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The congeneric approach assesses the relative role of exotic invasive plants compared to native plants on associated species. However, most studies on seed germination have been conducted in Petri dishes that do not reflect natural soil conditions. Here, we compared the effects of different litter extracts of the exotics Prosopis juliflora (Sw.) DC. and Prosopis pallida (Willd.) Kunth, as well as native Prosopis cineraria (L.) Druce, on seed germination and seedling dry weight of two weedy plants (Amaranthus graecizans L. and Sisymbrium irio L.) and the native Senecio flavus (Decne.) Sch.Bip. in both Petri dishes and potted soil experiments. The results indicate that non-treated seeds (control) of the three species attained more than 95% germination in the Petri dishes (in vitro). The increase in the litter concentrations of both invasive Prosopis species inhibited the native Senecio flavus germination and significantly reduced germination and seedling weight of the weedy A. graecizans and Sisymbrium irio. Nevertheless, the native P. cineraria extracts had significant depressive effects on seed germination and seedling growth of the native Senecio flavus but limited effects on the weedy A. graecizans and Sisymbrium irio. The results support a greater impact of exotic than native congener on native plants. To better assess allelopathic effects, it is recommended to not rely on germination in Petri dishes.

The cucurbitaceae family comprises of economically important vegetable crops grown for food and medicine. Most cucurbit crops produce cucurbitacins in leaves, flowers, fruit, seed and roots which possess various pharmacological and pharmaceutical values. Cucurbitacins are toxic to pests and diseases, and allelopathic to noxious weeds thus providing opportunities for improving tolerance to biotic stresses. Further, cucurbitacins are responsive to environmental stimuli and can therefore enhance tolerance to abiotic stress. The objective of this review was to highlight the breeding value of cucurbitacins to develop cucurbitacins-enriched genotypes for food and medicine, and for management of biotic and abiotic stresses. The following themes were discussed: a comparative analysis of cucurbitacin concentrations in edible and non-edible plant parts; genetic control and associated quantitative trait loci and molecular markers associated with cucurbitacins; pharmacological and pharmaceutical values of cucurbitacins, and potential applications for management of biotic and abiotic stresses. Results of the present study will guide genetic improvement of cucurbitacins for use as food and medicine, and in the development of genotypes tolerant to biotic and abiotic stresses.

Over the decades the presence of aquatic weeds has caused immense biodiversity loss to the ecosystem. The use of herbicides has arisen emergence of herbicide-resistant weeds and loss of inherent flora and fauna due to the recalcitrant nature of the chemicals used. Hence, there is a need to use nontoxic, ecosustainable, low-cost, and efficient biological molecules that are analogous to chemical herbicides. Various plants, bacteria, fungi as well a few viruses are reported to secrete allelopathic biomolecules that inhibit the growth and development of weeds. However, majorly fungal pathogens and their metabolites are found to be effective biocontrol agents for the water hyacinth. The present review puts forward major findings and interventions in the biological control of the weed, water hyacinth. The biosynthesis, mechanism of action and factors regulating the activity of bioherbicides are discussed. In addition, the issues associated with the in situ application of these bioherbicides are also conferred focusing on the available mode of applications and formulation used. The major factors include the type and concentration of allelopathic biomolecules, age, type, and morphology of targeted weed, formulation type, mode of application and other physiological and environmental factors. Among various modes for the application of bioherbicides, emulsions are found to be most effective for the control of water hyacinth. Most of the toxicity studies indicated no toxicity of this fungal pathogen to other ecological plant species except water hyacinth. Yet, in-depth investigations are needed of these allelochemicals and toxins before field applications. Overall, lab-scale studies have shown promising results and highlighted a few potential fungi that need to be further explored for optimizing their bioherbicidal activity.

Pruning Ficus trees in urban green spaces may lead to the accumulation and spread of their leaf litter on the understory vegetation. This study was conducted to evaluate the allelopathic effect of Ficus retusa L. leaf litter on the understory species in urban gardens. A field study showed that the plant cover and species richness of litter-affected plots were lower than those of litter-free areas. The litter-affected soils had substantially lower pH and higher electrical conductivity. In a greenhouse experiment, litter-affected soil significantly inhibited the emergence and growth of understory species selected for the purpose of this study: Melilotus indicus (L.) All., Trifolium resupinatum L. and Amaranthus viridis L. Osmotic potentials equivalent to those of the litter-affected soils did not affect emergence or growth of these species. A spectrophotometric analysis indicated that the litter-affected soils contained larger amounts of phenolics and flavonoids. An HPLC analysis revealed that the litter-affected soils contained higher concentrations of free phenolic and flavonoid allelochemicals. These results demonstrate that F. retusa leaf litter may reduce plant cover and species richness. The significant inhibition in both field and greenhouse experiments could be attributed to phenolic and flavonoid allelochemicals released from the tree litter, as the osmotic potential of the litter had no effect on the understory species. The allelopathic potential of F. retusa leaf litter plays at least a partial role in reducing urban vegetation.

Tradescantia spathacea Sw. (Commelinaceae) is widely cultivated as an ornamental and medicinal plant in Southeast Asia, and its pharmacological properties are well known. On the other hand, this plant species is classified as an invasive weed in some countries. As a noxious weed, T. spathacea has been reported to disrupt the growth of native plants. However, no study has reported on its allelopathic activity. Thus, we investigated the allelopathic property and inhibitory substance of T. spathacea. The extracts of T. spathacea significantly inhibited the shoots and roots of alfalfa (Medicago sativa L.), cress (Lepidium sativum L.), lettuce (Lactuca sativa L.), barnyard grass (Echinochloa crus-galli (L.) P. Beauv.), Italian ryegrass (Lolium multiflorum Lam.), and timothy (Phleum pratense L.) at concentrations ≥ 3 mg dry weight (D.W.) equivalent extract/mL. As the extract concentration increased, the growth of the shoots and roots decreased. The I50 values of the test plant shoots and roots were 11.6–72.4 and 5.4–19.5 mg D.W. equivalent extract/mL, respectively. The extracts were purified by column chromatography, and an inhibitory substance was separated, which inhibited the shoots and roots of cress to 18.8 and 11.6% of control growth, respectively. The results of present findings indicate that T. spathacea extracts possess an allelopathic property, and its inhibitory substance may contribute this activity.

