Rhizosphere Soil Of Plants Research Articles

In vitro Assessment of Pseudomonas sp. Strain FCBB-2 for Effective Plant Growth Promotion and Antifungal Activity under Drought Stress

The significance of plant growth-promoting rhizobacteria (PGPR) in plant adaptation to harsh conditions is still unknown. Native bacteria were isolated from rhizospheric soils and tested for growth-promoting qualities as well as antagonistic capabilities against phytopathogenic fungi in this investigation. All the Pseudomonas spp. strains were characterized for in vitro drought tolerance in trypticase soy broth supplemented with different concentrations of polyethylene glycol (PEG6000). Out of nine isolates, only one strain was able to tolerate maximum level of stress (−1.03 MPa) and is further screened for plant growth promoting (PGP) properties under non-stress and drought stress conditions. Strain FCBB-2 isolated from cluster bean plant rhizosphere soil, showed multiple PGP activities such as indole-3-acetic acid (IAA) production, siderophore, hydrogen cyanide (HCN) production and exopolysaccharide (EPS) production and antifungal activity under non-stress and drought stress conditions against various plant fungal pathogens like Fusarium oxysporum, Macrophomina phaseolina, Alternaria alternata, Sclerotium hydrophilium, Pythium aphanidermatum and Rhizoctonia solani. The strain FCBB-2 was identified as Pseudomonas aeruginosa based on morphological and 16S rRNA gene sequence analysis and the sequence was submitted to NCBI GenBank under the accession number KT311003.

Responses of Soil PhoC and PhoD Gene Microbial Communities to the Combined Application of Biochar with Chemical Fertilizers and Organic Fertilizers

Soil microorganisms have an important influence on the transformation of soil nutrients. As functional genes encoding phosphatase, phoC and phoD provide effective means for detecting the types, abundance, and community structure of microorganisms in the environment, and studying the changes in the diversity of phoC and phoD gene microbial communities in the rhizosphere and non-rhizosphere soil of the plant rhizosphere and non-rhizosphere soil under the treatment of chemical fertilizer and organic fertilizer combined with biochar can provide a scientific basis for the agricultural utilization of biochar. In this study, corn stalks and rice husk stalks were used as test materials, and the pot experiment method was used to set the following treatments:control (CK), traditional fertilization (F), chemical fertilizer+20 t·hm-2 rice husk biochar (FP), chemical fertilizer+10 t·hm-2 rice husk biochar+10 t·hm-2 corn biochar (FPM), organic fertilizer+20 t·hm-2 rice husk biochar (PP), and fresh organic fertilizer+20 t·hm-2 rice husk biochar (NPP). The community structure of phoC and phoD genes in rhizosphere and non-rhizosphere soil was analyzed by using T-RFLP and fluorescence quantitative PCR technology to clarify the response characteristics of phoC and phoD genes to the addition of biochar. The results showed that:① In rhizosphere soil and non-rhizosphere soil, the phoD gene community structure was more complicated than that of phoC, and the number of end restriction fragments of the phoC gene increased after chemical fertilizer and organic fertilizer were combined with biochar. ② The combined application of biochar with chemical fertilizer and organic fertilizer reduced the copy number of the phoC gene in non-rhizosphere soil compared with that in the CK. Compared with that in the CK, the copy number in the FP, FPM, PP, and NPP treatments decreased by 9.18%, 11.46%, 10.97%, and 13.76%, respectively. Organic fertilizer combined with biochar increased the copy number of the phoD gene in rhizosphere soil by 2.48% and 5.16% in the PP and NPP treatments, respectively, compared with that in the CK. ③ Total phosphorus in the soil was the main factor affecting the phoC gene microbial community structure in non-rhizosphere soil (P<0.01), whereas the phoC gene microbial community structure in rhizosphere soil was regulated by a variety of environmental factors. pH was the most critical factor affecting the phoD gene copy number, and the copy number of phoD gene was significantly correlated with soil nitrate nitrogen and pH. The combined application of biochar with chemical fertilizers and organic fertilizers can promote the growth and reproduction of microorganisms that function in soil phosphorus conversion, which is of great significance for improving the utilization of phosphorus fertilizers.

