Melon/cowpea intercropping pattern influenced the N and C soil cycling and the abundance of soil rare bacterial taxa

Intercropping improves the yield by increasing nutrient metabolism capacity and crucial microbial abundance in root of Camellia oleifera in purple soil

Intercropping system influences the endophytic microbial abundance, hormone balance, nutrient metabolism and yield, but the molecular mechanism of yield advantage in Camellia oleifera intercropping with peanut is not clear. In this study, the C. oleifera monoculture (CK) and C. oleifera-peanut intercropping (CP) treatments in purple soil were conducted, and the physicochemical properties, gene expressions, signal pathways and crucial microbial abundances were investigated to reveal the molecular mechanism of the yield advantage of intercropped C. oleifera. The results showed that the intercropping system increased in contents of pigment, carbohydrate, available nitrogen and phosphorus in leaf and root, as well as the abundances of Burkholderia, Ralstonia, Delftia, Pseudoalteromonas and Caulobacter, enhanced the relative expression levels of CoSPS, CoGBE, CoGlgP, CoGBSS/GlgA genes to promote sugar metabolism, decreased the relative expression levels of CoASA, CoTSB, CoPAI, CoTDC and CoCYP71A13 genes for inhibiting IAA biosynthesis and signal transduction, as well as microbial diversity, Fusarium, Albifimbria and Coniosporium abundances in root, ultimately improved the fruit yield of C. oleifera. These findings indicate that intercropping system improves the fruit yield by enhancing the nutrient metabolism capability and crucial microbial abundances in root of C. oleifera in purple soil.

Metagenomic insights into nitrogen cycling functional gene responses to nitrogen fixation and transfer in maize-peanut intercropping

The fixation and transfer of biological nitrogen from peanuts to maize in maize-peanut intercropping systems play a pivotal role in maintaining the soil nutrient balance. However, the mechanisms through which root interactions regulate biological nitrogen fixation and transfer remain unclear. This study employed a 15N isotope labelling method to quantify nitrogen fixation and transfer from peanuts to maize, concurrently elucidating key microorganisms and genera in the nitrogen cycle through metagenomic sequencing. The results revealed that biological nitrogen fixation in peanut was 50 mg and transfer to maize was 230 mg when the roots interacted. Moreover, root interactions significantly increased nitrogen content and the activities of protease, dehydrogenase (DHO) and nitrate reductase in the rhizosphere soil. Metagenomic analyses and structural equation modelling indicated that nrfC and nirA genes played important roles in regulating nitrogen fixation and transfer. Bradyrhizobium was affected by soil nitrogen content and DHO, indirectly influencing the efficiency of nitrogen fixation and transfer. Overall, our study identified key bacterial genera and genes associated with nitrogen fixation and transfer, thus advancing our understanding of interspecific interactions and highlighting the pivotal role of soil microorganisms and functional genes in maintaining soil ecosystem stability from a molecular ecological perspective.

Interplanting potato with grapes improved yield and soil nutrients by optimizing the interactions of soil microorganisms and metabolites

Interplanting crops is the best method to grow crops synergistically for better utilization of land and agro-resources. Grape (Vitis vinifera) and potato (Solanum tuberosum L.) have highly efficient agricultural planting systems in China, however, how soil physicochemical properties and soil microbial communities and metabolites affect the output of grape-potato interplanting remained unknown. In this study, we employed three planting patterns (CK: grape monocropping; YY: grape interplanted with potato (variety 'Favorita'); LS: grape interplanted with potato (variety 'Longshu7')) at two experimental sites i.e., the Huizhou (2022) site and the Qingyuan site (2023). The grape variety for all planting patterns was 'Sunshine Rose'. Soil samples (top 0-20 cm) at both sites were collected to observe the diversity of bacterial communities and soil metabolites. Our findings revealed that, compared with monocropping, the interplanted systems resulted in higher concentrations of total nitrogen, available phosphorus, and available potassium and enhanced the activities of acid phosphatase, urease, and protease. The potato root exudates also altered the relative abundance of Bacillus, Kaistobacter, and Streptomyces in the rhizosphere. Among the soil metabolites, lipids and organic acids showed the most significant changes. Notably, 13-L-hydroperoxylinoleic acid is the key differentially abundant metabolite involved in the regulation of linoleic acid metabolism pathways. The association analyses of the metabolome, microbiome, and soil physicochemical properties revealed that the interactions of microbes and metabolites resulted in differences in the soil nutrient content, whereas the interactions of 13-L-hydroperoxylinoleic acid and Firmicutes improved the soil nutrient levels and bacterial composition in the interplanting systems. In summary, our findings demonstrated that intercropping grapes with potato 'Favorita' was better with respect to improving soil nutrients, soil enzyme activity, the diversity of soil bacteria, and soil metabolites without causing adverse impacts on grape yield. Overall, this study explained the physiological mechanisms by which soil microorganisms and metabolites promote potato growth in grape interplanting and provided new perspectives for the utilization of soil resources in vineyards.

