Tengqi Xu's research while affiliated with Northwest A & F University and other places

Sunflower broomrape (Orobanche cumana Wallr.) has severely restricted the development of the sunflower industry in China, and more efficient and convenient control methods are urgently needed. In this experiment, we investigated the effects of N, P and silica fertilizers on the parasitism rate of O. cumana, as well as on the yield of sunflower and native microbial communities in the field. Firstly, pot experiments were conducted to select the most effective fertilization method and to determine the physiological and biochemical indexes of sunflowers. Subsequently, field application studies were carried out to determine the physiological indexes, yield, O. cumana parasitism on sunflower, and the effect on the indigenous microbial community. The results demonstrate that compared with the CNP treatment (Control), the number of parasites under the N1P5 treatment significantly decreased by 66.15%. The exogenous application of silica can significantly reduce the number of O. cumana parasites. The treatments with N1P5 (N/P = 1:5) and available SiO2 content higher than 40 mg/kg (NS2, NS3, SF2 and SF3) significantly increased superoxide dismutase (SOD) activity and decreased malondialdehyde (MDA) content in sunflower leaves. In the field, fertilization significantly decreased the number of O. cumana parasites. The S treatment improved the native microbial community structure and enriched beneficial microorganisms, including Vicinamibacteria and Pyrinomonadaceae. Additionally, applying the S treatment significantly increased sunflower yield by 23.82% and crude protein content by 20.20%. In summary, the application of silicon fertilizer can effectively improve the host microbial community, reduce O. cumana parasitism and improve the yield and quality of sunflower.

Main conclusion Synthetic consortia performed better in promoting Schisandra chinensis growth than individual strains, and this result provides valuable information for the development of synthetic microbial fertilizers. Abstract Schisandra chinensis is an herbal medicine that can treat numerous diseases. However, the excessive reliance on chemical fertilizers during the plantation of S. chinensis has severely restricted the development of the S. chinensis planting industry. Plant growth-promoting rhizobacteria (PGPR) can promote the growth of a wide range of crops, and synthetic consortia of them are frequently superior to those of a single strain. In this study, we compared the effects of four PGPR and their synthetic consortia on S. chinensis growth. The pot experiment showed that compared with the control, synthetic consortia significantly increased the plant height, biomass, and total chlorophyll contents of S. chinensis, and their combined effects were better than those of individual strains. In addition, they improved the rhizosphere soil fertility (e.g., TC and TN contents) and enzyme activities (e.g., soil urease activity) and affected the composition and structure of soil microbial community significantly, including promoting the enrichment of beneficial microorganisms (e.g., Actinobacteria and Verrucomicrobiota) and increasing the relative abundance of Proteobacteria, a dominant bacterial phylum. They also enhanced the synergistic effect between the soil microorganisms. The correlation analysis between soil physicochemical properties and microbiome revealed that soil microorganisms participated in regulating soil fertility and promoting S. chinensis growth. This study may provide a theoretical basis for the development of synthetic microbial fertilizers for S. chinensis.

Soil heavy metal pollution is one of the most serious environmental problems in China, especially cadmium (Cd), which has the most extensive contaminated soil coverage. Therefore, more economical and efficient remediation methods and measures are needed to control soil Cd contamination. In this study, different amendments (biochar (B), organic fertilizer (F), lime (L)) and actinomycetes (A) inoculants were applied to Cd contaminated farmland to explore their effects on wheat growth. Compared with Control, all treatments except A treatment were able to significantly increase the underground parts dry mass of wheat, with the highest increase of 57.19 %. The results showed that the B treatment significantly increased the plant height of wheat by 3.45 %. All treatments increased wheat SOD activity and chlorophyll content and reduced the MDA, which contributes to wheat stress resistance under Cd contamination. F, L and AF treatments can significantly reduce the Cd content in wheat above- and underground parts by up to 56.39 %. Soil amendments can modify the physical and chemical properties of the soil, which in turn affects the absorption of Cd by wheat. Moreover, the addition of soil amendments significantly affects the composition and structure of the rhizospheric soil bacterial community at the wheat jointing stage. The application of organic fertilizer increases the richness and diversity of the bacterial community, while lime makes it significantly decreases it. T-test and microbiome co-occurrence networks show that actinomycetes could not only effectively colonize in local soil, but also effectively enhance the complexity and stability of the rhizosphere microbial community. Considering the practical impact of different treatments on wheat, soil microorganisms, economic benefits and restoration of soil Cd contamination, the application of organic fertilizer and actinomycetes in Cd contaminated soil is a more ideal remediation strategy. This conclusion can be further verified by studying larger repair regions and longer consecutive repair cycles to gain insight into the repair mechanism.

Orobanche cumama wallr. is the sunflower root parasitic weed with special life stage in which seed germination and parasitism take place in the soil. In practice, applying microbial agents and trapping crop rotation are utilized separately, or just one of them is selected to control O. cumana. The development of the sunflower industry is severely constrained on the farmland, where there is high density of O. cumana’s seed banks. In this study, two biological control methods were combined to solve the problem of O. cumana parasitism. The bioassay experiment showed that the high concentration fermentation filtrates of Streptomyces rochei D74 could effectively inhibit the germination and growth of the germ tube of O. cumana seeds. As the concentration was increased to 3.1 mg/mL, O. cumana was almost unable to sprout. A two-year pot experiment revealed that the use of D74 agents and sunflower–maize–sunflower rotation together promoted sunflower growth, as shown by the biomass accumulation, plant height, and denser root systems. The combined method resulted in a significant decrease in the number of O. cumana parasitism, compared to one method alone. Additionally, it affected the bacterial community composition of sunflower rhizosphere, mostly leading to an increase in Streptomyces and Brevibacterium and a decrease in Arthrobacter. This experiment, combined with multiple biological control, means significantly reducing the parasitism of O. cumana, which provides an effective foundation for practical application.