Allelochemicals, chemical cues that, among other things, mediate insect-plant interactions, such as host plant recognition, have attracted notable interest as tools for ecological control of pest insects. Advances have recently been made in methods for sampling and analyzing volatile compounds and technology for tracking insects in their natural habitat. However, progress in odor-mediated behavioral bioassays of insects has been relatively slow. This perspective highlights this odor-mediated insect behavior, particularly in a natural setting and considering the whole behavioral sequence involved in the host location, which is the key to understanding the mechanisms underlying host plant recognition. There is thus a need to focus on elaborate behavioral bioassays in future studies, particularly if the goal is to use allelochemicals in pest control. Future directions for research are discussed.

Plant Growth-Promoting Rhizobacteria (PGPR) induce systemic resistance (SR) in plants, decreasing the development of phytopathogens. The FZB42 strain of Bacillus velezensis is known to induce an SR against pathogens in various plant species. Previous studies suggested that it could also influence the interactions between plants and associated pests. However, insects have developed several strategies to counteract plant defenses, including salivary proteins that allow the insect escaping detection, manipulating defensive pathways to its advantage, deactivating early signaling processes, or detoxifying secondary metabolites. Because Brown Marmorated Stink Bug (BMSB) Halyomorpha halys is highly invasive and polyphagous, we hypothesized that it could detect the PGPR-induced systemic defenses in the plant, and efficiently adapt its salivary compounds to counteract them. Therefore, we inoculated a beneficial rhizobacterium on Vicia faba roots and soil, previous to plant infestation with BMSB. Salivary gland proteome of BMSB was analyzed by LC-MS/MS and a label-free quantitative proteomic method. Among the differentially expressed proteins, most were up-regulated in salivary glands of insects exposed to PGPR-treated plants for 24 h. We could confirm that BMSB was confronted with a stress during feeding on PGPR-treated plants. The to-be-confirmed defensive state of the plant would have been rapidly detected by the invasive H. halys pest, which consequently modified its salivary proteins. Among the up-regulated proteins, many could be associated with a role in plant defense counteraction, and more especially in allelochemicals detoxification or sequestration.

Plants can respond to competition with a myriad of physiological or morphological changes. Competition has also been shown to affect the foraging decisions of plants belowground. However, a completely unexplored idea is that competition might also affect plants' foraging for specific elements required to inhibit the growth of their competitors. In this study, we examined the effect of simulated competition on root foraging and accumulation of heavy metals in the metal hyperaccumulating perennial plant Arabidopsis halleri, whose metal accumulation has been shown to provide allelopathic ability. A. halleri plants originating from both metalliferous and non-metalliferous soils were grown in a "split-root" setup with one root in a high-metal pot and the other in a low-metal one. The plants were then assigned to either simulated light competition or no-competition (control) treatments, using vertical green or clear plastic filters, respectively. While simulated light competition did not induce greater root allocation into the high-metal pots, it did result in enhanced metal accumulation by A. halleri, particularly in the less metal-tolerant plants, originating from non-metalliferous soils. Interestingly, this accumulation response was particularly enhanced for zinc rather than cadmium. These results provide support to the idea that the accumulation of metals by hyperaccumulating plants can be facultative and change according to their demand following competition.

Allelochemicals are secondary metabolites which are not edible and can be used as growth regulators and bio-herbicides. The goal of current study was to assess allelopathic ability of Lantana camara (Sage-plant) flowers against weeds viz. Avena fatua (Wild oat), Euphorbia helioscopia (Sun-spurge), Chenopodium album (Goosefoot), Phalaris minor (Canary-grass), and Rumex dentatus (Knotweed). Bioassay analysis of three methanolic fractions of the Combiflash from L. camara was performed at 50%, 75% and 100% concentration using germination percentage parameters, inhibition of plumule and radicle size. The fraction II of Combiflash strongly suppressed all weeds with negligible effect on T. aestivum. Gas chromatography-mass spectroscopy was conducted for the fraction, and isolated compounds were used to perform bioassays. From fraction II GC-MS detected four methyl esters of allelopathic fatty acid viz. Methyl oleate, methyl palmitate, methyl stearate and methyl linoleate. The evaluation of physiological effects of the bioassay revealed substantial suppression of chlorophyll, antioxidant enzymes (superoxide, dismutase peroxidase) and protein material in all weeds by methyl palmitate. Bioassay activity and study of physiological parameters revealed that the effective bio-herbicidal compound in Lantana camara flowers is methyl palmitate. This is the first time that methyl palmitate (a fatty acid methyl ester) has been related to herbicidal activity in L. camara flowers. It is proposed that field studies based on hormesis research and the mechanism of action of this compound be carried out.

Soil legacies mediate interactions between native and introduced plants, contributing to both invasion and biotic resistance to invasion. Given that nitrogen deposition can promote allelochemical release, reduce the benefits of soil microbes, and affect trait plasticity, nitrogen deposition likely alters soil legacies as well. However, it is not clear how mechanisms that facilitate adaptation to soil legacies are altered by nitrogen deposition. In a greenhouse setting, we investigated how an invasive and a native plant in northern China (Rhus typhina and Ailanthus altissima, respectively) acclimate to soil legacies and how these dynamics change with nitrogen availability. We measured plant functional traits, soil microbial abundance, microbial enzyme activities, and soil allelopathic effects to characterize plant responses to soil legacies from plants of the same and of the other species. Rhus typhina had a stronger growth response to soil legacies than did A. altissima. Rhus typhina established a novel plant-soil feedback by increasing fungi and bacteria, changing the composition of the microbial community, and effectively transforming negative effects of soil allelopathy to positive effects. Nitrogen deposition promoted the growth of R. typhina and alleviated the negative effects of heterospecific soil legacies on the performance of R. typhina. Invasive plants can acclimate to the soil legacies of native species through a combination of high trait plasticity, manipulating soil microbes, and establishing novel plant-soil feedbacks. Nitrogen deposition can facilitate invasive species acclimating to soil legacies by monopolizing nitrogen absorption, though this may diminish the benefit of soil microbes.

