Invasive mechanism and control strategy of Ageratina adenophora (Sprengel)

Effects of soil pH on the growth, soil nutrient composition, and rhizosphere microbiome of Ageratina adenophora

Ageratina adenophora is an invasive weed species found in many countries. Methods to control the spread of this weed have been largely unsuccessful. Soil pH is the most important soil factor affecting the availability of nutrients for plant and impacting its growth. Understanding the mechanisms of the influence of soil pH on the growth of A. adenophora may help to develop effective control measures. In this study, we artificially changed the soil pH in pot experiments for A. adenophora. We studied the effects of acidic (pH 5.5), weakly acidic (pH 6.5), neutral (pH 7.2), and alkaline (pH 9.0) soils on the growth, availability of soil nutrients, activity of antioxidant enzymes, levels of redox markers in the leaves, and the structure and diversity of the rhizosphere microbiome. Soil with a pH 7.2 had a higher (47.8%) below-ground height versus soils of pH 5.5 at day 10; plant had a higher (11.3%) above-ground height in pH 7.2 soils than pH 9.0 soils at day 90; no differences in the fresh and dry weights of its above- and belowground parts, plant heights, and root lengths were observed in plants growing in acid, alkaline, or neutral pH soil were observed at day 180. Correspondingly, the antioxidant enzymes SOD (superoxide dismutase), POD (peroxidase), CAT (catalase) and redox markers GSH (glutathione) and MDA (malondialdehyde) were measured in the leaves. Significant differences existed in the activities of CAT and the levels of GSH between those growing in acidic and alkaline soils and those in neutral pH soil at day 90; however, only lower (36.8%) CAT activities in those grown at pH 5.5 than those grown at pH 7.2 were found at day 180. Similarly, significant differences in available P (16.89 vs 3.04 mg Kg-1) and total K (3.67 vs 0.96 mg Kg-1), total P (0.37 vs 0.25 g Kg-1) and total N (0.45 vs 1.09 g Kg-1) concentrations were found between the rhizosphere soils of A. adenophora grown at pH 9.0 and 7.2 at day 90; no such differences were seen at day 180. High throughput analyses of the 16S rRNA and ITS fragments showed that the rhizosphere microbiome diversity and composition under different soil pH conditions changed over 180 days. The rhizosphere microbiomes differed in diversity, phylum, and generic composition and population interactions under acid and alkaline conditions versus those grown in neutral soils. Soil pH had a greater impact on the diversity and composition of the prokaryotic rhizosphere communities than those of the fungal communities. A. adenophora responded successfully to pH stress by changing the diversity and composition of the rhizosphere microbiome to maintain a balanced nutrient supply to support its normal growth. The unusual pH tolerance of A. adenophora may be one crucial reason for its successful invasion. Our results suggest that attempts use soil pH to control its invasion by changing the soil pH (for example, using lime) will fail.

Antifungal Activity of Cadinane-Type Sesquiterpenes from Eupatorium adenophorum against Wood-Decaying Fungi

The present study aimed to evaluate the antifungal activities of Eupatorium adenophorum against four strains of wood-decaying fungi, including Inonotus hispida, Inonotus obliquus, and Inonotus cuticularis. Bioguided isolation of the methanol extract of E. adenophorum by silica gel column chromatography and high-performance liquid chromatography afforded six cadinane-type sesquiterpenes. Their structures were identified by nuclear magnetic resonance and MS analyses. According to the antifungal results, the inhibition rate of the compound was between 59.85 % and 77.98 % at a concentration of 200 μg/mL. The EC50 values ranged from 74.5 to 187.4 μg/mL.

Allelopathic Activity of the Invasive Plant Polygonum chinense Linn. and Its Allelopathic Substances

Polygonum chinense Linn., belonging to the Polygonaceae family, is distributed mostly in northern temperate climates. This species is a high-risk invasive plant and is thought to possess allelopathic potential. This study aimed to isolate and identify the allelopathic substances from P. chinense. Aqueous methanol extracts of P. chinense significantly inhibited the growth of alfalfa and Italian ryegrass seedlings in a species- and concentration-dependent manner. Activity-guided fractionation led to the isolation of two active compounds: dehydrovomifoliol and loliolide. A cress bioassay was used to determine the biological activity of dehydrovomifoliol, and cress, alfalfa, and Italian ryegrass were used to determine loliolide. Dehydrovomifoliol significantly suppressed the seedling growth of cress at the concentration of 1 mM, and the concentrations necessary for 50% growth inhibition (I50 values) of the roots and shoots were 1.2 and 2 mM, respectively. Loliolide significantly suppressed the shoot growth of cress, alfalfa, and Italian ryegrass at the concentration of 1 mM, and the concentrations necessary for I50 values of the shoots and roots were 0.15 to 2.33 and 0.33 to 2.23 mM, respectively. The findings of our study suggest the extracts of P. chinense might have growth-inhibitory potential and that dehydrovomifoliol and loliolide might contribute as allelopathic agents.

Equine Crofton Weed (Ageratina spp.) Pneumotoxicity: What Do We Know and What Do We Need to Know?

Crofton weed (Ageratina adenophora) is a global and highly invasive weed, with ingestion causing severe respiratory disease in horses, leading to irreversible and untreatable pulmonary fibrosis and oedema. While reports of equine pneumotoxicity remain common in Australia and New Zealand, equine pneumotoxicity may be underdiagnosed in other countries where Crofton weed is endemic but poorly differentiated. The pathogenesis of Crofton weed toxicity following ingestion has been well described in a number of different animal models, including rodents, rabbits, and goats. However, induced toxicity is organ-selective across different animal species, and these vastly differ from the pathogenesis described in horses, both clinically and after experimental exposure. Sources of variation may include species-specific susceptibility to different toxins present in the plant, different mechanistic processes of toxicity, and species differences in toxin biotransformation and bioactivation across different organs. Considering disease severity and Crofton weed's invasiveness globally, assessing published toxicological and exposure data is necessary to advance research, identify specific toxins for horses, and possible prophylactic and therapeutic strategies. This review presents an overview of the available literature on equine toxicity, parallels between toxicity in horses and other animal species, and important aspects to be included in the future research agenda.

