Colonize Plant Roots Research Articles

Functional and genomic analyses of plant growth promoting traits in Priestia aryabhattai and Paenibacillus sp. isolates from tomato rhizosphere

This study investigated plant growth-promoting (PGP) mechanisms in Priestia aryabhattai VMYP6 and Paenibacillus sp. VMY10, isolated from tomato roots. Their genomes were initially assessed in silico through various approaches, and these observations were then compared with results obtained in vitro and in vivo. Both possess genes associated with the production of siderophores, indole acetic acid (IAA) and cytokinins (CKs), all of which have been shown to promote plant growth. The two strains were able to produce these compounds in vitro. Although both genomes harbor genes for phosphorus solubilization, only VMY10 demonstrated this ability in vitro. Genes linked to flagellar assembly and chemotaxis were identified in the two cases. Both strains were able to colonize plant roots, even though VMYP6 lacked motility and no flagella were observed microscopically. In the greenhouse, tomato plants inoculated with the strains showed increased biomass, leaf area, and root length. These findings underscore the importance of integrating in vitro assays, genomic analyses, and plant trials to gain a comprehensive insight into the PGP mechanisms of rhizobacteria like VMYP6 and VMY10. Such insight may contribute to improving the selection of strains used as biofertilizers in tomato, a major crop worldwide.

The effectiveness of arbuscular mycorrhizal fungal species (Funneliformis mosseae, Rhizophagus intraradices, and Claroideoglomus etunicatum) in the biocontrol of root and crown rot pathogens, Fusarium solani and Fusarium mixture in pepper.

This study evaluated the effectiveness of arbuscular mycorrhizal fungi (AMF) species, including Funneliformis mosseae (FM), Rhizophagus intraradices (RI), Claroideoglomus etunicatum (CE), and a Mycorrhizal mix (MM) comprising these three species, on pepper plants (Capsicum annuum L.) inoculated with two isolates of Fusarium solani (48-F. solani and 18-F. solani) and two isolates of Fusarium mix (50-F. mixture and 147-F. mixture). Analysis of variance (ANOVA)-Tukey statistics revealed that the effects of AMF inoculations on morphological parameters, disease severity, root colonization, and total spore numbers in pathogen-infected plants varied significantly depending on the AMF species and pathogen group. AMF colonization significantly reduced disease severity, with disease inhibition (DI) reaching up to 58%, depending on the specific pathogen. However, there were a few instances where the application of AMF did not lead to a reduction in disease severity. Single AMF species were more effective in enhancing the growth of pathogen-treated host plants and suppressing disease compared to the mixed AMF. The mixed AMF was only more effective in balancing pathogen-induced decreases in plant nutrients (Copper (Cu), Magnesium (Mg), Zinc (Zn), and Phosphorus (P)). Among the compared mycorrhizae, C. etunicatum (CE) was the most effective in disease suppression due to its relatively more positive effects on plant root structure, increasing root fresh weight by up to 49% in the CE+pathogen plant group compared to the control group. Root colonization rates were generally higher in plants treated with both mycorrhiza and pathogens compared to plants treated with mycorrhiza alone. Overall, the curative effects of AMFs on plants following pathogen application varied concurrently with disease severity rates caused primarily by pathogens. AMFs demonstrated greater efficacy in combating 18-F. solani, which causes less severe plant disease. However, the effectiveness of AMFs was comparatively lower against 48-F. solani and 147-F. mix., which cause more severe plant disease. This indicates that the efficacy of AMFs varies depending on the specific strain of Fusarium solani, with better results observed against strains that cause less severe plant disease.

A pipeline for validation of Serendipita indica effector-like sRNA suggests cross-kingdom communication in the symbiosis with Arabidopsis.

Bidirectional communication between pathogenic microbes and their plant hosts via small (s)RNA-mediated cross-kingdom RNA interference (ckRNAi) is a key element for successful host colonisation. Whether mutualistic fungi of the Serendipitaceae family, known for their extremely broad host range, use sRNAs to colonize plant roots is still under debate. To address this question, we developed a pipeline to validate the accumulation, translocation, and activity of fungal sRNAs in post-transcriptional silencing of Arabidopsis thaliana genes. Using stem-loop RT-qPCR, we detected the expression of a specific set of Serendipita indica (Si)sRNAs, targeting host genes involved in cell wall organization, hormonal signalling regulation, immunity, and gene regulation. To confirm the gene silencing activity of these sRNAs in plant cells, SisRNAs were transiently expressed in protoplasts. Stem-loop PCR confirmed sRNAs expression and accumulation, while qPCR validated post-transcriptional gene silencing of their predicted target genes. Furthermore, Arabidopsis ARGONAUTE 1 immunoprecipitation (AtAGO1-IP) revealed the loading of fungal SisRNAs into the plant RNAi machinery, suggesting the translocation of SisRNA from the fungus into root cells. In conclusion, this study provides a blueprint for rapid selection and analysis of sRNA effectors and further supports the model of cross-kingdom communication in the Sebacinoid symbiosis.