Understanding the fire-prone arid-zone pine species and maquis vegetation's response to fire is very important to reveal the ecology and evolution of these species. During the succession of vegetation, there are complex relationships between allelopathic metabolites and fires. Many plant communities such as pines, maquis, savannas and woodlands are known to play a critical role in the development of succession. However, studies revealing the relationship between succession processes and allelopathic mechanisms in fire-prone ecosystems are quite limited. Most evergreen maquis vegetations are one of the most studied fire ecosystems. In maquis vegetation, fire causes the formation of plant communities that continue with allelochemicals produced by plants, as well as shaping the climate of the region. The event of a living species inhibiting another species by secreting toxic compounds is expressed as allelopathy. These toxic compounds are generally referred to as allelochemicals. Many maquis species that grow in fire-prone ecosystems excrete their allelochemicals, preventing the development of herbaceous species around them and invade their habitats. These chemicals, which accumulate in the soil during the dry season, affect the succession processes in vegetation in the event of a fire and determine which species will follow each other. Considering these relationships, it can be said that allelopathic plants have the potential to change plant diversity in vegetation by changing their functional plant characteristics. The purpose of this review is to determine the relationship between allelochemicals and fire of plant species in fire-prone ecosystems, and to reveal how this affects the succession processes.

Weeds are unwanted plants in crop that can be control by different methods among them use of aqueous extract of crop is an imperative method. To investigate the allopathic potential of aqueous extract of winter crop Papavare somniferum (opium) on summer weed Echinochloa cruss-galli (barnyard grass) laboratory experiments were conducted. The experiment coomprised seven concentrations (0, 0.25, 0.50, 1, 2, 4, and 8%) of different plant parts i.e., leaves, stem and flower of P. somniferumwere. All the tested concentrations and plant parts of P. somniferum significantly reduced mean emergence time, germination index, germination percentage, time to 50% germination as well as well growth of E. cruss-galliweed. However, maximum mean emergence time (9.07 days), time to 50% germination (3.67 days) was noted at leaves and stem extract, respectively. Application of aqueous extract of stem at 8% concentration resulted in greatest time to complete 50% germination (5.42 days) and lowest fresh weight (6.28 g), dry weight (1.00 g) and root length (0.33 cm) of E. cruss-galli. Whereas leaf extract at 8% concentration produces less shoot length (1.13 cm) and more emergence time (9.18 days). Lowest emergence percentage (6.67%) and germination index (0.89) were produced by aqueous extract of fruit at 8% concentration. On the basis of this experiment, it can be concluded that higher concentration (8%) of stem extract of P. somniferumwas used to biologically control the infestation of E. cruss-galli weed.

Solanum elaeagnifolium Cav. is one of the most invasive plant species worldwide that colonizes crops and human disturbed lands, while it appears at the edge of forest ecosystems. Its control still remains an unsolved problem around the world. Understanding its distribution under predicted climate change, could contribute to an effective management and conservation of ecosystems in the future. This research was conducted in order to investigate the capacity of this species to invade Mediterranean forest ecosystems, and if the allelopathy effects of forest tree species could control its regeneration, thus contributing to a natural and biological management practice aimed to prevent the species from pervading into Mediterranean forest ecosystems. Results showed that S. elaeagnifolium can establish itself outside and along the forest edges, but not in a typical forest environment. The leaf extracts of Pinus brutia, Cupressus sempervirens, Quercus coccifera and Quercus pubescens significantly inhibited the germination of S. elaeagnifolium. Root regenerative ability of the cuttings was also significantly affected by the leaf extract treatments. P. brutia leaf extract had significantly the highest inhibitory activity on root regenerative ability of the species. Despite the promising findings of this study, absence of S. elaeagnifolium in Mediterranean forest ecosystems can be attributed to a combination of factors. In the context of climate change, especially in hot and dry Mediterranean areas, and the expected increase of forest disturbances (e.g., fires), the findings of the study could contribute towards the restriction of this invasive alien species by an appropriate management of forest ecosystems.

PREMISE Invasion processes involve several mechanisms, some of which have received little attention. Allelopathy has been invoked as an invasion driver according to the novel weapon hypothesis (NWH), and polyploidization can also be an important factor for invasion success. However, very few studies have addressed both topics together. We analyzed the allelopathic effect of the polyploid Oxalis pes-caprae, an invader in mediterranean-climate areas worldwide, from different origins and ploidy levels (native: South Africa; invaded: Chile, Australia, California, and the Mediterranean Basin) on Lactuca sativa as a model species. METHODS We measured seed germination, initial plant height, and aboveground and belowground biomass of Lactuca grown in field soil mixed with Oxalis material and with or without activated carbon in a common garden experiment. We performed the experiment twice, when Oxalis was vigorous and when senescent. RESULTS Vigorous plants of Oxalis tended to reduce Lactuca germination, but both vigorous and senescent Oxalis plants increased Lactuca biomass, probably due to an increase in nutrients provided by plant material. The highest increase in Lactuca traits occurred with Oxalis plants from the Iberian Peninsula. Allelopathy only happened when Oxalis was senescent and was especially strong with plants from Chile. CONCLUSIONS Although we did not find broad evidence for the NWH considering all areas together, we reported differences in the allelopathic potential of Oxalis plants depending on their origin. These results highlight the independent evolution of invasiveness traits in distant introduced ranges and the importance of the invaders' origin when testing hypotheses about invasion drivers.

Species interactions and mechanisms affect plant coexistence and community assembly. Despite increasing knowledge of kin recognition and allelopathy in regulating interspecific and intraspecific interactions among plants, little is known about whether kin recognition mediates allelopathic interference. We used allelopathic rice cultivars with the ability for kin recognition grown in kin vs. non-kin mixtures to determine their impacts on paddy weeds in field trials and a series of controlled experiments. We experimentally tested potential mechanisms of the interaction via altered root behavior, allelochemical production, and soil microbial community composition, as well as carbon and nitrogen partitioning in the weeds. We consistently found that the establishment and growth of paddy weeds were more inhibited by kin mixtures compared to non-kin mixtures. The effect was driven by kin recognition that induced altered root placement, established similar soil microbial communities, and altered weed carbon and nitrogen partitioning. Importantly, genetic relatedness enhanced the production of intrusive roots towards weeds and reduced the production of rice allelochemicals. These findings suggest that relatedness allows allelopathic plants to discriminate their neighboring collaborators (kin) or competitors and then adjust their growth, competitiveness and chemical defense accordingly.