Identification and expression analysis of heat shock protein family genes of gall fly (Procecidochares utilis) under temperature stress

Heat shock proteins (HSP) are molecular chaperones involved in many normal cellular processes and environmental stresses. At the genome-wide level, there were no reports on the diversity and phylogeny of the heat shock protein family in Procecidochares utilis. In this study, 43 HSPs were identified from the genome of P. utilis, including 12 small heat shock proteins (sHSPs), 23 heat shock protein 40 (DNAJs), 6 heat shock protein 70 (HSP70s), and 2 heat shock protein 90 (HSP90s). The characteristics of these candidates HSP genes were analyzed by BLAST, and then phylogenetic analysis was carried out. Quantitative real-time PCR (qRT-PCR) was used to analyze the spatiotemporal expression patterns of sHSPs and HSP70s in P. utilis after temperature stress. Results showed that most sHSPs could be induced under heat stress during the adult stage of P. utilis, while a few HSP70s could be induced at the larval stage. This study provides an information framework for the HSP family of P. utilis. Moreover, it lays an important foundation for a better understanding of the role of HSP in the adaptability of P. utilis to various environments.

Patterns of understory invasion in invasive timber stands of a tropical sky island

Current climate and land cover change threaten global mountaintops with increased spread of invasive species. Long-established plantations of invasive trees on these mountaintops can alter their surroundings, further increasing invader-facilitated invasion. Identifying the ecological conditions promoting such associations can help develop better management interventions. The Western Ghats's Shola Sky Islands (>1400 m MSL) host vast stretches of invasive tree plantations that sustain the colonization of other invasive woody, herbaceous, and fern species in their understories. Here, we analyzed vegetation and landscape variables from 232 systematically placed plots in randomly selected grids using non-metric multidimensional scaling and Phi coefficient approaches to examine patterns of association (positive interactions) between understory invasive species with specific invasive overstory species. We also conducted GLMM with zero inflation to determine the influence of environmental variables where such associations occur. We find that understory invasion of multiple species under the canopy of other invasives is widespread across the Shola Sky Islands. Stands of Eucalyptus host the colonization of 70% of non-native invasive species surveyed across the Shola Sky Islands. In particular, the Lantana camara invasion is strongly associated with Eucalyptus stands. We also found that climatic variables affect the colonization of understory woody invasive species, while invasion by exotic herbaceous species is associated with the density of road networks. Canopy cover impacts all invasives negatively, while fire incidence was negatively associated with invasion by Lantana spp. and the Pteridium spp. While the restoration of natural habitats primarily targets the highly invasive Acacia, less invasive Eucalyptus and Pinus are often not included. Our study suggests that retaining such invasive species in natural habitats, particularly protected areas, can hinder ongoing grassland restoration efforts by facilitating further invasions by multiple woody and herbaceous species.

Influences of environment, human activity, and climate on the invasion of Ageratina adenophora (Spreng.) in Southwest China

With economic and social globalization, invasive alien species have significantly threatened local ecological security. Identifying the invasive mechanisms of invasive alien species can aid in preventing species invasions and protecting local ecological and economic security. As a globally invasive plant, Ageratina adenophora (Asteraceae) has spread to many parts of the world and had a seriously impacted the ecology and economy of its invaded areas. Using observational data and Landsat OLI images in an arid valley region in southwest China, this study examined how climate, human activity and environmental factors influence the invasion of A. adenophora and its underlying mechanism. Our results showed that the invasion abundance of A. adenophora was significantly affected by environmental factors (the relative importance was 87.2%), but was less influenced by human activity and climate factors (the relative importance was 2% and 10.8%, respectively). The A. adenophora abundance significantly decreased with aspect, community canopy density, shrub layer coverage, herb layer coverage, Simpson diversity index of shrub and herb layers, the shortest distance to residential areas and temperature seasonality, whereas it increased with soil moisture, temperature annual range, precipitation of wettest month and precipitation of driest month. We conclude that biotic competition is the most influential factor in the invasion of this plant in the arid valley regions. Our results are of great significance for invasion prevention and forest conservation and management in southwest China. Our work emphasized that optimizing the community structure, such as by increasing canopy and shrub coverage and species biodiversity, may help control and mitigate the A. adenophora invasion in southwest China.

Alkaloid Extract of Ageratina adenophora Stem as Green Inhibitor for Mild Steel Corrosion in One Molar Sulfuric Acid Solution

Green corrosion inhibitors are of great interest due to their exciting and environmentally friendly behavior in mild steel corrosion control during and after the acid cleaning process. Herein, alkaloids were extracted from the stem of Ageratina adenophora and were ensured by qualitative chemical tests as well as spectroscopic test methods. The corrosion inhibition efficacy of the alkaloids against mild steel corrosion was evaluated by gravimetric, electrochemical and EIS measurement methods. In addition, the adsorption isotherm, free energy of adsorption and thermodynamic parameters of the process were evaluated. The investigations indicated the most promising inhibition efficacy of the alkaloids for mild steel corrosion. The adsorption isotherm study revealed that the adsorption of inhibitor molecules on the MS interface was manifested by dominant physisorption followed by chemisorption. Free energy and thermodynamic parameters are well suited to endothermic processes.

Screening plant growth-promoting bacteria from the rhizosphere of invasive weed Ageratina adenophora for crop growth