In vitro efficacy of plant growth-promoting rhizobacteria isolated from ginger (Zingiber officinale) rhizosphere for biological control of plant pathogens

The excessive use of synthetic chemical pesticides in controlling plant diseases poses significant challenges to sustainable agriculture. As an environmentally friendly alternative, plant growth-promoting rhizobacteria (PGPR) have shown promise by colonizing plant roots and forming symbiotic relationships that enhance plant growth and suppress plant pathogens. Research on the isolation of PGPR from ginger (Zingiber officinale) rhizosphere in Indonesia remains limited, highlighting the need for further exploration to support genetic resource conservation and sustainable agricultural practices. This study aims to evaluate the potential of PGPR isolates from Z. officinale rhizosphere in Semarang, Indonesia, as biological control agents. Isolates were characterized based on morphology, biochemical traits, and their antagonistic activity against fungal pathogens, including Fusarium oxysporum, Colletotrichum sp., and Alternaria sp. A total of 14 isolates were obtained, exhibiting diverse morphological, biochemical, and antagonistic properties. Among them, isolate 235A2 demonstrated the highest potential as a biological control agent, with capabilities including phosphate solubilization, nitrogen fixation, protease enzyme production, and significant inhibition rates of F. oxysporum (13.79%), Colletotrichum sp. (55.56%), and Alternaria sp. (35.61%) in vitro. These findings underscore the potential of PGPR as a sustainable alternative for biological control of plant pathogens, supporting both enhanced plant productivity and environmental conservation.

Herbicide-treated soil as a reservoir of beneficial bacteria: microbiome analysis and PGP bioinoculants in maize

BackgroundHerbicides are integral to agricultural weed management but can adversely affect non-target organisms, soil health, and microbiome. We investigated the effects of herbicides on the total soil bacterial community composition using 16S rRNA gene amplicon community profiling. Further, we aimed to identify herbicide-tolerant bacteria with plant growth-promoting (PGP) capabilities as a mitigative strategy for these negative effects, thereby promoting sustainable agricultural practices.ResultsA bacterial community analysis explored the effects of long-term S-metolachlor application on soil bacterial diversity, revealing that the herbicide’s impact on microbial communities is less significant than the effects of temporal factors (summer vs. winter) or agricultural practices (continuous maize cultivation vs. maize-winter wheat rotation). Although S-metolachlor did not markedly alter the overall bacteriome structure in our environmental context, the application of enrichment techniques enabled the selection of genera such as Pseudomonas, Serratia, and Brucella, which were rare in metagenome analysis of soil samples. Strain isolation revealed a rich source of herbicide-tolerant PGP bacteria within the culturable microbiome fraction, termed the high herbicide concentration tolerant (HHCT) bacterial culture collection.Within the HHCT collection, we isolated 120 strains that demonstrated significant in vitro PGP and biocontrol potential, and soil quality improvement abilities. The most promising HHCT isolates were combined into three consortia, each exhibiting a comprehensive range of plant-beneficial traits. We evaluated the efficacy and persistence of these multi-strain consortia during 4-week in pot experiments on maize using both agronomic parameters and 16S rRNA gene community analysis assessing early-stage plant development, root colonization, and rhizosphere persistence. Notably, 7 out of 10 inoculated consortia partners successfully established themselves and persisted in the maize root microbiome without significantly altering host root biodiversity. Our results further evidenced that all three consortia positively impacted both seed germination and early-stage plant development, increasing shoot biomass by up to 47%.ConclusionsHerbicide-treated soil bacterial community analysis revealed that integrative agricultural practices can suppress the effects of continuous S-metolachlor application on soil microbial diversity and stabilize microbiome fluctuations. The HHCT bacterial collection holds promise as a source of beneficial bacteria that promote plant fitness while maintaining herbicide tolerance.