The use of synthetic pesticides to alleviate the notorious weeds in farms has caused environmental pollution, consumption of chemicals absorbed by plants and resistance posed by the weeds putting agricultural development and ecological systems under threat. The main reason for study of allelopathic effect of the plant include; its application of observed allelopathic effects to agricultural production, reduction of inputs to chemical pesticides uses, resultant environmental pollution and for provision of fruitful method for sustainable development of agriculture and ecological systems. This study made the use of allelochemicals produced by the invasive Ipomoea hildebrandtii to provide an effective method of controlling weeds through biological control method which is environmentally friendly as compared to the conventional chemical method. Extraction was done and concentrated by rotary evaporator, pH of the soil under which the plant grew was determined. The allelopathic test was done at different concentrations in petri dishes on Phaseolus vulgaris and the characterization of the plant compounds done by Ultra Violet coupled to visible region, Fourier Transform Infra-Red, and Gas Chromatograph -Mass Spectroscopy. The leave extract was more effective in allelopathic effect on the plant than the stem extract, that means the inhibiting compounds are more concentrated in the leaves than the stem.

Agriculture is livelihood of rural people world wide. The different cultivated crops viz. wheat, rice, groundnut, chickpea, mung bean, potato, tomato, cucumbers, etc. suffer heavy yield losses due to biotic stresses viz. soil borne fungal pathogens i.e. species of Fusarium, Rhizoctonia, Sclerotium, Pythium, etc. and abiotic stresses i.e. extreme weather; drought; deteriorating soil health due to salinity, alkalinity, allelopathic, oxidative stresses, heavy metal accumulation, etc. Often these stresses are difficult to manage due to limitations of chemical pesticides in many ways. More than 200 spp. of Trichoderma have been recorded from different habitats, ecosystems and as symbiont/endophytes in plants. These Trichoderma spp. have been found as efficient agents of biological control and bioremediation to manage these stresses due to presence of different hydrolytic enzymes, antibiotics, peptaibols, competence in utilizing nutrients and playing the mechanisms of competition for space and nutrition, Antibiosis, Mycoparasitism, Induction of host defense; etc. Some of the Trichoderma spp. has emerged as an alternative of chemical management of these stresses. Technologies of production, delivery, etc. have been developed for the efficient use of Trichoderma. There is great demand of Trichoderma among the agriculturists all over the globe.Therefore, if supported financially by the financial agencies, the rural people and youths can take up the production to meet huge demand of the agriculture, and simultaneously they can earn the money to raise their socio-economic status, which make the rural people prosperous.

The present study reveals allelopathic potential of aqueous leaf extracts of two invasive weeds Euphorbia hirta L. and Parthenium hysterophorus L. on seed germination, growth performance and protein content of jowar (Sorghum vulgare Pers.) seedlings. Laboratory experiments were conducted to check the allelopathic potential of aqueous extract of selected weeds on germination and seedling growth of jowar. Enfluence of aqueous extrats (25, 50, 75 and 100 % concentrations) of two weed plants were studied on seed germination, growth performance, biomass and protein content of jowar seedlings. The observations of experiments revealed a significant stimulatory allelopathic potential of both the weeds on root and shoot growth. Similar results were obtained in case of performed bioassays. Among all concentrations, 25 % concentration of both the weed extracts shows maximum stimulation in biomass and protein content in jowar seedlings.

Rhizosphere microbial communities play important roles in facilitating or inhibiting the establishment of exotic species. Since some invasive plants interact with soil microbial communities such as rhizosphere bacteria, changes triggered by rhizosphere bacteria may alter competitive interactions between exotic and native plants. This study compared the Bacillus cereus content in soils with different degrees of Ageratina adenophora invasion, and investigated the effects of A. adenophora allelochemicals on B. cereus growth and soil characteristics and the feedback effects of B. cereus on A. adenophora growth. Bacillus cereus content in the rhizosphere of A. adenophora increased with intensification of the invasion process, and newly invaded soil contained almost twice as much bacteria as noninvaded soil. When rhizosphere soil was added to the root exudates of A. adenophora, the contents of B. cereus were twice as much as the control, except on the first day. Certain soil parameters increased significantly, such as ammonium nitrogen (NH4+-N) and available phosphorus (AP), which were increased by 41 and 27%, respectively. Soil treatment with B. cereus promoted the degradation of two allelochemicals from the rhizosphere of A. adenophora, amorpha-4,7(11)-dien-8-one and 6-hydroxy-5-isopropy1-3,8-dimethyl-4a,5,6,7,8,8a-hexahydraphthalen-2(1H)-one, to varying degrees; and increased the germination rate by 50%, root length by 117%, shoot length by 48% and fresh weight by 81% for A. adenophora compared to those of untreated soil. Our results confirmed that the invasion of A. adenophora will promote an increase of B. cereus, a beneficial rhizosphere bacterium, which in turn induces a positive feedback effect on A. adenophora.

Green tides have been increasing in frequency and severity in coastal areas in recent years, and thus, the adverse effects of green tides on the environment have attracted much research attention. Allelopathy is one of the most significant effects of green tide algae on the surrounding organisms. In this study, a series of experiments were developed to fully investigate the allelopathic effects of the green tide alga Ulva linza on two common coastal phytoplankton species and to isolate and identify the chemical compositions of the allelochemicals. Our results indicated that the fresh tissue, dry powder, and aqueous extracts all inhibited the population growth of the two experimental phytoplankton species, indicating the occurrence of allelopathy; further analysis of the allelochemicals identified multiple kinds of fatty acids as allelopathic compounds, in which the most abundant ones were hexadecanoic acid; 9Z, 12Z, 15Z-octadecatetrienoic acid; and 9E-octadecenoic acid. Our findings enrich the database for research on allelopathy between marine green tide algae and phytoplankton. Both algae and phytoplankton could increase their own competitive abilities during bloom formation, thereby changing the phytoplankton community structure.

