Rhizosphere最新文献

Phosphorus (P) deficiency is a major limiting factor for rice production in the tropics. The root system architecture (RSA) may play a significant role to capture P efficiently in soils; however, its function is poorly understood in flooded and puddled soil cultures. Two near-isogenic lines (NILs) contrasting RSA—qsor1-NIL (nonfunctional allele of qSOR1; shallow RSA) and Dro1-NIL (functional allele of DRO1; deep RSA)—were repeatedly grown for approximately 6 weeks in pots with three stratified P treatments. The treatments simulated P deficient conditions in puddled and subsoil layers, P available in the puddled layer, and P available in puddled and subsoil layers, that is, −P−P: no P applied in either the top-half (0–14 cm) or bottom-half (14–28 cm) layers; +P−P: P applied only in the top-half layer; and +P + P: P applied in the top-half and bottom-half layers, respectively. A significant interaction was observed between genotype and P treatment. The Dro1-NIL had a greater root surface area in the bottom half layer, which was advantageous for capturing P in the subsoil layer and resulted in greater biomass and P uptake in the +P + P treatment. Contrarily, the qsor1-NIL had a greater root surface area and longer root hair, resulting in greater biomass and P uptake in the −P−P treatment. The mechanism is unclear; however, the pleiotropic effect of qsor1, namely enhancing root hair elongation, might be more advantageous to explore P with minimal carbon costs than elongating nodal and lateral roots when P is not available in deep soil layers. No genotype differences were observed in the +P−P treatment, implying no apparent topsoil P-foraging effect of the shallow RSA in the flooded soil culture. The roles of RSA and root hairs should attract further attention for the genotypic improvement of lowland rice under P deficiency conditions in the tropics.

Predicting root water uptake (RWU) of wide-distributed alpine meadow on the Qinghai-Tibet Plateau (QTP) is essential to precisely reveal the complex hydrothermal behaviors of alpine meadow soil under warming and humidifying climate. In this study, a model for RWU of alpine meadows on the QTP is proposed, which comprehensively considers the actual root characteristics of alpine meadow and the influence of soil temperature. In the proposed model, a root density function is newly derived to describe the root characteristics of alpine meadows, where root biomass (RB) is taken as root characteristics index. Meanwhile, a temperature-dependent reduction function is developed to reflect the impact of soil temperature on the RWU of alpine meadows. The proposed model for RWU is highly competent compared to the model for RWU not considering soil temperature. Furthermore, the proposed model for RWU is applied to explore the influence of RWU effect on the water movement of soil under different soil temperatures. Results indicate that the increment of soil temperature can lead to the exponentially increasing trend for the RWU rate of alpine meadows. Under the RWU effect, the alpine meadows with the thickness of 0.25 m have contributed to the moisture redistribution of soil layer within the range of 0.75 m. At the maximum soil temperature of 23 °C, the maximum RWU rate of 25.16 × 10⁻⁹ 1/s leads to the maximum decline in volumetric water content of 6.31%. Higher soil temperature is beneficial to the stability of the shallow freeze-thaw slope covered by alpine meadows, which is the opposite of the influence of humidifying climate. It is helpful to disclose the failure mechanism of shallow freeze-thaw slopes of the QTP.

Soil microorganisms play a critical role in influencing plant growth and managing soil pathogens. Tobacco mosaic virus (TMV) induces significant economic losses in global agriculture and can impact the composition and function of soil microbial communities. Despite its importance, the interactions between viruses and soil microbial communities remain inadequately understood. In this study, we employed 16S rRNA gene sequencing coupled with bioinformatics analyses to thoroughly investigate the bacterial communities and physicochemical properties of the rhizosphere soils of healthy tobacco plants under both sterilized (WJ) and non-sterilized (YJ) conditions, as well as TMV-infected tobacco plants under both sterilized (WT) and non-sterilized (YT) conditions. Our findings demonstrated that TMV infection significantly modifies the physicochemical properties and bacterial community structure of rhizosphere soils, with these changes being more pronounced in non-sterilized soils. Moreover, the YT samples exhibited a more intricate network of bacterial interactions. They showed significant differences from WT samples in key bacterial genera that might be involved in the response to or antagonism of TMV. The genera Burkholderia-Caballeronia-Paraburkholderia and Dyella were highlighted. These results suggest that rhizosphere microorganisms actively respond to TMV infection, with a more pronounced response observed in non-sterilized soils. This study provides novel insights into the microbial dynamics associated with TMV infection and underscores the importance of soil microbial communities in plant health and disease resistance. Additionally, it offers an experimental framework for future research on soil-borne diseases, emphasizing the pivotal role of soil microbiota in disease ecology and soil impact.

