Guanchu Zhang

The Cation/H ⁺ exchanger (CAX) is an important class of transmembrane transporter protein that plays a crucial role in regulating plant Ca ²⁺ balance, resisting abiotic stresses, and transporting heavy metal ions. The peanut CAX gene family was identified at the genome-wide level, including analyses of their physicochemical properties, phylogenetic relationships, exon-intron composition, chromosomal localization, gene duplication events, cis-acting elements, transcriptional regulatory network prediction, and expression patterns. The results showed that 10 AhCAX genes were identified in the whole genome, distributed on eight chromosomes, and five pairs of gene segment duplication events occurred. These genes encode proteins ranging from 371 to 501 amino acids, with isoelectric points of 5.1 to 8.7. Phylogenetic analysis indicated that AhCAXs were divided into two subfamilies, and members of the same subfamily exhibit similar gene structures, conserved motifs, and numbers of transmembrane domains. It was found that hormone-responsive and stress-responsive elements exist in the promoter regions of AhCAXs . The expression patterns of AhCAX genes showed that AhCAX1 , AhCAX4 , AhCAX7 , AhCAX8 , and AhCAX9 were significantly up-regulated under drought or salt stress. Notably, overexpression of the AhCAX8 gene conferred salt tolerance in transgenic Arabidopsis plants by enhancing antioxidant enzyme activity. The results provide a basis for further exploring the function of the peanut CAX genes, and provide candidate gene resources for the cultivation of stress-resistant peanut varieties.

Legume–rhizobium symbiosis represents a crucial biological nitrogen fixation system. The AP2/ERF transcription factor ERN1 plays a vital role in nodulation of model legumes; however, its function in peanut (Arachis hypogaea), a typical crack-entry infection legume, remains unclear. To explore this, we performed transcriptome sequencing of peanut roots at 3 days post-inoculation (dpi) with rhizobium. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses showed that differentially expressed genes (DEGs) were mainly enriched in DNA-binding transcription factor activity, plant–pathogen interaction, and plant hormone signal transduction pathways. The most strongly up-regulated gene was AhERN1, which was highly expressed in peanut roots and nodules. Subcellular localization indicated that AhERN1 was a nuclear-localized protein, and yeast transcriptional activation assays confirmed that AhERN1 functions as a transcriptional activator relying on its C-terminal domain. Furthermore, hairy root overexpression of AhERN1 significantly increased the number of peanut nodules. Collectively, these results reveal that AhERN1 acts as a positive regulator to promote rhizobium-induced nodule development in peanut, providing new insights into the regulatory mechanism of nodulation in dalbergoid legumes.

Accurate evaluation of peanut seedling emergence is critical for ensuring agronomic research accuracy and planting benefit efficiency, but traditional manual methods are limited by strong subjectivity and inconsistent batch inspection standards. In order to quickly and accurately evaluate the emergence rate and quality of peanuts, this study proposes an intelligent evaluation system for peanut seedling conditions, which is constructed based on an improved YOLOv11 combined with the Segment Anything Model (SAM) for peanut seedling emergence evaluation, using high-resolution images collected by Unmanned Aerial Vehicles as the data foundation. Experimental results show that the improved YOLOv11 model achieves a detection precision of 96.36%, a recall rate of 96.76%, and an mAP@0.5 of 99.03%. The segmentation performance of SAM is outstanding in terms of integrity. In practical applications, the detection time for a single image by the system is as low as 83.4 ms, and the efficiency of video counting is 6–10 times higher than that of manual counting. Without extensive data annotation, this method performs excellently in peanut seedling emergence quantity statistics and growth status classification, providing efficient, accurate technical support for refined peanut cultivation management and mechanical sowing quality evaluation.

Peanut (Arachis hydropoaea L.) demonstrates a prominent adaptability to diverse soil types. However, the specific effects of soil types on peanut growth and bacterial communities remain elusive. This study conducted a thorough examination of the agronomic traits, the corresponding physicochemical properties, and bacterial structure of rhizosphere soil in acidic (AT), neutral (NT), and saline–alkali (ST) soils, elucidating the internal relationship between soil type and peanut yield. Our results showed that different soil types exhibited significant differences in peanut yield, with ST demonstrating the lowest yield per plant, showing an 85.05% reduction compared to NT. Furthermore, available phosphorus content, urease, and invertase activities were substantially reduced in both ST and AT, particularly in ST by 95.35%, 38.57%, and 62.54%, respectively. Meanwhile, metagenomic sequencing unveiled a notable decline in Bradyrhizobium and Streptomyces in these soils, which is crucial for soil improvement. Further metabolic pathway analysis revealed that the reduction in pathways related to soil remediation, fertility improvement, and stress response in AT and ST may lead to slower peanut growth. In conclusion, peanuts cultivated in acidic and saline–alkali soils can increase yield via implementing soil management practices such as improving soil quality and refining micro-environments. Our study provides practical applications for enhancing peanut yield in low- to medium-yield fields.