Plant-growth promoting rhizobacteria (PGPR) play a vital role in soil fertility and crop production. The rhizosphere of many crop plants has been well documented by screening PGPR for their plant-growth promoting (PGP) mechanisms. However, the rhizosphere of grass species that may act as potential habitats for novel PGPR remains relatively unexplored. Ageratina adenophora is a noxious weed that has invaded more than 40 tropical and subtropical countries in Asia, Oceania, Africa, and Europe. Its presence has led to changes in plant species composition, reducing their biodiversity and destroying ecosystem function. In this study, we screened 1,200 bacterial strains isolated from the rhizosphere soil of A. adenophora in three floristic regions in Yunnan Province, China. Samples were screened for their in vitro ability for N-fixation, production of the plant growth regulator indole-3-acetic acid (IAA), and the synthesis of 1-amino-cyclopropane-1-carboxylate (ACC) deaminase, which controls the levels of ethylene in developing plant roots. We found that 144 strains showed at least one of these PGP attributes. 16S rRNA gene sequencing showed that most (62.5%) of the samples were bacteria closely related to members of the genera Pseudomonas (27 strains), Providencia (20 strains), Chryseobacterium (14 strains), Ensifer (12 strains), Enterobacter (nine strains), and Hafnia (eight strains). Their abundance and biodiversity in the soil of individual floristic regions correlate positively with the invasion history of A. adenophora. From these PGP bacterial strains, KM_A34 (Pantoea agglomerans), KM_C04 (Enterobacter asburiae), and KM_A57 (Pseudomonas putida), which had the greatest in vitro ability of N-fixation, and IAA and ACC deaminase production, respectively, were selected. The strains were evaluated for their effect on the seed germination and growth of soybean, faba bean, pea, wheat, and Chinese cabbage other than A. adenophora. Chamber experiments showed these strains significantly (P < 0.05) increased (14.2-43.4% over the controls) germination rates of the soybean, faba bean, pea, and/or Chinese cabbage seeds. They also reduced relative seed germination times (20.8-48.8% over the controls) of soy bean, faba bean and/or wheat seeds. Greenhouse pot experiments showed that they significantly (P < 0.05) promoted the aboveground and belowground height of plant foliage (12.1-23.1% and 11.5-31.4% over the controls, respectively) and/or the dry weights (16.1-33.5% and 10.6-23.4% over the controls, respectively) of the soy bean, faba bean, pea, wheat and/or Chinese cabbage. These data indicate that the rhizosphere microbiota of A. adenophora contain a PGPR pool that may be used as bioinoculants to improve the growth and productivity of these crops.

Ageratina adenophora (Spreng.) King & H. Rob. Standardized leaf extract as an antidiabetic agent for type 2 diabetes: An in vitro and in vivo evaluation

Type 2 diabetes has become one of the major health concerns of the 21st century, marked by hyperglycemia or glycosuria, and is associated with the development of several secondary health complications. Due to the fact that chemically synthesized drugs lead to several inevitable side effects, new antidiabetic medications from plants have gained substantial attention. Thus, the current study aims to evaluate the antidiabetic capacity of the Ageratina adenophora hydroalcoholic (AAHY) extract in streptozotocin-nicotinamide (STZ-NA)-induced diabetic Wistar albino rats. The rats were segregated randomly into five groups with six rats each. Group I was normal control, and the other four groups were STZ-NA-induced. Group II was designated diabetic control, and group III, IV, and V received metformin (150 mg/kg b.w.) and AAHY extract (200 and 400 mg/kg b.w.) for 28 days. Fasting blood glucose, serum biochemicals, liver and kidney antioxidant parameters, and pancreatic histopathology were observed after the experimental design. The study concludes that the AAHY extract has a significant blood glucose lowering capacity on normoglycemic (87.01 ± 0.54 to 57.21 ± 0.31), diabetic (324 ± 2.94 to 93 ± 2.04), and oral glucose-loaded (117.75 ± 3.35 to 92.75 ± 2.09) Wistar albino rats. The in vitro studies show that the AAHY extract has α-glucosidase and α-amylase inhibitory activities which can restore the altered blood glucose level, glycated hemoglobin, body weight, and serum enzymes such as serum glutamic pyruvic transaminase, serum glutamic oxaloacetic transaminase, serum alkaline phosphatase, total protein, urea, and creatinine levels close to the normal range in the treated STZ-NA-induced diabetic rats. The evaluation of these serum biochemicals is crucial for monitoring the diabetic condition. The AAHY extract has significantly enhanced tissue antioxidant parameters, such as superoxide dismutase, glutathione, and lipid peroxidation, close to normal levels. The presence of high-quantity chlorogenic (6.47% w/w) and caffeic (3.28% w/w) acids as some of the major phytoconstituents may contribute to the improvement of insulin resistance and oxidative stress. The study provides scientific support for the utilization of A. adenophora to treat type 2 diabetes in the STZ-NA-induced diabetic rat model. Although the preventive role of the AAHY extract in treating Wistar albino rat models against type 2 diabetes mellitus is undeniable, further elaborative research is required for efficacy and safety assessment in human beings.

Monitoring the distribution pattern and invasion status of Ageratina adenophora across elevational gradients in Sikkim Himalaya, India

Understanding the spread intensity and population dynamics of invasive plant species is a prerequisite for developing management strategies in the Himalayan Forest ecosystems that are experiencing an accelerated rate of climate change. Although there are studies on the occurrence of few invasive species in the Himalayan ecosystems, systematic information on their intensity of spread and species association is still missing. Considering existing data gaps, we aimed to assess the intensity of spread and distribution pattern of A. adenophora, one of the high-concern invasive species (HiCIS) of India that is causing havoc in the Himalayas, across an elevational gradient. Field data were collected in 2018 and 2021 in the Indian federal state of Sikkim, located in the Eastern Himalayas. We analyzed the population status and species association of A. adenophora along an elevational gradient ranging from > 600 m to 2700 m above sea level, which was divided into seven gradients of 300 m width, and each gradient was further randomly sampled. Overall, 81 species were present in association with A. adenophora, including 58 herbs, 19 shrubs, and 4 climbers, belonging to 30 families and 67 genera in the region. No other species continuously co-occurred along with A. adenophora throughout the elevation ranging from > 600 m to 2700 m. The species observed increased frequency (100%), density (40.51 ind./100 m²), and basal cover (11.25 cm²/m²) in the elevational gradient 1500-1800 m in 2018. In 2021, A. adenophora dominated the highest elevational gradient (< 2400-2700 m) with increased frequency (99.96%), density (58.41 ind./100m²), and basal cover (42.54 cm²/100m²), which demonstrated rapid invasion and improved plant health and reproductive vigor in comparison to the lower elevational gradient in Sikkim Himalaya. Despite being completely absent at the highest elevation (< 2400-2700 m), in 2018, it observed gregarious spread at the highest elevation in 2021, which is of serious concern to ecologists. The presence of the targeted species in all seven studied altitudinal gradients reflects stage III of the species invasion. An enormous shift in the distribution pattern along elevational gradients within a short time span is alarming for the Himalayan ecosystem since it is becoming a thriving habitat for invasive species owing to anthropogenic activity. We mapped the potential geographical extent using the species distribution model (SDM) and predicted the suitable habitat of distribution in Sikkim Himalaya. In order to curtail the spread and counteract the negative impact of this species on native vegetation in Sikkim Himalaya and ultimately reverse the process, local and regional initiatives for its biological control and management must be taken.