Desert-adapted plant growth-promoting pseudomonads modulate plant auxin homeostasis and mitigate salinity stress.

By providing adaptive advantages to plants, desert microorganisms are emerging as promising solutions to mitigate the negative and abrupt effects of climate change in agriculture. Among these, pseudomonads, commonly found in soil and in associationwith plants' root system, have been shown to enhance plant tolerance to salinity and drought, primarily affecting root system architecture in various hosts. However, a comprehensive understanding of how these bacteria affect plant responses at the cellular, physiological and molecular levels is still lacking. In this study, we investigated the effects of two Pseudomonas spp. strains, E102 and E141, which were previously isolated from date palm roots and have demonstrated efficacy in promoting drought tolerance in their hosts. These strains colonize plant roots, influencing root architecture by inhibiting primary root growth while promoting root hair elongation and lateral root formation. Strains E102 and E141 increased auxin levels in Arabidopsis, whereas this effect was diminished in IAA-defective mutant strains, which exhibited reduced IAA production. In all cases, the effectiveness of the bacteria relies on the functioning of the plant auxin response and transport machinery. Notably, such physiological and morphological changes provide an adaptive advantage to the plant, specifically under stress conditions such as salinity. Collectively, this study demonstrates that by leveraging the host's auxin signalling machinery, strains E102 and E141 significantly improve plant resilience to abiotic stresses, positioning them as potential biopromoters/bioprotectors for crop production and ecosystem restoration in alignment with Nature-based Solution approaches.

Transcriptomic responses of Solanum tuberosum cv. Pirol to arbuscular mycorrhiza and potato virus Y (PVY) infection

Arbuscular mycorrhizal fungi (AMF) serve as both plant symbionts and allies in resisting pathogens and environmental stresses. Mycorrhizal colonization of plant roots can influence the outcomes of plant-pathogen interactions by enhancing specific host defense mechanisms. The transcriptional responses induced by AMF in virus-infected plants remain largely unexplored. In the presented study, we employed a comprehensive transcriptomic approach and qPCR to investigate the molecular determinants underlying the interaction between AMF and potato virus Y (PVY) in Solanum tuberosum L. Our primary goal was to identify the symbiosis- and defense-related determinants activated in mycorrhizal potatoes facing PVY. Through a comparative analysis of mRNA transcriptomes in experimental treatments comprising healthy and PVY-infected potatoes colonized by two AMF species, Rhizophagus regularis or Funneliformis mosseae, we unveiled the overexpression of genes associated with mycorrhiza, including nutrient exchange, lipid transfer, and cell wall remodeling. Furthermore, we identified several differentially expressed genes upregulated in all mycorrhizal treatments that encoded pathogenesis-related proteins involved in plant immune responses, thus verifying the bioprotective role of AMF. We investigated the relationship between mycorrhiza levels and PVY levels in potato leaves and roots. We found accumulation of the virus in the leaves of mycorrhizal plants, but our studies additionally showed a reduced PVY content in potato roots colonized by AMF, which has not been previously demonstrated. Furthermore, we observed that a virus-dependent reduction in nutrient exchange could occur in mycorrhizal roots in the presence of PVY. These findings provide an insights into the interplay between virus and AMF.

Pseudomonas rhodesiae HAI-0804 suppresses Pythium damping off and root rot in cucumber by its efficient root colonization promoted by amendment with glutamate.

Plant diseases caused by soil-borne fungi and oomycetes significantly reduce yield and quality of many crops in the agricultural systems and are difficult to control. We herein examine Pseudomonas rhodesiae HAI-0804, a bacterial biological control agent that was originally developed for control of bacterial diseases on the surface of vegetables, and assessed its efficacy at controlling soil-borne diseases caused by oomycetes. Strain HAI-0804 did not exhibit detectable antibiotic activity toward Pythium ultimum, a causal agent of damping-off and root rot; however, it effectively protected against Pythium damping-off and root rot in cucumber. Exogenous glutamate enhanced the efficacy of biocontrol, the production of siderophore pyoverdine, root colonization in cucumber plants, and the ratio of biofilm formation to planktonic cells. The epiphytic fitness of strain HAI-0804 appears to contribute to plant protection efficacy against a broad spectrum of pathogens for both above-ground plant parts and the rhizosphere.

