Rhizosphere最新文献

The objective of this study was to investigate the control effect of organophosphorus nematicide fosthiazate on cucumber plant parasitic nematode and to explore the impact of fosthiazate treatment on the bacterial and fungal communities within the rhizosphere. The results of a cucumber pot experiment indicated that fosthiazate treatment significantly reduced the root-knot index to 7.1, which is much lower than the control group's index of 85.7. The microbial community analysis revealed that the fosthiazate treatment altered the composition of the rhizosphere soil microbial community and reduced microbial diversity. The predominant species in the rhizosphere soil from different treatment groups were determined, and the results indicated that the fosthiazate treatment decreased the abundance of Pseudomonas and Flavobacterium among bacteria, while increasing the abundance of Sphingomonadales and Novosphingobium. In the fungal community, there was a reduction in the abundance of Hypocreales and Nectriaceae, accompanied by an increase in Olpidium. Predictive analyses using PICRUSt2 demonstrated that bacterial metabolic pathways were generally upregulated in the fosthiazate treatment group. Additionally, FUNGuild predictions indicated a significant decrease in the abundance of Animal Pathogen pathways. These findings provide a scientific basis for the development of more environmentally friendly nematode management strategies based on the rhizosphere microbiome. The findings provide a novel understanding of the control mechanism of an organophosphorus nematicide for plant parasitic nematodes that leverage the rhizosphere microbiome. This understanding offers a scientific foundation for the development of more environmentally sustainable nematode management strategies.

Interspecific interactions between intercropped maize and soybean are expected to cycle soil nitrogen efficiently and avoid N₂O emissions. However, the unique interactions of maize and soybean with nitrogen cycling bacteria makes it hard to predict the crop-specific impact on soil N₂O production. We conducted a field microcosm experiment with root separation to simulate monoculture and intercropping with maize and soybean. Intercropped maize reduced the N₂O emissions by 16–41%, compared to monoculture maize. This was related to reduced nitrification by ammonia-oxidizing bacteria and denitrification reactions (as indicated by the abundance of nirS and nirK gene copies), as well as drier soil conditions and lower soil NO₃⁻-N levels. Soil N₂O emissions were the same in monoculture and intercropped soybean, suggesting stable denitrification (based on nirS, nirK and nosZ genes) with constant soil physicochemical conditions. As monoculture maize can stimulate soil N₂O emission through denitrification, this work justifies the adoption of maize-soybean intercropping as a low N₂O-emitting practice in sustainable agriculture, due to its beneficial effects on soil biology and biochemistry.

Vegetable nitrate accumulation is a major threat to food security and human health. The application of a non-toxic and non-nitrogen-fixing cyanobacterium, Chroococcus sp., was found to reduce soil nitrate content; however, the influence of Chroococcus sp. on vegetable growth and nitrate accumulation remains unclear. In this study, Chroococcus sp. was introduced to soil fertilized with NaNO₃, (NH₄)₂SO₄, and CO(NH₂)₂. Variations in growth performance and nitrate content of pakchoi (Brassica chinensis L.), coupled with changes in soil fertility, were investigated through pot experiments. The varied abundance of rhizosphere bacteria and differential expression of bacterial functional genes were studied using 16S rRNA and meta-transcriptomic sequencing analyses, respectively. Chroococcus sp. reduced vegetable nitrate content by 42.29%, 21.34%, and 27.10% in pakchoi planted in soil fertilized with NaNO₃, (NH₄)₂SO₄, and CO(NH₂)₂, respectively. This reduction was mainly attributed to regulation of the rhizosphere bacterial community by Chroococcus sp. First, Chroococcus sp. stimulated denitrifying bacteria (such as Methylotenera, Gemmatimonas, Nitrosomonas, Nocardioides, Gaiella, Lysobacter and Sphingomonas) that contributed to a reduction in soil nitrate content. Second, Chroococcus sp. stimulated several rhizosphere bacteria such as Methylibium, Micromonospora, Bacillus, Pedomicrobium, Hyphomicrobium, Steroidobacter, Pseudolabrys, Streptomyces, Methylobacillus and Pseudomonas that directly participated in the reduction of vegetable nitrate accumulation, according to their negative correlation with vegetable nitrate content. Chroococcus sp. increased soil fertility and consequently promoted the growth of pakchoi by reducing soil salinity and increasing soil polysaccharide content, available phosphorus, and functional enzyme activity. The increased abundances of various rhizosphere bacteria genera also contributed to an increase in soil fertility and the promotion of vegetable growth. In general, this study demonstrated the effectiveness of Chroococcus sp. in reducing vegetable nitrate accumulation and explored the related mechanisms.

