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Coffee beans contain compounds with allelopathic activity, such that some beans that do not meet quality standards might rather be used to obtain a natural herbicide which consequently might be employed to control undesired plants and avoid economic losses. Thus, the objectives of this study were: (1) to investigate the allelopathic effect of different concentrations of green (GC) and roasted (RC) coffee extracts on the inhibition of germination and initial growth of Lactuca sativa L. Bidens pilosa L. and Cyperus rotundus L. and (2) determine the induction of changes in the cell cycle of L. sativa L. and (3) quantify some compounds in the GC and RC extracts with possible allelopathic effects. Seeds and tubers were sown on germination paper, moistened with water or different concentrations of extracts, stored in transparent plastic boxes, and maintained in a germination chamber. Caffeine was found at higher concentrations of 79.768 and 15.532 g/L in GC and RC extracts, respectively. In general, RC extract for L. sativa L. and GC for B. pilosa L. diminished germination parameters. For C. rotundus L. GC extract decreased growth regardless of the concentration. An increased frequency of cell cycle alterations was observed in the root cells of L. sativa L. This study is the first to report that the studied extracts possess allelopathic potential, as they are effective in reducing germination and/or initial growth of weed species and L. sativa L. as well as inducing alterations in the cell cycle of L. sativa L. [ABSTRACT FROM AUTHOR]

Goat weed (Ageratum conyzoides L.) possesses several phytochemicals, which can be used environment friendly alternatives to synthetic chemical pesticides and herbicides. The major chemicals can serve as natural herbicides and pesticides to expand the range of the green biosphere. This paper: (i) overviews A. conyzoides L.; (ii) classification of A. conyzoides L.; (iii) botanical characteristics; (iv) invasiveness of A. conyzoides. (v) bioactivity of major compounds identified in Ageratum conyzoides L. and (vi) effects of A. conyzoides on different pathogens as biopesticide. [ABSTRACT FROM AUTHOR]

Large quantities of chemical herbicides are used in agroecosystems every year, which not only imposes a significant financial burden on farmers but also leads to environmental pollution. To address this challenge, the present study aimed to replace Treflan with Fedaleh essential oils (EO). Treflan is a commonly used chemical herbicide for spring-summer crops, and Chenopodium album has been chosen as a prevalent and abundant weed in many agricultural ecosystems. Four types of inhibitors, including Treflan herbicide and essential oils extracted from the leaf, stem, and flower of Fedaleh, were used in this experiment. These inhibitors were tested at five different concentrations: 0, 0.5, 1, 2, and 5 μL/mL. Based on GC-MS results, the key compounds found in Fedaleh EO were α-pinene, α-phellandrene, γ-terpinene, linalool, sabinol, β-myrcene, neric acid, carvacrol, β-phellandrene, thymol, and spathulenol. A dose-dependent increase in hydrogen peroxide, malondialdehyde, electrolyte leakage, and proline content was observed with Fedaleh EO or Treflan. However, a decline in cell viability, germination, radicle length, radicle weight, plumule length, plumule weight, and seedling vigor index was observed in a dose-dependent manner with Fedaleh EO or Treflan. The weight of the radicle and plumule was noticeably decreased by 27 %, 28 %, and 14 %, 19 % respectively when treated with essential oils derived from the stem and flower of the Fedaleh, as compared to Treflan. Interestingly, at concentrations of 5 μL/mL EO, the germination, radicle length, plumule length, and seedling vigor index significantly decreased by 64–72 %, 56-56 %, 41–44 % and 90–93 % % as compared with control, respectively. The essential oils extracted from different parts of Fedaleh showed no significant difference in terms of hydrogen peroxide, electrolyte leakage, cell viability, and proline content, compared to Treflan (P > 0.05). Compared to the control, Treflan did not affect germination (P > 0.05), but the EO of Fedaleh's different parts significantly inhibited germination (P