Abstract Orobanche cumana Wallr. is a holoparasite weed that extracts water and nutrients from its host the sunflower, thereby causing yield reductions and quality losses. However, the number of O. cumana parasites in the same farmland is distinctly different. The roots of some hosts have been heavily parasitized, while others have not been parasitized. What are the factors contributing to this phenomenon? Is it possible that sunflower interroot microorganisms are playing a regulatory role in this phenomenon? The role of the microbial community in this remains unclear. In this study, we investigated the rhizosphere soil microbiome for sunflowers with different degrees of O. cumana parasitism, that is, healthy, light infection, moderate infection, and severe infection on the sunflower roots. The microbial structures differed significantly according to the degree of parasitism, where Xanthomonadaceae was enriched in severe infections. Metagenomic analyses revealed that amino acid, carbohydrate, energy, and lipid metabolism were increased in the rhizosphere soils of severely infected sunflowers, which were attributed to the proliferation of Lysobacter. Lysobacter antibioticus (HX79) was isolated and its capacity to promote O. cumana seed germination and increase the germ tube length was confirmed by germination and pot experiments. Cyclo(Pro‐Val), an active metabolite of strain HX79, was identified and metabolomic and molecular docking approaches confirmed it was responsible for promoting O. cumana seed germination and growth. And we found that Pseudomonas mandelii HX1 inhibited the growth of O. cumana in the host rhizosphere soil. Our findings clarify the role of rhizosphere microbiota in regulating the parasite O. cumana to possibly facilitate the development of a new weed suppression strategy.

The degradable plastic poly(butylene adipate-co-terephthalate) (PBAT) is considered a potential replacement for low-density polyethylene (LDPE) as the main component of mulch film. However, it is not clear whether PBAT is harmful to the plant-soil system. Thus, we determined the effects of LDPE microplastics (LDPE-MPs) and PBAT microplastics (PBAT-MPs) on the growth of Arabidopsis. The inhibitory effect of PBAT-MPs was greater than that of LDPE-MPs on the growth of Arabidopsis. Transcriptome analysis showed that PBAT-MPs severely disrupted the photosynthetic system of Arabidopsis and increased the expression levels of genes in drug transport-related pathways. PBAT-MPs increased the relative abundances of Bradyrhizobium, Hydrogenophaga, and Arthrobacter in the bulk soil and rhizosphere soil. The abundances of Variovorax, Flavobacterium, and Microbacterium increased in the plant root zone only under PBAT-MPs. Functional prediction analysis suggested that microorganisms in the soil and plant root zone could degrade xenobiotics. Furthermore, the degradation products from PBAT comprising adipic acid, terephthalic acid, and butanediol were more toxic than PBAT-MPs. Our findings demonstrate that PBAT-MPs may be degraded by microorganisms to produce chemicals that are highly toxic to plants. Thus, biodegradable plastics may pose a great risk to the environment.

Wasted polyethylene (PE) products caused pollution has become a global issue. Researchers have identified PE-degrading bacteria which have been considered as a sustainable alleviation to this crisis. However, the degradation mechanism employed by currently isolated bacteria is unclear and their degradation efficiencies are insufficient. More importantly, there is little research into bacteria capable of degrading PE mulching film to solve “white” pollution in agriculture. We determined the PE degradation efficiency of two Pseudomonas, identified by 16 S rDNA analysis, and elucidated their potential mechanisms through whole genome sequencing. During an 8-week period, PE mulch lost 5.95 ± 0.03% and 3.62 ± 0.32% of its mass after incubated with P. knackmussii N1-2 and P. aeruginosa RD1-3 strains, respectively. Moreover, considerable pits and wrinkles were observed on PE.The hydrophobicity of PE films also decreased, and new oxygenic functional groups were detected on PE mulch by Fourier Transform Infrared Spectrometry (FTIR). Complete genome sequencing analysis indicated that two Pseudomonas strains encode genes for enzymes and metabolism pathways involved in PE degradation. The results provide a theoretical basis for further research that investigates the mechanism driving the degradation and metabolism of discarded PE in the environment.

Restoring degraded land is an efficient strategy for improving biodiversity and ecosystem functioning. However, the effects of aboveground and belowground biodiversity on multiple ecosystem functions (multifunctionality) during ecological restoration are not well understood. Here, the relationships between plant and microbial communities and soil multifunctionality were assessed in a 30-year natural grassland restoration chronosequence on the Loess Plateau, China. Soil multifunctionality, in relation to the carbon, nitrogen, phosphorus, and sulfur cycles, was quantified. Soil bacterial and fungal communities were analyzed by high-throughput sequencing using the Illumina HiSeq platform. The results showed that soil multifunctionality was significantly increased with the increasing period of grassland restoration. Plant and bacterial diversity, rather than fungal diversity, were significantly and positively correlated with soil multifunctionality based on single functions, averaging, and multiple threshold approaches. Random forest and structural equation modeling analyses showed that soil multifunctionality was affected by both biotic and abiotic factors. Plant diversity and bacterial community composition had direct effects, whereas plant community composition had both direct and indirect effects on soil multifunctionality. Restoration period and soil pH indirectly affected soil multifunctionality by altering plant and bacterial communities. This work demonstrates the importance of aboveground and belowground biodiversity in driving soil multifunctionality during grassland restoration. The results provide empirical evidence that conserving biodiversity is crucial for maintaining ecosystem functions in restored areas.