Plant Growth Promoting Bacteria and Mycorrhizas as Biocontrol and Biostimulats Agents

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

Deadline for manuscript submissions: 31 July 2024 | Viewed by 9947

Special Issue Editors


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Guest Editor
Postgraduate Program in Biotechnology Applied to Agriculture, Paranaense University, Umuarama 87502-210, PR, Brazil
Interests: plant growth promoting bacteria

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Guest Editor
Department of Microbiology, Biological Sciences Center, State University of Londrina, Londrina 86057-970, PR, Brazil
Interests: soil ecology; mycorrhiza; rhizophere; biological control

Special Issue Information

Dear Colleagues,

We are faced with increasing demand for food from an ever-growing world population and over one-third of the world’s crop yields are lost due to pests, diseases, and environmental stresses. To promote agricultural production in a sustainable way, i.e., to reduce the negative impact of agrochemicals, it is very important to exploit the functions of plant-associated microbes, such as plant growth-promoting bacteria (PGPB) and Mycorrhizal fungi. The plant microbiome may increase the genetic potential of its host, triggers the plant’s immune system, improves nutrient acquisition capacity and root architecture, and enhances environmental stress tolerance. An important part of the plant microbiome includes plant growth-promoting bacteria (PGPB), which can reside in the rhizosphere and phyllosphere or can colonize the plant’s interior tissues (endophytic bacteria). PGPB may promote plant growth directly by facilitating nutrient acquisition or modulating hormone levels or indirectly by reducing the negative effects of pathogens on plant growth and development.

In plants, mycorrhizal fungi play a fundamental role in maintaining the optimal vegetative state and in limiting damage from both stress and parasites. Mycorrhizal fungi acting as a physical barrier against root pathogens, produce several organic compounds that are able to interfere with the pathogenicity of bacteria and fungi at the soil level and beyond. Additionally, mycorrhizal fungi have been shown to play an important role in containing the damage from pathogens and pests, albeit with different mechanisms and improve the nutrient acquisition capacity of the plants. This Special Issue of Plants will highlight the activity of PGPB and mycorrhizal fungi in the biological control of plant parasites (pathogens and pests) and as biostimulate, agents, aiming to find applications in agriculture and environmental sustainability

Dr. Odair Alberton
Prof. Dr. Galdino Andrade
Guest Editors

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Keywords

  • abiotic and biotic stresses
  • arbuscular mycorrhiza
  • biocontrol
  • bioinoculants
  • biological control
  • biostimulate agents
  • mycorrhizal symbiosis
  • PGPB
  • plant–microbe interactions

Published Papers (7 papers)

