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Advanced Research of Rhizosphere Microbial Activity—Series II

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A special issue of Agriculture (ISSN 2077-0472). This special issue belongs to the section "Agricultural Soils".

Deadline for manuscript submissions: 20 October 2024 | Viewed by 12348

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Special Issue Editors

Dr. Tibor Szili-Kovács

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Guest Editor

Centre for Agricultural Research, Institute for Soil Sciences, Herman O. út 15., 1022 Budapest, Hungary
Interests: soil biology; microbial ecology; sodic soils; karst soils; long-term experiments; restoration ecology
Special Issues, Collections and Topics in MDPI journals

Dr. Tünde Takács

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Guest Editor

Centre for Agricultural Research, Institute for Soil Sciences, Herman O. út 15., 1022 Budapest, Hungary
Interests: arbuscular mycorrhizal fungi (AMF); microbial inoculation; organic farming; long-term experiments; plant stress physiology; bioremediation/phytoremediation
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The rhizosphere is one of the most important hotspots in soils and it harbors a huge number of microbial species, including archaea, bacteria and fungi. Root exudates serve as carbon and energy sources for heterotrophic microbes and have selective power to shape the microbial communities around root systems. The microbial activity of the rhizosphere can be one or two orders of magnitude higher than that of the surrounding bulk soil, and it is also a very dynamic and sensitive system. Microbes in the rhizosphere can aid plant nutrition and water uptake and promote plant growth by hormone and siderophore production; in addition, they can protect plants against pathogenic microbes, while in certain conditions some of them also become pathogenic. Climate change, land use change and different management options pose challenges to evaluating soil health in connection with plant–microbe interactions, and the microbial activity of the rhizosphere can be detected and measured in several ways. This Special Issue welcomes newly developed methods, such as community-level physiological profiling, the measurement of enzyme activity—alone or together with microbiome diversity by next-generation DNA sequencing—and other methodical approaches focusing on the microbial activity of the rhizosphere in all types of agricultural soils, including grassland and pasture soils.

Dr. Tibor Szili-Kovács
Dr. Tünde Takács
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. Agriculture 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
microbial activity
functional diversity
community-level physiological profile
soil health
bacterial and fungal community
PGPR bacteria
root exudates
root colonization
mycorrhizal fungi

Published Papers (6 papers)

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Research

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10 pages, 644 KiB

Open AccessCommunication

The Effect of Combined Application of Biocontrol Microorganisms and Arbuscular Mycorrhizal Fungi on Plant Growth and Yield of Tomato (Solanum lycopersicum L.)

by Alaa Abdulkadhim A. Almuslimawi, Borbála Kuchár, Susana Estefania Araujo Navas, György Turóczi and Katalin Posta

Agriculture 2024, 14(5), 768; https://doi.org/10.3390/agriculture14050768 - 16 May 2024

Viewed by 275

Abstract

Sustainable plant production requires less use of synthetic chemicals in plant nutrition and protection. Microbial products are among the most promising substitutes for chemicals. With the increasing popularity and availability of such products, it has become obligatory to use different microbes together. The effect of this has been tested in several studies, but their results have sometimes been contradictory depending on the microbial strains tested and the mode of application. We tested the effect of two commercially available antagonists and Funneliformis mosseae alone and in combination on tomato. Mycorrhizal treatment increased plant growth and yield, both alone and combined with the antagonists; however, mycorrhizal root colonization was not influenced by the antagonist. This treatment also led to a slight decrease in the occurrence of Trichoderma spp. on tomato roots but did not impede the colonization of roots by the applied Trichoderma strain. Our result confirmed that Trichoderma asperellum (T34) and Streptomyces griseoviridis (K61) can be safely combined with arbuscular mycorrhizal fungi (AMF), namely with F. mosseae. Full article

(This article belongs to the Special Issue Advanced Research of Rhizosphere Microbial Activity—Series II)

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15 pages, 2699 KiB

Open AccessArticle

Microbial Biomass and Rhizosphere Soil Properties in Response to Heavy Metal-Contaminated Flooding

by Tibor Szili-Kovács and Tünde Takács

Agriculture 2024, 14(5), 756; https://doi.org/10.3390/agriculture14050756 - 13 May 2024

