Qi Wu

Peanut (Arachis hypogaea L.) yield depends on biological nitrogen fixation, but the molecular mechanisms underlying the combined effects of arbuscular mycorrhizal fungi (AMF) and calcium fertilizer on nodulation remain unclear. Here, we used integrated transcriptomic and metabolomic analyses to investigate potential mechanisms in peanut roots. Compared with the non-inoculated control, AMF inoculation alone was associated with a 22.1% higher nodule number per plant. The combined application of AMF and CaO showed a 35.9% higher nodulation than AMF alone, and a 30.9% higher AMF colonization rate than AMF alone was also observed. Mechanistically, AMF colonization was associated with enhanced carbon-nitrogen metabolic profiles and up-regulation of phenylpropanoid metabolism-related pathways, suggesting a potential role in providing energy, carbon skeletons, and signaling molecules for nodule formation. Calcium fertilizer correlated with strengthening of the glyoxylate cycle and pentose phosphate pathway, possibly contributing to the energy supply for nodulation. It also affected genes related to protein secretion and lipid metabolism, with observed changes in membrane lipids and transport metabolites, which may enhance symbiotic interface function. This study reveals the multi-level mechanisms through which AMF and calcium fertilizer collectively promote peanut nodulation, providing a systems-level perspective on plant–microbe–nutrient relationships during symbiosis. Our findings offer new insights for sustainable agriculture by reducing chemical nitrogen inputs and promoting nodulation in legumes.

Excessive fertilization often causes soil acidification, adversely affecting crop growth and yield. While calcium uptake by peanut pods is documented, the absorption of other nutrients remains less explored. This study investigated the effects of localized phosphorus (P) fertilizer application solely to the pod zone on pod quality, yield, and the microbial community (phosphorus-solubilizing bacteria, PSB, and nitrogen-fixing bacteria, NFB) in the geocarposphere, with the root zone isolated and left unfertilized. Results demonstrated that pod-zone P application significantly increased the nitrogen and phosphorus content in kernels. Microbiome analysis revealed that this targeted fertilization altered the diversity, abundance, and dominant species of PSB. In contrast, while the abundance of NFB increased, their species diversity and dominant flora remained unchanged. These findings indicate that precise P fertilization to the pod zone enhances peanut quality and modifies the geocarposphere microbiome structure. This study highlights the significant nutrient absorption capacity of pods themselves and its role in plant development. It also suggests that rational, localized fertilization strategies can improve yield and quality by optimizing nutrient uptake and influencing the rhizosphere microbiome, offering a potential approach to mitigate the negative impacts of conventional fertilization practices.

Peanut (Arachis hypogaea L.) continuous cropping reduces yield and quality, but the effects of specific rotation methods on yield and endophytic bacterial colonization remain unclear. Based on five years of continuous cropping trial data, three different cropping systems (WF, annual summer peanut and winter fallow; GM, annual summer peanut and winter ryegrass; CR, summer peanut rotated with summer maize and winter wheat) were employed in this study to systematically analyze and evaluate the effectiveness of crop rotation in mitigating peanut continuous cropping obstacles and its underlying mechanisms. The results showed that CR increased pod yield by 33% and kernel nitrogen content by 6.8% compared to WF, while GM had a marginal effect (1.4% nitrogen increase). Microbial analysis (LEfSe/LDA) revealed that CR enriched beneficial bacteria (e.g., Actinobacteria, Corynebacteriales) in pods while suppressing potential pathogens (e.g., Gammaproteobacteria, Burkholderiales). These findings demonstrate that strategic crop rotation, particularly CR, mitigates continuous cropping obstacles by enhancing yield, improving kernel quality, and promoting beneficial endophytic bacterial communities. Our findings highlight the complexity of crop rotation system functioning and how interactions between cropping patterns and endophytic microbiota affect peanut yield and kernel quality.