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Research

15 pages, 1150 KiB  
Article
Growth and Phytochemistry of Cymbopogon citratus Stapf Inoculated with Plant Growth-Promoting Bacteria under Different Lead Levels
by Rayane Monique Sete da Cruz, Henrique Ferreira, Jonas Marcelo Jaski, Marcelo Coelho Esperança Vieira, Mariana Moraes Pinc, Silvia Graciele Hülse de Souza and Odair Alberton
Plants 2024, 13(7), 944; https://doi.org/10.3390/plants13070944 - 25 Mar 2024
Viewed by 950
Abstract
This study aimed to investigate the phytochemistry of lemongrass (Cymbopogon citratus) inoculated with Azospirillum brasilense and grown in lead (Pb)-contaminated soil to assess its responses to inoculation under different Pb levels. The experimental design was completely randomized in a 2 × 5 [...] Read more.
This study aimed to investigate the phytochemistry of lemongrass (Cymbopogon citratus) inoculated with Azospirillum brasilense and grown in lead (Pb)-contaminated soil to assess its responses to inoculation under different Pb levels. The experimental design was completely randomized in a 2 × 5 factorial scheme: two levels of A. brasilense (absence or presence) and five Pb levels. After four months of treatment, the following were analyzed: total and reducing sugars, total phenolic content, flavonoids, antioxidant activity, antioxidant enzymes, proline, and essential oil (EO) content and composition. Soil Pb levels and A. brasilense inoculation affected phytochemicals in lemongrass plants. Azospirillum inoculation reduced total sugars in the roots at all soil Pb levels, while increasing Pb levels favored a rise in sugar contents. There was an increase in flavonoid content in treatments associated with Pb and inoculated with A. brasilense. Antioxidant capacity was lower at lower Pb levels, regardless of bacterial inoculation. Enzymatic response was mainly affected by Pb concentrations between 50 and 100 mg kg−1 soil. EO content was influenced by soil Pb levels, with higher EO production at 500 mg Pb kg−1 soil and without A. brasilense inoculation. Overall, lemongrass cultivation in Pb-contaminated areas can be an alternative to phytoremediation and EO production for the industry. Full article
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17 pages, 3938 KiB  
Article
Characterization of Rhizosphere Microbial Diversity and Selection of Plant-Growth-Promoting Bacteria at the Flowering and Fruiting Stages of Rapeseed
by Mengjiao Wang, Haiyan Sun and Zhimin Xu
Plants 2024, 13(2), 329; https://doi.org/10.3390/plants13020329 - 22 Jan 2024
Viewed by 1046
Abstract
Plant rhizosphere microorganisms play an important role in modulating plant growth and productivity. This study aimed to elucidate the diversity of rhizosphere microorganisms at the flowering and fruiting stages of rapeseed (Brassica napus). Microbial communities in rhizosphere soils were analyzed via [...] Read more.
Plant rhizosphere microorganisms play an important role in modulating plant growth and productivity. This study aimed to elucidate the diversity of rhizosphere microorganisms at the flowering and fruiting stages of rapeseed (Brassica napus). Microbial communities in rhizosphere soils were analyzed via high-throughput sequencing of 16S rRNA for bacteria and internal transcribed spacer (ITS) DNA regions for fungi. A total of 401 species of bacteria and 49 species of fungi in the rhizosphere soil samples were found in three different samples. The composition and diversity of rhizosphere microbial communities were significantly different at different stages of rapeseed growth. Plant-growth-promoting rhizobacteria (PGPRs) have been widely applied to improve plant growth, health, and production. Thirty-four and thirty-one PGPR strains were isolated from the rhizosphere soil samples collected at the flowering and fruiting stages of rapeseed, respectively. Different inorganic phosphorus- and silicate-solubilizing and auxin-producing capabilities were found in different strains, in addition to different heavy-metal resistances. This study deepens the understanding of the microbial diversity in the rapeseed rhizosphere and provides a microbial perspective of sustainable rapeseed cultivation. Full article
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14 pages, 10683 KiB  
Article
Employing a Plant Probiotic Actinomycete for Growth Promotion of Lettuce (Lactuca sativa L. var. longifolia) Cultivated in a Hydroponic System under Nutrient Limitation
by Benyapa Kitwetch, Pharada Rangseekaew, Yupa Chromkaew, Wasu Pathom-Aree and Sirasit Srinuanpan
Plants 2023, 12(22), 3793; https://doi.org/10.3390/plants12223793 - 07 Nov 2023
Cited by 2 | Viewed by 1584
Abstract
The consumption of lettuce is associated with an increased risk of ingesting nitrate, a naturally occurring and potentially harmful compound that can have adverse effects on human health. Hydroponic cultivation systems serve as effective tools for regulating nutrient solutions and nitrogen availability, which [...] Read more.