Fungal endophytes are known as promising plant growth-promoting microorganisms. Surprisingly, despite the economic importance of avocado, the antimicrobial and plant growth-promoting properties of its fungal endophytes have seldom been investigated. Our objectives were to evaluate the anti-oomycete activity of avocado fungal endophytes and assess their potential plant growth-promoting properties, using Arabidopsis thaliana as a model plant. In total, 89 fungal isolates were obtained from the roots of avocado trees and grouped into 24 morphotypes. One isolate per morphotype was randomly selected to assess its antagonistic activity against Phytophthora cinnamomi through dual culture assays. The strongest inhibition of P. cinnamomi was induced by endophytic fungi belonging to the Fusarium, Mortierella and Penicillium genera. The six most promising fungal isolates were selected to assess their plant growth-promoting traits in co-inoculation assays with A. thaliana. All tested fungal endophytes were able to modify the plant root architecture and increase the number of lateral roots. Moreover, an accumulation of auxins was detected in the xylem and meristematic zone of plants inoculated with Mortierella sp. PC-T3-3.1 and Metapochonia sp. PC-T2-4.2, whilst auxin accumulation was restricted to the emerging lateral roots of plants inoculated with Penicillium sp. C-T0-3.1. Indole quantification showed that Penicillium sp. C-T0-3.1 produced the highest concentration of indole acetic acid (IAA) and indole butyric acid (IBA), despite the lack of auxin responsiveness in plants in the co-inoculation assays. Mortierella sp. PC-T3-3.1 and Metapochonia sp. PC-T2-4.2 produced more IAA and IBA when co-inoculated with A. thaliana than when growing alone, which suggests that sensing of plant signals could induce the production of auxin-like compounds by these two endophytes. Collectively, our findings contribute to elucidate the mechanisms underpinning the plant growth-promoting activity of avocado fungal endophytes, which will be key to harness their full metabolic potential.

The competition between tree and grass roots for water and nutrients under the canopies of forest species may reduce the grass cover and thus increase rill erosion and shallow instability up to the values that are typical of the bare soils. This study has carried out flume experiments at different soil slopes and water flow rates, in order to evaluate rill detachment capacity (D_c) and erodibility (K_r) as well as the stability factors of hillslopes with Gleditsia caspica L. (a Fabaceae species, commonly called ‘Persian honeylocust’, a local endemic tree of Northern Iran) in comparison to bare soils. The variability of D_c has been associated to soil aggregate stability and plant root characteristics as key descriptors of rill erosion and surface stability. D_c was significantly lower (−41%) in the soil under the canopies compared to the bare sites. This was due to the higher soil aggregate stability (+83%) as well as to the denser and more extended plant root system, as confirmed by the negative correlations between D_c and soil and root parameters including root total length, mass density and specific root length. K_r was instead similar for the two soil conditions. The root system of the surface soil layer also played a beneficial action for slope stabilization, increasing the mean safety factor between soils with Gleditsia caspica and bare soils to 1.52 (well over the threshold of 1.3 identifying possible shallow instability). However, this safety factor was the highest at the lower slopes (1.63), and decreased with slope down to 1.39 in the steepest soils. Overall, this study provides indications to land managers on how to contrast soil erosion and shallow instability in delicate forestlands under semi-arid conditions.

To ensure food security, foster agri-environmental sustainability, and prevent agricultural expansion into preserved areas, it is imperative to intensify plus diversify agriculture within integrated farming systems in the coming decades. Maximizing productivity and carbon sequestration through such systems demands understanding below-ground interactions and further research into plant root dynamics, which have often been neglected or overlooked. This study examined the effects of integrated farming systems, specifically crop-livestock and crop-livestock-forestry, on fine-root dynamics of crops and pastures (i.e., herbaceous plants). Using an extensive grazing pasture as a control, and intensification through crop-livestock and crop-livestock-forestry, we aimed to evaluate if integrated systems (i) enhance herbaceous root growth and necromass addition, and (ii) accelerate root turnover. We also investigated whether multiple linear regression modeling could predict root production and decomposition using the edaphoclimatic variables monitored in the areas. Herbaceous fine-root dynamics were observed over two years using the minirhizotron technique. Installation involved five 70 cm-deep acrylic tubes in extensive grazing and crop-livestock and fifteen in crop-livestock-forestry (1.9, 4.3, and 7.5m tree inter-row distances). In integrated systems, annual corn cropping was succeeded by grazing on a palisadegrass pasture. The trial measured eight additional soil and climatic parameters for a regression model using a stepwise selection procedure, including average soil temperature, photosynthetically active radiation, available soil water, soil bulk density, soil pH, available soil phosphorus, the sum of soil bases, and cation exchange capacity. Extensive grazing accumulated 124.8 m m⁻² of roots, constituting 48% of crop-livestock (259.7 m m⁻²) and 66% of crop-livestock-forestry (189.5 m m⁻²). Root growth near Eucalyptus trees was reduced by 51% compared to crop-livestock. Root turnover followed the order of extensive grazing < crop-livestock < crop-livestock-forestry. The peak daily root productivity was from 31 to 80 days of the crop cycle when corn was intercropped with palisade grass in the integrated systems. Multiple regression models were superior for predicting root decomposition, reaching adjusted R² values of 0.81 and 0.71 for crop and pasture cycles, but were ineffective for root growth (R² < 0.25). Therefore, additional parameters are needed to fit the root growth accurately. We conclude that integrated farming enhances fine-root production and root necromass accrual, accelerating root cycling compared to extensive pasture. However, as introducing Eucalyptus in crop-livestock impairs herbaceous root development near trees, we recommend adjusting tree density and inter-row spaces to alleviate these adverse effects, especially for annual crop cul