Mapping the Distribution and Dispersal Risks of the Alien Invasive Plant Ageratina adenophora in China

Identifying the distribution dynamics of invasive alien species can help in the early detection of and rapid response to these invasive species in newly invaded sites. Ageratina adenophora, a worldwide invasive plant, has spread rapidly since its invasion in China in the 1940s, causing serious damage to the local socioeconomic and ecological environment. To better control the spread of this invasive plant, we used the MaxEnt model and ArcGIS based on field survey data and online databases to simulate and predict the spatial and temporal distribution patterns and risk areas for the spread of this species in China, and thus examined the key factors responsible for this weed’s spread. The results showed that the risk areas for the invasion of A. adenophora in the current period were 18.394° N–33.653° N and 91.099° E–121.756° E, mainly in the tropical and subtropical regions of China, and densely distributed along rivers and well-developed roads. The high-risk areas are mainly located in the basins of the Lancang, Jinsha, Yalong, and Anning Rivers. With global climate change, the trend of continued invasion of A. adenophora is more evident, with further expansion of the dispersal zone towards the northeast and coastal areas in all climatic scenarios, and a slight contraction in the Yunnan–Guizhou plateau. Temperature, precipitation, altitude, and human activity are key factors in shaping the distribution pattern of A. adenophora. This weed prefers to grow in warm and precipitation-rich environments such as plains, hills, and mountains; in addition, increasing human activities provide more opportunities for its invasion, and well-developed water systems and roads can facilitate its spread. Measures should be taken to prevent its spread into these risk areas.

Bio-accumulation effects of heavy metals Pb, Zn and Cd on Procecidochares utilis parasitism to Eupatorium adenophorum at Suzu metal mines, Yunnan

Procecidochares utilis is an obligatory parasitic insect to Eupatorium adenophorum. Both organisms have been spread to some metal mines areas. The objective of this study is to comprehend the trend of heavy metals transfer and the process of their bio-accumulation in the soil-E. adenophorum-P. utilis system and particularly their impact on the parasitic effect of P. utilis to E. adenophorum to reflect the impact of heavy metals on obligate parasitic insect and its host. Therefore, a detailed investigation was carried out at the Suzu Lead–Zinc Mine in Yunnan Province using the concentric circle's method. The results showed that the parasitic rate of P. utilis to a single plant and branch is positively correlated with distance. The metals content of the soil in E. adenophorum and P. utilis, decreased dramatically with an increase in distance away from the center of the mining area. From which is cleared that these metals could enter to E. adenophorum and P. utilis through the soil-E. adenophorum-P. utilis system which likely to affect its parasitic activities. In addition, the parasitic rate is impacted by per Zn content greatly, and the parasitic rate per plant is affected by Cd content enormously. This work could provide important basis of data for further understanding and clarifying the effects of bioaccumulation and heavy metals pollution on various aspects of the food chain. Simultaneously, it could clarify and simplify whether heavy metal contamination affects the parasitic behaviour of some obligatory parasitic insects.

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Concentric circles method was used to assess heavy metals accumulation.

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Heavy metals pollution in mining area reduced the amount of Procecidochares utilis.

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The content of heavy metals uptrend alongside drawing closer to mine center.

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The parasitic rate is positively correlated with the distance from mine center.

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Metals bioaccumulation lowered parasitic effect of P. utilis on Crofton weed.

Rhizospheric Bacillus-Facilitated Effects on the Growth and Competitive Ability of the Invasive Plant Ageratina adenophora

The rhizospheric microbial community affects the population establishment of invasive plants in introduced areas, among which Bacillus has numerous functions in promoting plant growth. This study isolated and enriched the Bacillus community in the rhizospheric soil of the invasive plant Ageratina adenophora and the native accompanying plant Rabdosia amethystoides. The effects of these rhizospheric Bacillus communities on the growth and competition of A. adenophora and R. amethystoides were evaluated in pot experiments. The results showed that the number and diversity of Bacillus in the rhizospheric soil of A. adenophora were higher than those of R. amethystoides (A. adenophora: 122 strains in soil, 16 Bacillus taxa; R. amethystoides: 88 strains in soil, 9 Bacillus taxa). After Bacillus inoculation of A. adenophora in a pot experiment, Bacillus idriensis, Bacillus toyonensis and Bacillus cereus were accumulated in the rhizospheric of A. adenophora, which significantly increased the nitrate nitrogen (NO₃ ^--N) content in the soil and the total carbon and nitrogen concentrations in A. adenophora in the mixed treatment. The selective accumulation of Bacillus enhanced the competitive advantage of A. adenophora over the native accompanying plant; the corrected index of relative competition intensity of A. adenophora-inoculated Bacillus reached double that of the uninoculated treatment, and the growth of native plants was greatly suppressed under mixed planting. Our study confirmed that invasion of A. adenophora can lead to the accumulation of specific Bacillus taxa in the rhizospheric soil, which in turn can increase the competitive advantage of A. adenophora.

Antibacterial Activity of Two Metabolites Isolated From Endophytic Bacteria Bacillus velezensis Ea73 in Ageratina adenophora

Ageratina adenophora, as an invasive and poisonous weed, seriously affects the ecological diversity and development of animal husbandry. Weed management practitioners have reported that it is very difficult to control A. adenophora invasion. In recent years, many researchers have focused on harnessing the endophytes of the plant as a useful resource for the development of pharmacological products for human and animal use. This study was performed to identify endophytes with antibacterial properties from A. adenophora. Agar well diffusion method and 16S rRNA gene sequencing technique were used to screen and identify endophytes with antibacterial activity. The response surface methodology and prep- high-performance liquid chromatography were used to determine the optimizing fermentation conditions and isolate secondary metabolites, respectively. UV-visible spectroscopy, infrared spectroscopy, nuclear magnetic resonance, and high-resolution mass spectrum were used to determine the structures of the isolated metabolites. From the experiment, we isolated a strain of Bacillus velezensis Ea73 (GenBank no. MZ540895) with broad-spectrum antibacterial activity. We also observed that the zone of inhibition of B. velezensis Ea73 against Staphylococcus aureus was the largest when fermentation broth contained 6.55 g/L yeast extract, 6.61 g/L peptone, 20.00 g/L NaCl at broth conditions of 7.95 pH, 51.04 h harvest time, and a temperature of 27.97°C. Two antibacterial peptides, Cyclo (L-Pro-L-Val) and Cyclo (L-Leu-L-Pro), were successfully extracted from B. velezensis Ea73. These two peptides exhibited mild inhibition against S. aureus and Escherichia coli. Therefore, we isolated B. velezensis Ea73 with antibacterial activity from A. adenophora. Hence, its metabolites, Cyclo (L-Pro-L-Val) and Cyclo (L-Leu-L-Pro), could further be developed as a substitute for human and animal antibiotics.