Reduction of pesticide use to benefit the environment is a topical issue in the EU. There is a call for development and more widespread use of sustainable alternative weed control measures. Pyrolysis liquid (PL), a by‐product of charcoal and biochar production, contains numerous compounds, including organic acids, alcohols, phenols and furans. PL has shown promising results when used against several broad‐leaved weeds but its effect on grassy weeds is largely untested. To provide an alternative to synthetic herbicides, PL should be effective and applicable at field scale. In this research, we initially evaluated the potential of birch (Betula sp.) based PL to control mono‐ and dicotyledonous plants under greenhouse conditions and determined if efficacy is improved by addition of an adjuvant. Second, the efficacy of PL for controlling Elymus repens (L.) Gould was compared with glyphosate and two other synthetic herbicides in a no‐tillage system under field conditions. As expected, dicotyledonous plants were more sensitive to acid‐based herbicides than monocotyledonous plants. In contrast to our expectations, the herbicidal efficacy of PL was lower than an acetic acid‐based herbicide and addition of an adjuvant did not improve efficacy. In conclusion, when used at commercially and practically realistic doses, the efficacy of PL control on monocotyledonous weeds such as E. repens is weak. More product development is needed to improve PL quality and efficacy and to establish practical and cost‐effective application levels for weed control on the field scale. [ABSTRACT FROM AUTHOR]

Copyright of Revista de Ciências Agrárias is the property of Sociedade de Ciencias Agrarias de Portugal and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Weeds are plants that disturb or harm human interests, especially in the process of plant growth. Weeds are one of the main factors that can cause a decrease in agricultural yields. Weeds can also harm farmers or agricultural businesses by reducing the quality of agricultural production. Weed control or weeding can be done by means of preventive, mechanical, biological, technical culture, chemical and synthetic. Weed control with herbicides is the main choice compared to other methods because they are considered more effective in controlling weeds, besides being more cost-effective and time-effective. Weeding is an effort that must be done against it so as not to inhibit plant growth. With this activity, it can increase the community's ability to use palm vinegar as a natural herbicide to help farmers increase their crop yields, reduce the use of incendiary herbicides in weed control so as to increase the community's ability in organic farming.

