A Systematic Review on the Continuous Cropping Obstacles and Control Strategies in Medicinal Plants

Fumigant dazomet induces tobacco plant growth via changing the rhizosphere microbial community

After continuous cropping for many years, crops are often subject to growth inhibition, which seriously affects their yields.In agricultural production, soil fumigation can effectively alleviate the biological stress on plants. However, the relationship between the microbial groups that respond to soil fumigation changes and plants, as well as whether their existence makes a beneficial contribution to plants, remains unclear. We explored the mechanism of soil fumigation promoting plant growth by affecting microorganisms. The results showed that dazomet treatment significantly alleviated the growth retardation of tobacco, and this difference was most obvious in the flourishing period of tobacco, when the plant height and leaf area increased by 3.33 times and 3.24 times respectively. In addition, the growth advantage of the above-ground tissue was significantly correlated with the root advantage (P < 0.05). At the same time, we found that dazomet treatment significantly increased a large number of microbial groups positively related to roots, such as g_Pedobacter, g_Microbacterium and g_Brevundimonas. The results of structural equation modeling indicated that the microbial community, which was positively correlated with the amount of dazomet applied and also positively correlated with roots (P < 0.05), was an important factor contributing to the growth advantage of tobacco. Overall, the findings of this study are of great significance for enhancing our understanding of soil remediation by fumigation and may have far reaching implications for the practical application of dazomet fumigation.

Genome-Wide Identification of the CIF Gene Family and Protein Interaction with GSO1s Under the p-HBA-Induced Continuous Cropping Obstacle in Pogostemon cablin

Casparian strip integrity factors (CIFs), which are tyrosine-sulfated small peptides, are crucial genes involved in the formation and regulation of the Casparian strip and play an important role in the regulation of plant stress response. In order to explore the evolution, characteristics, role, and function of CIFs in response to continuous cropping obstacles (CCOs), the bioinformatics and gene expression analysis of CIF genes in Pogostemon cablin was carried out by determining the phylogenetic relationship, chromosome location, gene structure, and RT-qPCR results. Results showed that a total of 12 PatCIF family genes were identified on 12 different chromosomes. Promoter prediction analysis revealed 16 different cis-regulatory elements. A systematic evolutionary study of 33 species indicates CIF family genes originated from Spermatophyta. Collinearity analysis revealed P. cablin shared 19 syntenic genes with Solanum lycopersicum and only 8 with Oryza sativa. Transcriptome analysis indicated that the expression of PatCIF1-4 and PatGSO1b/1c/1f genes decreased under p-hydroxybenzoic acid treatment, and further RT-qPCR validation of four PatCIF genes was consistent with the results. AlphaFold prediction showed a protein interaction region between PatCIF1-4 mature peptide and PatGSO1b/1c/1f via the LRR domain, which provides a key binding surface for mature PatCIFs. This study offers a theoretical basis to investigate the roles of PatCIFs and PatGSO1s in CCOs and their protein interactions in P. cablin.

Plant-microbe interactions influence plant performance via boosting beneficial root-endophytic bacteria

BACKGROUND

Salvia miltiorrhiza is a highly valuable medicinal plant and its cultivation is constrained by limited suitable land. Long-term continuous cropping practices alleviate limitations in planting area as well as causes the decline in plant yield and quality. Endophytic microorganisms colonize inside plant roots and are known to play important roles in improving the performance of model plants (such as Arabidopsis thaliana) and food crops (such as wheat, soybean, rice and maize). However, the understanding of how medicinal plants with different growth status (i.e., healthy and disease) shape the assembly of root-endophytic microorganisms and the functional importance of these microorganisms in improving plant performance remains largely unknown.

RESULTS

Here, we investigated the assembly of root-endophytic microorganisms in medicinal plants with different growth status and its links with plant performance improvement. We found that medicinal plants with different growth status had distinct root-endophytic bacterial communities. Healthy plant roots recruited some potentially beneficial bacteria partners, particularly Pseudomonas into the endosphere. We further investigated the functional importance of these potentially beneficial bacteria on plant performance in subsequent greenhouse and field experiments. We found that root-endophytic Pseudomonas effectively increased medicinal plant seedling growth, crop yield, and the content of effective medicinal components.

CONCLUSIONS

Taken together, we demonstrate that healthy medicinal plants can form a distinct root-endophytic bacterial community, leading to an increase in plant growth-promoting endophytic bacteria (PGPEB) that contribute to the improvement of crop growth and quality. Our research provides valuable insights into the significant role of PGPEB in enhancing crop growth and improving medicinal plants quality for human health development in the future.