Links between Arbuscular Mycorrhizal Fungal and Nitrogen-Fixing Bacterial Communities from Plant Rhizosphere Soils in the Karst Region of Southwest China

Links between Arbuscular Mycorrhizal Fungal and Nitrogen-Fixing Bacterial Communities from Plant Rhizosphere Soils in the Karst Region of Southwest China

Metagenomic analysis of rhizosphere microbiome provides insights into occurrence of iron deficiency chlorosis in field of Asian pears

BackgroundFe-deficiency chlorosis (FDC) of Asian pear plants is widespread, but little is known about the association between the microbial communities in the rhizosphere soil and leaf chlorosis. The leaf mineral concentration, leaf subcellular structure, soil physiochemical properties, and bacterial species community and distribution had been analysed to gain insights into the FDC in Asian pear plant.ResultsThe total Fe in leaves with Fe-deficiency was positively correlated with total K, Mg, S, Cu, Zn, Mo and Cl contents, but no differences of available Fe (AFe) were detected between the rhizosphere soil of chlorotic and normal plants. Degraded ribosomes and degraded thylakloid stacks in chloroplast were observed in chlorotic leaves. The annotated microbiome indicated that there were 5 kingdoms, 52 phyla, 94 classes, 206 orders, 404 families, 1,161 genera, and 3,043 species in the rhizosphere soil of chlorotic plants; it was one phylum less and one order, 11 families, 59 genera, and 313 species more than in that of normal plant. Bacterial community and distribution patterns in the rhizosphere soil of chlorotic plants were distinct from those of normal plants and the relative abundance and microbiome diversity were more stable in the rhizosphere soils of normal than in chlorotic plants. Three (Nitrospira defluvii, Gemmatirosa kalamazoonesis, and Sulfuricella denitrificans) of the top five species (N. defluvii, G. kalamazoonesis, S. denitrificans, Candidatus Nitrosoarchaeum koreensis, and Candidatus Koribacter versatilis). were the identical and aerobic in both rhizosphere soils, but their relative abundance decreased by 48, 37, and 22%, respectively, and two of them (G. aurantiaca and Ca. S. usitatus) were substituted by an ammonia-oxidizing soil archaeon, Ca. N. koreensis and a nitrite and nitrate reduction related species, Ca. K. versatilis in that of chlorotic plants, which indicated the adverse soil aeration in the rhizosphere soil of chlorotic plants. A water-impermeable tables was found to reduce the soil aeration, inhibit root growth, and cause some absorption root death from infection by Fusarium solani.ConclusionsIt was waterlogging or/and poor drainage of the soil may inhibit Fe uptake not the amounts of AFe in the rhizosphere soil of chlorotic plants that caused FDC in this study.

Effect of Combined Application of Biochar with Chemical Fertilizer and Organic Fertilizer on Soil Phosphatase Activity and Microbial Community

To study changes in phosphatase activity, we examined the diversity of phoC and phoD gene microbial communities in the rhizosphere and non-rhizosphere soil of plants under the treatment of chemical fertilizer and organic fertilizer combined with biochar. These results can provide a certain theoretical guidance for the conversion of insoluble phosphorus in the soil phosphorus pool to the inorganic phosphate ion that can be absorbed by plant roots and also provide a certain experimental basis for the improvement of the availability of phosphorus in the soil and the agricultural utilization of biochar. In this study, corn stalks and rice husk stalks were used as test materials, and the pot experimental method was adopted using the following treatments:set control (CK), traditional fertilization (F), chemical fertilizer+20 t·hm-2 rice husk biochar (FP), chemical fertilizer+10 t·hm-2rice husk biochar+10 t·hm-2 corn biochar (FPM), organic fertilizer+20 t·hm-2 rice husk biochar (PP), and fresh organic fertilizer+20 t·hm-2 rice husk biochar (NPP). We determined the rhizosphere and non-rhizosphere soil acid phosphatase (ACP) activity and alkaline phosphatase (ALP) activity and used T-RFLP technology to analyze the diversity of phoC and phoD genes in order to clarify the impact of biochar on the micro-ecosystem formed by the plants, soil, and microorganisms. The results showed that:① the ALP and ACP activities of each treatment in the non-rhizosphere soil were lower than that of CK. In the rhizosphere soil, the ALP activity was significantly increased after the combined application of chemical fertilizer and organic fertilizer with biochar, and the ACP activity in the rhizosphere soil was higher than that in the non-rhizosphere soil. ② The combined application of biochar with chemical fertilizers and organic fertilizers significantly increased the diversity of phoC and phoD genes communities in rhizosphere and non-rhizosphere soils (P<0.05); the diversity and richness of microbial communities in rhizosphere soil were higher than that in non-rhizosphere soils. ③ ACP activity was negatively correlated with phoC gene microbial community, and most ALP activity was positively correlated with phoD microbial community.