Introduction: Saffron is obtained from the dried red stigmas of Crocus sativus L., an autumnal herbaceous flowering plant belonging to the Iridaceae family. It is largely cultivated in Iran, India, Afghanistan, Greece, Morocco, Spain and Italy. Due to the increase of crop living stresses and side effects of chemical pesticides, recent investigations have been conducted to study herbicidal and fungicidal potential of medicinal plant such as Saffron. Saffron is one of the plants, whose allelopathic effect on various organs has been reported to affect the seed germination of some weed species. It is well known that saffron leaves and corms produce bioactive compounds. Some of these compounds have a role in the inhibition of plant growth and seed germination in their vicinity. The present research was conducted with the aim of evaluating the allelopathic and antifungal effect of extraction solution of leaves and corms of saffron (Crocus sativus) on wild mustard and Alternaria sp. Materials and Methods: To evaluate the allelopathic and fungicidal effect of saffron leaf and corm extracts on the germination and growth characteristics wild mustard and Alternaria sp., independent factorial experiments were conducted as factorial arrangement based on the completely randomized design with four replications at the Faculty of Agriculture of Birjand University in 2022. Treatments to test the inhibitory effect of the saffron extract on weed seed germination characteristics included two types of saffron organs (leaf and corm) and seven extract concentrations (0, 0.25, 0.5, 1, 1.5, 2, and 4 w/v %). Experimental treatments to investigate the inhibitory effect of saffron extract on the growth of Alternaria sp. fungus included two types of saffron organs (leaf and corm) and seven extract concentrations (0, 1, 0.5, 25. 0, 0.125, 0.625, and 0.0312 w/v %). The measured and calculated traits included germination percentage, germination rate, mean germination time, radicle length and weight, plumule length and weight, seedling weight and seed vigor, and wild mustard allometric coefficient, as well as the growth rate of fungi colonies. Results and Discussion: The results showed that the type of extract has an effect on germination rate, mean germination time, radicle length and weight, shoot length and weight, seedling weight, seedling vigor, and allocation coefficient of wild mustard were significant, and the corm extract had more negative effects compared to the leaf extract. By increasing extract concentration; its effectiveness also increased as by increasing extract concentration to 4 % significant decrease in the length and weight of the radicle, the length and weight of the shoot, the weight and the length plumule of the wild mustard seedling compared to the control. The results of the interaction effect of the type of extract and the concentration of the extract on the growth characteristics of the wild mustard primary seedling showed that the lowest root length, fresh and dry weight of the root, stem length and fresh and dry weight of the stem, the weight of the seedling and the root of the plant related to the concentration of 4 % root extract. 75.2, 68.7, 68.4, 68.7, 75.2, 75.4, 73.5, and 72.3 percent decrease compared to the control, respectively, while the reduction values of root length, fresh weight and root dry weight, stem length and stem wet and dry weight, seedling weight and seedling stem in the case of leaf extract are 48.2, 46.7, 44, 48, 48.8, 46.8, 47.4 and 47 respectively. It was a percentage. The results of the interaction effect of the treatments showed that on the ninth and twelve days, concentrations of 0.125, 0.25, 0.5, and 1% of corm extract and 1% concentration of leaf extract inhibited 100% of Alternaria fungus growth. Conclusion: Finally, the results of these experiments showed that the effect of inhibiting the germination and growth of wild mustard as well as the antifungal effect is greater in saffron corm extract than in leaf extract. Therefore, considering the results of this research and conducting more research in the field of allelopathic and fungicidal effects of saffron organ extracts, we can proceed to produce natural herbicides and fungicides. Conflict of Interest: Authors declared no conflict of interest. [ABSTRACT FROM AUTHOR]

Wood vinegar, a by-product of wood pyrolysis, is mostly discarded. Wood vinegar has a phytotoxic effect and could be potentially used as a naturally derived herbicide for weed control. The objective of this research was to evaluate the efficacy of wood vinegar from the pyrolysis of apple (Malus × domestica Borkh.) tree branch wastes to control weeds. The wood vinegar concentrations required to inhibit 50% motherwort (Leonurus cardiaca L.), redroot pigweed (Amaranthus retroflexus L.), Spanish needles (Bidens pilosa L.), and tall fescue (Festuca arundinacea L.) seed germination measured 0.51%, 0.48%, 0.16%, and 1.1%, respectively. The wood vinegar application rates (spray volume) required to provide 50% control of motherwort and Spanish needles measured 1911 L ha−1 and 653 L ha−1, respectively, while the highest evaluated rate at 4000 L ha−1 controlled 35% tall fescue by 10 days after treatment (DAT). Common purslane (Portulaca oleracea L.) control increased as the wood vinegar application rate increased from 500 L ha−1 to 2000 L ha−1. Wood vinegar was more effective in dark than light conditions for controlling common purslane. By 5 DAT, averaged over application rates, wood vinegar provided 95% and 87% control of common purslane in dark and light conditions, respectively. These findings suggest that wood vinegar obtained from the pyrolysis of apple tree branches could be used for weed management. [ABSTRACT FROM AUTHOR]