The consumption of lettuce is associated with an increased risk of ingesting nitrate, a naturally occurring and potentially harmful compound that can have adverse effects on human health. Hydroponic cultivation systems serve as effective tools for regulating nutrient solutions and nitrogen availability, which are essential for controlling nitrate levels. However, the techniques for reducing nutrient levels need to be appropriately calibrated based on lettuce growth responses and their interactions with the environment and growing conditions. Previous studies have demonstrated that plant probiotic actinomycetes can alleviate nutritional stress in various crops. However, there is a noticeable gap in research concerning the effects of actinomycetes on hydroponically grown lettuce, particularly under nutrient-limiting conditions. This study aimed to evaluate the effectiveness of the actinomycete Streptomyces thermocarboxydus S3 in enhancing lettuce growth in a nutrient-restricted hydroponic system. The results indicated that the detrimental effects of nutrient stress on lettuce were mitigated by the inoculation of lettuce with S. thermocarboxydus S3. This mitigation was evident in various growth parameters, including leaf count, shoot length, and the fresh and dry weights of both shoots and roots. In the presence of nutritional stress, S. thermocarboxydus S3 likely mitigated the negative effects on lettuce by reducing hydrogen peroxide levels, presumably through the synthesis of H2O2-scavenging enzymes. Furthermore, S. thermocarboxydus S3 successfully survived and colonized lettuce roots. Therefore, the inoculation of lettuce with S. thermocarboxydus S3 offers significant advantages for promoting lettuce growth in nutrient-limited hydroponic systems. Full article
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12 pages, 1057 KiB  
Article
Impact Assessment of Lead-Tolerant Rhizobacteria to Improve Soil Health Using Indian Mustard (Brassica juncea) as an Indicator Plant
by Zain Mushtaq, Adnan Akhter, Hafiz Azhar Ali Khan, Waheed Anwar, Abeer Hashem, Graciela Dolores Avila-Quezada and Elsayed Fathi Abd_Allah
Plants 2023, 12(16), 3005; https://doi.org/10.3390/plants12163005 - 21 Aug 2023
Cited by 2 | Viewed by 1278
Abstract
Due to ongoing human activities, heavy metals are heavily accumulated in the soil. This leads to an increase in the discharge and the quick spread of heavy metal pollution in human settlements and natural habitats, having a disastrous effect on agricultural products. The [...] Read more.
Due to ongoing human activities, heavy metals are heavily accumulated in the soil. This leads to an increase in the discharge and the quick spread of heavy metal pollution in human settlements and natural habitats, having a disastrous effect on agricultural products. The current experiment was planned to evaluate the effect of lead-tolerant-plant-growth-promoting rhizobacteria (LTPGPR) on growth, yield, antioxidant activities, physiology, and lead uptake in the root, shoot, and seed of Indian mustard (Brassica juncea) in lead-amended soil. Three pre-isolated well-characterized lead-tolerant rhizobacterial strains—S10, S5, and S2—were used to inoculate seeds of Indian mustard grown at three different levels of lead (300 mg kg−1, 600 mg kg−1, 900 mg kg−1) contaminated soil. The experiment was designed following a completely randomized design (CRD) under factorial arrangements. Lead nitrate was used as a source of lead contamination. At harvesting, data regarding growth, physiology, yield per plant, antioxidant activities, malondialdehyde and proline content, and lead uptake in the root, shoot, and seed of Indian mustard were recorded. Results demonstrated that lead contamination at all levels significantly reduced the plant growth, yield, and physiological processes. Plants inoculated with lead-tolerant rhizobacteria showed a significant improvement in plant growth, yield, antioxidant activities, and physiological attributes and cause a valuable reduction in the malondialdehyde contents of Indian mustard in lead-contaminated soil. Moreover, plants inoculated with lead-tolerant rhizobacteria also showed an increment in lead uptake in the vegetative parts and a significant reduction of lead contents in the seed of Indian mustard. Full article
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11 pages, 2310 KiB  
Article
Mycorrhizal Fungal Effects on Plant Growth, Osmolytes, and CsHsp70s and CsPIPs Expression in Leaves of Cucumber under a Short-Term Heat Stress
by Xin-Ran Liu, Zi-Yi Rong, Xiao Tian, Abeer Hashem, Elsayed Fathi Abd_Allah, Ying-Ning Zou and Qiang-Sheng Wu
Plants 2023, 12(16), 2917; https://doi.org/10.3390/plants12162917 - 11 Aug 2023
Cited by 1 | Viewed by 1207
Abstract
Arbuscular mycorrhizal (AM) fungi enhance plant stress tolerance, but it is unclear whether AM fungi affect heat tolerance in cucumbers. This study aimed to analyze how an AM fungus, Diversispora versiformis, affected growth, chlorophyll, five osmolytes, and plasma membrane intrinsic proteins ( [...] Read more.