Viewed by 412

Abstract

Mining and metallurgy are the main sources of soil contamination with harmful metals, posing a significant threat to human health and ecosystems. River floodplains in the vicinity of metal mines or industrial plants are often subject to flooding with sediments containing heavy metals, which can be harmful to the soil ecosystem. This study aimed to investigate the microbial properties of the soil at a metal-contaminated site and to determine the significant relationships between the biological and chemical properties of the soil. The study site was located near the village of Gyöngyösoroszi, in the Mátra mountain region of Northwest Hungary. A phytoremediation experiment was conducted in a metal-polluted floodplain using willow and corn plantations. The soil basal respiration, substrate-induced respiration, soil microbial biomass carbon (MBC), acid phosphatase activities, and soil chemical properties were measured. The soil of the contaminated sites had significantly higher levels of As, Pb, Zn, Cu, Cd, and Ca, whereas the unpolluted sites had significantly higher levels of phosphorus and potassium. The substrate-induced respiration showed a positive correlation with MBC and negative correlations with the metabolic quotient (qCO₂). The soil plasticity index and phosphorus showed a positive correlation with MBC, whereas salinity and the presence of Cd, Pb, Zn, As, and Cu showed a negative correlation. Acid phosphomonoesterase activity negatively correlated with the plant-available phosphorus content and MBC, but was positively correlated with the contents of toxic elements, including cadmium, lead, zinc, arsenic, and copper. This study found a significant correlation between the qCO₂ and the toxic element content. This suggests that an enhanced metabolic quotient (qCO₂), together with a decreased MBC/SOC ratio, could be used to indicate the harmful effect of soil contamination by heavy metals in floodplain soils. Full article

(This article belongs to the Special Issue Advanced Research of Rhizosphere Microbial Activity—Series II)

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11 pages, 1233 KiB

Open AccessArticle

Growth Performance and Osmolyte Regulation of Drought-Stressed Walnut Plants Are Improved by Mycorrhiza

by Yue Wen, Li-Jun Zhou, Yong-Jie Xu, Abeer Hashem, Elsayed Fathi Abd_Allah and Qiang-Sheng Wu

Agriculture 2024, 14(3), 367; https://doi.org/10.3390/agriculture14030367 - 25 Feb 2024

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Abstract

This study aims to evaluate whether a selected arbuscular mycorrhizal fungus, Diversispora spurca, improves growth in drought-stressed walnut (Juglans regia L. cv. Qingxiang) plants and whether this improvement is associated with changes in osmolyte (fructose, glucose, sucrose, soluble protein, proline, and betaine) levels. After 60 days of soil drought treatment (50% of maximum field water-holding capacity), root D. spurca colonization rate and soil mycelium length decreased by 13.57% and 64.03%, respectively. Soil drought also inhibited the growth performance of aboveground (stem diameter, leaf number, leaf biomass, and stem biomass) and underground (root projected area, surface area, and average diameter) parts, with uninoculated plants showing a stronger inhibition than D. spurca-inoculated plants. D. spurca significantly increased these growth variables, along with aboveground part variables and root areas being more prominent under drought stress versus non-stress conditions. Although drought treatment suppressed the chlorophyll index and nitrogen balance index in leaves, mycorrhizal inoculation significantly increased these indices. Walnut plants were able to actively increase leaf fructose, glucose, sucrose, betaine, and proline levels under such drought stress. Inoculation of D. spurca also significantly increased leaf fructose, glucose, sucrose, betaine, proline, and soluble protein levels under drought stress and non-stress, with the increasing trend in betaine and soluble protein being higher under drought stress versus non-stress. Drought stress dramatically raised leaf hydrogen peroxide (H₂O₂) levels in both inoculated and uninoculated plants, while mycorrhizal plants presented significantly lower H₂O₂ levels, with the decreasing trend higher under drought stress versus non-stress. In conclusion, D. spurca symbiosis can increase the growth of drought-stressed walnut plants, associated with increased osmolyte levels and decreased H₂O₂ levels. Full article

(This article belongs to the Special Issue Advanced Research of Rhizosphere Microbial Activity—Series II)

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11 pages, 2404 KiB

Open AccessArticle

Serendipita indica: A Biostimulant Enhancing Low-Temperature Tolerance and Active Constituent Levels in Polygonum cuspidatum

by Junhao Shen and Yongqin Chen

Agriculture 2024, 14(1), 7; https://doi.org/10.3390/agriculture14010007 - 20 Dec 2023

Viewed by 800

Abstract

Polygonum cuspidatum is a traditional medicinal plant enriched with resveratrol and polydatin. However, low temperatures reduce the medicinal component contents of P. cuspidatum, and prolonged low temperatures also affect the growth and survival of P. cuspidatum at the seedling stage. It is unclear whether a culturable endophytic fungus Serendipita indica is able to enhance P. cuspidatum’s low-temperature tolerance and medicinal components. The objective of this study was to examine the biomass, leaf gas exchange, antioxidant enzyme activity, proline levels, medicinal constituent levels, and the expression of the resveratrol synthase (PcRS) and resveratrol-forming stilbene synthase 11 (PcRS11) genes of potted P. cuspidatum plants inoculated with S. indica at low temperatures (10 °C/6 °C, 12 h/12 h, day/night temperature). The six-week low-temperature treatment significantly reduced the root fungal colonization, biomass production, and leaf gas exchange variables, whereas S. indica inoculation significantly increased shoot and root biomass, photosynthetic rate, stomatal conductance, and transpiration rate at low temperatures. S. indica inoculation significantly increased superoxide dismutase and catalase activity as well as proline levels in leaves at low temperatures. The magnitude of root chrysophanol, emodin, polydatin, and resveratrol levels decreased by low temperatures was greater in uninoculated plants than in inoculated plants. Inoculation of S. indica, on the other hand, significantly increased the four medicinal component levels in roots at low temperatures, with a greater magnitude rise in chrysophanol, polydatin, and resveratrol at low temperatures than at suitable temperatures. The low-temperature treatment down-regulated the expression of PcRS and PcRS11 genes in roots, while S. indica up-regulated the expression of PcRS and PcRS11 genes at low temperatures. This implies that S. indica acts as a powerful microbial stimulant on P. cuspidatum to promote low-temperature resistance and medicinal component levels. Full article