Optimization of Intercropping Modes in Placodon grandiflorus

Intercropping enhances plant growth, increases yield, and boosts the accumulation of secondary metabolites. Platycodon grandiflorus (P. grandiflorus), a traditional Chinese medicinal herb, has limited research available regarding its intercropping practices. We aimed to (1) examine the changes in the physiological and biochemical indicators of plant growth during the intercropping process of P. grandiflorus, (2) assess the quality of P. grandiflorus when intercropped with different crops, and (3) evaluate the optimal intercropping mode for P. grandiflorus. This study utilized the two-year seedlings of P. grandiflorus as the test material in a field study. The intercropping treatments included P. grandiflorus monoculture (JG-JG), intercropping with Achyranthes bidentata (JG-NX), Saposhnikovia divaricata (JG-FF), Adenophora stricta (JG-SS), Zea mays (JG-YM), Setaria italica (JG-GZ), and Glycine max (JG-DD). We investigated the effects of these different intercropping modes on the growth, physiological and biochemical indicators, and the accumulation of five saponins in P. grandiflorus at various growth and development stages. Compared with JG-JG, the chlorophyll and the MDA contents significantly increased and decreased, respectively, in the JG-YM, JG-DD, and JG-NX treatments. All the three treatments enhanced the biomass and exhibited the higher levels of antioxidant enzyme activity and osmoregulatory substance content. JG-YM and JG-SS significantly (p < 0.05) improved the quality of P. grandiflorus, with JG-SS intercropping notably maintaining a high content of platycodin D. The results of this study provide a scientific basis for optimizing intercropping planting systems and advancing the sustainable development of the traditional Chinese medicine industry.

Continuous cropping of Patchouli alters soil physiochemical properties and rhizosphere microecology revealed by metagenomic sequencing

Continuous cropping (CC) profoundly impacts soil ecosystems, including changes in soil factors and the structure and stability of microbial communities. These factors are interrelated and together affect soil health and plant growth. In this research, metagenomic sequencing was used to explore the effects of CC on physicochemical properties, enzyme activities, microbial community composition, and functional genes of the rhizosphere soil of patchouli. We found that this can lead to changes in various soil factors, including the continuous reduction of pH andNH 4 + -N and the unstable changes of many factors. In addition, S-PPO enzyme activity increased significantly with the cropping years, but S-NAG increased in the first 2 years and decreased in the third cropping year. Metagenomic sequencing results showed that CC significantly changed the diversity and composition of rhizosphere microbial communities. The relative abundance of Pseudomonas and Bacteroides decreased substantially from the phylum level. At the genus level, the number of microbial genera specific to the zero-year cropping (CK) and first (T1), second (T2), and third (T3) years decreased significantly, to 1798, 172, 42, and 44, respectively. The abundance of many functional genes changed, among which COG0823, a gene with the cellular process and signaling functions, significantly increased after CC. In addition,NH 4 + -N, S-CAT, S-LAP, and SOC were the main environmental factors affecting rhizosphere-dominant microbial communities at the phylum level, while pH, SOC, and AK were the key environmental factors affecting rhizosphere functional genes of Pogostemon cablin. In summary, this study showed the dynamic changes of soil factors and rhizosphere microorganisms during CC, providing a theoretical basis for understanding the formation mechanism and prevention of CC obstacles and contributing to the formulation of scientific soil management and fertilization strategies.

Exploring the link between soil health and crop productivity

Understanding the complex interactions of plants and soils in the face of global food security and environmental degradation challenges is critical to the future of sustainable agriculture. This review discusses the important link between soil health and crop productivity by providing and comprehensive assessment of soil properties and management methods. By examining the physical, chemical, and biological properties of soil, it uncovers the key limitations posed by the soil environment on crop growth. The review highlights how soil texture, nutrient availability, and moisture levels directly impact on root growth, water uptake, and nutrient use efficiencies, while also exploring how diverse cropping systems enhance soil ecology and biodiversity. By utilizing state-of-the-art bioinformatics, we offer an in-depth exploration of rhizosphere microbial communities, emphasizing the functions of phosphate-solubilizing and nitrogen-fixing bacteria in promoting vital nutrient cycles. The potential of using microbial fertilizers to increase crop resistance to disease and stress hold a major premise for future sustainability in agriculture. In this regard, this review highlights the long-term impacts of crop cultivation on soil microbial diversity, revealing intricate selection processes between crops and their microbial partners in shaping crop-soil-microbe interactions. In terms of soil management, practical nutrient management strategies are proposed based on soil testing, emphasizing the benefits of organic farming and conservation tillage for soil health. Modern precision agricultural tools and remote sensing technologies are encouraged to be refined for effective nutrient management. At the policy level, we evaluate international guidelines aimed at fostering agricultural sustainability, suggesting new research pathways for crop-soil dynamics and offering approaches for developing soil health indicators in the face of global environmental challenges.