Euphorbia hypericifolia, a non-native herbaceous weedy plant was found to often form disproportionately dense, virtually monospecific stands in the Mount Bambouto Caldera, Cameroon. This observation is within the purview of allelopathy and is attributed to the release of botanicals by non native plants that harm naïve native flora, creating significant problems for agriculture and the environment. We investigated if the invasiveness of E. hypericifolia could be explained by its allelopathic potential at varying concentrations on five indicator plants. The results showed that the leaf, root and stem aqueous extracts of the plant exhibited significant inhibitory effects on the germination, radicle and plumule lengths of Biden pilosa, Amaranthus spinosus, Lactuca sativa, Zea mays and Lycopersicon esculentum at 100 % by 75.0, 69.4, 95.6, 28.0 and 97.2 %, respectively. The leaf extract was the most potent, while the stem extract was the least. The extract of E. hypericifolia was stimulatory (Lower concentrations) and inhibitory to the germination and growth of the test plants and its effect was concentration-dependent with the roots of target plants being more sensitive to the extracts than the plumule. L. esculentum was the most susceptible species to E. hypericifolia extracts while Z. mays was more tolerant than any of the tested plants. Results of total chlorophyll pigment accretion showed declining levels of chlorophyll detected in the leaves of tomato transplants cultivated in the augmented soils with rising dosage of the leaf residue of E. hypericifolia. B. pilosa planted on E. hypericifolia infested soil (EIS) showed very poor emergence recording only 7.5 % after 6 weeks as compared to 83.0 % in non E. hypericifolia infested soil (NIS). Qualitative phytochemical screening indicates E. hypericifolia is rich in secondary metabolites including alkaloids, glycosides, flavonoids, phenolics, tanins, Steriods and saponins. Acetone was the best extractant amongst the solvents used. This study has proven the allelopathic potential of E. hypericifolia and revealed some allelochemicals that may be exploited for the development of bioherbicides and plant growth promotion from natural products.

The damage to crops and food commodities by pests and diseases remains a major public health concern. Globally, investigations were carried out to develop harmless natural products from essential oils (EOs) and advances were made to meet users’ acceptance as an alternative to chemical fungicides and insecticides. Recently, many EOs have shown potential results against a wide range of plant pathogens and insect pests, and are thus, attractive substitutes to synthetic chemicals. Remarkably, EOs based commercial pesticides remain lesser in number and this opens several prospects for their claim for use in present agriculture. The present paper provides a summary of the current status and prospects in evaluating the efficiency of the use of EO of Dysphania ambrosioides (L.) Mosyakin & Clemants syn. Chenopodium ambrosioides L. (Mexican tea) belonging to the family Amaranthaceae, in crop protection strategies against plant pathogens and insect pests, considering the opportunities and problems linked with the prospects of sustainable environment-friendly agriculture in the future. In addition, the chemical composition of D. ambrosioides EO from different geographical regions along with the pharmacological application, probable modes of action, and indication for or against the use of this EO as an alternative to chemicals, in several applications have been discussed. The EO of D. ambrosioides possessed potential pharmacological activities, such as antitumor, antiprotozoal, allelopathic, antiviral, immunoregulatory, anti-inflammatory, and antioxidant activities. Most of the chemically characterized EO of D. ambrosioides contained ascaridole, α-terpinene, p-cymene, and caryophyllene oxide as major components, and have shown efficient antibacterial, antifungal, and insecticidal activities against pests and pathogens of economically important crops. Thus, the EO of D. ambrosioides and its major constituents can be utilized as potential botanical pesticides for crop protection after large-scale evaluation.

Agriculture development remains the most significant and integral part of the economic growth of any country with pests, such as plant pathogens, weeds, insects, nematodes and animal, imposing a ma...

The present investigation reports antioxidant and osmotic components of Marigold at different developmental stages and also presents influence of its leachates on germination and growth of wheat (Triticum aestivum L.) seedlings. Leaves of younger plants exhibit more phenols, tannins and flavonoids as compared to root and stem. Leaves and flowers of CV. PBG exhibited greater contents of total phenols and flavonoids in comparison to CV. PNG. Leaves and flowers had greater free amino acids and free proline as compared to stem and root. Sodium was more in roots than in stem and leaves, whereas potassium and nitrogen are greater in leaves and stem of younger plants. Leaves of CV. PBG accumulated greater contents of potassium, nitrogen and calcium in comparison to those of PNG. Activity of PAL, SOD and CAT was greater in older plants and in flowers as compared to leaves. Non-enzymatic antioxidant components like ascorbic acid and reduced glutathione also exhibited the same trend. Nevertheless, APX, GPX and GR activity was less in the older plants and more in flowers than leaves. APX and GR activity was higher in CV. PBG than CV. PNG, whereas the activity of GPX and GST was more in PNG in comparison to PBG. The two cultivars (PNG and PBG) of Tagetes erecta L., their different parts and developmental stages showed considerable variation in their antioxidant and osmotic constituents. Accumulation of various antioxidant and osmotic components reported above may probably help Tagetes erecta L. adapt to varying environments. Higher concentration of leachates of leaves and flowers of marigold reduced germination percentage and seedling growth of wheat, whereas treatments of leachates of lower concentration somewhat stimulated the growth of wheat seedlings. Flower leachates showed more pronounced effects than leaf leachates. Further experimentation may lead to identification of allelochemicals in these leachates which may pave way for exploring the possibility of their use along with synthetic herbicides/weedicides in order to minimize the toxicity of soil caused by the use of synthetic compounds.

Drought is the most threatening abiotic constraint, affecting more than 43% of the cropped area around the globe. The use of allelopathic hormesis offers a pragmatic solution for mitigating the negative effects of drought on field crops. The present study evaluated the potential of sorghum water extract in enhancing drought tolerance in wheat and examined the possible underlying mechanisms. The experiment comprised of three factors viz. drought with three levels (100%, 60% and 30% field capacity; FC), sorghum water extracts with eight levels (control, water spray, 0.5%, 1.0%, 1.5%, 2.0%, 2.5% and 3.0% of sorghum water extract) and two wheat cultivars Ihsan-2016 (drought tolerant) and Galaxy-2013 (drought-sensitive). Drought stress, particularly at 30% FC, profoundly decreased the morpho-physiological attributes of both wheat cultivars; nevertheless, the application of sorghum water extract at 2.0% effectively enhanced the tolerance against drought stress. Compared with control, application of 2.0% sorghum water extract increased the morphological attributes such as shoot and root length as well as fresh and dry weight of both wheat cultivars in the range of 3–146% under 30% field capacity. In addition, 2.0% sorghum water extract triggered (9–165%) the activities of superoxide dismutase, catalase, and peroxidase, decreased the hydrogen peroxide contents (42–48%), and enhanced the contents of chlorophyll a, b, and carotenoid (6–151%) as compared to control in both wheat cultivars under 30% field capacity suggesting that these measures helped to reduce the drought-induced oxidative stress. Vigorous growth and higher drought tolerance derived from sorghum water extract was related to improved chlorophyll contents and a better antioxidant defense system in wheat.