Enhancing the Phytoremediation of Heavy Metals by Plant Growth Promoting Rhizobacteria (PGPR) Consortium: A Narrative Review.

Heavy metal pollution has become a significant concern as the world continues to industrialize, urbanize, and modernize. Heavy metal pollutants impede the growth and metabolism of plants. The bioaccumulation of heavy metals in plants may create chlorophyll antagonism, oxidative stress, underdeveloped plant growth, and reduced photosynthetic system. Finding practical solutions to protect the environment and plants from the toxic effects of heavy metals is essential for long-term sustainable development. The direct use of suitable living plants for eliminating and degrading metal pollutants from ecosystems is known as phytoremediation. Phytoremediation is a novel and promising way to remove toxic heavy metals. Plant growth-promoting rhizobacteria (PGPR) can colonize plant roots and help promote their growth. Numerous variables, such as plant biomass yield, resistance to metal toxicity, and heavy metal solubility in the soil, affect the rate of phytoremediation. Phytoremediation using the PGPR consortium can speed up the process and increase the rate of heavy metal detoxification. The PGPR consortium has significantly increased the biological accumulation of various nutrients and heavy metals. This review sheds light on the mechanisms that allow plants to uptake and sequester toxic heavy metals to improve soil detoxification. The present review aids the understanding of eco-physiological mechanisms that drive plant-microbe interactions in the heavy metal-stressed environment.

Influence of Enhanced Synthesis of Exopolysaccharides in Rhizobium ruizarguesonis and Overproduction of Plant Receptor to these Compounds on Colonizing Activity of Rhizobia in Legume and Non-Legume Plants and Plant Resistance to Phytopathogenic Fungi.

Rhizobial exopolysaccharides (EPS) may provide stabilization of membranes against external factors, as well as improved surface adhesion, but their role in interaction with legume and non-legume plants is still far from understanding. In this work, the transcriptional regulator RosR of Rhizobium ruizarguesonis, which regulates the synthesis of EPS, was overproduced in a pHC60 plasmid and expressed in the RCAM 1026 strain. This resulted in an improved production of EPS by this recombinant strain. Comparative analysis of the inoculation of pea Pisum sativum plants with R. ruizarguesonis pHC60-rosR and strain carrying the empty plasmid revealed an essential increase in the number of nodules, root length and biomass in plants inoculated with this EPS-overproducing strain. It demonstrates that the enhanced EPS synthesis by rhizobia may stimulate plant root colonization and subsequent nodule formation in pea plants. The influence of enhanced EPS synthesis in rhizobia on colonizing activity was also estimated in non-legume plant tomato Solanum lycopersicum. Our findings shown the increased colonization of the root surface and stimulation of the shoot biomass of inoculated plants. Inoculation of pea and tomato with EPS-overproducing rhizobial strain essentially increased plant resistance to phytopathogenic fungi Fusarium culmorum and F. oxysporum in both legume and non-legume plants, demonstrating a significant biocontrol effect of this recombinant strain. Furthermore, we have identified the PsLYK10 gene that encodes a putative EPS receptor in P. sativum, although no significant effect of PsLYK10 overexpression on nodulation in legume (pea P. sativum) and colonization of roots of non-legume plants by rhizobia was found compared to enhanced production of EPS by rhizobia.

The biology and chemistry of a mutualism between a soil bacterium and a mycorrhizal fungus

Arbuscular mycorrhizal (AM) fungi (e.g., Rhizophagus species) recruit specific bacterial species in their hyphosphere. However, the chemical interplay and the mutual benefit of this intricate partnership have not been investigated yet, especially as it involves bacteria known as strong producers of antifungal compounds such as Bacillus velezensis. Here, we show that the soil-dwelling B.velezensis migrates along the hyphal network of the AM fungus R.irregularis, forming biofilms and inducing cytoplasmic flow in the AM fungus that contributes to host plant root colonization by the bacterium. During hyphosphere colonization, R.irregularis modulates the biosynthesis of specialized metabolites in B.velezensis to ensure stable coexistence and as a mechanism to ward off mycoparasitic fungi and bacteria. These mutual benefits are extended into a tripartite context via the provision of enhanced protection to the host plant through the induction of systemic resistance.

New Aspects of the Effects of Climate Change on Interactions Between Plants and Microbiomes: A Review.