Analysing the composite's adhesion mechanism is necessary to gain a deep understanding of the pipeline blockage phenomenon encountered during negative pressure matrix removal. This study considers the interface suction and liquid bridge changes between the roots and the matrix. In particular, the liquid bridge volume and the interface's effective stress parameters were combined to establish a theoretical model of the shear strength of the root–matrix composite. The main factors affecting root–matrix composite adhesion stability were the root friction coefficient and the composite moisture content. Regarding the influence of the root friction coefficient, the surface structures of the primary and lateral roots were observed using a laser confocal microscope. Using the principal component analysis method, the main factors influencing the friction properties of the root system were identified as the taproot's maximum valley depth (Rv) and the average roughness (Ra) of the profile, as well as the lateral root's maximum peak-to-valley height (Rz) and the average roughness (Rq) of the lateral root profile. The influence of both the main and lateral roots cannot be overlooked when removing inferior seedlings from the substrate. Furthermore, the bond efficiency of the root–matrix composite was calculated, revealing values of 16.03%, 49.87%, and 58.31% under low, medium, and high moisture content conditions, respectively. Finally, direct shear tests were conducted on the complex under dry-wet-dry conditions, yielding an internal friction angle of 14.1656° and a cohesion force of 1.738 ± 0.3 kPa at a water content of 20% (dry-wet). In conclusion, it is recommended to perform the negative pressure removal of inferior seedling substrate blocks during the seedling stage with low water content and underdeveloped root systems. Related research lays the foundation for preventing blockages in negative pressure pipelines.

Using microbial inoculant partial substitution synthetic fertilizer is a new type of environmentally friendly way to significantly improve the corps production and ecological environment. The effects of supplementing Enterobacter cloacae Rs-2 with synthetic fertilizer on the maize growth and soil microbial community diversity in field were investigated in this paper. The optimal fermentation conditions were determined as 5 g·L⁻¹ industrial glucose, 30 g·L⁻¹ industrial peptone, 1 g·L⁻¹ MgSO₄ and 0.5 g·L⁻¹ KCl firstly. Field experiment showed that the fresh weight of shoots and roots was increased by 39.69% and 32.46% when half synthetic fertilizer was replaced by microbial inoculant. The soil physical and chemical properties were also greatly improved, especially the contents of available phosphorus, water-soluble calcium and alkali-hydrolyzed nitrogen were significantly increased in T4 (Rs-2 and half chemical fertilizer) and full chemical fertilizer treatment. This result was accompanied by increased the relative abundance of genes related to phospholipid metabolism, phosphotransferase system (PTS) and oxidative phosphorylation metabolism, indicating that Rs-2 may play an important role in the transformation and utilization of phosphorus in soil. The richness, dominance of Proteobacteria, Enterobacteriaceae in the microbial communities were further improved when the microbial inoculant applied. Function prediction PICRUSt analysis indicated that amines and amino acids were the most representative of the total carbon source utilization by the soil microbial communities. It was concluded that the application of 50% of the synthetic fertilizer supplemented with 30 mL microbial inoculant enhanced both the functional diversity of soil microbial communities and maize yield.