Purpose: The experiment was conducted to investigate into the allelopathic potential of the aqueous extracts of different parts of Jatropha curcuson seven selected field crop species. Research method: The leaf, stem, bark, twig, root, pericarp, seed and oilcake extracts of J. curcus at four different concentrations (1:5, 1:10, 1:15 and 1:20 (w/v)) were tested against jute, mungbean, mustard, radish, rice, wheat and tomato. Control i.e. distilled water without extracts was also maintained in each case. The experiments were conducted following completely randomized design with three replications. Findings: Except few, the aqueous extracts of J. curcas plant parts significantly inhibited the seedling growth of all the test species at concentration more than 1:15 (w/v) whereas, at or below this level stimulated the seedling growth. Percent shoot and root growth inhibition of the test crops varied among J. curcus parts extract from 10 to 100, at 1:5 (w/v) concentration. At the same concentration, J. curcas oilcake extract completely (100%) inhibited the shoot and root growth of all the test crop species except rice. Similarly, seed extract completely inhibited (100%) the shoot and root growth of jute and mustard, whereas around or more than 70% inhibition of the shoot and root growth of all the test species except rice. These results confirm that J. curcushas allelopathic properties and may possess allelochemicals. Since oilcake of J. curcus extract had greater inhibitory activity than other parts, this could be used for isolation and identification of allelochemical(s). The results of this experiment will be helpful for the researchers to know the plant-plant interaction of J. curcus with its neighboring plant species or the intercrops introduce in Jatropha field. Limitations: There was no significant limitation to the report. Originality/Value: This research compares the allelopathic properties of different parts of Jatropha curcus on seven selected field crop species.

Allelopathy represents a valuable biochemical strategy in plant-plant interactions among different plants, e.g. among crops and weeds. It is an important strategy in the colonization of many invasive alien plants. Allelopathic plants affect the growth of other plants in the vicinity through the release of secondary metabolites (allelochemicals) into the soil. In particular, many allelochemicals suppress the root growth of target plants, but little is known about the mechanism involved in root growth inhibition. In this review, we will highlight the mechanism of root suppression involving: (i) Alterations in auxin homeostasis affecting polar auxin transport and root gravitropism, (ii) Biochemical and physiological processes in inhibited roots associated with oxidative stress due to direct production and accumulation of reactive oxygen species or suppression of antioxidative response and (iii) The ultrastructural modifications in root tip exposed to allelochemicals that drastically suppress the cell division and eventually lead to shorter roots of target plants.

We studied the effects of 7-crop rotations and continuous - monocropping systems on soil microorganism and its feedback. The results showed that absolute abundance of soil bacteria (Pseudomonas and Bacillus) in tomato - celery - cucumber - cabbage and cucumber - tomato - cucumber - cabbage rotation were significantly higher than control (CK). Absolute abundance of soil fungi in tomato - celery - cucumber - cabbage, kidney bean - celery - cucumber - cabbage, cucumber - kidney bean - cucumber - cabbage and cucumber - tomato - cucumber - cabbage rotation were significantly higher than CK. Dry weight of cucumber seedlings was significantly positively correlated with bacterial (Pseudomonas and Bacillus) abundance, and negatively correlated with fungal count. The results of inoculation with Fusarium oxysporum f.sp. cucumerinum showed that plant dry weight of cucumber seedlings in tomato - celery - cucumber - cabbage, cucumber - kidney bean - cucumber - cabbage, cucumber - tomato - cucumber - cabbage rotation soil was significantly higher than other treatments, and their disease index was significantly lower than other treatments. There was no significant difference in dry weight of cucumber seedlings in rotation and CK in the soil sterilization test. The results of plant - soil feedback experiment showed that soil microbial changes caused by different rotation patterns had a positive feedback effect on growth of cucumber seedlings.

There is evidence that signal (SG) and ruzi (RG) grass have an allelopathic effect on weeds. This study aim to evaluate this effects on difficult-to-control weeds: hairy beggarticks (HB), benghal dayflower (BD), horseweed (H), sourgrass (S) and tall windmill grass (TWG). The first experiment was installed in a completely randomized design with 2 donor species (SG and RG) × 4 extract concentrations (0, 75, 150 and 225 mg ml−1) in factorial scheme with four replicates. Weed germination percentage was evaluated in three-day intervals. In the second experiment, the weeds emerged in substrates previously cultivated with SG and RG, in completely randomised block design with four replicates. The emergence, shoot growth and root growth were evaluated. The results were as follows: (i) on horseweed (H), 84% germination inhibition by RG leaf extracts and 38% emergence inhibition by SG root exudates were observed; (ii) on benghal dayflower (BD), 84% germination inhibition by RG leaf extracts and 37% emergence inhibition and 4.3 times the SRL values than control by RG root exudates; (iii) on hairy beggarticks (HB) 52% germination inhibition by RG leaf extracts scored, while SG root exudates reduced 43% of the emergence, 24% shoots biomass accumulation and 11.3% root length; (iv) on sourgrass (S) 71% germination inhibition by both donor plants and 75% germination inhibition by RG leaf extracts were measured. Finally, on tall windmill grass (TWG) 69% germination inhibition was observed upon using both donor plants. It can be concluded that foliar allelochemicals inhibit the germination of: BD > S > TWG > H > HB, while root exudate allelochemicals, inhibit the emergence and root development of all weeds

International audience; The current agricultural scenario faces a range of challenges, with phytosanitary ones being paramount. In most cases, plant diseases are treated with chemicals; however, they cause environmental pollution and face the acquired resistance of pathogens. Alternatively, biochar is a valuable tool for inducing the systemic resistance of plants since it is an effective and widely used resource to improve the physical, chemical, and biological attributes of the soil, consequently providing an adequate environment for healthy plant development. The effectiveness of the application of biochar in the control of plant diseases has been attributed to its alkaline pH, which contributes to the growth of beneficial microorganisms and increases the availability of nutrients, and to its porous structure, which provides a habitat and protection for the development of the soil microbiome. Therefore, the combined effect of improvements to soil attributes through biochar creates its role in controlling pathogens. This review assesses the beneficial and potential effects of biochar in agricultural soils, as well as showing the positive effects of biochar in the management of soil pathogens. Besides, we deeply evaluate twenty papers that used biochar as a strategy to manage plant diseases caused by pathogens inhabiting the soil in different soil-pathogen-plant systems. Among these studies, 70 % validate biochar as a strategy for the management of plant diseases; 10 % of studies showed that the efficiency of biochar as a disease management tool depends on the type of feedstock, and 20 % of studies describes that the biochar is not a management tool for suppressive diseases, caused by Pythium ultimum and Rhizoctonia solani in some host plants. The biochar is a strategy to manage plant diseases caused by pathogens inhabiting the soil, due different mechanisms as fungitoxic effect of biochar, sorption of allelopathic and phytotoxic compounds that can harm the plant, induction of plant resistance, increase of activities and abundance of beneficial microorganism’s, changes in soil quality as nutrient availability and abiotic conditions.