One of the most talked about issues of the 21st century is climate change, as it affects not just our health but also forestry, agriculture, biodiversity, the ecosystem, and the energy supply. Greenhouse gases are the primary cause of climate change, having dramatic effects on the environment. Climate change has an impact on the function and composition of the terrestrial microbial community both directly and indirectly. Changes in the prevailing climatic conditions brought about by climate change will lead to modifications in plant physiology, root exudation, signal alteration, and the quantity, makeup, and diversity of soil microbial communities. Microbiological activity is very crucial in organic production systems due to the organic origin of microorganisms. Microbes that benefit crop plants are known as plant growth-promoting microorganisms. Thus, the effects of climate change on the environment also have an impact on the abilities of beneficial bacteria to support plant growth, health, and root colonization. In this review, we have covered the effects of temperature, precipitation, drought, and CO2 on plant-microbe interactions, as well as some physiological implications of these changes. Additionally, this paper highlights the ways in which bacteria in plants' rhizosphere react to the dominant climatic conditions in the soil environment. The goal of this study is to analyze the effects of climate change on plant-microbe interactions.

Effect of O-Polysaccharide Modifications on Successful Plant Colonization by Bacteria

O-polysaccharides of gram-negative bacteria are a highly variable component of the lipopolysaccharide molecules located at the cell wall surface and involved in microbial interaction with plant and animal cells. Activity of prophage genes often results in various non-stoichiometric modifications (methylation, acetylation, etc.) of glycans at bacterial cell surface. The share of modified O-polysaccharides increases during the stationary growth phase and results in increased hydrophobicity of microbial surface. Bacterial cells with different hydrophobicity showed difference in attachment to plant roots. Increased cell hydrophobicity index was found to result in a significant increase in the number of adsorbed microorganisms per unit root length. Thus, acetyl transferase and methyl transferase genes of viral origin may be indirectly involved in successful colonization of plant roots by rhizosphere bacteria.

Contrasting responses of naturalized alien and native plants to native soil biota and drought

Abstract Terrestrial plant communities often become invaded by alien species, which may benefit from high growth rates, strong phenotypic plasticity and reduced negative impacts from local soil communities. At the same time, terrestrial communities are increasingly more often exposed to periods of drought. However, how drought affects the competition between alien and native plants directly, and indirectly, through changing impacts of soil communities on plant performance, remains poorly understood. Here, we performed a greenhouse pot experiment in which we examined biomass responses of five native and five naturalized alien species (all occurring in mesic grasslands) to drought and benign soil moisture conditions, while growing in interspecific, intraspecific or absence of competition, in the presence or absence of native soil biota. We expected that alien plant species are less negatively affected by soil biota, but more negatively affected by drought than native species, and that drought indirectly weakens soil‐community‐driven competitive benefits of alien plant species over native ones. On average, soil‐community effects on plant biomass were positive, but native performance was less positively affected by soil communities than alien performance, suggesting reduced impacts of soil‐borne enemies on alien plants. Drought more negatively affected alien‐ than native plant performance. Drought impacts on plant biomass did not depend on soil community presence, but in the presence of soil biota, plants overall invested more in root biomass when exposed to drought. The effects of competition were subtle and species‐specific. To better understand the observed positive soil‐community effects on plant performance in our study, we examined mycorrhizal root colonization of plants grown in absence of competition. Among‐species variation in mycorrhizal colonization explained plant performance differences between soils with and without live soil communities, indicating a key role for arbuscular mycorrhizal fungi as driver of plant performance. However, mycorrhizal colonization did not differ between alien and native plants and was unaffected by drought. Overall, our study suggests that drought may weaken alien plant invasions through stronger direct negative impacts on alien than on native plant performance, but that drought does not affect soil‐biota‐driven differences in plant performance between alien and native plants. Read the free Plain Language Summary for this article on the Journal blog.

The First Observation of the Filamentous Fungus Neurospora crassa Growing in the Roots of the Grass Brachypodium distachyon.