Mechanism of Action of Fusarium oxysporum CCS043 Utilizing Allelochemicals for Rhizosphere Colonization and Enhanced Infection Activity in Rehmannia glutinosa

Rehmannia glutinosa is an important medicinal herb; but its long-term cultivation often leads to continuous cropping problems. The underlying cause can be attributed to the accumulation of and alterations in root exudates; which interact with soil-borne pathogens; particularly Fusarium oxysporum; triggering disease outbreaks that severely affect its yield and quality. It is therefore crucial to elucidate the mechanisms by which root exudates induce F. oxysporum CCS043 outbreaks. In this study; the genome of F. oxysporum CCS043 from R. glutinosa's rhizosphere microbiota was sequenced and assembled de novo; resulting in a 47.67 Mb genome comprising 16,423 protein-coding genes. Evolutionary analysis suggests that different F. oxysporum strains may adapt to the host rhizosphere microecosystem by acquiring varying numbers of specific genes while maintaining a constant number of core genes.The allelopathic effects of ferulic acid; verbascoside; and catalpol on F. oxysporum CCS043 were examined at the physiological and transcriptomic levels. The application of ferulic acid was observed to primarily facilitate the proliferation and growth of F. oxysporum CCS043; whereas verbascoside notably enhanced the biosynthesis of infection-related enzymes such as pectinase and cellulase. Catalpol demonstrated a moderate level of allelopathic effects in comparison to the other two. Furthermore; 10 effectors were identified by combining the genomic data. Meanwhile; it was found that among the effector-protein-coding genes; ChiC; VRDA; csn; and chitinase exhibited upregulated expression across all treatments. The expression patterns of these key genes were validated using qRT-PCR. Transient overexpression of the two effector-encoding genes in detached R. glutinosa leaves provided further confirmation that ChiC (GME8876_g) and csn (GME9251_g) are key effector proteins responsible for the induction of hypersensitive reactions in R. glutinosa leaf cells. This study provides a preliminary indication that the use of allelochemicals by F. oxysporum CCS043 can promote its own growth and proliferation and enhance infection activity. This finding offers a solid theoretical basis and data support for elucidating the fundamental causes of fungal disease outbreaks in continuous cropping of R. glutinosa and for formulating effective mitigation strategies.

Microalgae-based biofertilizers improve fertility and microbial community structures in the soil of potted tomato

Continuous cropping decreases soil nutrients and destroys microbial community structure, so the development of eco-friendly and effective biofertilizers is necessary under present conditions. In this study, the preserving microalgal strain Tribonema sp. (H) was firstly selected to be combined with agroforestry waste (shell powder, straw fermentation liquid) and the agroforestry microorganism Bacillus sp. to form microalgae-based fertilizers for the continuous cropping soil of potted tomato. Compared to the control (CK), microalgae-based fertilizers (concentration: 4.45 × 106 cells/ml, dosage: 20 ml/day) improved soil nutrients and salinization indicators. Specifically, the combination of Tribonema sp. and shell powder (HB) reduced electrical conductivity (EC) by 33.7% and significantly increased the Ca2+ content by 59.4%; Tribonema sp. and Bacillus sp. (HY) improved the effects of available phosphorous (AP), DOC, DON, NH4 +-N, NO3 --N, and Mg2+ in the soil by 27.4%, 231.3%, 403.4%, 125.2%, 215.6%, and 73.4%, respectively. Microalgae-based fertilizers alter the abundance of soil bacteria and fungi, causing beneficial bacteria such as Thermonaerobaculia, Subgroup_10, Sordariomycetes, and Microascaceae to increase, while pathogenic bacteria like Pseudomonas, Togniniaceae, and Phaeoacremonium decreased. Combining microalgae with agroforestry wastes as a biofertilizer is promising to improve the microbial community structure of the soil with continuous cropping, which will aid in the increase of tomato production and promote green agricultural development.