Natural herbicide is considered as a sustainable approach for weed management in agriculture. Here, allelopathic activities of Piper betle L. extract (BE) and known allelochemical eugenol (EU) were studied against rice and associated weeds in terms of germination and seedling growth. Five plant species including a rice crop (Oryza sativa L.); a dicot weed, false daisy (Eclipta prostrata (L.) L.); and three monocot weeds, barnyard grass (Echinochloa crus-galli (L.) P. Beauv.), swollen fingergrass (Chloris barbata Sw.), and weedy rice (Oryza sativa f. spontanea Roshev.) were studied. The paper-based results demonstrated that BE and EU had inhibitory effects on seed germination and seedling growth. The IC50 values of BE and EU for seed germination were ranked from swollen fingergrass, to false daisy, barnyard grass, rice, and weedy rice, respectively. The ratio of root to shoot length of the seedlings indicated that the roots were more affected by the treatments than the shoots. In addition, the gel-based results showed the reduction of the rice seedling root system, especially on lateral root length and the numbers upon the treatments. Taken together, BE had an allelopathic activity similar to that of EU. Interestingly, the major paddy weed, barnyard grass, was more sensitive to BE than rice, underlining BE as a natural herbicide in rice agriculture. [ABSTRACT FROM AUTHOR]

The increasing use of synthetic herbicides in agriculture creates severe ecological and environmental threats. Several essential oils (EOs) (Thymol, Carvacrol, Cinnamaldehyde, and Eugenol) were investigated as natural herbicides, and their potential use as a substitute for synthetic and toxic chemicals for preventing roots intrusion in subsurface drip irrigation systems. To overcome their high volatility and to increase their thermal stability during processing, multiphase hybrid blends based on polymer/nanoclays (NCs) were prepared, enabling control of the EOs migration rate from the final active film. Germination experiments on mash bean seeds in open and closed systems have been conducted to evaluate the EOs efficacy as germination inhibitors. The amount of EO remaining in the films, after processing and for varying timepoints, was determined by UV–Vis spectroscopy through extraction. From these two experiment's results, we identified Thymol as the most effective herbicide. The effects of polymers/Thymol affinity and organoclay polarity were investigated to achieve a slow‐release effect. Linear low‐density polyethylene/polyamide 6 system showed better efficiency compared to the linear low‐density polyethylene in retaining Thymol during processing due to the thermodynamic affinity of the polyamide 6 phase with Thymol. NCs have been found to be nuclear foci during the first thermal process to obtain smaller highly surface voids allowing better absorption of the Thymol during the second thermal processing. NC Cloisite 15A showed better dispersion in the polymer matrix and improved chemical affinity between the nanocomposite and the Thymol. As a result, Thymol's desorption was delayed and a controlled release was obtained. Eventually, it was concluded that Thymol could be a natural and environmentally friendly alternative to the synthetic herbicides and use as root‐repellent agent. [ABSTRACT FROM AUTHOR]

Mechanical methods are labor-intensive and time-consuming whereas, using herbicides not only creates hazardous impacts on agricultural products but also enhances environmental pollution. Therefore, allelopathic approaches have been considered to suppress weeds in agricultural systems. Field experiments were conducted during the Fall season of 2011 and were repeated during Fall 2012 at the experimental field of Agricultural Research Institute, Tarnab, Peshawar, Khyber Pakhtunkhwa, Pakistan. The treatments were sprayed as post-emergence and the weedy check was maintained as a control treatment for comparison. Statistical analysis of the data showed that the allelopathic effect of plant water extracts in combination with reduced doses of herbicides had a significant effect on fresh and dry weed biomass (kg ha-1), plant height (cm) and yield attributes. However, the improvement in leaf area plant-1of wheat was found insignificant. Lower fresh weeds biomass (253 kg ha-1) and dry weeds biomass (87.5 kg ha-1) was noted in Parthenium hysterophorus + ½ Buctril super treated plots. Both the fresh and dry biomass was almost 80% lower than the control treatment. During the instant studies, it was observed that taller plants were observed in plots treated with Datura alba + ½ Puma super and Datura alba + ½ Buctril super as compared to untreated plants that produced short stature plants. D. alba + ½ Puma super and D. alba + ½ Buctril super gave a maximum (400 and 396) number of spikes compared to control plots that produced 244 spikes. The treatment combination of allelopathic plant water extract with a reduced dose of herbicides produced 63.46 and 63.20 grain spike-1 in Phragmites australis + ½ Puma super and Phragmites australis + ½ Buctril super, respectively. Biological treatment with highly allelopathic plants like P. australis, P. hysterophorus, D. alba and Oryza sativa seems to be environment friendly, and economical in many cases. In this way, we can manage the weed problem in our fields as well as could be used as a bio-fertilizer because some allelopathic plants have a positive effect on crop vegetative parameters, yields and yield components. [ABSTRACT FROM AUTHOR]