Water and fertilizer application strategies seriously affect the healthy growth of peanuts. The stoichiometric ratio can directly reflect the elemental requirements for crop growth, which are very important for improving fertilizer utilization efficiency. In order to investigate the response of C (carbon), N (nitrogen), and P (phosphorus) allocation pattern and stoichiometric characteristics in peanut seedlings to water and nitrogen addition, we designed a greenhouse pot experiment which had different water treatments (W1, 75–80% field capacity; W2, 45–50% field capacity) and nitrogen addition treatments (N0, 0 kg hm⁻²; N1, 90 kg hm⁻²; N2, 180 kg hm⁻²). The distribution and content changes in C, N, and P in different organs were measured and analyzed by ecological stoichiometry. The results showed that drought stress significantly increased the N or P content of different organs. The average N/P value of peanut roots treated with W2 decreased by 13.02% compared to W1. Restoring irrigation relieved this stress while reducing the C/N and C/P of roots, stems, and leaves, as well as the N/P of roots and stems. The water treatment after rehydration showed significant differences in the C/N, C/P, and N/P ratios of peanut roots. The average values of the C/N, C/P, and N/P ratios of peanut roots in W2 treatment were reduced by 13.54%, 28.66%, and 16.34%, respectively, compared to W1 treatment. On the other hand, nitrogen application significantly increased the N content of stems and leaves, while reducing C/N. On the contrary, it significantly reduced the P content of roots and stems, and increased the N/P ratio of roots, stems, and leaves. Overall, there is a significant interaction between water and nitrogen treatment on the stoichiometric characteristics of C, N, and P in different organs, with water treatment playing a dominant role. In terms of nutrient distribution in organs, the average N content in leaves is the highest. The coefficient of variation (CV) of P content is greater than that of C and N content. The CV of N content, P content, and C/N and N/P ratios of the stem are all greater than those of the roots or leaves, while the stems are more sensitive to water and nitrogen conditions. And the N and P content of roots, stems, and leaves were positively correlated. Meanwhile, peanut seedlings have the phenomenon of ionic synergism that occurs between nitrogen and phosphorus ions. In summary, studying the stoichiometric ratios can reflect the water and fertilizer demand status of peanuts, thereby better improving water and fertilizer utilization efficiency.

Peanuts grown in saline alkali soil are also subjected to drought stress caused by water scarcity. Therefore, we used HY25 (peanut variety) as an experimental material to investigate the effects of drought on the height of peanut main stems, length of the first lateral branch, leaf area per plant, SPAD value, net photosynthetic rate, and accumulation and distribution of photosynthetic products in saline alkali soil. The results showed that the combined stress of short-term drought and salt significantly reduced the main stem height, first lateral branch length, single plant leaf area, SPAD value, net photosynthetic rate (Pn), intercellular carbon dioxide concentration (Ci), and dry matter accumulation of peanuts, including a decrease in single plant pod yield, 100-pod weight, 100-kernel weight, and peanut yield. And the impact of drought stress on peanut yield varies at different growth stages. For example, under drought stress alone, the sensitive period is the 40th day after planting (40D) > 60th day after planting (60D) > 30th day after planting (30D). Short-term drought has the greatest impact on peanut yield at 40D, while in contrast, resuming watering after drought at 30D results in a slight but not significant increase in peanut yield in comparison with the control. Under the combined stress of drought and salt, the sensitive period of peanuts was 40D > 30D > 60D, and the single pod weight of peanuts was significantly reduced by 15.26% to 57.60% from the flowering stage to the pod stage under drought treatment compared to salt treatment, indicating a significant interaction between drought and salt stress, reducing the single leaf area and net photosynthetic rate of peanut leaves, ultimately leading to a decrease in peanut yield. Therefore, when planting peanuts in saline alkali soil, drought should be avoided, especially early drought, in order to prevent the combined effects of drought and salt stress from harming peanut yield.

Short-term drought events occur more frequently and more intensively under global climate change. Biochar amendment has been documented to ameliorate the negative effects of water deficits on plant performance. Moreover, biochar can alter the soil microbial community, soil properties and soil metabolome, resulting in changes in soil functioning. We aim to reveal the extent of biochar addition on soil nutrients and the soil microbial community structure and how this improves the tolerance of legume crops (peanuts) to short-term extreme drought. We measured plant performances under different contents of biochar, set as a gradient of 2%, 3% and 4%, after an extreme experimental drought. In addition, we investigated how soil bacteria and fungi respond to biochar additions and how the soil metabolome changes in response to biochar amendments, with combined growth experiments, high-throughput sequencing and soil omics. The results indicated that biochar increased nitrites and available phosphorus. Biochar was found to influence the soil bacterial community structure more intensively than the soil fungal community. Additionally, the fungal community showed a higher randomness under biochar addition when experiencing short-term extreme drought compared to the bacterial community. Soil bacteria may be more strongly related to soil nutrient cycling in peanut agricultural systems. Although the soil metabolome has been documented to be influenced by biochar addition independent of soil moisture, we found more differential metabolites with a higher biochar content. We suggest that biochar enhances the resistance of plants and soil microbes to short-term extreme drought by indirectly modifying soil functioning probably due to direct changes in soil moisture and soil pH.

