Rhizosphere最新文献

The immense benefit of chemical nematicides in controlling plant parasitic nematodes in high-value crops is counterbalanced by the development of resistance in nematodes due to their overuse. Bacillus subtilis is a promising bacterium that not only confers resistance against plant parasitic nematodes but also promotes plant growth through nutrient acquisition. Considering the multifaceted action of B. subtilis attempts were made to sequence the whole genome of endophytic B. subtilis GEB5 to find the genome complexity of the potential bio-control agent isolated from the guava. The results confirmed the isolate as B. subtilis sub sp. subtilis with a circular genome of 8,341,276 bp (8.3 Mb) length and 41.8% GC content. The results of genome annotation revealed the presence of 8209 coding sequences (CDS) genes, 136 transfer RNA (tRNA) genes, and 6 ribosomal RNA (rRNA) genes. Nonribosomal peptide synthetase (NRPS) gene clusters in the genome of GEB5 included fengycin, bacillaene, plipastatin, subtilin, subtilosin A, bacilysin, surfactin, sporulation killing factor, bacillibactin. Moreover, the GEB5 genome assembly had 21 homologs corresponding to nematode-virulent proteases. Furthermore, the results of greenhouse experiments showcased that GEB5 quenched the population of M. enterolobii (72% reduction) and also boosted the plant growth of guava. A plurality of the putatively encoded nematode virulence protease and its ability to boost plant growth suggests its environmentally robust bio-control potential in protecting plants against invading plant parasitic nematodes.

Understanding how water availability affects different caatinga passionfruit accessions (Passiflora cincinnata Mast.) and their drought tolerance is crucial for successful cultivation in semi-arid environments. Additionally, assessing the impact of this stress on arbuscular mycorrhizal fungi (AMF) communities' structure and dynamics is also essential. A greenhouse experiment was conducted with the purpose of identifying tolerant and sensitive P. cincinnata accessions under drought stress and how the water availability would affect AMF communities, which were taxonomically identified based on morphological characters. Results show that water availability influenced height, stem diameter, total chlorophyll, dry and fresh shoot biomass, fresh root biomass, leaf area, number of leaves and tendrils, and root/shoot ratio of accessions of P. cincinnata. However, water availability did not influence root dry biomass, only the identity of P. cincinnata accessions differed from each other. In the PCA-based ranking, based on the morpho-descriptors traits, and on the indices of drought stress tolerance, accessions 01 and 48 were considered tolerant and sensitive to drought, respectively. The abundance of glomerospores and the AMF richness are not influenced by the factors studied, but water availability has increased the frequency of mycorrhizal colonization, diversity, and evenness of AMF species, in addition to reducing its dominance. AMF communities’ composition was modulated by P. cincinnata accessions and by water availability. Utilizing morpho-agronomic traits, it becomes feasible to differentiate P. cincinnata accessions exhibiting tolerance and sensitivity to drought stress. Particular emphasis is placed on fresh and dry shoot biomass, leaf area, and height, each contributing approximately 12% to these outcomes. Changes on the composition of AMF communities after imposition of water deficit suggest that some AMF species may show some drought tolerance and that preferences for P. cincinnata genotypes may exist.

In order to identify an effective rhizoplane Pseudomonas species to combat sugarcane wilt pathogen (Fusarium sacchari), twenty Pseudomonas isolates were obtained from the sugarcane rhizoplane of different genotypes. The three-tier confrontation (direct, indirect and remote) tests revealed antagonistic activity of the bacteria, bacterial non-volatile and volatile compounds. In dual culture assay, SRP19 (46.30%) and SRP20 (39.30%) have shown the highest inhibition against F. sacchari. 16S-23S rDNA sequencing identified them as Pseudomonas chlororaphis subsp. aurantiaca (SRP19) and Pseudomonas aeruginosa (SRP20). Exploration of biocontrol mechanisms revealed the potential roles for IAA production, extracellular enzyme secretion (proteases, cellulases and chitinases), HCN synthesis, siderophore production, pyocyanin or fluorescein production and phosphate solubilization. The molecular analysis revealed the presence of genes (phz, prnD, phlD and pltC) involved in the biosynthesis of antimicrobial peptides like phenazines, pyrrolnitrin, 2,4-diacetyl phloroglucinol and pyoleuteorin, involved in suppressing Fusarium. The antagonistic activity was further confirmed under greenhouse conditions by sett treatment with potential antagonistic isolates, which increased germination and reduced the pre-emergent mortality by 60% and post-emergent seedling mortality by 76% in SRP19 treated pots. The study revealed that the isolate Pseudomonas chlororaphis subsp. aurantiaca strain SRP19 can act as PGPR with both plant growth promoting and pathogen suppressing activity that can be used as an effective biocontrol agent against Fusarium wilt of sugarcane.

Root water potentials, essential for understanding drought tolerance and transpiration, can also influence root tensile strength, which is valuable for selecting plants for slope stabilization and erosion control in extreme wet and dry climates. This study investigated the relationships between root suction, water content, diameter and tensile strength of Cnidoscolus aconitifolius and Bougainvillea glabra to explore their potential for slope stabilization. Both species showed an increase in root water content and a decrease in suction with larger root diameter, despite their inherent difference in the tensile strength and suction relationship. The tensile strength versus suction plots clearly showed that Bougainvillea glabra can sustain higher load as root suction increases and is likely to perform better in extremely dry condition than Cnidoscolus aconitifolius. Observation of field performance indicated that this is the case which warrants further study on root suction for selecting species in stabilization of slopes in extreme climates.

