Search Results (12)

Pine wilt disease (PWD) poses a significant threat to pine forest health, making sanitation thinning of infected trees and cultivation of disease-resistant pine stands crucial measures for forest ecosystem restoration. To date, limited studies have systematically investigated how post-sanitation planting of pine-wilt-disease-resistant Pinus species affects soil microbiome, especially regarding bacterial and fungal diversity characteristics, functional succession patterns, and community assembly processes. In this study, we performed a comparative analysis of soil microbial community characteristics and biochemical properties between experimental plots subjected to sanitation thinning and those replanted with disease-resistant pine species. The results indicated that compared to the sanitation-thinned experimental plot, the disease-resistant experimental plots (Pinus taeda experimental plot and Pinus thunbergii experimental plot) exhibited significantly higher activities of β-glucosidase (S-β-GC), N-acetyl-β-D-glucosidase (S-NAG), and soil arylsulfatase (S-ASF). Compared with the sanitation logging stands, our analysis revealed that the Pinus taeda experimental plot and Pinus thunbergii experimental plot exhibited significantly higher fungal community evenness (OTUs), greater species abundance (OTUs), and more unique fungal taxa. Furthermore, the edaphic properties—specifically soil moisture content (SMC), pH levels, and total potassium (TK)—significantly influenced the structures of soil bacterial and fungal communities. Compared to the sanitation-thinned experimental plot, wood saprotrophic fungi and ectomycorrhizal fungi exhibited increased abundance in both the P. taeda experimental plot and Pinus thunbergii experimental plot. Furthermore, the null models indicated that both the P. taeda experimental plot and P. thunbergii experimental plot enhanced the undominated processes of bacteria and fungi. In summary, our data elucidate the differences in bacterial and fungal responses between pine forests undergoing thinning due to infected trees and those cultivated for disease resistance. This deepens our understanding of microbial functions and community assembly processes within these ecosystems. Full article

Background and Clinical Significance: In the clinical management of major pediatric traumatic injuries and other hypoxic conditions, lactate is widely recognized as a key indicator of tissue hypoxia and potential necrosis. However, its prognostic value remains uncertain. Several factors influence post-surgical outcomes, including the time between amputation and replantation, transport conditions, asepsis, the extent of tissue necrosis, hemorrhagic shock, coagulation disorders, and the heightened risk of contamination. Case presentation: We present this case to emphasize the utility of systemic lactate versus lactate levels in the replanted limb for monitoring post-transplantation outcomes in a pediatric patient with traumatic limb amputation. Significant fluctuations in lactate levels within the replanted limb were observed at the onset of unfavorable evolution, specifically on the seventh postoperative day, coinciding with the identification of Aspergillus spp. infection. This necessitated the use of synthetic saphenous vein grafts and Amphotericin B administration. Despite these interventions, disease progression ultimately led to limb amputation. Conclusions: Lactate levels in the replanted limb may serve as an early biomarker for assessing post-surgical evolution. However, further case reports are required to confirm its predictive value. Full article

This study investigated the expression profiles of microRNA-like RNAs (milRNAs) in Fusarium oxysporum HS2 (FoHS2), a key pathogen causing Apple replant disease (ARD), across spore to mycelium formation stages. Using small RNA sequencing (sRNA-seq) and bioinformatics, we identified and analyzed milRNAs, revealing their targeting of 2364 mRNAs involved in 20 functional categories, including metabolic and cellular processes, based on gene ontology (GO) analysis. An analysis of Kyoto Encyclopedia of Genes and Genomes (KEGG) showed that these mRNAs are related to carbohydrate and amino acid metabolism pathways. Notably, the highest number of differentially or specifically expressed milRNAs (DEmilRNAs/SEmilRNAs) was found during the spore stage, with FoHS2-milR19 targeting genes encoding histone acetyltransferases, methyltransferases, and cell wall-degrading enzymes (CWDEs), which are crucial for growth, development, and pathogenicity. We validated the reliability of our sRNA-seq data and the expression of target genes using stem-loop RT-PCR and qRT-PCR. Our results highlight the stage-specific expression of milRNAs in FoHS2, particularly in the spore stage, suggesting a key role in regulating host life activities and providing a theoretical basis for developing RNA-based pesticides to control ARD. Full article