The putative competitive endophytic bacteria with plant-growth-promoting attributes could be potential bio inputs to enhance agricultural sustainability. These special rhizosphere colonizing bacteria possess distinct strategies to enter and colonize the host plant asymptomatically and offer several plant growth-promoting benefits. However, the molecular interaction between the endophyte and host plant remains unclear in many crop spheres. In this study, we categorize putative endophytes in rice into two groups—common endophytes and genotype-specific endophytes—based on their ability to colonize alternative hosts. The putative competitive endophytes of rice landrace Norungan and high-yielding cultivar Co51 were cross-inoculated with each other under gnotobiotic conditions and attempted to re-isolate from the inoculated plants. Two Norungan endophytes (Priestia endophytica NE14 and NE21) and one Co51-endophyte (Peribacillus endoradicis CE10) could not colonize the internal tissues of the alternate hosts, and they were considered as genotype-specific endophytes. In contrast, the rest of the strains could colonize both genotypes (common endophytes). The bait trap assay with flow cytometry revealed that the Norungan root exudate significantly enhanced the chemotactic movement of NE14 and NE21 compared to Co51-endophyte (CE10) and common endophytes (NE09 and CE07). Likewise, the Co51-root exudate triggered high levels of chemotaxis of CE10 but not the others. The root exudates did not alter the growth and biofilm-producing capability of genotype-specific and common endophytes. The cell wall degrading enzyme, pectinase of genotype-specific endophytes (NE14 and NE21), had positively enhanced due to Norungan root exudate but not with Co51 exudate. When the genotype-specific endophytes were inoculated to alternate host, a strain-level difference was observed in the induction of rice defense enzymes. NE14 inoculation in Co51 rice had high levels of peroxidase, polyphenol oxidase, phenylalanine ammonia lyase, and glutathione reductase; NE21 induced high levels of glutathione reductase and peroxidase alone in Co51. Likewise, CE10 triggered relatively high levels of catalase, glutathione reductase, peroxidase, and polyphenol oxidase in Norungan rice. No apparent difference between the two rice genotypes in defense enzymes’ levels was observed due to common endophytes (NE09 and CE07). These results authenticate the occurrence of genotype-specific putative competitive endophytes in rice, and exploring them for crop growth and yield would be a better choice for rice sustainability.

Plant-parasitic nematodes cause significant losses in agriculture worldwide. Among these parasites, the root-knot nematode (Meloidogyne spp.) stands out. Consequently, control methods are being developed to combat this pest. Among these methods is biological control, the main agents of which are bacteria. This study aimed to evaluate the impact of 102 bacterial isolates on the mortality of Meloidogyne incognita J2 juveniles, hypothesizing that certain isolates could effectively control the nematode and promote tomato plant growth. Five experiments were conducted to test this hypothesis. First, the effect of the 102 bacterial isolates on J2 mortality was assessed under laboratory conditions. Second, five isolates (Bacillus cereus IBCBb130, Bacillus cereus IBCBb116, Pseudomonas aeruginosa IBCBb122, Bacillus proteolyticus IBCBb136, and Serratia sp. IBCBb118), which showed >68% J2 mortality, were evaluated over 72 h. Third, these isolates were tested at seven different concentrations. Fourth, their efficacy in controlling M. incognita on tomato plants was assessed in a greenhouse setting. Fifth, their potential to promote tomato plant growth without nematode inoculation was evaluated. The results revealed that the 102 bacterial isolates caused mortality ranging from 2 to 79.57% for M. incognita J2. At a 10% dilution, five isolates (B. cereus IBCBb130, P. aeruginosa IBCBb122, B. cereus IBCBb116, B. proteolyticus IBCBb136, and Serratia sp. IBCBb118) maintained mortality rates above 68%. Among these strains, B. cereus IBCBb130 and P. aeruginosa IBCBb122 were particularly effective, with B. cereus IBCBb130 showing high mortality rates under laboratory conditions and P. aeruginosa IBCBb122 significantly reducing nematode populations in greenhouse pots. Additionally, Serratia sp. IBCBb118 demonstrated notable potential for promoting tomato plant growth. In conclusion, specific bacterial isolates exhibit strong potential for the biocontrol of M. incognita and enhancement of tomato plant growth, suggesting a viable alternative to chemical nematicides. These findings provide insight into the development of sustainable agricultural practices through targeted manipulation of the soil microbiota. Future research should explore the underlying mechanisms of these interactions and their long-term effects on crop yield and soil health.