Composition, Distribution, and Factors Affecting Invasive Plants in Grasslands of Guizhou Province of Southwest China

Southwest China is an important route for invasive species. In this study, 49 invasive plants of 15 families and 41 genera were found within 373 grassland sampling sites of Guizhou Province, a typical karst mountainous region with a high invasion risk located in Southwest China. Invasive plants could be found within over 90% of the grassland sampling sites, and malignant invasive species were found in 60% of the sites. In about 30% of the sampling sites, more than one malignant species coexisted. The malignant invasive species were mainly distributed in the southwestern part of Guizhou Province. Their distribution patterns were affected by environmental and traffic factors; they preferred areas with low elevation, high temperature, high rainfall, high soil nutrient content, and traffic accessibility and could adversely affect plant cover and biomass. Conversely, seriously invasive species and other low-level invasive species had a positive or neutral effect on grassland communities. Therefore, the focus of invasive plant control measures should be on malignant invasive species. Specific control policies and practices, especially in areas with resource-rich environments and well-developed traffic networks, should be carried out to facilitate grassland ecosystem sustainability and to prevent the spread of invasive species to inland China.

Phytotoxic effects of invasive Ageratina adenophora on two native subtropical shrubs in Nepal

The response of native plants to allelopathic interference of invasive species may differ from species to species. In this study, the phytotoxic effects of Ageratina adenophora were tested on two native shrubs (Osbeckia stellata and Elsholtzia blanda) of Nepal. Both the shrubs were grown in pots under treatments of A. adenophora fresh leaves and root leachates, and litter. Then, the seedling length and biomass were compared among the treatments. The results show that A. adenophora litter has stimulatory effects but the leachates from fresh leaves and root are phytotoxic to the growth and development of native shrubs. Infrared Spectroscopy (IR) analysis confirmed the presence of O–H (Hydroxyl), N–H (Amines), C≡C (Alkynes), and C–H stretching (Aromatic) or C–O–C stretching (Ethers) in the leachates representing harmful allelochemicals. The invaded soil by A. adenophora had low pH and a high amount of organic matter, total nitrogen, phosphorus, and potassium than the uninvaded soil. The results indicate that the native O. stellata and E. blanda are harmed by A. adenophora in nature by leaching of allelochemicals and probably by reducing the soil pH. Overall, this study has provided valuable insights regarding the effects of A. adenophora invasion on native shrubs and revealing the potential mechanism of its invasiveness.

Potential use of Helianthus tuberosus to suppress the invasive alien plant Ageratina adenophora under different shade levels

BACKGROUND

An ecological approach for managing biological invasions in agroecosystems is the selection of alternative crop species to manage the infestation of invasive alien plants through competition. In the current study, plant growth, photosynthesis, and competitive ability of the crop Helianthus tuberosus L. (Jerusalem artichoke) and the invasive alien plant Ageratina adenophora (Spreng.) R. M. King and H. Rob were compared under varying shade levels by utilizing a de Wit replacement series method. We hypothesized that H. tuberosus had higher competitive ability than A. adenophora even under shaded conditions.

RESULTS

The results showed the main stem, leafstalk length, leaf area, underground biomass, and aboveground biomass of A. adenophora were significantly lower compared to H. tuberosus in monoculture although A. adenophora had a greater number of branches that were longer on average. Under full sunlight, the total shoot length (stem + branch length), main stem length and branch length of A. adenophora were significantly suppressed (P < 0.05) by increasing proportions of H. tuberosus, and the same morphological variables of H. tuberosus were significantly higher with decreasing proportions of H. tuberosus. With increasing shade rates and plant ratios, the plant height, branch, leaf, and biomass of both plants were significantly suppressed, but to a greater degree in the case of A. adenophora. The net photosynthetic rate (Pn) of H. tuberosus and A. adenophora increased gradually from July to September, then decreased in October. The Pn of H. tuberosus was consistently higher than that of A. adenophora. Although the Pn for both species was significantly reduced with increasing shade rates and plant ratios, A. adenophora experienced greater inhibition than H. tuberosus. The relative yield (RY) of A. adenophora was significantly less than 1.0 (P < 0.05) in mixed culture under all shade levels, indicating that the intraspecific competition was less than interspecific competition. The RY of H. tuberosus was significantly less than 1.0 under 40-60% shade and greater than 1.0 (P < 0.05) under 0-20% shade in mixed culture, respectively, showing that intraspecific competition was higher than interspecific competition under low shade, but the converse was true under high shade. The relative yield total (RYT) of A. adenophora and H. tuberosus was less than 1.0 in mixed culture, indicating that there was competition between the two plants. The fact that the competitive balance (CB) index of H. tuberosus was greater than zero demonstrated a higher competitive ability than A. adenophora even at the highest shade level (60%).

CONCLUSIONS

Our results suggest that H. tuberosus is a promising replacement control candidate for managing infestations of A. adenophora, and could be widely used in various habitats where A. adenophora invades.

Ageratina adenophora Inhibits Spleen Immune Function in Rats via the Loss of the FRC Network and Th1-Th2 Cell Ratio Elevation

The objective of this study was to determine the impact of Ageratina adenophora (A. adenophora) on splenic immune function in a rat model. Rats were fed with 10 g/100 g normal feed and an experimental feed, which was composed of 3:7 A. adenophora powder and normal feed for 60 days. On days 14, 28, and 60, subsets of rats (n = 8 rats/group/time point) were selected for blood and spleen tissue sample collection. The results showed that the proportion of CD3⁺ T cells in the spleen was decreased at day 60 (vs. control). Also, mRNA and protein expression of chemokines CCL21 and CCL19 and functional protein gp38 in spleen decreased significantly versus the control at day 60. In addition, ER-TR7 antigen protein expression was also decreased at day 60. Levels of T-helper (Th)1 cells significantly increased, whereas those of Th2 cells decreased significantly versus the control at day 60 in spleen. The finding revealed that A. adenophora could affect splenic immune function in rats by altering the fibroblast reticulocyte (FRC) network, as well as by causing an imbalance in Th1/Th2 cell ratios. This research provides new insights into potential mechanisms of spleen immunotoxicity due to exposures to A. Adenophora.