Arbuscular mycorrhizal (AM) fungi enhance plant stress tolerance, but it is unclear whether AM fungi affect heat tolerance in cucumbers. This study aimed to analyze how an AM fungus, Diversispora versiformis, affected growth, chlorophyll, five osmolytes, and plasma membrane intrinsic proteins (PIPs) and heat shock protein 70 (Hsp70) gene expression in cucumber leaves after a short-term (80 h) heat stress. Heat treatment significantly reduced root AM fungal colonization rate (0.26 folds). Heat treatment also distinctly suppressed plant height, stem diameter, and biomass, whereas AM fungal inoculation improved these growth variables as well as the chlorophyll index, with the benefit being more obvious under heat than under no-heat stress conditions. Heat treatment triggered differential changes in osmolytes (sucrose, fructose, and betaine) of inoculated and uninoculated cucumbers, whereas inoculation with AM fungus significantly raised leaf sucrose, fructose, glucose, betaine, and proline levels when compared to non-AM fungal inoculation. Heat treatment increased the expression of two (CsPIP1;6 and CsPIP2;1) of eight CsPIPs in inoculated and uninoculated plants, whereas AM fungal inoculation up-regulated the expression of CsPIP1;6, CsPIP2;1, and CsPIP2;6 under heat stress conditions. Hsp70s expressed differently in inoculated and uninoculated plants under heat versus no-heat stress, with 6 of 11 CsHsp70s down-regulated in inoculated plants. Under heat stress conditions, AM fungus only up-regulated CsHsp70-8 expression in 11 Hsp70s, while another eight CsHsp70s were down-regulated. Heat treatment and AM fungal inoculation both increased the expression of CsHsp70-8 and CsPIP1;6. It was concluded that AM fungus-inoculated cucumbers have high levels of growth, chlorophyll, and osmolytes under heat stress and do not require high CsPIPs and CsHsp70s expression to tolerate a short-term heat treatment. Full article
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15 pages, 7187 KiB  
Article
Characterization of Antagonistic Bacteria Paenibacillus polymyxa ZYPP18 and the Effects on Plant Growth
by Xiangying Li, Sujing Ma, Yuan Meng, Wei Wei, Chen Peng, Chunli Ling, Susu Fan and Zhenyu Liu
Plants 2023, 12(13), 2504; https://doi.org/10.3390/plants12132504 - 30 Jun 2023
Cited by 1 | Viewed by 1493
Abstract
Paenibacillus polymyxa is a plant growth–promoting rhizobacteria (PGPR) that has significant biocontrol properties. Wheat sheath blight caused by Rhizoctonia cerealis is a significant soil–borne disease of wheat that causes significant losses in wheat production, and the biological control against the disease has received [...] Read more.
Paenibacillus polymyxa is a plant growth–promoting rhizobacteria (PGPR) that has significant biocontrol properties. Wheat sheath blight caused by Rhizoctonia cerealis is a significant soil–borne disease of wheat that causes significant losses in wheat production, and the biological control against the disease has received extensive attention. P. polymyxa ZYPP18 was identified using morphological and molecular characterization. An antagonistic activity experiment verified that ZYPP18 inhibits the growth of R. cerealis on artificial growth media. A detached leaf assay verified that ZYPP18 inhibits the expansion of wheat sheath blight on the detached leaf. ZYPP18 has been found to possess plant growth–promoting properties, as well as the ability to solubilize phosphate and generate indole–3–acetic acid. Results from hydroponic experiments showed that wheat seedlings treated with ZYPP18 grew faster. Additionally, pot experiments and field experiments demonstrated that ZYPP18 effectively controls the occurrence of wheat sheath blight. ZYPP18 reduced the incidence of wheat sheath blight in wheat seedlings by 37.37% and 37.90%, respectively. The control effect of ZYPP18 on wheat sheath blight was 56.30% and 65.57%, respectively. These findings provide evidence that P. polymyxa ZYPP18 is an effective biological factor that can control disease and promote plant growth. Full article
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13 pages, 1452 KiB  
Article
Plant-Mediated Effects of Beneficial Microbes and a Plant Strengthener against Spider Mites in Tomato
by Konstantinos Samaras, Soultana Mourtiadou, Theodoros Arampatzis, Myrsini Kakagianni, Maria Feka, Felix Wäckers, Kalliope K. Papadopoulou, George D. Broufas and Maria L. Pappas
Plants 2023, 12(4), 938; https://doi.org/10.3390/plants12040938 - 18 Feb 2023
Cited by 2 | Viewed by 1573
Abstract
The two-spotted spider mite Tetranychus urticae is a polyphagous herbivore with a worldwide distribution, and is a serious pest in tomato and other crops. As an alternative to chemical pesticides, biological control with the release of natural enemies such as predatory mites represent [...] Read more.
The two-spotted spider mite Tetranychus urticae is a polyphagous herbivore with a worldwide distribution, and is a serious pest in tomato and other crops. As an alternative to chemical pesticides, biological control with the release of natural enemies such as predatory mites represent an efficient method to control T. urticae in many crops, but not in tomato. Other biological control agents, such as beneficial microbes, as well as chemical compounds, which can act as plant defense elicitors that confer plant resistance against pests and pathogens, may prove promising biological solutions for the suppression of spider mite populations in tomato. Here, we assessed this hypothesis by recording the effects of a series of fungal and bacterial strains and the plant strengthener acibenzolar-s-methyl for their plant-mediated effects on T. urticae performance in two tomato cultivars. We found significant negative effects on the survival, egg production and spider mite feeding damage on plants inoculated with microbes or treated with the plant strengthener as compared to the control plants. Our results highlight the potential of beneficial microbes and plant strengtheners in spider mite suppression in addition to plant disease control. Full article
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