Cadmium (Cd) toxicity is a universal environmental threat to plant growth. Either arbuscular mycorrhizal fungi (AMF) or biochar have been shown to effectively mitigate Cd toxicity in plants. Additionally, the camphor tree (Cinnamomum camphora) has been used for phytoremediation of Cd-contaminated soils. However, the potential interacting effects of these treatments and their underlying mechanisms remain unclear. Therefore, we conducted a mesocosm experiment to examine the effects of mycorrhizal inoculation (inoculation with sterilized AMF, with Rhizophagus intraradices and Diversispora versiformis, either alone or their mixture) and/or rice-husk biochar amendment on camphor trees grown in Cd-spiked soils (0, 15, 150 mg Cd per kg soil). We found that Cd addition significantly reduced plant biomass and increased Cd accumulation in plant tissues and soil. Single application of either AMF or biochar significantly inhibited Cd uptake by plants. Nevertheless, AMF inoculation alone improved plant biomass, net photosynthetic rate (P_n), phosphorus (P) uptake and glomalin-related soil protein (GRSP) production, as well as alleviated Cd accumulation in plant shoots to a greater extent than biochar amendment; biochar performed better than AMF in reducing soil Cd mobilization under the highest Cd contamination. These results suggest that AMF and biochar adopt different strategies to reduce Cd toxicity in plants. Moreover, the combination of AMF and biochar showed the highest mycorrhizal colonization, P_n and plant biomass, as well as the lowest Cd uptake by plants under the highest Cd contamination. Particularly, the mixed fungi of R. intraradices and D. versiformis combined with biochar produced the most profound effect on plant biomass under Cd contaminations. These results suggested that the combination of AMF inoculation and biochar amendment had synergistic effects, and their combination performed better than their single application under Cd-contaminated soil. Furthermore, these additive benefits were mainly attributed to the higher total GRSP and mycorrhizal viability. This work suggests that applying mixed fungi of R. intraradices and D. versiformis together with biochar amendment may be a potential method not only for camphor production but also for the phytoremediation of soil exposed to Cd contamination.

Rainfall infiltration plays a critical role in the instability of soil slopes. In this study, using laboratory rainfall infiltration model tests and numerical modeling, we explored the soil-water retention capabilities of three common slope protection vegetation, namely the herbaceous vegetation Festuca arundinaria (Fa) and Ophiopogon japonicus (Oj), and the shrub vegetation Ligustrum lucidum (Ll). The distribution of volumetric water content (VWC) and matric suction were measured under different rainfall intensities through a lab-built experimental device. Meanwhile, the experimental results were further used in finite element software to simulate rainfall infiltration. Experimental results showed that roots could effectively reduce the peak value of VWC and slow down the infiltration rate of rainfall. Ophiopogon japonicus demonstrated the best water-holding effect with the slowest rainfall infiltration rate. For example, under a rainfall intensity of 15.0 mm/h, the mitigation degree of rainfall infiltration of Ligustrum lucidum, Festuca arundinaria, and Ophiopogon japonicus was 130.77%, 79.49%, and 182.05%, respectively. The hydraulic conductivity of bare soil was the largest under different matric suctions, while the hydraulic conductivity of Ophiopogon japonicus was the smallest. Moreover, vegetation roots mainly influence the soil-water properties in the root area. Numerical simulation results revealed that Ligustrum lucidum showed better slope protection effects under short-duration rainfall conditions, while Ophiopogon japonicus exhibited better results under long-duration rainfall conditions.

Rhizobacteria's effects on commercial banana plants in different generations remain unclear. In the present field-level investigation, we evaluated the effect of three types (injection, edaphic, and foliar) of applications of a local rhizobacterial consortium on Black leaf spot (BLS), chlorophyll content, morphological components, and fruit production in two generations of commercial banana plants cv. Williams. The rhizobacteria-treated mother and daughter plants received one and two applications, respectively, while the untreated plants constituted the control group. Results of the present investigation indicated that the rhizobacteria differently affect the aerial tissues of different generations of banana plants. Regardless of how the rhizobacteria were applied, they reduced an average of 40 % the BLS incidence on leaves (P ≤ 0.0001) and increased an average 9 % the plant height and pseudostem circumference (P ≤ 0.0001 – P = 0.0475) of mother and daughter plants were observed. However, both morphological variables improved even more in daughter plants edaphically treated with rhizobacteria. Leaf pigments like chlorophyll B (P = 0.0262) and the total content (P = 0.0230) only increased an average of 40 % in daughter plants treated with rhizobacteria. Rhizobacteria edaphic application and injection improved bunch weight (P = 0.0048) and hands per bunch (P ≤ 0.0001) in mother plants. Meanwhile, the edaphic application significantly increased the bunch weight (P = 0.0031), hands per bunch (P = 0.0074), and rachis weight (P = 0.023) by 17% on average in edaphically and foliar-treated mother plants, while the finger length (P = 0.0064) increased by 5% on average. Generally, the morphological and productive components increased much more in daughter plants than in mother. These findings demonstrate the potential of edaphically and foliar rhizobacterial applications to enhance plant health and productivity, providing a sustainable management strategy for banana cultivation.