Continuous Cropping of Patchouli Alleviate Soil Properties, Enzyme Activities, and Bacterial Community Structures

Pogostemon cablin (Patchouli), an essential medicinal plant in the Lamiaceae family, faces significant challenges under continuous cropping (CC) obstacles. This study examined the rhizospheric soil bacterial communities of patchouli under four different CC years, zero (CK), one (T1), two (T2), and three (T3) years through high-throughput 16S rRNA gene amplicon sequencing. Results showed long-term CC led to significant soil properties and enzyme activity shifts. Key parameters such as soil pH and total potassium (TK) decreased, while ammonium nitrogen (NH4+-N), soil organic carbon (SOC), nitrate nitrogen (NO3--N), available potassium (AK), available phosphorus (AP), total nitrogen (TN), and total phosphorus (TP) increased over the cropping years. Enzyme activities, including ß-glucosidase (ß-GC), polyphenol oxidase (PPO), catalase (CAT), N-acetyl-β-D-glucosaminidase (NAG), and leucine aminopeptidase (LAP), were notably affected. The CC altered the bacterial community structure and composition, reducing the relative abundance of Proteobacteria, Firmicutes, Actinobacteria, and Planctomycetota over time. These findings highlight the impact of CC on patchouli rhizosphere bacteria, providing insights for improved soil management and fertilization strategies in CC systems.

Identification and Molecular Characterization of Telosma Mosaic Virus (TelMV) and East Asian Passiflora Virus (EAPV) from Patchouli in China

Patchouli is a valuable medicinal herb and cash crop in China, but viral infections cause significant yield losses. This study identified six viruses in patchouli transcriptome data, including the first-ever detection of East Asian Passiflora Virus (EAPV) in patchouli. RT-PCR validated three viruses from diseased patchouli plants in Haikou, China: telosma tosaic virus (TelMV), broad bean wilt virus-2 (BBWV-2), and pogostemom alphacytorhabdovirus 1 (PogACRV1_Pog). The complete genomic sequence of TelMV from patchouli (TelMV) was determined, revealing a 9691-nucleotide RNA genome encoding a 3083-amino-acid polyprotein. Comparative analysis showed 77.66% to 81.01% nucleotide sequence identity with previously reported TelMV isolates. TelMV was also shown to be infectious in Nicotiana benthamiana through sap rub-inoculation. Additionally, a large portion of the EAPV genome was reconstructed from RNA-seq data, with coat protein analysis confirming its identity. This study presents the first complete TelMV genome in patchouli and the first detection of EAPV in the plant.

Metabolomic Analysis of Specific Metabolites in Codonopsis pilosula Soil Under Different Stubble Conditions

To investigate the soil-specific metabolites of Codonopsis pilosula under different stubble management practices, this study analyzed differentially abundant metabolites in the rhizosphere soils of rotational (DS) and continuous (LS) cropping systems via liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based metabolomic approaches. The results revealed that 66 metabolites, including amino acids and their derivatives, nucleic acids, alcohols, organic acids, amines, fatty acids, purines, and sugars, were significantly different (p < 0.05) between the DS and LS groups. Under continuous cropping, the levels of amines, fatty acids, organic acids, and sugars in the rhizosphere soil were significantly greater (p < 0.05) than those under rotational cropping, whereas the levels of amino acids and their derivatives, nucleic acids, and purines and pyrimidines were significantly lower (p < 0.05). KEGG pathway enrichment analysis revealed that these differentially abundant metabolites were enriched in metabolic pathways such as amino acid metabolism (e.g., alanine, aspartate, and glutamate metabolism), carbon metabolism, the cAMP signaling pathway, ABC transporter proteins, phenylalanine metabolism, and the biosynthesis of plant secondary metabolites. These metabolic pathways were involved in osmoregulation, energy supply, and resilience in plants. In conclusion, inter-root soil metabolites in rotational and continuous cropping of Codonopsis pilosula were able to influence soil physicochemical properties and microbial populations by participating in various biological processes.

Flue-cured tobacco intercropping with insectary floral plants improves rhizosphere soil microbial communities and chemical properties of flue-cured tobacco

BACKGROUND

Continuous cropping of the same crop leads to land degradation. This is also called the continuous-cropping obstacle. Currently, intercropping tobacco with other crops can serve as an effective strategy to alleviate continuous cropping obstacles.