The model organism Neurospora crassa has been cultivated in laboratories since the 1920s and its saprotrophic lifestyle has been established for decades. However, beyond their role as saprotrophs, fungi engage in intricate relationships with plants, showcasing diverse connections ranging from mutualistic to pathogenic. Although N. crassa has been extensively investigated under laboratory conditions, its ecological characteristics remain largely unknown. In contrast, Brachypodium distachyon, a sweet grass closely related to significant crops, demonstrates remarkable ecological flexibility and participates in a variety of fungal interactions, encompassing both mutualistic and harmful associations. Through a comprehensive microscopic analysis using electron, fluorescence, and confocal laser scanning microscopy, we discovered a novel endophytic interaction between N. crassa and B. distachyon roots, where fungal hyphae not only thrive in the apoplastic space and vascular bundle but also may colonize plant root cells. This new and so far hidden trait of one of the most important fungal model organisms greatly enhances our view of N. crassa, opening new perspectives concerning the fungus' ecological role. In addition, we present a new tool for studying plant-fungus interspecies communication, combining two well-established model systems, which improves our possibilities of experimental design on the molecular level.

Root endophytic bacterial communities are shaped by the specific microbiota associated to mycorrhizal symbionts

Abstract Background and aims Arbuscular mycorrhizal fungi (AMF) are beneficial soil microorganisms establishing mutualistic symbioses with most crop plants and promoting plant growth and health. AMF beneficial activities are complemented by their associated microbiota, leading to synergistic interactions positively affecting plant performance. In this work we assessed whether AMF may act as drivers of root bacterial endophytes, facilitating root colonization of host plants by their associated bacteria. Methods Two AMF isolates were used, Funneliformis mosseae from Indiana (USA) and Septoglomus sp. from Tuscany (Italy) in an original experimental microcosm system, utilizing micropropagated plants of Prunus persica x Prunus amygdalus inoculated with either intact or mechanically crushed AMF spores, the former able and the latter unable to establish the symbiosis. Spore and root endophytic bacterial communities diversity were analysed by Illumina Miseq sequencing. Results This study revealed that AMF with their associated bacteria can shape the root endophytic bacterial communities, inducing differential recruitment depending on the composition of spore-associated microbiota. Such data were consistent between two AMF isolates, associated with diverse bacterial communities, as shown by PERMANOVA, Bray Curtis dissimilarity, hierarchical clustering and indicator species analyses. Moreover, specific bacterial taxa were found exclusively in mycorrhizal roots. Our findings suggested also a differential recruitment depending on the ability of AMF to establish mycorrhizal symbioses. Conclusion This work revealed that AMF represent drivers of the endophytic bacterial communities diversity and composition, facilitating root colonization of host plants by their associated bacteria, that become an integral part of the root microbiome as endophytes.

An Azospirillum brasilense chemoreceptor that mediates nitrate chemotaxis has conditional roles in the colonization of plant roots.

Motile plant-associated bacteria use chemotaxis and dedicated chemoreceptors to navigate gradients in their surroundings and to colonize host plant surfaces. Here, we characterize a chemoreceptor that we named Tlp2 in the soil alphaproteobacterium Azospirillum brasilense. We show that the Tlp2 ligand-binding domain is related to the 4-helix bundle family and is conserved in chemoreceptors found in the genomes of many soil- and sediment-dwelling alphaproteobacteria. The promoter of tlp2 is regulated in an NtrC- and RpoN-dependent manner and is most upregulated under conditions of nitrogen fixation or in the presence of nitrate. Using fluorescently tagged Tlp2 (Tlp2-YFP), we show that this chemoreceptor is present in low abundance in chemotaxis-signaling clusters and is prone to degradation. We also obtained evidence that the presence of ammonium rapidly disrupts Tlp2-YFP localization. Behavioral experiments using a strain lacking Tlp2 and variants of Tlp2 lacking conserved arginine residues suggest that Tlp2 mediates chemotaxis in gradients of nitrate and nitrite, with the R159 residue being essential for Tlp2 function. We also provide evidence that Tlp2 is essential for root surface colonization of some plants (teff, red clover, and cowpea) but not others (wheat, sorghum, alfalfa, and pea). These results highlight the selective role of nitrate sensing and chemotaxis in plant root surface colonization and illustrate the relative contribution of chemoreceptors to chemotaxis and root surface colonization.IMPORTANCEBacterial chemotaxis mediates host-microbe associations, including the association of beneficial bacteria with the roots of host plants. Dedicated chemoreceptors specify sensory preferences during chemotaxis. Here, we show that a chemoreceptor mediating chemotaxis to nitrate is important in the beneficial soil bacterium colonization of some but not all plant hosts tested. Nitrate is the preferred nitrogen source for plant nutrition, and plants sense and tightly control nitrate transport, resulting in varying nitrate uptake rates depending on the plant and its physiological state. Nitrate is thus a limiting nutrient in the rhizosphere. Chemotaxis and dedicated chemoreceptors for nitrate likely provide motile bacteria with a competitive advantage to access this nutrient in the rhizosphere.