Peanut (Arachis hypogaea L.) is an important oil and cash crop. An efficient utilization of saline–alkali soil resources, the development of peanut planting in saline–alkali soil, and obtaining high and stable yield have become urgent needs to ensure peanut production. Arbuscular mycorrhizal fungi (AMF) have been reported to develop the potential productivity of host plants and improve their salt resistance and tolerance. However, there is still limited research on promoting the growth and morphology of peanut roots. Therefore, in this study, seeds of salt-tolerant peanut variety “HY 25” were coated with commercial AMF inoculant before being planted in saline–alkali and normal soils to investigate the effects of AMF on peanut root growth and rhizosphere soil. The results showed that root morphological characteristics were significantly increased by the use of AMF at the podding stage in saline–alkali soil and from the flowering and pegging stage to the maturity stage in normal soil. Of note, the total root volume of peanut inoculated with AMF significantly increased by 31.57% during the podding stage in saline–alkali soil. Meanwhile, AMF significantly increased the phosphatase and invertase activities in the peanut rhizosphere of saline–alkali soil from the flowering stage to maturity stage and soil CAT activity at the maturity stage (41.16~48.82%). In normal soil, soil phosphatase and urease activities were enhanced by AMF at the flowering stage and the podding stage, respectively. AMF also increased the contents of soil organic matter, available phosphorus, and hydrolysable nitrogen, but decreased soil EC in saline–alkali soil. In addition to the significant increase in soil available phosphorus content, AMF had no significant effect on the physical and chemical properties of the soil and other soil nutrients in normal soil. AMF significantly increased pod biomass and yield in saline–alkali soil and normal soil, and improved their agronomic characteristics. In conclusion, peanut seeds coated with AMF improved the root morphological characteristics of peanuts and improved the physical and chemical properties in peanut rhizosphere, especially in saline–alkali soil. The process of rhizosphere soil nutrient transformation was also enhanced. Finally, AMF improved plant agronomic traits to increase the pod yield (16.5~21.9%). This study provides the theoretical basis and technical support for the application of AMF in peanut production in saline–alkali soil.

The yield and quality of peanut (Arachis hypogaea L.), an oil crop planted worldwide, are often limited by drought stress (DS) and nitrogen (N) deficiency. To investigate the molecular mechanism by which peanut counteracts DS and N deficiency, we conducted comprehensive transcriptomic and metabolomic analyses of peanut leaves. Herein, 829 known differentially accumulated metabolites, 324 differentially expressed transcription factors, and 5294 differentially expressed genes (DEGs) were identified under different water and N conditions. The transcriptome analysis demonstrated that drought-related DEGs were predominantly expressed in “glycolysis/gluconeogenesis” and “glycerolipid metabolism”, while N-deficiency-related DEGs were mainly expressed in starch and sucrose metabolism, as well as in the biosynthesis of amino acid pathways. The biosynthesis, transport, and catabolism of secondary metabolites accounted for a large proportion of the 1317 DEGs present in water and N co–limitation. Metabolomic analysis showed that the metabolic accumulation of these pathways was significantly dependent on the stress conditions. Additionally, the roles of metabolites and genes in these pathways, such as the biosynthesis of amino acids and phenylpropanoid biosynthesis under different stress conditions, were discussed. The results demonstrated that different genes, metabolic pathways, and metabolites were related to DS and N deficiency. Thus, this study elucidates the metabolic pathways and functional genes that can be used for the improvement of peanut resistance to abiotic stress.

Long-term excessive application of chemical fertilizers can cause many problems, such as soil degradation and environmental pollution. Therefore, we reduced conventional nitrogen fertilization and added organic fertilizers in some cases to investigate the response of photosynthetic characteristics, root nodules and yield on reduced nitrogen fertilization. Compared to conventional nitrogen fertilization, the 25% and 35% nitrogen reduction treatments reduced the leaf area index, net photosynthetic rate, 100-fruit weight, 100-kernel weight and the yield of peanut, but had no significant effect on the kernel rate. With constant N fertilizer, adding organic fertilization alone increased leaf area index, chlorophyll, net photosynthetic rate and yield of peanut. In compounded treatments of nitrogen and organic fertilizer, the highest yields were achieved in the 25% N reduction with the 3000 kg/hm⁻² organic fertilizer treatment (T3) and the 4500 kg/hm⁻² organic fertilizer treatment (T4); furthermore, the net photosynthetic rate, leaf area index, yield and fertilizer contribution were significantly higher in these two treatments than in the conventional fertilizer treatments. Nitrogen fertilizer had significant effects on the quantity and fresh weight of root nodules. Concretely, nitrogen reduction increased the quantity and fresh weight of root nodules of peanut in the early stage of fertility but decreased them in the harvest stage. Nitrogen reduction with an additional organic fertilizer in the late stage of fertility increased the quantity and fresh weight of root nodules of peanut. Considering the property of root nodules was significantly positively correlated with net photosynthetic rate and yield, the arguments above may be the mechanism of the highest yields found in T3 and T4. This work can provide empirical and instructional support for a balanced fertilization strategy in peanut agriculture and high-yielding and efficient cultivation of peanut.