RESULTS

In this study, tobacco K326 and insectary floral plants were used as materials, and seven treatments of tobacco monoculture (CK), tobacco intercropped with Tagetes erecta, Vicia villosa, Fagopyrum esculentum, Lobularia maritima, Trifolium repens, and Argyranthemum frutescens respectively, were set up to study their effects on rhizosphere soil chemical properties and composition and structure of rhizosphere soil microbial community of tobacco. The 16 S rRNA gene and ITS amplicons were sequenced using Illumina high-throughput sequencing. tobacco/insectary floral plants intercropping can influence rhizosphere soil chemical properties, which also change rhizosphere microbial communities. The CK and treatment groups tobacco rhizosphere soil microorganisms had significantly different genera, such as tobacco intercropping with T. repens and A. frutescens significantly increased the number of Fusarium and intercropping T. erecta, V. villosa, L. maritima, T. repens, and A. frutescens significantly increased the number of Sphingomonas and unknown Gemmatimonadaceae. Additionally, intercropping T. erecta, V. villosa and L. maritima changed the rhizosphere fungal and bacteria community and composition of tobacco and the positive correlation between tobacco rhizosphere the genera of fungi and bacterial were greater than CK. The pathway of the carbohydrate metabolism, amino acid metabolism, and energy metabolism in rhizosphere bacteria were significantly decreased after continuous cropping. Fungal symbiotic trophic and saprophytic trophic were significantly increased after intercropping V. villosa, L. maritima and plant pathogen and animal pathogen were increased after intercropping T. repens and A. frutescens. Additionally, bacterial and fungal communities significantly correlated with soil chemical properties, respectively.

CONCLUSION

This study reveals that intercropping tobacco with insectary floral plants, particularly T. erecta, V. villosa, L. maritima and A. frutescens significantly affects soil chemical properties and alters rhizosphere microbial communities, increasing the abundance of certain microbial genera. Additionally, intercropping enhances pathways related to carbohydrate, amino acid, and energy metabolism in rhizosphere bacteria. These findings suggest that intercropping could provide a promising strategy to overcome challenges associated with continuous tobacco cropping by regulating the rhizosphere environment.

Effects of Trichoderma harzianum on Growth and Rhizosphere Microbial Community of Continuous Cropping Lagenaria siceraria

This study analyzed the effects of Trichoderma harzianum on the growth of continuous cropping Lagenaria siceraria and the physical and chemical properties of rhizosphere soil and microbial community structure, using Illumina Miseq (PE300) high-throughput sequencing technology along with physiological and biochemical detection. The results indicated that after applying T. harzianum, the growth of L. siceraria was significantly promoted, with increases in plant height, fresh weight, and dry weight of 21.42%, 24.5%, and 4.5%, respectively. The pH of the rhizosphere soil decreased from 7.78 to 7.51, while the electrical conductivity, the available phosphorus, the available potassium, and the total nitrogen were markedly higher compared to the control group and increased by 13.95%, 22.54%, 21.37%, and 16.41%, respectively. The activities of catalase and sucrase in the rhizosphere increased by 18.33% and 61.47%, and the content of soil organic carbon (SOC) increased by 27.39%, which indicated that T. harzianum could enhance soil enzyme activity and promotes the transformation of organic matter. The relative abundance of beneficial bacteria such as Pseudomonas increased, while the relative abundance of harmful fungi such as Fusarium and Podosphaera decreased significantly.

Biological Decline of Alfalfa Is Accompanied by Negative Succession of Rhizosphere Soil Microbial Communities

The growth and biological decline of alfalfa may be linked to the rhizosphere microbiome. However, plant-microbe interactions in the rhizosphere of alfalfa and associated microbial community variations with stand age remain elusive. This study explored the successional pattern of rhizosphere microbial communities across different aged alfalfa stands and its relationship with alfalfa decline. Rhizosphere soils were collected from 2- and 6-year-old alfalfa stands. Control soils were collected from interspaces between alfalfa plants in the same stands. Soil bacterial and fungal communities were characterized by 16S and ITS rRNA gene sequencing, respectively. Specific microbial taxa colonized the rhizosphere soils, but not the control soils. The rhizosphere-specific taxa mainly included potentially beneficial genera (e.g., Dechloromonas, Verrucomicrobium) in the young stand and harmful genera (e.g., Peziza, Campylocarpon) in the old stand. Alfalfa roots regulated soil microbial communities by selective promotion or inhibition of distinct taxa. The majority of time-enriched taxa were reported as harmful fungi, whose relative abundances were negatively correlated with plant traits. Time-depleted taxa were mostly known as beneficial bacteria, which had relative abundances positively correlated with plant traits. The relative abundances of functional bacterial genes associated with vancomycin biosynthesis, zeatin biosynthesis, and amino acid metabolism trended lower in rhizosphere soils from the old stand. An upward trend was observed for fungal pathogens and wood saprotrophs with increasing stand age. The results suggest that root activity drives the negative succession of rhizosphere microbial communities during alfalfa decline in old stands.