Geographical distribution of the dispersal ability of alien plant species in China and its socio-climatic control factors

Dispersal ability is important for the introduction, establishment, and spread of alien plant species. Therefore, determination of the geographical distribution of the dispersal ability of such species, and the relationship between dispersal ability and socio-climatic factors are essential to elucidate the invasion strategies of the alien plant species. Analytic hierarchy process and inventory, risk rank, and dispersal mode data available on Chinese alien plant species were used to determine their dispersal ability, the geographical distribution thereof, and the relationship between socio-climatic factors and dispersal ability. High-risk alien plant species had a higher natural dispersal ability (or several natural dispersal modes) but a lower anthropogenic dispersal ability (or few anthropogenic dispersal modes) than low-risk alien plant species. The geographical distribution of the dispersal ability of the alien plant species showed an inverse relationship with species density. Alien plant species with low dispersal ability (i.e., with fewer dispersal modes and distribution in the southeast) showed a tendency to adapt to environments with mild climates, while those with high dispersal ability (i.e., with more disposal nodes and distribution in the northwest) showed a tendency to adapt to harsh environments. It is essential for land managers and policy makers to understand the geographical distribution of the dispersal ability of alien plant species and their socio-climatic control factors to formulate strategies to control the natural and anthropogenic dispersal of such plants.

Thymol derivatives with antibacterial and cytotoxic activity from the aerial parts of Ageratina adenophora

Three new thymol derivatives, 7-formyl-9-isobutyryloxy-8-hydroxythymol (1), 7,9-di-isobutyryloxy-8,10-dehydrothymol (2) and 2α-methoxyl-3β-methyl-6-methylol-2,3-dihydrobenzofuran (3), along with five known ones (4-8), were isolated from the aerial parts of the invasive plant Ageratina adenophora. Their structures were elucidated by extensive spectroscopic analysis and they were all isolated from the aerial part of A. adenophora for the first time. These compounds, except 8, selectively showed in vitro antimicrobial activity against three Gram-(+) and two Gram-(-) bacterial strains. In particular, compounds 1 and 5 showed notable in vitro antimicrobial activity against all five bacterial strains with IC50 values ranging from 3.9 to 15.6 μg mL-1, as compared to reference compound kanamycin sulfate with a MIC value 1.9-3.9 μg mL-1. Compounds 1 and 5 were further revealed to show in vitro cytotoxic activity against three tested human tumor (MCF-7, NCI-H460 and HeLa) cell lines, with IC50 values ranging from 7.45 to 28.63 μM. Compounds 7 and 8 selectively showed slight but detectable in vitro cytotoxicity toward MCF-7 and NCI-H460 cell lines, with IC50 values 44.65-83.19 μM. No cytotoxic effects were detected in the bioassay of the other four thymol derivatives. The present results provide new data to support that the aerial parts of A. adenophora are a rich source of bioactive chemicals valuable in medicinal applications.

An efficient, green, and easy-to-scale-up strategy for target-oriented isolating cadinene sesquiterpenoids from Eupatorium adenophorum Spreng

A green and efficient strategy was established and optimized for target-oriented extraction, enrichment and separation of cadinene sesquiterpenoids from Eupatorium adenophorum Spreng., using the combination of supercritical fluid extraction, molecular distillation, and industrial preparative chromatography for the first time. The extraction conditions of supercritical fluid extraction were initially optimized by orthogonal experimental design. Under the optimum conditions, the contents of 9-oxo-10,11-dehydroageraphorone and 10Hβ-9-oxo-ageraphorone, which were 55.00% and 6.01%, respectively, were much higher than conventional extraction methods. Then, the molecular distillation enrichment method was established and investigated by response surface methodology technology, which showed strong specificity for enriching target compounds and removing impurities from crude extracts. Under the optimum conditions of molecular distillation, total contents of cadinene sesquiterpenoids were increased to 89.19%. Finally, a total of 146 mg of 9-oxo-10,11-dehydroageraphorone and 29 mg of 10Hβ-9-oxo-ageraphorone were easily obtained by industrial preparative chromatography, from 200 mg of distillation fraction, with purities over 99%. The contents of target components were analyzed by HPLC, and structures of them were identified by high-resolution MS, ¹ H-NMR, and ¹³ C-NMR spectroscopy. These results indicate that it is a simple, effective, and eco-friendly strategy, which is easily converted into industrial scale.

Ageratina adenophora invasions are associated with microbially mediated differences in biogeochemical cycles

Invasive plant species may alter soil nutrient availability to facilitate their growth and competitiveness. However, the roles and functional mechanisms of plant-associated microbes that mediate these soil biogeochemical cycles remain elusive. Here, we studied how soil microorganisms and their functional processes differed between soils invaded by Ageratina adenophora and adjacent non-invaded soils in a region of China with heavy invasion. Our results indicated that soil nitrogen contents were over 4.32 mg/kg higher (p < 0.05) in both rhizosphere soils and bulk soils dominated by A. adenophora as compared with those in soils dominated by non-invaded plants. Concurrently, soil microbial-mediated functional processes, i.e. nitrogen fixation rate, nitrification rate and ammonification rate, were also significantly (p < 0.05) higher in either rhizosphere soils or bulk soils of invasive A. adenophora. Using a functional gene microarray, we found higher relative abundances of soil microbial genes involved in N cycling processes in A. adenophora soils, e.g. nifH, required for nitrogen fixation, which significantly correlated with ammonia contents (r = 0.35 in bulk soils, r = 0.37 in rhizosphere soils, p < 0.05) and the nitrogen fixation rate (r = 0.44, p < 0.05). We also found that the relative abundances of labile carbon decomposition genes were higher in invasive A. adenophora soils, implying a potential higher availability of carbon. These results suggest that the soil surrounding the invasive plant A. adenophora is a self-reinforcing environment. The plant litter and rhizosphere environment of the invasive may influence soil microbial communities, promoting self-supporting soil processes. Alternatively, the regions invaded by A. adenophora may have already had properties that facilitated these beneficial microbial community traits, allowing easier invasion by the exotics. Both scenarios offer important insights for the mitigation of plant invasion and provide an ecosystem-level understanding of the invasive mechanisms utilized by alien plants.

