across California to isolate endophytic and rhizospheric bacteria from different grapevine cultivars with the presence and absence of GTD symptoms. A collection of 1344 bacterial isolates were challenged in vitro against Neofusicoccum parvum and Diplodia seriata, from which a subset of 172 isolates exerted inhibition levels of mycelial growth over 40%. Bacterial isolates were identified as Bacillus velezensis (n = 154), Pseudomonas spp. (n = 12), Serratia plymuthica (n = 2) and others that were later excluded (n = 4). Representative isolates of B. velezensis, P. chlororaphis, and S. plymuthica were challenged against six other fungal pathogens responsible for GTDs. Mycelial inhibition levels were consistent across bacterial species, being slightly higher against slow-growing fungi than against Botryosphaeriaceae. Moreover, agar-diffusible metabolites of B. velezensis strongly inhibited the growth of N. parvum and Eutypa lata, at 1, 15, and 30% v/v. The agar-diffusible metabolites of P. chlororaphis and S. plymuthica, however, caused lower inhibition levels against both pathogens, but their volatile organic compounds showed antifungal activity against both pathogens. These results suggest that B. velezensis, P. chlororaphis and S. plymuthica constitute potential biocontrol agents (BCAs) against GTDs and their application in field conditions should be further evaluated. Full article
(This article belongs to the Special Issue The Hidden World within Plants 2.0)
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15 pages, 2460 KiB  
Article
Potential for Biological Control of Pythium schmitthenneri Root Rot Disease of Olive Trees (Olea europaea L.) by Antagonistic Bacteria
Microorganisms 2022, 10(8), 1635; https://doi.org/10.3390/microorganisms10081635 - 12 Aug 2022
Cited by 9 | Viewed by 2059
Abstract
Several diseases affect the productivity of olive trees, including root rot disease caused by Pythium genera. Chemical fungicides, which are often used to manage this disease, have harmful side effects on humans as well as environmental components. Biological management is a promising control [...] Read more.
Several diseases affect the productivity of olive trees, including root rot disease caused by Pythium genera. Chemical fungicides, which are often used to manage this disease, have harmful side effects on humans as well as environmental components. Biological management is a promising control approach that has shown its great potential as an efficient eco-friendly alternative to treating root rot diseases. In the present study, the antagonistic activity of ten bacterial isolates was tested both in vitro and in planta against Pythium schmitthenneri, the causal agent of olive root rot disease. These bacterial isolates belonging to the genera Alcaligenes, Pantoea, Bacillus, Sphingobacterium, and Stenotrophomonas were chosen for their potential antimicrobial effects against many pathogens. Results of the in vitro confrontation bioassay revealed a high reduction of mycelial growth exceeding 80%. The antifungal effect of the volatile organic compounds (VOCs) was observed for all the isolates, with mycelial inhibition rates ranging from 28.37 to 70.32%. Likewise, the bacterial cell-free filtrates showed important inhibition of the mycelial growth of the pathogen. Overall, their efficacy was substantially affected by the nature of the bacterial strains and their modes of action. A greenhouse test was then carried out to validate the in vitro results. Interestingly, two bacterial isolates, Alcaligenes faecalis ACBC1 and Bacillus amyloliquefaciens SF14, were the most successful in managing the disease. Our findings suggested that these two antagonistic bacterial isolates have promising potential as biocontrol agents of olive root rot disease. Full article
(This article belongs to the Special Issue The Hidden World within Plants 2.0)
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23 pages, 4090 KiB  
Article
Application of Indigenous Rhizospheric Microorganisms and Local Compost as Enhancers of Lettuce Growth, Development, and Salt Stress Tolerance
Microorganisms 2022, 10(8), 1625; https://doi.org/10.3390/microorganisms10081625 - 11 Aug 2022
Cited by 15 | Viewed by 2323
Abstract
This study aimed to mitigate salt stress effects on lettuce by using native biostimulants (arbuscular mycorrhizal fungi (M, consortium), plant growth-promoting rhizobacteria (R, Z2, and Z4 strains), and compost (C)) applied alone or in combination under salinity stress (0, 50, and 100 mM [...] Read more.
This study aimed to mitigate salt stress effects on lettuce by using native biostimulants (arbuscular mycorrhizal fungi (M, consortium), plant growth-promoting rhizobacteria (R, Z2, and Z4 strains), and compost (C)) applied alone or in combination under salinity stress (0, 50, and 100 mM NaCl). Physiological, biochemical, nutritional, mycorrhizal, growth, and soil characteristics were evaluated. Results revealed that growth and physiological traits were negatively affected by salinity. However, mycorrhizal colonization was enhanced under 100 mM NaCl after compost application. The applied biostimulants, particularly M and/or R improved the salinity tolerance of lettuce by increasing the dry biomass by 119% and 113% under 100 mM NaCl, respectively, for M and MR treatments. Similarly, MR enhanced stomatal conductance (47%), water content (260%), total chlorophyll (130%), phosphorus content (363%), and reduced the malondialdehyde (54%) and hydrogen peroxide (78%) compared to the control. Moreover, peroxidase activity (76%) and sugar content (36%) were enhanced by CM treatment, while protein (111%) and proline (104%) contents were significantly boosted by R treatment under 100 mM NaCl. Furthermore, glomalin content was enhanced by MR treatment under severe salinity. In conclusion, the applied biostimulants alone or in combination might help lettuce to tolerate salt stress and enhance its production in degraded areas. Full article
(This article belongs to the Special Issue The Hidden World within Plants 2.0)
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