Microbial perspective on restoration of degraded urban soil using ornamental plants

The urban soil where abandoned buildings are demolished is barren and structurally poor, and this degraded soil requires restoration. Ornamental plants enhance the urban environment, increase biodiversity, and affect soil physicochemical properties, microbial diversity; however, their effects remain unclear. Thus, in this study, a mixed-planting meadow consisting of 14 perennial ornamental flower species, including Iris tectorum, Iris lacteal, and Patrinia scabiosaefolia, etc. Was planted at a demolition site with sewage-contaminated soil in Beijing. Simultaneously, a single-planting lawn of I. tectorum was established in a nearby park. We aimed to examine soil physicochemical properties, sequence soil bacterial 16S rRNA and fungal ITS amplicons, and analyze soil microbial diversity and community structure at both sites at five time points in the year after planting, To explore the effect of herbaceous ornamental plants on degraded urban soil, we used FAPROTAX and FUNGuild to predict bacterial and fungal functions, the bin-based null model to evaluate the soil microbial community, and random matrix theory to construct soil microbial molecular networks. The mixed-planting meadow produced a visually appealing landscape and dynamic seasonal enrichment, significantly increasing soil total nitrogen (TN) and organic matter (SOM) contents by 1.99 and 1.21 times, respectively. TN had a positive correlation with soil microbial α diversity and community structure. Dominant phyla at both sites included Proteobacteria, Actinobacteria, and Ascomycota. Although soil microorganisms were primarily influenced by stochastic processes, stochasticity was notably higher in the mixed-planting meadow than in the single-planting lawn. The mixed-planting meadow significantly increased the relative abundance of beneficial microorganisms, improving nitrification and aerobic ammonium oxidation of soil bacteria, as well as symbiotroph of fungi. No significant changes were observed in the single-planting lawn. The mixed-planting meadow established a complex soil microbial molecular network, enhancing the correlation between bacteria and fungi and increasing the number of key microorganisms. Our findings suggest the potential of mixed-planting meadow in restoring degraded urban soils by influencing the soil microbial community and enhancing the ecological service function. Our study provides theoretical support for applying mixed-planting meadow communities to improve the soil environment of urban green spaces.

Insight into the soil bacterial community succession of Nicotiana benthamiana in response to Tobacco mosaic virus

Background

Tobacco mosaic virus (TMV) is one famous plant virus responsible for substantial economic losses worldwide. However, the roles of bacterial communities in response to TMV in the tobacco rhizosphere remain unclear.

Methods

We explored the soil physicochemical properties and bacterial community succession of the healthy (YTH) and diseased (YTD) plants with TMV infection by 16S rRNA gene sequencing and bioinformatics analysis.

Results

We found that soil pH in the YTD group was significantly lower than in the YTH group, and the soil available nutrients were substantially higher. The bacterial community analysis found that the diversity and structure significantly differed post-TMV disease onset. With TMV inoculated, the alpha diversity of the bacterial community in the YTD was markedly higher than that in the YTH group at the early stage. However, the alpha diversity in the YTD group subsequently decreased to lower than in the YTH group. The early bacterial structure of healthy plants exhibited higher susceptibility to TMV infection, whereas, in the subsequent stages, there was an enrichment of beneficial bacterial (e.g., Ramlibacter, Sphingomonas, Streptomyces, and Niastella) and enhanced energy metabolism and nucleotide metabolism in bacteria.

Conclusion

The initial soil bacterial community exhibited susceptibility to TMV infection, which might contribute to strengthening resistance of Tobacco to TMV.

How binomial (traditional rainfed olive grove-Crocus sativus) crops impact the soil bacterial community and enhance microbial capacities

Intercropping can favour the yield of the main crop. However, because of the potential competition among woody crops, this system is rarely used by farmers. To increase knowledge about the intercropping system, we have explored three different combinations of alley cropping in rainfed olive groves compared to conventional management (CP): (i) Crocus sativus (D-S); (ii) Vicia sativa/Avena sativa in annual rotation (D-O); and (iii) Lavandula x intermedia (D-L). Different soil chemical properties were analyzed to evaluate the effects of alley cropping, while 16S rRNA amplification and enzymatic activities were determined to study the changes that occurred in soil microbial communities and activity. In addition, the influence of intercropping on the potential functionality of the soil microbial community was measured. Data revealed that the intercropping systems highly affected the microbial community and soil properties. The D-S cropping system increased soil total organic carbon and total nitrogen that were correlated with the bacterial community, indicating that both parameters were the main drivers shaping the structure of the bacterial community. The D-S soil cropping system had significantly higher relative abundances of the phyla Bacteroidetes, Proteobacteria, and Patescibacteria compared to the other systems and the genera Adhaeribacter, Arthrobacter, Rubellimicrobium, and Ramlibacter, related to C and N functions. D-S soil was also related to the highest relative abundances of Pseudoarthrobacter and Haliangium, associated with the plant growth-promoting effect, antifungal activity, and a potential P solubilizer. A potentially increase of C fixation and N fixation in soils was also observed in the D-S cropping system. These positive changes were related to the cessation of tillage and the development of a spontaneous cover crop, which increased soil protection. Thus, management practices that contribute to increasing soil cover should be encouraged to improve soil functionality.