Background/Objectives: Rehmannia glutinosa, a highly valuable medicinal plant in China, is encountering severe replant disease. Replant disease represents a complex stress driven by multiple principal factors (RDFs), including allelochemicals, microbes, and their interactions. miRNAs are recognized as key regulators of plant response to stresses; however, their specific roles within RDFs are not entirely clear. Methods: This study builds six RDF treatments, comprising R. glutinosa continuously planted (SP), normally planted (NP), and NP treated with ferulic acid (FA), Fusarium oxysporum (FO), and a combination of FA with FO (FAFO). sRNA-seq technology was used to identify crucial miRNAs in response to diverse RDFs. Results: In total, 30 sRNA datasets were generated from the SP, NP, FA, FO, and FAFO samples. A total of 160 known and 41 novel miRNAs (RgmiRNAs) were identified in the R. glutinosa genome based on the sRNA database. Abundance analysis revealed that RgmiRNAs in SP exhibited a distinct expression profile in comparison with others. Of these, 124, 86, 86, and 90 RgmiRNAs were differentially expressed in SP, FA, FO, and FAFO compared with NP. Target analysis indicated that RgmiRNAs downregulated in both SP and RDFs impede the organism growth of R. glutinosa. RgmiRNAs upregulated in SP can disrupt root formation and nutrient metabolism, in which, two RgmiR398 were uniquely expressed in SP. It was confirmed to target RgCSD genes. The expression patterns of RgmiR398 and RgCSD indicated that replant disease induces the oxidative damage of R. glutinosa through RgmiR398. Conclusions: RgmiRNA profiling under RDFs provides a theoretical basis for the further clarification of RgmiRNA function in replant disease. Full article

The tree fruit industry in Nova Scotia, Canada, is dominated by the apple (Malus domestica) sector. However, the sector is faced with numerous challenges, including apple replant disease (ARD), which is a well-known problem in areas with intensive apple cultivation. A study was performed using 16S rRNA/18S rRNA and 16S rRNA/ITS2 amplicon sequencing to assess soil- and root-associated microbiomes, respectively, from mature apple orchards and soil microbiomes alone from uncultivated soil. The results indicated significant (p < 0.05) differences in soil microbial community structure and composition between uncultivated soil and cultivated apple orchard soil. We identified an increase in the number of potential pathogens in the orchard soil compared to uncultivated soil. At the same time, we detected a significant (p < 0.05) increase in relative abundances of several potential plant-growth-promoting or biocontrol microorganisms and non-fungal eukaryotes capable of promoting the proliferation of bacterial biocontrol agents in orchard soils. Additionally, the apple roots accumulated several potential PGP bacteria from Proteobacteria and Actinobacteria phyla, while the relative abundances of fungal taxa with the potential to contribute to ARD, such as Nectriaceae and plant pathogenic Fusarium spp., were decreased in the apple root microbiome compared to the soil microbiome. The results suggest that the health of a mature apple tree can be ascribed to a complex interaction between potential pathogenic and plant growth-promoting microorganisms in the soil and on apple roots. Full article

Lanzhou Lily(Lilium davidii) var. unicolor, which is also known as sweet lily in China, is used as a type of food. This lily is distributed in narrow regions, propagates asexually, cultivates perennially, and cultivates commonly in serious consecutive replant problems (CRPs). Soil fumigation is commonly used to control soil-borne disease to alleviate crops’ consecutive replant problems (CRPs). However, due to the improper fumigation application, it is common to cause chemical hazard to crops. In this study, we designed a two-factor experiment to explore the bacterial and fungal community structure and some specific microbial groups in the lily rhizosphere soil after chemical versus bacterial fertilizer treatments, by using a metagenomic analysis of the treated soils. The results showed that metham-sodium soil fumigation (SMF treatment) significantly decreased plant growth, as well as it significantly decreased both soil fungal diversity and abundance at the OTUs levels, while Special 8™ microbial fertilizer supplement (MF treatment) significantly improved plant growth and increased fungal diversity and abundance. Under FM treatment, Chao1 richness and Shannon’s diversity increased by 6.70% and 35.09% compared to CK (no treatment). However, the bacterial diversity and abundance were not significantly changed among these treatments. The fungal and bacterial community structure were different in all treatments. In SMF treatment, the pathogenic fungal species Fusarium oxysporum increased compared to CK, but it significantly decreased in MF treatment; in MF and MMF treatments, some beneficial bacteria groups such as the bacterial phylum Proteobacteria and its member genus Sphingomonas, as well as the fungal genus Mortierella, increased compared to CK and SFM treatments, but the harmful bacterial genera Gemmatimona was decreased, as well as the harmful fungal genus Cryptococcus. Thus, we concluded that under chemical fumigation conditions, both fungal diversity loss and overall microorganism reduction, which impair multiple ecosystem function, in conjunction with the increase of harmful fungal species such as Fusarium oxysporum, are causes for soil degradation. On the other hand, under microbial fertilizer supplement, it was the fungal diversity increase, as well as these beneficial microorganisms groups’ accumulation, together with those harmful groups’ depletion, played important roles in restoring and improving soil health that suffered from the chemical fumigant hazard. In addition, the bacterial phylum Proteobacteria and its member genus Sphingomonas are involved in soil health recovery and promotion. The results also emphasized that whether soil is chemically fumigated or not, beneficial microorganism supplementary is effective in ensuring soil productivity. Full article