Simultaneous Nitrogen Removal and Plant Growth Promotion Using Salt-‍tolerant Denitrifying Bacteria in Agricultural Wastewater.

Excess nitrate (NO3–) and nitrite (NO2–) in surface waters adversely affect human and environmental health. Bacteria with the ability to remove nitrogen (N) have been isolated to reduce water pollution caused by the excessive use of N fertilizer. To obtain plant growth-promoting rhizobacteria (PGPR) with salt tolerance and NO3–-N removal abilities, bacterial strains were isolated from plant rhizosphere soils, their plant growth-promoting effects were evaluated using tomato in plate assays, and their NO3–-N removal abilities were tested under different salinity, initial pH, carbon source, and agriculture wastewater conditions. The results obtained showed that among the seven strains examined, five significantly increased the dry weight of tomato plants. Two strains, Pseudomonas stutzeri NRCB010 and Bacillus velezensis NRCB026, showed good plant growth-promoting effects, salinity resistance, and NO3–-N removal abilities. The maximum NO3–-N removal rates from denitrifying medium were recorded by NRCB010 (90.6%) and NRCB026 (92.0%) at pH 7.0. Higher NO3–-N removal rates were achieved using glucose or glycerin as the sole carbon source. The total N (TN) removal rates of NRCB010 and NRCB026 were 90.6 and 66.7% in farmland effluents, respectively, and 79.9 and 81.6% in aquaculture water, respectively. These results demonstrate the potential of NRCB010 and NRCB026 in the development of novel biofertilizers and their use in reducing N pollution in water.

Advances in the studies on symbiotic arbuscular mycorrhizal fungi of traditional Chinese medicinal plants

Arbuscular mycorrhizal (AM) fungi reside in the rhizosphere and form mutualistic associations with plant roots. They promote photosynthesis, improve stress resistance, and induce secondary metabolite biosynthesis in host medicinal plants. The AM fungi that are symbiotic with medicinal plants comprise a wide array of species and have abundant germplasm resources. Though research on the AM fungi in medicinal plants began relatively recently, it has nonetheless become an investigative hot spot. Several scholars have explored the diversity and the growth-promoting effects of mycorrhizal fungi in hundreds of medicinal plants. Current research on symbiotic AM fungi in medicinal plants has focused mainly on the effects of inoculating host plants with symbiotic mycorrhizal fungi. However, research on the symbiotic AM fungi in medicinal plants continues to expand, and further study is required to determine the mechanisms by which AM fungi interact with host plants. This paper introduces the diversity of symbiotic AM fungi of medicinal plants and the effects of AM fungi on rhizosphere soil of medicinal plants, including soil structure, microbiota, enzyme activities, etc. This review focuses on the effects of AM fungi on medicinal plants, including antioxidant enzyme systems, drought resistance, nutrient absorption profiles of macro- and micronutrients, accumulation of secondary metabolites such as terpenes, phenolic compounds, and nitrogenous compounds, and prevention of diseases. This review is expected to provide a reference for the application of AM fungi in medicinal plant cultivation, biological control, resource conservation, and the sustainable development of the traditional Chinese medicine industry.

Sustainable agriculture practice using Trichoderma and nonpathogenic Fusarium to control Vanilla Shoot Rot disease

Vanilla shoots rot (VShR) disease in Indonesia is generally detrimental to the nursery, but due to the extreme climate change, the VShR disease attacks the vanilla plants grown in the field increases. This paper describes the development of research on the effectiveness of Trichoderma sp. and nonpathogenic Fusarium (FusNP) in controlling VShR, starting from isolation and identification of antagonistic fungi, in vitro testing to research results in the field, compared with the use of synthetic fungicides. The nonpathogenic fungi isolated from the rhizosphere soil of healthy vanilla plants were dominated by Trichoderma spp and nonpathogenic fusarium because they used selective media. The study showed that Trichoderma sp. and FusNP were quite effective in controlling the disease VShR in the field, similar to the effectiveness of synthetic fungicides, whereas the incidence of control was 32%. The use of synthetic fungicides intensively causes environmental pollution in the form of pesticide residues on leaves and fruit vanilla.