Tomato is widely cultivated all over the world, and long-term monoculture has resulted in decreased tomato yields and stunted plant growth. Soil bacterial communities have a profound effect on plant growth and health, and the effect of different planting years on rhizosphere soil microorganisms of tomato is not clear. In this study, metagenomic sequencing was used to analyze the rhizosphere soil microorganisms of tomatoes cultivated continuously for 3, 6 years (short-term continuous cropping), 9, and 12 years (long-term continuous cropping) (LZ3, LZ6, LZ9, LZ12). The results showed that the pH in LZ9 was significantly higher than that in the other treatments, the relative abundance of Planctomycetes and Candidatus Rokubacteria in LZ3 were higher than those in the other treatments, the relative abundance of Proteobacteria was significantly higher in LZ6 and LZ9 than that in the other treatments, and the relative abundance of Chloroflexi and Bacteroidetes in LZ12 were higher than those in the other treatments. At the genus level, the relative abundance of Nocardioides, Sphingomonas, Pseudolabrys were lower in LZ3 than that in other treatments, and the relative abundance of Gaiella was significantly higher in short-term continuous cropping than that in LZ9. The pH, hydrolyzable nitrogen (HN), and available potassium (AK) were the most important factors driving the changes in microbial communities. The relative abundance of amino acid metabolism, terpenoid and polyketide metabolism decreased significantly with years of continuous cropping, and that total nitrogen (TN), HN, and available phosphorus (AP) were significantly correlated with translation, amino acid metabolism, and cell growth and death. Continuous cropping leads to nutrient imbalance in tomato soils, which affects the structure and functional composition of soil microbial communities, providing insights into microbial community response to continuous tomato cropping, but further in-depth studies are needed.

Tree fine-root exudation and organic carbon compounds in the soil affect physiological functions through degradation by microorganisms around the roots and the enhancement of allelopathic effects on invasion attempts by other plant species. However, the underlying mechanism of fine-root action in vertically heterogeneous resource-distribution patterns along the soil profile is little known. Here, we quantified root exudation and its morphological and chemical traits in the soil layers down to 100-cm depth for three conifer species, Pinus densiflora (ectomycorrhiza), Chamaecyparis obtusa, and Cryptomeria japonica (arbuscular mycorrhiza), in a cool temperate Japanese forest. By using glass filter-trap method, root exudation rates in all three species varied with soil depth in a species dependent pattern. Specifically, the root exudation rate of P. densiflora was significantly higher in the middle soil layer, and lower in the topsoil layer, whereas the exudation rates significantly decreased in C. japonica and did not vary in C. obtusa along soil depth. Exudation strongly correlated with variation in root traits in C. obtusa and C. japonica but not in P. densiflora. These findings suggest that differences in exudation patterns among tree species are likely compensated for by structural modifications in fine roots in response to soil depth. In addition, the traits with mycorrhizal types might be related to adequate root exudation and enhanced soil-nutrient acquisition. Distinct differences among species in exudation, associated with vertical root distribution, will increase our understanding of root survival strategies for nutrient acquisition and carbon sequestration in forest tree species.

This study investigates the potential of functionally-enhanced periphyton enriched with phosphate-solubilizing bacteria (PSB) as a novel biofertilizer to improve the growth parameters and yield attributes of plants in rice paddy fields. The research represents the first farm-scale investigation of the PSB-enhanced periphyton. The study aimed to assess the ability of the periphytic biomass to act as a reservoir for phosphorus (P), regulating its bioavailability to rice plants and decreasing the demand for chemical inputs at the field-scale. In order to achieve this, superior P-solubilizing bacteria isolates were utilized to prepare the functionally-enhanced periphyton. The research revealed that PSB-enhanced periphyton acts as a controlled-release biofertilizer, minimizing P losses during low-demand growth stages and enhancing P supply during high-demand growth phases. The findings demonstrated that P concentration declined significantly (by 75.2%) in the paddies' overlying water under periphyton application. Conversely, periphyton increased soil P availability (24.2%) and plant P content (16.0%). The research shines a light in the possibility of utilizing the functionally-enhanced periphyton as an effective inoculant for sustainable rice production, with implications for reducing the heavy reliance on chemical inputs in agricultural systems. This research serves as a bridge between laboratory and greenhouse experiments and real farm conditions, offering practical applications for sustainable management of agrifood systems. The investigation's results enable a deeper understanding of periphyton and its role in sustainable rice production, providing a reliable source for researchers, producers, and policymakers involved in sustainable production systems.

Agricultural practices influence plant-microbe interactions in the rhizosphere and, particularly can drive the recruitment of plant growth-promoting bacteria (PGPB). This study assessed the PGPB community in soil under no-tillage (NT) and in the rhizosphere of maize and grass under integrated cro-livestock (ICL) to evaluate their influence on the recruitment of PGPB in the rhizosphere of soybean. Soil samples from the soybean rhizosphere under NT and ICL were collected and compared to samples collected from bulk soil and the rhizosphere of maize and grass in ICL, using the 16 S rRNA approach. The structure of the PGPB community differed (21.8% of variation) when comparing the rhizosphere of soybean in NT and ICL. The soybean rhizosphere in NT enriched distinct PGPB compared to those observed in ICL. The proportion of specialist PGPB was higher in the rhizosphere of soybean in ICL (33.8%) than in NT (26.5%). Regardless of the agricultural system, the rhizosphere of soybean showed a similar number of nodes, but ICL promoted a higher number of edges in the soybean rhizosphere. Bacillus and Mycobacterium were identified as the main keystone taxa in the rhizosphere of soybean in NT. In contrast, Streptomyces and Sphingomonas were keystone taxa in the rhizosphere of soybean in ICL. This study demonstrated distinct recruitment of PGPB by the rhizosphere of soybean based on agricultural systems, i.e., NT and ICL.

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.