Effect of Continuous Cropping on Growth and Lobetyolin Synthesis of the Medicinal Plant Codonopsis pilosula (Franch.) Nannf. Based on the Integrated Analysis of Plant-Metabolite-Soil Factors

The integrated plant-metabolite-soil regulation model of C. Pilosula growth and lobetyolin synthesis in response to continuous cropping lacks systematic investigation. In this study, we investigated the regulatory mechanisms of growth and lobetyolin synthesis in C. pilosula under continuous cropping stress based on high-performance liquid chromatography, transcriptome, and microbial sequencing on the root system and rhizosphere soil of C. pilosula from one year of cultivation and five years of continuous cropping. The findings of this study revealed that continuous cropping significantly inhibited the growth of C. pilosula and led to a notable decrease in the lobetyolin content. An effort was made to propose a potential pathway for lobetyolin biosynthesis in C. pilosula, which is closely linked to the expression of genes responsible for glucoside and unsaturated fatty acid chain synthesis. In addition, soil physicochemical properties and soil microorganisms had strong correlations with root growth and synthesis of lobetyolin, suggesting that soil physicochemical properties and microorganisms are the main factors triggering the succession disorder in C. pilosula. This study provides an in-depth interpretation of the regulatory mechanism of acetylenic glycoside synthesis and offers new insights into the triggering mechanism of C. pilosula succession disorder, which will guide future cultivation and industrial development.

The impact of salinization on soil bacterial diversity, yield and quality of Glycyrrhiza uralensis Fisch

Soil salinization seriously affects soil microbial diversity, and crop yield and quality worldwide. Microorganisms play a vital role in the process of crop yield and quality. Traditional Chinese medicine Glycyrrhiza uralensis Fisch. (licorice) can grow tenaciously in the heavily salinized land. However, the relationship between licorice plants and soil microorganisms is not clear. A field experiment was carried out to explore the effects of three different degrees of salinized soils on (i) licorice crop performance indicators, (ii) soil physical and chemical properties, and (iii) the changes in soil bacterial community structure and functional diversity in a semi-arid area of northwest China. The results showed that with the aggravation of soil salinization, the licorice yield, soil nutrients, and the bacterial abundance of Gemmatimonadetes and Myxococcota showed a downward trend, while the concentration of glycyrrhizic acid and liquiritin, and the bacterial abundance of Actinobacteria and Firmicutes showed an upward trend. The change of licorice yield mainly depended on the soil physical and chemical properties (e.g., EC and alkaline hydrolysable nitrogen). The change of licorice quality was more closely related to the change of bacterial diversity. The effect of bacterial diversity on liquiritin was greater than that on glycyrrhizic acid. Among them, Gemmatimonadetes were significantly negatively correlated with liquiritin and glycyrrhizic acid. These findings suggest that the increased soil Actinobacteria and Firmicutes or reduced Gemmatimonadetes and Myxococcota may provide a healthy and suitable living condition for the sustainable development of medicinal plant crops in a salinized soil ecosystem.

AMF inhibit the production of phenolic acid autotoxins at the seed-filling stage in soybeans with continuous monocropping

BACKGROUND

Soybean is the main oil crop in Northeast China. Continuous monocropping is more commonly used for soybean production due to rising market demand and arable land constraints. However, autotoxic substances, such as phenolic acids, produced by continuously cropped soybean can reduce yield and quality. The mycorrhiza formed of Arbuscular mycorrhizal fungi (AMF) and plant roots regulate the metabolic activities of the host plant and increase its disease resistance. The main purpose of this study was to inhibit the production of phenolic acids and determine the adverse effects on the growth of continuous monocropping soybean by inoculating Funneliformis mosseae (F. mosseae).