A Systematic Review of Terrestrial Plant Invasion Mechanisms Mediated by Microbes and Restoration Implications

Terrestrial invasive plant species continue to wreak havoc on a global economic and ecological scale. With the advent of climate change and pending future catastrophes, the spread of resilient invasive plants will only increase exponentially. Here, the search continues for a better understanding of the below-ground microbially driven mechanisms involved in plant invasion where other above-ground mechanisms have been exhausted. Microbes govern the world around us and interact with every living and non-living facet of the world. To reinforce the important underpinnings of the role of microorganisms in plant invasion, a systematic review of recently published articles was undertaken. Using the ScienceDirect database, five (5) search queries were used to generate 1221 research articles. After a two-step reduction was made based on relevance of the articles, a final total of 59 articles were retrieved. An additional 18 relevant articles were also assessed through the PubMed database for analysis to account for other invasive plants. Thirty-seven (37) invasive species were investigated where soil physiochemical and microbial community structure changes were most prevalent (32% & 39% respectively) while enhanced mutualism, allelopathy and pathogen accumulation were reported less (16%, 10% & 3% respectively). In all invasive species assessed, the impact on plant invasion and inability of the native plants to compete was due to specific microbial associations of the invasive plant or disruption of the soil microbial community. This microbial community shift coincided with changes in physiochemical properties of the soil and the subsequent negative soil feedback for native plants. There is still an expanding potential for the use of biocontrol agents to aid restoration once the underpinnings of biotic resistance and enemy release are understood in a microbial and physiochemical context. The active and functional microbial community structure of the invasive plant rhizosphere and adjacent soil in its native and non-native region can offer a better inference of how they can be controlled using novel-below ground biocontrol methods.

甘草根际土壤微生物群落对长期连作的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 甘草根际土壤微生物群落对长期连作的响应 DOI: 10.5846/stxb202008122101 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31360047）；科技基础性工作专项（2015FY111200） Response of rhizosphere soil microbial community to long-term continuous cropping of Glycyrrhiza glabra L. Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:光果甘草连年种植所引起的甘草产量下降、植株发育不良、根腐病频发严重影响甘草产业的持续发展，造成了重大的经济损失。然而，其机制却并不清楚。应用下一代测序技术，对未种植过光果甘草的土壤（Control），生长1a （Gg1）和生长5a （Gg5）光果甘草的根际土壤行16S rDNA和18S rDNA ITS测序，并对比分析了甘草根际土壤和对照组之间，以及不同种植年限甘草根际土壤之间的微生物群落结构差异，以期探究光果甘草连作障碍的原因。结果表明，光果甘草连作增加了根际土壤细菌群落的丰富度，降低了真菌群落的丰富度（P>0.05）。主坐标分析显示，光果甘草的根际土壤微生物组成与对照组之间存在显著差异，并且光果甘草的种植年限显著地影响了根际土壤微生物的群落组成。在门水平上，光果甘草连作显著地增加了真菌Blastocladiomycota和Mortierellomycota的相对多度（P<0.05）。在属水平上，光果甘草连作显著地降低了有益细菌Arthrobacter和Pseudomona及有益真菌Naganishia的相对多度，而增加了病原真菌Fusarium和Thanatephorus的相对多度。由此推测，光果甘草根际土壤微生物群落结构的改变，以及有益微生物相对多度的降低和病原微生物相对多度的增加可能是导致光果甘草发生连作障碍的重要原因之一。 Abstract:The continuous cropping of Glycyrrhiza glabra L. caused the decline of G. glabra yield, poor plant development and frequent root rot, which seriously affected the development of G. glabra industry and caused serious economic losses. However, their mechanisms were unknown. The 16S rDNA and 18S rDNA internal transcribed spacer sequences of soil without plant cover (Control) and rhizosphere soil of 1- (Gg1) and 5-year-old G. glabra (Gg5) in fields were determined by next generation sequencing technology. Differences in microbial community structures among the three soil types were analyzed to explain obstacles associated with continuous G. glabra cropping. The results show that monoculture of G. glabra respectively increased and reduced bacterial and fungal community richness in rhizosphere soil over time (P>0.05). Principal co-ordinates analysis illustrated that there were obvious differences between the rhizosphere soil microbial composition of G. glabra and the control group, and the planting years of G. glabra observably affected the microbial community composition in rhizosphere soil. At the phyla level, monoculture of G. glabra observably enhanced the relative abundance of Blastocladiomycota and Mortierellomycota. At the genus level, monoculture of G. glabra observably decreased the relative abundance of beneficial microbes Arthrobacter, Pseudomonas and Naganishia, and enhanced the relative abundance of pathogenic fungi Fusarium and Thanatophorus. Therefore, variances in the microbial community structures in the rhizosphere soil of G. glabra, especially the respectively decreased and increased beneficial and pathogenic microbes, might explain obstacles with continuously cropped G. glabra. 参考文献 相似文献 引证文献