Dark septate endophytes enhance the drought tolerance of Haloxylon ammodendron in sterilized and nonsterilized soil

Dark septate endophytes (DSEs) are a type of endophytic fungus that commonly colonize plant root systems in extreme environments, and play a role in enhancing resistance to drought stress. To investigate the potential applications of DSEs in improving drought tolerance of desert plants, three DSE strains isolated from Haloxylon ammodendron for strong drought tolerance - Alternaria tellustris (AT), Cladosporium sp. (CL), and Paraphoma radicina (PR) - were screened through pure culture in vitro. Pot experiments of H. ammodendron were then conducted with different DSE, water, and soil treatments. In both sterilized and nonsterilized soil, DSEs showed growth-promoting and drought-resistant properties, with a stronger effect observed under sterilized soil treatment. The results showed that in sterilized soil, AT and CL increased root biomass, total biomass and root shoot ratio under high drought treatment, while PR effectively enhanced branch number and root biomass under normal water treatment. Physiologically, DSEs improved plant drought tolerance by increasing soluble sugar content and superoxide dismutase activity. Notably, DSE inoculation facilitated the uptake and utilization of soil nutrients such as available phosphorus, nitrate nitrogen, and free amino acids by plants in both sterilized and nonsterilized soil. Overall, our study highlights the potential of DSEs in improving drought resistance and promoting the growth of desert plants.

Application of Plant Growth Promoting Rhizobacteria on Vegetative Growth in Chili Plants (Capsicum frutescens L.)

Cayenne pepper is a significant plant in tropical regions, utilized not only as a culinary spice but also in the pharmaceutical industry. An effective strategy for enhancing the physical, chemical, and biological quality of soil is the employment of plant growth-promoting rhizobacteria (PGPR). PGPR, a soil microorganism that colonizes plant roots, can accelerate growth and protect against certain pathogens. The use of PGPR, particularly in biocontrol of plant pathogens and biofertilization, is prevalent across various global regions. This study evaluates the effectiveness of PGPR in boosting the growth of cayenne pepper and was conducted in Peresak Village, Narmada District, West Lombok Regency, NTB Province. The methodology implemented was a Completely Randomized Design (CRD) experiment with five treatments and five replications, totaling 25 plant units. The treatments included a control (P0 ml/L) and four PGPR concentrations: P1 (10 ml/L), P2 (20 ml/L), P3 (30 ml/L), and P4 (40 ml/L). Each PGPR dose was dissolved in 1 liter of water and administered at 200 ml per polybag. The findings indicated that PGPR application significantly impacted the growth of cayenne pepper plants, notably increasing plant height, leaf count, branch count, and flower count. The 30 ml/L PGPR concentration (P3) proved most effective in enhancing these growth parameters. The results underscore the substantial benefits of incorporating PGPR as a biofertilizer agent in agricultural practices to optimize crop yields.

Diversity of Arbuscular Mycorrhizal Fungi of the Rhizosphere of Lycium barbarum L. from Four Main Producing Areas in Northwest China and Their Effect on Plant Growth.

Arbuscular mycorrhizal fungi (AMF) can help plants absorb more mineral nutrients after they colonize plant roots, and the mycelia harmonize the soil structure and physical and chemical properties by secreting compounds. AMF species co-evolve with their habitat's geographic conditions and hosts; this gradually causes differences in the AMF species. By using Melzer's reagent to analyze the morphology and using Illumina Miseq sequencing technology to perform the molecular identification of AMF communities among the four typical L. barbarum planting areas (Zhongning, Guyuan, Jinghe, and Dulan) investigated, the variety of L. barbarum roots and rhizosphere AMF communities was greater in the Zhongning area, and every region additionally had endemic species. The successfully amplified AMF was re-applied to the L. barbarum seedlings. We found that the total dry weight and accumulation of potassium increased significantly (p < 0.05), and the root volume and number of root branches were significantly higher in the plants that were inoculated with Paraglomus VTX00375 in the pot experiment, indicating that AMF improves root development and promotes plant growth. We have investigated AMF germplasm species in four regions, and we are committed to the development of native AMF resources. The multiplication and application of AMF will be conducive to realizing the potential role of biology in the maintenance of agroecology.