Shading stress is a major negative abiotic environmental factor seriously affecting peanut growth, development, and ultimately resulting in a yield decrease in peanut in peanut/maize intercropping systems. However, 5-aminolevulinic acid (ALA) is a potential plant growth regulator that can enhance its tolerance to various abiotic stresses. However, there is limited information on how ALA affects plant physiology and molecular mechanisms under shading stress. To address this, field experiments were designed involving two shading conditions (CK and AS0, no shading; S40 and AS40, 40% shading) and two ALA foliar sprayed levels (CK and S40, no ALA application; AS0 and AS40, 20 mg L⁻¹ (0.15 mM) ALA application) to investigate the effects of the exogenous application of ALA under shading stress via the evaluation of both transcriptome and metabolome. The research results suggested that the exogenous ALA application under normal light conditions significantly enhanced photosynthesis, while exogenous ALA application could improve the stability of the cell membrane structure and biological function in response to shading stress and thereby enhance shading tolerance of the plant. The results also implied that exogenous ALA regulates the adaptability of peanuts under different light conditions by affecting the concentration of endogenous ALA. This finding improves the understanding of ALA’s regulatory molecular mechanisms and the metabolic pathways of peanuts under shading stress. Our results extend the application of ALA in agricultural production and will provide a reference for crop cultivation, especially for peanut/maize intercropping systems.

Soil properties, including soil compaction and the nutrient content, influence the composition and functions of rhizosphere microbial communities. There is limited information on how soil compaction and phosphorus application affect phosphate-solubilizing (PSB) and nitrogen-fixing bacteria (NFB). This study aimed to examine the responses of PSB and NFB in the rhizosphere of peanut (Arachis hypogaea L.) plants under varying soil compaction and phosphorus application levels. To address this, pot experiments were conducted to assess the composition and assembly processes of rhizosphere PSB and NFB in peanut cultivar Hua Yu 22 under two soil compaction levels (T1, 1.25 g/cm³ compaction, and T2, 1.00 g/cm³ compaction) and two phosphorus (P) levels (P0, no P applied, and P1, 1.2 mM P/kg soil applied). The results showed that PSB community shifts were closely correlated with the content of soil available phosphorus, soil acid phosphatase activity, soil nitrogenase activity, and soil compaction. Additionally, the content of soil available phosphorus and soil compaction were correlated with changes in operational taxonomic units of NFB. A network analysis revealed that the complexities of PSB were significantly higher than those of NFB. A stronger negative relationship was identified among NFB communities. The assembly of PSB communities was primarily driven by drift processes, whereas NFB communities were influenced by a combination of homogenizing selection and drift. Both PSB and NFB community compositions were significantly affected by phosphorus limitations and soil compaction. These findings enhance our understanding of the impacts of soil compaction and phosphorus application on PSB and NFB communities, with implications for optimizing peanut crop production. Our results will provide reference for crop cultivation in compacted and low-phosphorus soils. The important phosphate-solubilizing and nitrogen-fixing bacteria screened in the interaction network in this study will become candidate microbial agents for alleviating soil compaction and low phosphorus levels.

Soil compaction is one of the crucial factors that restrains the root respiration, energy metabolism and growth of peanut (Arachis hypogaea L.) due to hypoxia, which can be alleviated by ventilation. We therefore carried out a pot experiment with three treatments: no ventilation control (CK), (2) ventilation volumes at 1.2 (T1), and 1.5 (T2) times of the standard ventilation volume (2.02 L/pot). Compared to no-ventilation in compacted soil, ventilation T1 significantly increased total root length, root surface area, root volume and tips at the peanut anthesis stage (62 days after sowing), while T2 showed a negative impact on the above-mentioned root morphological characteristics. At the podding stage (S2, 95 days after sowing), both ventilation treatments improved root morphology, especially under T1. Compared to CK, both ventilation T1 and T2 decreased the activities of enzymes involving the anaerobic respiration, including root lactate dehydrogenase, pyruvate decarboxylase and alcohol dehydrogenase. The activities of antioxidant enzymes of root superoxide dismutase, peroxidase and catalase also decreased at S1, while superoxide dismutase and peroxidase significantly increased under T1 at S2. The ventilation of compacted soil changed soil nitrogen-fixing bacterial communities, with highest bacterial alpha diversity indices under T1. The Pearson correlation analyses indicated a positive relationship between the relative abundance of Bradyrhizobiaceae and root activity, and between unclassified_family of Rhizobiales and the root surface area, while Enterobacteriaceae had a negative impact on the root nodule number. The Pearson correlation test showed that the root surface, tips and activity positively correlated with root superoxide dismutase and peroxidase activities. These results demonstrate that soil ventilation could enhance plant root growth, the diversity and function of soil nitrogen-fixing bacterial communities. The generated results from this present study could serve as important evidence in alleviating soil hypoxia caused by compaction.