Biodiversity of arbuscular mycorrhizal fungi in plant roots and rhizosphere soil from different arid land environment of Qatar.

Recently more attention has been observed toward the role of arbuscular mycorrhizal fungi (AMF) in plant growth. Qatar belongs to the Arabian Gulf region with hot and dry climatic conditions. The study aims to investigate the species composition and abundance of AMF in Qatar, rhizosphere soil samples, and roots of plants from 12 families and 8 different locations. The AMF were identified based on the sequencing of the polymerase chain reaction (PCR) product of the amplified conserved ITS region. The reported AMF infection rate was found to vary with location and plant species. Tamarix aphylla recorded the highest AMF infection rate (100%), followed by Blepharis ciliaris (98%) and Sporobolus ioclados (92%). AMF spore counts ranged from 29.3 spores in Blepharis ciliaris to 643 spores/100 g soil in Fagonia indica. No correlation was detected between colonization rate and spore counts. While all AMF identified at species levels were reported in other regions, new species are still expected since some were identified only at higher taxonomic levels. Claroideoglomus drummondii and Rhizophagus irregularis were the most widespread while Claroideoglomus claroideum and Diversispora aurantia were the least present. Our results fill the gap of knowledge of AMF in the region and opens new research toward its future applications for sustainable agriculture.

Antifungal activity of Trichoderma atroviride against Fusarium oxysporum.f.sp.lycopersici causing wilt disease of tomato

Fusarium oxysporum f. sp. lycopersici causing tropical wilt of tomato is a destructive phytopathogen. To study bio efficacy of fungal bio agents, fifteen isolates of Trichoderma species were isolated from rhizosphere soil of healthy tomato plants. Among the isolates, TA12 showed higher antagonistic efficacy against the pathogen. Upon analysis of the rDNA of internal transcribed spacers (ITS) and molecular data, the isolate was identified as Trichoderma atroviride. The in vitro antagonistic assessment indicated that the T. atroviride isolate caused significant inhibition of F. oxysporum f. sp. lycopersici. Trichoderma atroviride (TA12) showed antagonistic activity against F. oxysporum with mycelial inhibition of 71.25%. The culture filtrates of Trichoderma atroviride exhibited its antifungal activity against F. oxysporum with a suppression of 77.77%. Moreover, the ethyl acetate extracts of T. atroviride TA12 showed the highest antifungal potency against F. oxysporum f. sp. lycopersici. The main bioactive constituents of T. atroviride were 6-pentyl - 2H-pyran-2-one, quinoline, phenol, 2-(6-hydrazino-3-pyridazinyl) and heptadecane. In conclusion, the isolate TA12 could be exploited to develop an effective biocontrol management practice for combating Fusarium wilt disease of Fusarium oxysporum f.sp. lycopersici in tomato.

Nitrogen uptake and biochemical activity in maize rhizosphere during growth on acidic and neutralized soils

This work aimed to understand the effects of liming and no tillage on the pH stability and inorganic N uptake in the rhizosphere of maize plants on an acidic soil depleted in organic matter, reclaimed by liming and no tillage in a long-term field trial. We analyzed the inorganic N dynamics, respiration, microbial biomass and enzyme activities in the rhizosphere and bulk soil of maize plants grown in rhizoboxes on acidic soil under conventional tillage or no tillage management with or without liming and amendment (sugar beet foam and red gypsum). Analysis of inorganic N in the rhizosphere showed preferential NH4+-N uptake and reduced NO3−-N uptake by maize plant grown on acidic non tilled soil. With few exceptions, soil respiration, microbial biomass and enzyme activities were higher in the maize rhizosphere than in bulk soil. Soil respiration and enzyme activities were generally higher in the rhizosphere of non-tilled soils, whereas microbial biomass was higher in the rhizosphere of the amended soils. The study, based on rhizobox, showed effectiveness of sugar beet lime and red gypsum in the neutralization of the pH value in the rhizosphere during the early stages of maize growth, and the limited capacity of the plant to neutralize the acidic soil pH value in the rhizosphere of the non-amended soil. Positive interactive effects of tillage and liming were observed on the biochemical activity in the plant rhizosphere that could contribute to explain the positive effects of this management practice on the soil fertility observed at field scale on the long term.