Allelopathy means that one plant produces chemical substances to affect the growth and development of other plants. Usually, allelochemicals can stimulate or inhibit the germination and growth of plants, which have been considered as potential strategy for drug development of environmentally friendly biological herbicides. Obviously, the discovery of plant materials with extensive sources, low cost and markedly allelopathic effect will have far-reaching ecological impacts as the biological herbicide. At present, a large number of researches have already reported that certain plant-derived allelochemicals can inhibit weed growth. In this study, the allelopathic effect of Artemisia argyi was investigated via a series of laboratory experiments and field trial. Firstly, water-soluble extracts exhibited the strongest allelopathic inhibitory effects on various plants under incubator conditions, after the different extracts authenticated by UPLC-Q-TOF-MS. Then, the allelopathic effect of the A. argyi was systematacially evaluated on the seed germination and growth of Brassica pekinensis, Lactuca sativa, Oryza sativa, Portulaca oleracea, Oxalis corniculata and Setaria viridis in pot experiments, it suggested that the A. argyi could inhibit both dicotyledons and monocotyledons not only by seed germination but also by seedling growth. Furthermore, field trial showed that the A. argyi significantly inhibited the growth of weeds in Chrysanthemum morifolium field with no adverse effect on the growth of C. morifolium. At last, RNA-Seq analysis and key gene detection analysis indicated that A.argyi inhibited the germination and growth of weed via multi-targets and multi-paths while the inhibiting of chlorophyll synthesis of target plants was one of the key mechanisms. In summary, the A. argyi was confirmed as a potential raw material for the development of preventive herbicides against various weeds in this research. Importantly, this discovery maybe provide scientific evidence for the research and development of environmentally friendly herbicides in the future.

Sustainable weed management strategies are important for reducing chemical inputs and development of weed resistance. This study aimed to evaluate the effect of extracts from winter cover crops (ce...

Essential oils, extracts and chemical components from aromatic plants are widely used as flavors and fragrances by the food and cosmetics industries because they act highly effective against plant pathogens and pests. According to recent research studies, some botanicals derived from higher plants are efficient insecticides against particular pests, and fungicidal against necrotrophic and biotrophic plant pathogens, in addition to their use in food production. Towards substituting synthetic insecticides/fungicides with natural substitutes, which do not carry negative health effects, the essential oils, extracts and chemical components of Curcuma species have been examined against various plant pathogens and insect pests that harm food crops. The present review discusses the efficacy of essential oils, extracts and few main components derived from a wide range of Curcuma plants against a wide variety of pests and pathogens of food crops. In addition, their mechanism of action against insects and plant pathogens as well as their potential impact on crops (i.e. the allelopathic nature) are discussed. Finally, the commercialization of Curcuma-based pesticides is reviewed and challenges and knowledge gaps are highlighted.

The aim of this study was to determine the allelopathic effects of Azadirachta indica oil and aqueous extracts of Tithonia diversifolia and Thevetia peruviana on the growth and stimulation of metabolites involved in tomato plant resistance. Randomized in blocks within a shaded area, the different treatments prepared at 10% and 15% (v/v and w/v) in water were subsequently applied on tomatoes seeds to monitor the effect on germination, and on tomatoes leaves to monitor the effect on growth and resilience of the plants. The result showed that in stressful conditions all the treatments significantly inhibit (p < 0.05) the germination capacity of the seeds from 21.22% to 92.61%, the germination rate from 39.82% to 92.76% and the germination viability of the seedlings from 64.67% to 100%. However, the negative allelopathic effect of the treatment was significantly reduced (p < 0.05) when used for germination initiation by botanical priming. In addition, while T. diversifolia at 10% promotes a better aerial and root growth in tomato plants, T. peruviana at 15% induces the activation of resistance mechanisms in tomato plants by increasing protein levels to 104.5%, phenol levels to 183.33% and peroxidase enzyme activity to 586.15%. Therefore, allelopathic compound of wild plants would be a good alternative for growth promotion and resistance of tomato crops.

The inhibitory allelopathic activity of Pueraria montana (Kudzu), and activities of two putative allelochemical isoflavones, puerarin and daidzein, were evaluated using the protoplast co-culture method with digital image analysis using lettuce as a recipient (DIA-PP method). Cotyledon protoplasts of Kudzu were isolated using Cellulase R10 and Driselase 20 in 0.6 M mannitol solution. Optimal hormonal condition and density for growth of Kudzu protoplasts were surveyed. Medium for co-culture of Kudzu or isoflavones with lettuce protoplasts was 50 μl liquid MS basal medium containing 1 μM 2,4-dichlorophenoxyacetic acid, 0.1 μM benzyladenine, 3% sucrose, and 0.4 M or 0.6 M mannitol. Protoplast division of lettuce was strongly inhibited by Kudzu at a low density (104/ml). Slightly less inhibition by Kudzu on cell wall formation and yellow pigment accumulation stages of lettuce growth was also observed. Puerarin did not inhibit the growth of lettuce protoplasts at three growth stages but slightly stimulated growth at high concentrations. By contrast, daidzein, aglycon of puerarin, inhibited growth at three stages of lettuce protoplast growth and strongly inhibited cell division at 100 μM. Daidzein might be one cause of the strong inhibitory allelopathic activity of Kudzu. Grade of inhibitory activities was compared with that of other allelopathic plants including an invader plant and their allelochemicals studied using the DIA-PP method.