A study was conducted for endophytic antagonistic fungi obtained from the roots of healthy apple trees growing in nine replanted orchards in Shandong Province, China. The fungi were assessed for their ability to inhibit Fusarium proliferatum f. sp. malus domestica MR5, a fungal strain associated with apple replant disease (ARD). An effective endophyte, designated as strain 6S-2, was isolated and identified as Trichoderma asperellum. Strain 6S-2 demonstrated protease, amylase, cellulase, and laccase activities, which are important for the parasitic and antagonistic functions of pathogenic fungi. The inhibition rate of 6S-2 against Fusarium proliferatum f. sp. malus domestica MR5 was 52.41%. Strain 6S-2 also secreted iron carriers, auxin, ammonia and was able to solubilize phosphorus. Its fermentation extract and volatile substances inhibited the growth of MR5, causing its hyphae to twist, shrink, swell, and rupture. The antifungal activity of the 6S-2 fermentation extract increased with increasing concentrations. It promoted the production and elongation of Arabidopsis thaliana lateral roots, and the strongest effects were seen at a concentration of 50 mg/mL. A GC-MS analysis of the 6S-2 fermentation extract and volatile substances showed that they comprised mainly alkanes, alcohols, and furanones, as well as the specific volatile substance 6-PP. The application of 6S-2 spore suspension to replanted apple orchard soils reduced plant oxidative damage and promoted plant growth in a pot experiment. Therefore, the endophytic strain T. asperellum 6S-2 has the potential to serve as an effective biocontrol fungus for the prevention of ARD in China, and appears to promote plant growth. Full article

Brassicaceae seed meal (SM) soil amendment has been utilized as an effective strategy to control the biological complex of organisms, which includes oomycetes, fungi, and parasitic nematodes, that incites the phenomenon termed apple replant disease. Soil-borne disease control attained in response to Brassicaceae SM amendment is reliant on multiple chemical and biological attributes, including specific SM-generated modifications to the soil/rhizosphere microbiome. In this study, we conducted a comparative analyses of apple root gene expression as influenced by rootstock genotype combined with a seed meal (SM) soil amendment. Apple replant disease (ARD) susceptible (M.26) and tolerant (G.210) rootstocks cultivated in SM-amended soil exhibited differential gene expression relative to corresponding non-treated control (NTC) orchard soil. The temporal dynamics of gene expression indicated that the SM-amended soil system altered the trajectory of the root transcriptome in a genotype-specific manner. In both genotypes, the expression of genes related to plant defense and hormone signaling were altered in SM-amended soil, suggesting SM-responsive phytohormone regulation. Altered gene expression was temporally associated with changes in rhizosphere microbiome density and composition in the SM-treated soil. Gene expression analysis across the two rootstocks cultivated in the pathogen-infested NTC soil showed genotype-specific responses indicative of different defensive strategies. These results are consistent with previously described resistance mechanisms of ARD “tolerant” rootstock cultivars and also add to our understanding of the multiple mechanisms by which SM soil amendment and the resulting rhizosphere microbiome affect apple rootstock physiology. Future studies which assess transcriptomic and metagenomic data in parallel will be important for illuminating important connections between specific rhizosphere microbiota, gene-regulation, and plant health. Full article