Screening and Identification of Trichoderma Strains isolated from Natural Habitats in China with Potential Agricultural Applications.

Trichoderma spp. are widely distributed in natural habitats and have been evaluated as a potential biocontrol agent (BCA) for disease control and plant growth promotion. In this study, 1308 Trichoderma strains were obtained from the plant rhizosphere soil, above-ground plants, and decaying wood from natural habitats in China. Among them, 49 Trichoderma strains showed a good inhibitory effect, especially against Botrytis cinerea, Fusarium oxysporum, and Colletotrichum gloeosporioides with inhibition rate above 85% in the dual culture test. Among these 49 strains, the 13 strains with broad-spectrum inhibitory effects also significantly promoted the seed germination of five crops (rice, cucumber, tomato, melon, and pakchoi) and root growth of four crop seedlings (watermelon, tomato, eggplant, and chili). Furthermore, these strains showed effective colonization in the rhizosphere and root of cucumber. Trichoderma strains SC012 and NX043 showed the highest chitinase and β-1,3-glucanase activity among all strains. Based on the morphological characterization and phylogenetic analysis of the nuclear ribosomal internal transcribed spacer (ITS) and translation elongation factor 1 (tef1), twelve Trichoderma strains were identified as Trichoderma asperellum and one as Trichoderma afroharzianum. This study suggests that the 13 Trichoderma strains are promising BCAs and could be developed as biofertilizers and biological pesticides for agricultural applications.

Compositional and functional comparison on the rhizosphere microbial community between healthy and Sclerotium rolfsii-infected monkshood (Aconitum carmichaelii) revealed the biocontrol potential of healthy monkshood rhizosphere microorganisms

Southern blight of monkshood (Aconitum carmichaelii Debx.) caused by Sclerotium rolfsii is one of the most destructive diseases causing tuber rot in the monoculture system. No studies have explored the differences of rhizosphere microbial communities between healthy and S. rolfsii-infected monkshood plants. Further, it remains unknown whether the rhizosphere microorganisms are associated with plant resistance to S. rolfsii infection. Therefore, in this study, the relationship between rhizosphere microorganisms and plant health of monkshood was assessed after S. rolfsii infection. High-throughput sequencing and culture-dependent methods were used to analyze the rhizosphere microbiome of healthy and diseased monkshood plants. Petri dish assays were performed to determine the effects of 10 dominant isolates from healthy or diseased samples on the growth of S. rolfsii hyphae and melon seedlings (as a model plant to test the plant growth promotion effect of these isolates). Two synthetic communities were constructed to verify the effects of dominant isolates on the growth and resistance of monkshood plants in pots after infection. The results showed that there were pronounced structural and functional differences in the bacterial and fungal communities between the rhizosphere soils of healthy and diseased plants. The diluted culture filtrates of some dominant isolates from diseased samples (such as Humicola fuscoatra and Fusarium commune) either promoted hyphal growth of S. rolfsii or inhibited seedling growth of melon; the synthetic community showed an inhibitory effect on monkshood growth and leaf L-phenylalanin ammonia-lyase activity, resulting in early and severe symptoms. Conversely, the diluted culture filtrates of some dominant isolates from healthy samples (such as Trichoderma hamatum and Streptomyces fungicidicus) inhibited S. rolfsii growth while promoting melon growth; the synthetic community elicited an improvement of monkshood growth and defense enzyme activity, resulting in mild symptoms. The results provide new insight into the role of rhizosphere microorganisms in plant health and open new avenues for controlling southern blight of monkshood.