RESULTS

Transcriptomics results showed that the production of phenolic acids in continuous monocropping soybean roots was mainly regulated by the expression of the CHS6, PCL1, SAMT, SRG1, and ACO1 genes, and the expression of these genes was significantly downregulated after inoculation with F. mosseae. Metabolomics results showed that continuous monocropping soybean roots inoculated with F. mosseae inhibited phenolic acid production through the phenylpropane biosynthetic, α-linoleic acid, linoleic acid, and other metabolic pathways. Phenolic acids in the phenylpropane metabolic pathway, such as 4-hydroxybenzoic acid, phthalic acid, and vanillic acid, decreased significantly after inoculation with F. mosseae. The combined analysis of the two showed that genes such as YLS9 and ARF3 were positively correlated with 4-hydroxybenzoic acid and so on, while genes such as CHS6 and SRG1 were negatively correlated with butyric acid and so on.

CONCLUSION

F. mosseae regulated the expression of functional genes and related phenolic acid metabolic pathways produced by continuous monocropping soybean roots, inhibiting the production of phenolic acid autotoxic substances in continuous cropped soybean, and slowing down the disturbance of continuous monocropping. This study provides a new solution for continuous monocropping of plants to overcome the autotoxicity barrier and provides a new basis for the development and utilization of AMF as a biological agent.

Changes in Rhizosphere Soil Microorganisms and Metabolites during the Cultivation of Fritillaria cirrhosa

Fritillaria cirrhosa is an important cash crop, and its industrial development is being hampered by continuous cropping obstacles, but the composition and changes of rhizosphere soil microorganisms and metabolites in the cultivation process of Fritillaria cirrhosa have not been revealed. We used metagenomics sequencing to analyze the changes of the microbiome in rhizosphere soil during a three-year cultivation process, and combined it with LC-MS/MS to detect the changes of metabolites. Results indicate that during the cultivation of Fritillaria cirrhosa, the composition and structure of the rhizosphere soil microbial community changed significantly, especially regarding the relative abundance of some beneficial bacteria. The abundance of Bradyrhizobium decreased from 7.04% in the first year to about 5% in the second and third years; the relative abundance of Pseudomonas also decreased from 6.20% in the first year to 2.22% in the third year; and the relative abundance of Lysobacter decreased significantly from more than 4% in the first two years of cultivation to 1.01% in the third year of cultivation. However, the relative abundance of some harmful fungi has significantly increased, such as Botrytis, which increased significantly from less than 3% in the first two years to 7.93% in the third year, and Talaromyces fungi, which were almost non-existent in the first two years of cultivation, significantly increased to 3.43% in the third year of cultivation. The composition and structure of Fritillaria cirrhosa rhizosphere metabolites also changed significantly, the most important of which were carbohydrates represented by sucrose (48.00-9.36-10.07%) and some amino acid compounds related to continuous cropping obstacles. Co-occurrence analysis showed that there was a significant correlation between differential microorganisms and differential metabolites, but Procrustes analysis showed that the relationship between bacteria and metabolites was closer than that between fungi and metabolites. In general, in the process of Fritillaria cirrhosa cultivation, the beneficial bacteria in the rhizosphere decreased, the harmful bacteria increased, and the relative abundance of carbohydrate and amino acid compounds related to continuous cropping obstacles changed significantly. There is a significant correlation between microorganisms and metabolites, and the shaping of the Fritillaria cirrhosa rhizosphere's microecology by bacteria is more relevant.

The factors affecting the development of medicinal plants from a value chain perspective

MAIN CONCLUSION

From a value chain perspective, this paper examines the important factors from the selection of planting areas to storage, which restrict the development of medicinal plants. The purpose of this paper is to provide theoretical basis for the sustainable development of medicinal plants. Medicinal plants have significant economic and medicinal value. Due to the gradual depletion of wild medicinal plant resources, cultivators of medicinal plants must resort to artificial cultivation to cope. However, there are still many problems in the production process of medicinal plants, resulting in decreases in both yield and quality, thus hindering sustainable development. To date, research on the value chain of medicinal plants is still limited. Therefore, this paper analyzes the factors affecting the development of medicinal plants from the perspective of the value chain, including the selection of growing areas to the storage process of medicinal plants, and summarizes the challenges faced in the production process of medicinal plants. The purpose of this paper is to provide theoretical basis for the sustainable development of medicinal plants.