The study aims to report the ethnobotanical significance of medicinal plants for the treatment of various diseases, phytochemical constituents of those plants, their allelopathic effect, and impact of those plants on the socioeconomic aspect in Gulmi and Okhaldhunga district of Nepal. Altogether 41 species of medicinal plants from two areas were documented, using a semi-structured questionnaire. They have been using those species for the treatment of different ailment ranging from gastrointestinal problems, respiratory tract related problems, cuts and wounds, and dermatological problems. 18 of the potentially valuable medicinal plants were brought for performing secondary metabolites tests in methanol extract. The extracts have shown the presence of alkaloid, carbohydrate, glycosides, flavonoids, tannins, terpenoids, saponins, oil and protein, out of which alkaloid was found to be present in every sample. In contrast, only 5 possessed protein. Out of 18 plant extracts, 11 most valued ones were isolated to carry out allelopathy tests on mungbean seed. Only the control treatment bored germination of the mungbean with full radicle and plumule development. This study also reports the impact of the use of medicinal plants in people‘s daily life.

BackgroundSclerotium rolfsiiis a soil-borne fungal pathogen causing diseases in more than 500 plant species. It causes southern blight disease in chili. Chemical fungicides are used to control this disease, which also pollute the environment. The present study was designed to assess the potential of two species of plant-growth-promoting rhizobacteria (PGPR) viz.Bacillus megateriumandPseudomonas fluorescence, and an allelopathic weed,Anagallis arvensisL., for the control of southern blight disease of chili.ResultsInitially, three PGPR strains, viz.B. megateriumOSR3,B. megateriumZMR6, andP. fluorescencePF-097, were selected for their in vitro antagonistic assessment againstS. rolfsiiby dual culture technique on potato dextrose agar medium. OSR3 showed the highest antagonistic potential (68%), followed by PF-097 (54%) and ZMR6 (33%).In a pot experiment, the two best strains of PGPR, namely OSR3 and PF-097, and dried biomass ofA. arvensis(DBA) in different concentrations (1, 2 and 3%) were used to manage southern blight disease of chili.In positive control treatment (S. rolfsiionly), plant survival was low (73%) than the negative control (100%). OSR3, PF-097, OSR3 + 2% DBA, and PF-097 + 2% DBA significantly enhanced plant survival over positive control. The highest increase in chili growth over positive control was recorded due to OSR3, followed by PF-097 inoculations. Contents of carotenoid and chlorophyll were significantly decreased due to the fungal pathogen and improved due to PGPR strains. Application of the two PGPR strains and different concentrations ofA. arvensisdistinctly increased the catalase (CAT), peroxidase (POX), and polyphenol peroxidase (PPO) activities over positive control.ConclusionsThe present study concluded that PGPR strainsB. megateriumOSR3 andP. fluorescencePF-097 can control southern blight disease effectively and increase growth and yield of chili.

Allelopathy plays crucial role in effective weed control. Opium (Papaver somniferum L.) crop release different allelochemicals at maturity which have potential to act as natural weeds control in different crops. Phytotoxic effect of Papaver somniferum was examined on germination and initial seedling growth of red rice (Oryza punctata L.). Aqueous extract of different plant parts (leaves, stem and flower) were used at various concentrations (0.25%, 0.5%, 1%, 2%, 4% and 8%) along with distilled water as control. The aqueous extracts of leaves, stem and flower of P. somniferum were significantly inhibited the emergence, seedling growth as well as root length (cm), shoot length (cm), fresh weight (g) and dry weight (g) of O. punctata. Maximum mean emergence time (9.18 days) and minimum shoot length (1.13 cm) whereas minimum emergence index (0.89) and emergence percentage (6.67%) was observed under fruit extract at 8% concentration. P. somniferum aqueous extract of stem at 8% concentration take maximum time to complete 50% emergence minimum root length, fresh weight, dry weight of O. punctata. Based on this finding it can be concluded that the phyto-chemicals present in P. somniferum at 8% concentration may cause losses to the related as well as succeeding weeds through allelopathy and must be removed from the field to avoid destructive effects of these weeds.

Vernonia zeylanica (L.) belongs to the family Asteraceae, is one of the major endemic weed species present in coconut (Cocos nucifera L.) plantations of the tropics, which propagates very easily. There is a possibility that this plant could also possess allelopathic effects, but this has not been scientifically tested. Thus, a study was carried out to determine the seed germination of V. zeylanica under soil moisture stress conditions, shoot propagation methods and possible allopathic effects of this species, on selected species in bioassay tests. Germination of V. zeylanica seeds was not observed at higher osmotic potential (-0.9 MPa). The highest sprouting percentage of this species were obtained with soft wood cuttings. The aqueous leaf extract was highly phytotoxic, and it significantly reduced germination and seedling growth of all bioassay species tested. Full strength (33.3 g L-1) aqueous extracts of leaves significantly reduced the germination percentage, root and hypocotyl growth rates of all species tested. The inhibitory effects were often dependent on concentration. However, the degree of inhibition varied among the test plant species. The seedling emergences of all four tested plants were severally inhibited when planted in V. zeylanica contaminated soil. The results indicated that incorporated aqueous leaf extract of V. zeylanica and its rhizosphere contaminated soil can suppress seed germination, seedling growth and seedling emergence of certain plant species indicating a possible allelopathic effect.

Rivina humilis L. (Petiveriaceae) is an invasive plant occurring throughout the tropics and subtropics. As successful plant invasion involves phenotypic plasticity; rapid seed germination and high competitiveness through the release of allelochemicals, the reasons behind the ability of R. humilis to establish and thrive under diverse environmental conditions were explored through series of experiments. The influence of different soil types (Alluvial, Alfisol, Vertisol and Laterite), pH (4–10) and nutrient concentrations (0–100%) on seed germination and seedling development of R. humilis were examined. The effect of aqueous leaf or fruit pulp extracts on seed germination and seedling development of different test plants was determined. The role of root endophytic fungi on plant growth was assessed by growing R. humilis in the presence and absence of fungi. Shade tolerance was investigated by growing R. humilis under different light intensities and measuring the photosynthetic rates. The results of the study indicate that R. humilis was able to grow in different soil types and pH levels. As the fruit pulp fails to affect seed germination or development of test plants (finger millet, green gram, brinjal, maize) increasing concentrations of leaf extract negatively influenced these processes. Seed germination of R. humilis decreased at the highest alkaline pH 10 and increasing light intensity negatively affects the leaf chlorophyll content, photosynthetic rate and plant growth. The stomatal conductivity and transpiration rate of plants are not consistent under varying light intensities. R. humilis is not mycorrhizal dependent. These results suggest that R. humilis possess a wide range of plastic responses to different environmental conditions that could significantly contribute to the success in invading new habitats.