Apple replant disease (ARD) impacts the economic yield of orchards by physiological and morphological suppression of apple trees on replanted soils. The complexity of replant disease caused by a plethora of biological interactions and physical properties of the soil requires complex management strategies to mitigate these effects. Based on expert recommendations, we selected two management strategies linked to agroecological principles of (a) organic fertilisation with a specific mulch composition (MDK) and (b) biofertilisation with arbuscular mycorrhizal and bacterial strains (AMFbac), applied by a composition of existing products. For both management strategies we provide a proof-of-concept, by pot and field experiments. Both treatments have the potential to mitigate ARD effects on plant vigour. ARD effect was fully mitigated by MDK treatment in the short-term (one year) and was mitigated by up to 29% after seven years of MDK treatment (long-term). MDK provides an additional substrate for root growth. AMFbac has the potential to mitigate ARD effects on plant vigour but with non-replicable plant-beneficial effects in its current form of application. Thereby our results show a principal potential to mitigate economic effects but not to overcome replant disease inducing effects. While the MDK treatment is found resource intensive but reliable, the AMFbac treatment was found more user-friendly. Full article

The soil-borne apple replant disease (ARD) is caused by biotic agents and affected by abiotic properties. There is evidence for the interrelation of the soil fungal population and soil aggregate structure. The aim of this study conducted between March and October 2020 on an orchard in north-east Germany was to detect the correlations of soil fungal density, soil structure and tree vigour under replant conditions in a series of time intervals. By using the replant system as the subject matter of investigation, we found that replanting had an impact on the increase of soil fungal DNA, which correlated with a mass decrease of large macro-aggregates and an increase of small macro- and large micro-aggregates in the late summer. Increased proportions of water-stable aggregates (WS) with binding forces ≤ 50 J mL⁻¹, decreased proportions of WS > 100 J mL⁻¹ and a decrease of the mean weight diameter of aggregates (MWD) emphasised a reduction of aggregate stability in replant soils. Correlation analyses highlighted interactions between replant-sensitive soil fungi (Alternaria-group), the loss of soil structure and suppressed tree vigour, which become obvious only at specific time intervals. Full article

Consecutive monoculture practice facilitates enrichment of rhizosphere pathogenic microorganisms and eventually leads to the emergence of replant disease. However, little is known about the interaction relationship among pathogens enriched in rhizosphere soils, Nucleotide binding-leucine-rich repeats (NB-LRR) receptors that specifically recognize pathogens in effector-triggered immunity (ETI) and physiological indicators under replant disease stress in Rehmannia glutinosa. In this study, a controlled experiment was performed using different kinds of soils from sites never planted R. glutinosa (NP), replanted R. glutinosa (TP) and mixed by different ration of TP soils (1/3TP and 2/3TP), respectively. As a result, different levels of TP significantly promoted the proliferation of Fusarium oxysporum f.sp. R. glutinosa (FO). Simultaneously, a comparison between FO numbers and NB-LRR expressions indicated that NB-LRRs were not consecutively responsive to the FO proliferation at transcriptional levels. Further analysis found that NB-LRRs responded to FO invasion with a typical phenomenon of “promotion in low concentration and suppression in high concentration”, and 6 NB-LRRs were identified as candidates for responding R. glutinosa replant disease. Furthermore, four critical hormones of salicylic acid (SA), jasmonic acid (JA), ethylene (ET) and abscisic acid (ABA) had higher levels in 1/3TP, 2/3TP and TP than those in NP. Additionally, increasing extents of SA contents have significantly negative trends with FO changes, which implied that SA might be inhibited by FO in replanted R. glutinosa. Concomitantly, the physiological indexes reacted alters of cellular process regulated by NB-LRR were affected by complex replant disease stresses and exhibited strong fluctuations, leading to the death of R. glutinosa. These findings provide important insights and clues into further revealing the mechanism of R. glutinosa replant disease. Full article

After replanting apple (Malus domestica Borkh.) on the same site severe growth suppressions, and a decline in yield and fruit quality are observed in all apple producing areas worldwide. The causes of this complex phenomenon, called apple replant disease (ARD), are only poorly understood up to now which is in part due to inconsistencies in terms and methodologies. Therefore we suggest the following definition for ARD: ARD describes a harmfully disturbed physiological and morphological reaction of apple plants to soils that faced alterations in their (micro-) biome due to the previous apple cultures. The underlying interactions likely have multiple causes that extend beyond common analytical tools in microbial ecology. They are influenced by soil properties, faunal vectors, and trophic cascades, with genotype-specific effects on plant secondary metabolism, particularly phytoalexin biosynthesis. Yet, emerging tools allow to unravel the soil and rhizosphere (micro-) biome, to characterize alterations of habitat quality, and to decipher the plant reactions. Thereby, deep insights into the reactions taking place at the root rhizosphere interface will be gained. Counteractions are suggested, taking into account that culture management should emphasize on improving soil microbial and faunal diversity as well as habitat quality rather than focus on soil disinfection. Full article