PHOSPHORUS BIOTRANSFORMATION IN ROOT ZONE OF CORN PLANTS UNDER ACTION OF AHROBACTERYN AND MINERAL FERTILIZERS

Objective. To determine the intensity of phosphorus biotransformation in the root zone of corn plants under the action of the microbial preparation Ahrobacteryn and various rates of mineral fertilizers. Methods. Field experiment (on leached chernozem), microbiological (accounting for the number of phosphate-mobilizing bacteria in the rhizosphere of corn plants, biochemical (determination of phosphatase activity, the degree of mobility of phosphates in the rhizosphere soil of plants), statistical. Results. It was found that during the growing season, the number of bacteria that hydrolyze mineral phosphorus compounds and organic soil phosphates increases in the rhizosphere soil of corn plants under the influence of the microbial preparation Ahrobacteryn. Given the features of the influence of mineral fertilizers on the development of phosphate-mobilizing bacteria in the rhizosphere soil of corn plants, it is optimal to use fertilizers in doses not exceeding N90P90K90. At the same time, phosphatase activity of the rhizosphere soil reaches the highest values in the flowering phase; in the phase of milk-wax ripeness of corn grain, the parameters are significantly reduced due to the slowdown in the absorption of phosphorus by plants. The effect of inoculation increases the degree of phosphate mobility in the rhizosphere soil of plants, which is expressed in a decrease in their content due to increased uptake by plants. In the phase of milk-wax ripeness, the mobility of phosphates decreases from 0.42 (in the control without fertilizers) to 0.23 mg P2O5/dm3 of soil solution, which indicates increased absorption of phosphorus by plants. Conclusion. Under the influence of Ahrobacteryn, the processes of phosphorus transformation in the root zone of corn plants are activated, the number of phosphate-mobilizing bacteria increases, phosphatase activity improves and the degree of phosphate mobility, which has an effect on the absorption of phosphorus by plants. As a result, phosphorus removal increases with a crop yield from 51.2 (in the control without fertilizers) to 83.4 kg/ha (with Ahrobacteryn), the efficiency of phosphorus plant nutrition after introduction of N90P90K90 is 62.9 %.

In Vitro Study of Biocontrol Potential of Rhizospheric Pseudomonas aeruginosa against Pathogenic Fungi of Saffron (Crocus sativus L.).

Plant rhizosphere soil contains a large number of plant-growth promoting rhizobacteria, which can not only resist the invasion of pathogenic microorganisms and protect plants from damage, but also promote the growth and development of plants. In this study, Pseudomonas aeruginosa strain YY322, isolated and screened from the rhizosphere soil of saffron (Crocus sativus L.), was found through a plate confrontation experiment to show highly effectual and obvious antagonistic activity against the pathogens of saffron, including Fusarium oxysporum, Fusarium solani, Penicillium citreosulfuratum, Penicillium citrinum and Stromatinia gladioli. In addition, the volatile organic compounds of strain YY322 had great antagonistic activity against these pathogens. Observation under a scanning electron microscope and transmission electron microscope reflected that strain YY322 had a significant effect on the hyphae and conidia of F. oxysporum and F. solani. Through the detection of degrading enzymes, it was found that P. aeruginosa can secrete protease and glucanase. The plant growth promoting performance was evaluated, finding that strain YY322 had the functions of dissolving phosphorus, fixing nitrogen, producing siderophore and producing NH3. In addition, whole genome sequencing analysis indicated that the YY322 genome is comprised of a 6,382,345-bp circular chromosome, containing 5809 protein-coding genes and 151 RNA genes. The P. aeruginosa YY322 genome encodes genes related to phenazine (phzABDEFGIMRS), hydrogen cyanide(HCN) (hcnABC), surfactin (srfAA), salicylate (pchA), biofilm formation (flgBCDEFGHIJKL, motAB, efp, hfq), and colonization (minCDE, yjbB, lysC). These results collectively indicated the role of P. aeruginosa YY322 in plant growth enhancement and biocontrol mechanisms. All in all, this study provides a theoretical basis for P. aeruginosa as the PGPR of saffron, paving the way for the subsequent development and utilization of microbial fertilizer.

Inter-Kingdom Networks of Canola Microbiome Reveal Bradyrhizobium as Keystone Species and Underline the Importance of Bulk Soil in Microbial Studies to Enhance Canola Production.