De novo transcriptomic analysis of the alimentary tract of the tephritid gall fly, Procecidochares utilis

The tephritid gall fly, Procecidochares utilis, is an important obligate parasitic insect of the malignant weed Eupatorium adenophorum which biosynthesizes toxic secondary metabolites. Insect alimentary tracts secrete several enzymes that are used for detoxification, including cytochrome P450s, glutathione S-transferases, and carboxylesterases. To explore the adaptation of P. utilis to its toxic host plant, E. adenophorum at molecular level, we sequenced the transcriptome of the alimentary tract of P. utilis using Illumina sequencing. Sequencing and de novo assembly yielded 62,443 high-quality contigs with an average length of 604 bp that were further assembled into 45,985 unigenes with an average length of 674 bp and an N50 of 983 bp. Among the unigenes, 30,430 (66.17%) were annotated by alignment against the NCBI non-redundant protein (Nr) database, while 16,700 (36.32%), 16,267 (35.37%), and 11,530 (25.07%) were assigned functions using the Clusters of Orthologous Groups (COG), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Gene Ontology (GO) databases, respectively. Using the comprehensive transcriptome data set, we manually identified several important gene families likely to be involved in the detoxification of toxic compounds including 21 unigenes within the glutathione S-transferase (GST) family, 22 unigenes within the cytochrome P450 (P450) family, and 16 unigenes within the carboxylesterase (CarE) family. Quantitative PCR was used to verify eight, six, and two genes of GSTs, P450s, and CarEs, respectively, in different P. utilis tissues and at different developmental stages. The detoxification enzyme genes were mainly expressed in the foregut and midgut. Moreover, the unigenes were higher expressed in the larvae, pupae, and 3-day adults, while they were expressed at lower levels in eggs. These transcriptomic data provide a valuable molecular resource for better understanding the function of the P. utilis alimentary canal. These identified genes could be pinpoints to address the molecular mechanisms of P. utilis interacting with toxic plant host.

Understanding the dynamics in distribution of invasive alien plant species under predicted climate change in Western Himalaya

Invasive alien plant species (IAPS) can pose severe threats to biodiversity and stability of native ecosystems, therefore, predicting the distribution of the IAPS plays a crucial role in effective planning and management of ecosystems. In the present study, we use Maximum Entropy (MaxEnt) modelling approach to predict the potential of distribution of eleven IAPS under future climatic conditions under RCP 2.6 and RCP 8.5 in part of Kailash sacred landscape region in Western Himalaya. Based on the model predictions, distribution of most of these invasive plants is expected to expand under future climatic scenarios, which might pose a serious threat to the native ecosystems through competition for resources in the study area. Native scrublands and subtropical needle-leaved forests will be the most affected ecosystems by the expansion of these IAPS. The present study is first of its kind in the Kailash Sacred Landscape in the field of invasive plants and the predictions of potential distribution under future climatic conditions from our study could help decision makers in planning and managing these forest ecosystems effectively.

Processes affecting altitudinal distribution of invasive Ageratina adenophora in western Himalaya: The role of local adaptation and the importance of different life-cycle stages

The spread of invasive plants along elevational gradients is considered a threat to fragile mountain ecosystems, but it can also provide the opportunity to better understand some of the basic processes driving the success of invasive species. Ageratina adenophora (Asteraceae) is an invasive plant of global importance and has a broad distribution along elevational gradients in the Western Himalayas. Our study aimed at understanding the role of evolutionary processes (e.g. local adaptation and clinal differentiation) and different life history stages in shaping the distribution pattern of the invasive plant along an elevational gradient in the Western Himalaya. We carried out extensive distributional surveys, established a reciprocal transplant experiment with common gardens at three elevational levels, and measured a suite of traits related to germination, growth, reproduction and phenology. Our results showed a lack of local adaptation, and we did not find any evidence for clinal differentiation in any measured trait except a rather weak signal for plant height. We found that seed germination was the crucial life-cycle transition in determining the lower range limit while winter mortality of plants shaped the upper range limit in our study area, thus explaining the hump shaped distribution pattern. Differences in trait values between gardens for most traits indicated a high degree of phenotypic plasticity. Possible causes such as apomixis, seed dispersal among sites, and pre-adaptation might have confounded evolutionary processes to act upon. Our results suggest that the success and spread of Ageratina adenophora are dependent on different life history stages at different elevations that are controlled by abiotic conditions.

Two New Thymol Derivatives from the Roots of Ageratina adenophora

Two new thymol derivatives, 7,9-diisobutyryloxy-8-ethoxythymol (1) and 7-acetoxy-8-methoxy-9-isobutyryloxythymol (2), were isolated from fresh roots of Ageratina adenophora, together with four known compounds, 7,9-di-isobutyryloxy-8-methoxythymol (3), 9-oxoageraphorone (4), (−)-isochaminic acid (5) and (1α,6α)-10-hydroxycar-3-ene-2-one (6). Their structures were established on the basis of detailed spectroscopic analysis, and they were all isolated from the roots of A. adenophora for the first time. All the compounds were tested for their in vitro antibacterial activity toward three Gram-positive and two Gram-negative bacterial strains. Thymol derivatives 1–3 only selectively showed slight in vitro bacteriostatic activity toward three Gram-positive bacteria. The two known carene-type monoterpenes 5 and 6 were found to show moderate in vitro antibacterial activity against all five tested bacterial strains, with MIC values from 15.6 to 62.5 μg/mL. In addition, compounds 5 and 6 were further revealed to show in vitro cytotoxicity against human tumor A549, HeLa and HepG2 cell lines, with IC₅₀ values ranging from 18.36 to 41.87 μM. However, their cytotoxic activities were inferior to those of reference compound adriamycin.