Pigmentiphaga kullae CHJ604 improved the growth of tobacco by degrading allelochemicals and xenobiotics in continuous cropping obstacles

Plant autotoxicity is considered to be one of the important causes of continuous cropping obstacles in modern agriculture, which accumulates a lot of allelochemicals and xenobiotics and is difficult to solve effectively. To overcome tobacco continuous obstacles, a strain Pigmentiphaga kullae CHJ604 isolated from the environment can effectively degrade these compounds in this study. CHJ604 strain can degrade 11 types of autotoxicity allelochemicals and xenobiotics (1646.22 μg/kg) accumulated in the soil of ten-years continuous cropping of tobacco. The 11 allelochemicals and xenobiotics significantly reduced Germination Percentage (GP), Germination Index (GI), and Mean Germination Time (MGT) of tobacco seeds, and inhibited the development of leaves, stems, and roots. These negative disturbances can be eliminated by CHJ604 strain. The degradation pathways of 11 allelochemicals and xenobiotics were obtained by whole genome sequence and annotation of CHJ604 strain. The heterologous expression of a terephthalate 1,2-dioxygenase can catalyze 4-hydroxybenzoic acid, 4-hydroxy-3-methoxybenzoic acid, 4-hydroxybenzaldehyde, and 4-hydroxy-3-methoxy-benzaldehyde, respectively. The phthalate 4,5-dioxygenase can catalyze phthalic acid, diisobutyl phthalate, and dibutyl phthalate. These two enzymes are conducive to the simultaneous degradation of multiple allelochemicals and xenobiotics by strain CHJ604. This study provides new insights into the biodegradation of autotoxicity allelochemicals and xenobiotics as it is the first to describe a degrading bacterium of 11 types of allelochemicals and xenobiotics and their great potential in improving tobacco continuous obstacles.

A Genome-Wide Identification and Expression Analysis of the Casparian Strip Membrane Domain Protein-like Gene Family in Pogostemon cablin in Response to p-HBA-Induced Continuous Cropping Obstacles

Casparian strip membrane domain protein-like (CASPL) genes are key genes for the formation and regulation of the Casparian strip and play an important role in plant abiotic stress. However, little research has focused on the members, characteristics, and biological functions of the patchouli PatCASPL gene family. In this study, 156 PatCASPL genes were identified at the whole-genome level. Subcellular localization predicted that 75.6% of PatCASPL proteins reside on the cell membrane. A phylogenetic analysis categorized PatCASPL genes into five subclusters alongside Arabidopsis CASPL genes. In a cis-acting element analysis, a total of 16 different cis-elements were identified, among which the photo-responsive element was the most common in the CASPL gene family. A transcriptome analysis showed that p-hydroxybenzoic acid, an allelopathic autotoxic substance, affected the expression pattern of PatCASPLs, including a total of 27 upregulated genes and 30 down-regulated genes, suggesting that these PatCASPLs may play an important role in the regulation of patchouli continuous cropping obstacles by affecting the formation and integrity of Casparian strip bands. These results provided a theoretical basis for exploring and verifying the function of the patchouli PatCASPL gene family and its role in continuous cropping obstacles.

Continuous Cropping Inhibits Photosynthesis of Polygonatum odoratum

Polygonatum odoratum (Mill.) Druce possesses widespread medicinal properties; however, the continuous cropping (CC) often leads to a severe consecutive monoculture problem (CMP), ultimately causing a decline in yield and quality. Photosynthesis is the fundamental process for plant growth development. Improving photosynthesis is one of the most promising approaches to increase plant yields. To better understand how P. odoratum leaves undergo photosynthesis in response to CC, this study analyzed the physiochemical indexes and RNA-seq. The physiochemical indexes, such as the content of chlorophyll (chlorophyll a, b, and total chlorophyll), light response curves (LRCs), and photosynthetic parameters (Fv/Fm, Fv/F0, Fm/F0, Piabs, ABS/RC, TRo/RC, ETo/RC, and DIo/RC) were all changed in P. odoratum under the CC system. Furthermore, 13,798 genes that exhibited differential expression genes (DEGs) were identified in the P. odoratum leaves of CC and first cropping (FC) plants. Among them, 7932 unigenes were upregulated, while 5860 unigenes were downregulated. Here, the DEGs encoding proteins associated with photosynthesis and carbon assimilation showed a significant decrease in expression under the CC system, such as the PSII protein complex, PSI protein complex, Cytochorome b6/f complex, the photosynthetic electron transport chain, light-harvesting chlorophyll protein complex, and Calvin cycle, etc., -related gene. This study demonstrates that CC can suppress photosynthesis and carbon mechanism in P. odoratum, pinpointing potential ways to enhance photosynthetic efficiency in the CC of plants.