The subterranean microbiota of plants is of great importance for plant growth and health, as root-associated microbes can perform crucial ecological functions. As the microbial environment of roots is extremely diverse, identifying keystone microorganisms in plant roots, rhizosphere, and bulk soil is a necessary step towards understanding the network of influence within the microbial community associated with roots and enhancing its beneficial elements. To target these hot spots of microbial interaction, we used inter-kingdom network analysis on the canola growth phase of a long-term cropping system diversification experiment conducted at four locations in the Canadian Prairies. Our aims were to verify whether bacterial and fungal communities of canola roots, rhizosphere, and bulk soil are related and influenced by diversification of the crop rotation system; to determine whether there are common or specific core fungi and bacteria in the roots, rhizosphere, and bulk soil under canola grown in different environments and with different levels of cropping system diversification; and to identify hub taxa at the inter-kingdom level that could play an important ecological role in the microbiota of canola. Our results showed that fungi were influenced by crop diversification, which was not the case on bacteria. We found no core microbiota in canola roots but identified three core fungi in the rhizosphere, one core mycobiota in the bulk soil, and one core bacterium shared by the rhizosphere and bulk soil. We identified two bacterial and one fungal hub taxa in the inter-kingdom networks of the canola rhizosphere, and one bacterial and two fungal hub taxa in the bulk soil. Among these inter-kingdom hub taxa, Bradyrhizobium sp. and Mortierella sp. are particularly influential on the microbial community and the plant. To our knowledge, this is the first inter-kingdom network analysis utilized to identify hot spots of interaction in canola microbial communities.

Clover Species Specific Influence on Microbial Abundance and Associated Enzyme Activities in Rhizosphere and Non-Rhizosphere Soils

Legume cultivation, especially the clover species, has shown promoting effects on soil biological properties. However, the ways in which various clover species contribute to beneficial plant-rhizosphere soil interactions have remained neglected in the past. Therefore, we performed a field experiment to assess and compare the species-specific influence of five different clover species on plant traits, microbial soil health indicators, namely soil enzymes, microbial biomass and abundance and their potential nutrient cycling abilities under rhizosphere and non-rhizosphere soils. For this, soil samples from bulk soil and rhizosphere of each clover species were collected and analyzed for soil enzymes including β-glucosidase, arylsulfatase, phosphatase, N-acetyl-β-D-glucosaminidase, and urease and microbial communities’ abundance. Results revealed that the soil biological properties were more affected in the rhizosoil than in the bulk soil, although the individual legume crop variants differed in the rate and extent of the differential impact on either rhizosoil or bulk soil. The most significantly affected species-specific properties were ammonium oxidizing bacteria and phosphorus-solubilizing microbiota in the rhizosoil of white clover and alsike clover variants, whereas the least impact was exerted by sweet clover. The biological properties of rhizosoil showed a significant effect on the plant qualitative and quantitative properties. We further detected antagonism among N and P + K transfer from the rhizosoil to plants, which influenced above ground and root biomass. Overall, these results suggest that the positive effects of clover species cultivation on rhizosphere soil properties are species specific.

High Maintenance of Rhizosphere Soil C and N Equilibrium Regardless of Plant Species or Species Traits

Factors affecting the deposition of carbon and nitrogen into the rhizosphere soil have important implications for natural and managed ecosystems. These include the invasiveness of plants, extent to which ecosystems sequester soil carbon, through to regulation of N flow within and from agricultural ecosystems. This study determined if the close elemental ratios often measured in soils are evident within the highly active rhizosphere compartment, or rather potentially emerge to a conserved ratio (over time) from different initial rhizosphere states. Toward this, we assessed the rhizosphere C and N content (and C:N ratio) of 37 plant species; these were further grouped into the categories provenance (native or exotic to New Zealand), form (forb, grass, shrub, or tree), root-based nitrogen fixation symbiosis (+/– N-fixation), or mycorrhization type. Furthermore, the potential nitrification rate (PNR) among the plant rhizosphere soils was quantified to explore relationships between nitrate formation and the total C and C:N ratio. Mycorrhization status, provenance, and form had no significant influence on nutrient status nor PNR in rhizosphere soil samples (p &amp;gt; 0.05). However, total C and total N were significantly increased in the rhizosphere of N-fixing species (p &amp;lt; 0.02). These increased in proportion, with the C:N remaining constant for both groups (~12.24; p = 0.79). Rhizosphere PNR did not vary with categories of plants tested and had no correlation to rhizosphere total C, total N, nor C:N ratio (p &amp;gt; 0.3 for all). Overall, this study showed that conservation of nutrient ratios often measured in soils are present within the rhizosphere, where initial inputs of C and N enter the soil ecosystems. With the exception of N-fixing plant species, rhizosphere soils retain remarkably high conservation in C, N, C:P, and PNR among key groupings.