Effect of Ageratina adenophora invasion on the composition and diversity of soil microbiome

In the present study, high throughput 16S rRNA gene sequencing was used to investigate soil invaded by the aggressive weed Ageratina adenophora to determine its effect on the species composition, distribution, and biodiversity of the bacterial communities. Soil samples from 12 micro-sites containing a monoculture of A. adenophora plants, mixtures of A. adenophora and different native plant species, and native species alone were studied. We found that the invasion of this weed resulted in a selection of bacteria belonging to phyla Acidobacteria and Verrucomicrobia and the lack of bacteria belonging to phyla Actinobacteria and Planctomycetes, but did not affect significantly the percentage abundances of members of other phyla. A similar bacterial population selection was also observed at genus or subgroup levels. The NO₃^--N level was an important factor affecting soil bacterial communities and contributed to the dominance of A. adenophora. However, the numbers of total bacterial species, and the diversity and structure of soil bacterial microbiome did not (P > 0.05) change significantly following invasion by this weed.

Hepatotoxicity of Eupatorium adenophorum extracts and the identification of major hepatotoxic components

Eupatorium adenophorum can induce liver toxicity in animals. For the safe utilisation of the weed, the hepatotoxic components need to be discovered. In this study, in vitro hepatotoxicity of different extracts from E. adenophorum were determined on human hepatocyte cell line L02 and hepatocellular carcinoma cell line HepG2. The results showed that water extracts of E. adenophorum exhibited no hepatotoxicity in vitro while high concentrations of the organic solvent extracts had obvious hepatotoxicity. Sesquiterpenes may contribute to the toxicity based on the comparison of composition analysis. Three cadinene sesquiterpenes were purified and identified as 9-oxo-10,11-dehydroageraphorone, 10Hα-9-oxo-ageraphorone and 10Hβ-9-oxo-ageraphorone. In vitro hepatotoxic effects of these components were investigated, the IC₅₀ of the three compounds were 122.53, 87.52, and 108.80 μM in L02 cells and 151.92, 104.48, and 138.08 μM in HepG2 cells by Cell Counting Kit-8 (CCK-8) assay. The three components were confirmed to be, at least partial, hepatotoxic components.

Preparation, Phytochemical Investigation, and Safety Evaluation of Chlorogenic Acid Products from Eupatorium adenophorum

Eupatorium adenophorum is widely distributed throughout the world's tropical and temperate regions. It has become a harmful weed of crops and natural environments. Its leaves contain bioactive compounds such as chlorogenic acid and may be used as feed additives. In this study, chlorogenic acid was extracted and separated from leaves of E. adenophorum. Three chlorogenic acid products were prepared with different purities of 6.11%, 22.17%, and 96.03%. Phytochemical analysis demonstrated that the main toxins of sesquiterpenes were almost completely removed in sample preparation procedure. The three products were evaluated for safety via in vitro and in vivo toxicological studies. All the products exhibited no cytotoxic effects at a dose of 400 μg/mL in an in vitro cell viability assay. When administered in vivo at a single dose up to 1.5 g/kg bw, all three products caused no signs or symptoms of toxicity in mice. These results encourage further exploration of extracts from E. adenophorum in feed additive application.

Enrichment and separation of chlorogenic acid from the extract of Eupatorium adenophorum Spreng by macroporous resin

A simple and efficient chromatographic method for separation of chlorogenic acid from Eupatorium adenophorum Spreng extract was developed. The adsorption properties of nine macroporous resins were evaluated. NKA-II resin showed much better adsorption/desorption properties. The adsorption of chlorogenic acid on NKA-II resin at 25°C was well fitted to Langmuir isotherm model and pseudo-second-order kinetic model. The dynamic adsorption and desorption experiments were carried out on columns packed with NKA-II resin to optimize the separation process. The content of chlorogenic acid in the product increased to 22.17%, with a recovery yield of 82.41%.

Phenolics from Ageratina adenophora roots and their phytotoxic effects on Arabidopsis thaliana seed germination and seedling growth

A bioassay-directed phytochemical study was conducted to investigate potential allelochemicals in the roots of the invasive plant Ageratina adenophora. Eleven phenolic compounds, including seven new ones, 7-hydroxy-8,9-dehydrothymol 9-O-trans-ferulate (1), 7-hydroxythymol 9-O-trans-ferulate (2), 7,8-dihydroxythymol 9-O-trans-ferulate (3), 7,8-dihydroxythymol 9-O-cis-ferulate (4), methyl (7R)-3-deoxy-4,5-epoxy-D-manno-2-octulosonate 8-O-trans-p-coumarate (5), methyl (7R)-3-deoxy-4,5-epoxy-D-manno-2-octulosonate 8-O-cis-p-coumarate (6), and 3-(2-hydroxyphenyl)propyl methyl malonate (7), were isolated from a bioactive subfraction of the ethanol extract of the roots of A. adenophora. The new structures were established on the basis of detailed spectroscopic analysis. The potential phytotoxic effects of these compounds on the germination of Arabidopsis thaliana seeds were tested by a filter paper assay. Compound 7 and known compounds 3-(2-hydroxyphenyl)-1-propanol (8) and o-coumaric acid (9) remarkably showed inhibition activity against Arabidopsis seed germination at a concentration of 1.0 mM. Compounds 1, 2, 5, 6, and 10 showed slight inhibitory activity at the test concentration after treatment for 3 days, while the other compounds showed no obvious inhibitory effects. Moreover, 7-9 were further found to show obvious inhibitory activity on retarding the seedling growth of Ar. thaliana cultured in soil medium.

Bioactive quinic acid derivatives from Ageratina adenophora

A novel quinic acid derivative, 5-O-trans-o-coumaroylquinic acid methyl ester (1), together with three known ones, chlorogenic acid methyl ester (2), macranthoin F (3) and macranthoin G (4), were isolated from the aerial parts of the invasive plant Ageratina adenophora (Spreng.). The structure of new compound 1 was elucidated on the basis of extensive spectroscopic analysis, including 1D- and 2D-NMR techniques. Compounds 2–4 were isolated from plant A. adenophora for the first time. All the compounds showed in vitro antibacterial activity toward five assayed bacterial strains, especially 3 and 4, which showed in vitro antibacterial activity against Salmonella enterica with MIC values of 7.4 and 14.7 μM, respectively. Compound 1 was further found to display in vitro anti-fungal activity against spore germination of Magnaporthe grisea with an IC₅₀ value 542.3 µM. These four compounds were also tested for their antioxidant activity against DPPH (1,1-diphenyl-2-picrylhydrazyl) radical.