(This article belongs to the Special Issue Advanced Research of Rhizosphere Microbial Activity—Series II)

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18 pages, 3056 KiB

Open AccessArticle

Effects of Altitude and Continuous Cropping on Arbuscular Mycorrhizal Fungi Community in Siraitia grosvenorii Rhizosphere

by Limin Yu, Zhongfeng Zhang, Longwu Zhou and Kechao Huang

Agriculture 2023, 13(8), 1548; https://doi.org/10.3390/agriculture13081548 - 2 Aug 2023

Cited by 3 | Viewed by 2572

Abstract

Siraitia grosvenorii, a medicinal plant with continuous cropping, is cultivated in southern China. Changes in the soil microbial community during continuous cropping can cause soil-borne diseases in S. grosvenorii. This experimental study aimed to determine the differences in the arbuscular mycorrhizal fungi (AMF) community structure and root colonization in the rhizosphere soil of S. grosvenorii with different continuous cropping years and altitudes. We tested three altitude gradients (low, 200–300 m; middle, 500–600 m; and high, 700–800 m) and four continuous cropping years (1, 2, 3, and 5 years). AMF colonization, along with AMF spore density, and the soil physicochemical properties of S. grosvenorii roots at different altitudes and continuous cropping years were determined. Illumina high-throughput sequencing was used to determine the molecular diversity of AMF in the rhizosphere of S. grosvenorii as they exhibited a symbiotic relationship. The AMF species in the rhizosphere soil of S. grosvenorii included 28 species of nine genera, including Glomus, Claroideoglomus, Acaulospora, Paraglomus, Ambispora, and so on. With an increasing altitude, the AMF colonization of S. grosvenorii roots increased significantly (p < 0.01); available phosphorus (AP) content was negatively correlated with AMF colonization (p < 0.01). Glomus and Paraglomus were the common dominant genera in the rhizosphere soil of S. grosvenorii planted for 2–5 years at a low altitude and 1 year at middle and high altitudes. The average relative abundance of Glomus increased with increasing continuous cropping years and altitude in the low-altitude and 1-year S. grosvenorii areas, respectively. Slightly acidic rhizosphere soil contributed to AMF colonization and improved the richness and diversity of the AMF community. Our results showed that altitude, AP, and pH are essential factors for predicting AMF infection and community changes in the S. grosvenorii rhizosphere. Here, Illumina high-throughput sequencing was used to study the species resources and community composition of mycorrhizal fungi in S. grosvenorii in the hilly areas of Guangxi, China. This study provides a theoretical basis for the application and practice of mycorrhizal fungi including the isolation and screening of dominant strains, inoculation of mycorrhizal fungi, and exploration of the effects of mycorrhizal fungi on the growth and active ingredients of medicinal plants. Full article

(This article belongs to the Special Issue Advanced Research of Rhizosphere Microbial Activity—Series II)

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Review

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21 pages, 1575 KiB

Open AccessReview

Rhizobia: A Promising Source of Plant Growth-Promoting Molecules and Their Non-Legume Interactions: Examining Applications and Mechanisms

by Sara Fahde, Said Boughribil, Badreddine Sijilmassi and Ahmed Amri

Agriculture 2023, 13(7), 1279; https://doi.org/10.3390/agriculture13071279 - 21 Jun 2023

Cited by 12 | Viewed by 7101

Abstract

For over a century, the scientific community has had a comprehensive understanding of how rhizobia can promote the growth of legumes by forming nitrogen fixing nodules. Despite this knowledge, the interaction of rhizobia with non-legumes has remained largely ignored as a subject of study until more recent decades. In the last few years, research has shown that rhizobia can also associate with non-legume roots, which ultimately leads to the stimulation of growth through diverse direct and indirect mechanisms. For example, rhizobia can enhance growth through phytohormones production, the improvement of plant nutrient uptake, such as the solubilization of precipitated phosphorus, the production of siderophores to address iron needs, and also the reduction of ethylene levels through the ACC deaminase enzyme to cope with drought stress. Additionally, rhizobia can improve, indirectly, non-legume growth through biocontrol of pathogens and the induction of systemic resistance in the host plant. It can also increase root adherence to soil by releasing exopolysaccharides, which regulate water and soil nutrient movement. The objective of this review is to assess and analyze the existing knowledge and information regarding the mechanisms through which rhizobia promote the growth of non-legumes. By conducting a comprehensive analysis of these findings, we aim to gain new insights into the development of Rhizobium/non-legume interactions. Full article

(This article belongs to the Special Issue Advanced Research of Rhizosphere Microbial Activity—Series II)

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