The root-knot nematode (RKN) disease is a highly destructive soilborne disease that significantly affects peanut yield in Northern China. The composition of the soil microbiome plays a crucial role in plant disease resistance, particularly for soilborne diseases like RKN. However, the relationship between the occurrence of RKN disease and the structure and diversity of bacterial communities in peanut fields remains unclear. To investigate bacterial diversity and the community structure of peanut fields with severe RKN disease, we applied 16S full-length amplicon sequencing based on the third high-throughput sequencing technology. The results indicated no significant differences in soil bacterial α-diversity between resistant and susceptible plants at the same site. However, the Simpson index of resistant plants was higher at the site of peanut-wheat-maize rotation (Ro) than that at the site of peanut continuous cropping (Mo), showing an increase of 21.92%. The dominant phyla identified in the peanut bulk soil included Proteobacteria, Acidobacteria, Actinobacteria, Planctomycetes, Chloroflexi, Firmicutes, and Bacteroidetes. Further analysis using LEfSe (Linear discriminant analysis effect size) revealed that Sulfuricellaceae at the family level was a biomarker in the bulk soil of susceptible peanut compared to resistant peanut. Additionally, Singulisphaera at the genus level was significantly more enriched in the bulk soil of resistant peanut than that of susceptible peanut. Soil properties were found to contribute to the abundance of bacterial operational taxonomic units (OTUs). Available phosphorus (AP), available nitrogen (AN), organic matter (OM), and pH made a positive contribution to the bacterial OTUs, while available potassium (AK) made a negative contribution. The metabolic pathway of novobiocin biosynthesis was only enriched in soil samples from resistant peanut plants. Eleven candidate beneficial bacteria and ten candidate harmful strains were identified in resistant and susceptible peanut, respectively. The identification of these beneficial bacteria provides a resource for potential biocontrol agents that can help improve peanut resistance to RKN disease. Overall, the study demonstrated that severe RKN disease could reduce the abundance and diversity of bacterial communities in peanut bulk soil. The identification of beneficial bacteria associated with resistant peanut offered the possibility for developing biocontrol strategies to enhance peanut resistance to RKN disease.

Background: Phosphorus (P) is one of the most essential macronutrients for crops. The growth and yield of peanut (Arachis hypogaeaL.) are always limited by P deficiency. However, the transcriptional and metabolic regulatory mechanisms were less studied. In this study, valuable phenotype, transcriptome and metabolome data were analyzed to illustrate the regulatory mechanisms of peanut under P deficiency stress.Result: In present study, two treatments of P level in deficiency with no P application (–P) and in sufficiency with 0.6 mM P application (+ P) were used to investigate the response of peanut on morphology, physiology, transcriptome, microRNAs (miRNAs), and metabolome characterizations. The growth and development of plants were significantly inhibited under –P treatment. A total of 6088 differentially expressed genes (DEGs) were identified including several transcription factor family genes, phosphate transporter genes, hormone metabolism related genes and antioxidant enzyme related genes that highly related to P deficiency stress. The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses indicated that 117 genes were annotated in the phenylpropanoid biosynthesis pathway under P deficiency stress. A total of 6 miRNAs have been identified significantly differential expression between + P and –P group by high-throughput sequencing of miRNAs, including two up-regulated miRNAs (ahy-miR160-5p and ahy-miR3518) and four down-regulated miRNAs (ahy-miR408-5p, ahy-miR408-3p, ahy-miR398, and ahy-miR3515). Further, the predicted 22 target genes for 6 miRNAs andcis-elements in 2000 bp promoter region of miRNA genes were analyzed. A total of 439 differentially accumulated metabolites (DAMs) showed obviously differences in two experimental conditions.Conclusions: According to the result of transcripome and metabolome analyses, we can draw a conclusion that by increasing the content of lignin, amino acids, and levan combining with decreasing the content of LPC, cell reduced permeability, maintained stability, raised the antioxidant capacity, and increased the P uptake in struggling for survival under P deficiency stress.

Pseudomonas veronii is known for its ability of bioremediation of contaminated soils and water. In this study, the 6.48Mb draft genome of Pseudomonas veronii RZ strain was reported which is identified from a Arachis hypogaea plant with bacterial wilt (BW) in Ri Zhao city of China. The p. veronii may have relationship with peanut BW. The studies may be helpful to development new effective methods to control BW.