Crop infestation species have acquired resistance to herbicides, stimulating the search for new control methods. Plants secondary metabolites can hold more sustainable alternatives, as they can be used for development of natural herbicides. This study evaluated phytotoxic effects of aqueous extracts of Ilex paraguariensis leaves on Conyza bonariensis , an infesting species of Brazilian crops. Different concentrations of decoction and infusion extracts were tested in germination and growth bioassays. Adult plants were evaluated for leaf anatomy effects caused by the yerba mate extract. HPLC analysis was used to quantify the three major chemical constituents. The most effective aqueous extract (decoction 1.0%) decreased the percentage of seed germination, germination speed index, and percentage of germination-derived seedling formation, and increased the time for seedling formation. Shoot and root growth were not affected by this extract. In adult plants, the same extract damaged epidermis and palisade/lacunous parenchyma six hours after exposure. Caffeine was found as the major compound of this extract, followed by rutin and quercetin. Therefore, aqueous extract by decoction 1.0 % of I. paraguariensis leaves showed potential for control of C. bonariensis infestation and rather promising for the development of a natural herbicide. [ABSTRACT FROM AUTHOR]

The chemical profile and phytotoxic activity of the essential oil extracted from Artemisia sieversiana was investigated. In total 17 compounds were identified by GC/MS, representing 99.17% of the entire oil, among which α-thujone (64.46%) and eucalyptol (10.15%) were the most abundant constituents. The major components, their mixture as well as the essential oil exhibited significant phytotoxic activity against Amaranthus retroflexus, Medicago sativa, Poa annua and Pennisetum alopecuroides, with their IC50 values ranged from 1.55 ∼ 6.21 mg/mL (α-thujone), 1.42 ∼ 17.81 mg/mL (eucalyptol), 0.23 ∼ 1.05 mg/mL (the mixture), and 1.89 ∼ 4.69 mg/mL (the essential oil) on the four tested species. The mixture of the major constituents exerted more potent effect compared with each individual compound, indicating the possible involvement of synergistic effect of these two compounds. [ABSTRACT FROM AUTHOR]

Essential oils are a plentiful source of plant compounds for potential use in the development of natural herbicides. With this in mind, the phytotoxicity of ten major essential oil components of lavender (Lavandula angustifolia Mill.) on the weed species bristly foxtail (Setaria verticillata (L.) P. Beauv.) was determined using a perlite-based Petri-dish bioassay. Their phytotoxicity was also compared with that of well-known phytotoxic essential oil components (carvacrol, thymol, carvone and eugenol) of oregano (Origanum vulgare L.) and clove (Syzygium aromaticum (L.) Merr. & L.M. Perry) essential oils. Potential synergistic or antagonistic effects between carvacrol or eugenol with other components of lavender essential oil were investigated. Regarding the most phytotoxic components, terpinen-4-ol at 80 nL/cm3 completely inhibited the germination and root length of bristly foxtail, displaying similar phytotoxicity to carvone and thymol. Like carvacrol, lavandulol and linalyl acetate caused total (100%) germination and root length reduction of bristly foxtail at 160 nL/cm3, while the same effect was achieved by lavandulyl acetate at 320 nL/cm3. A synergistic effect was also observed when carvacrol or eugenol were combined with ocimene, 3-octanone, α-terpineol or terpinen-4-ol. Focusing on the development of alternative weed control strategies, lavender essential oils containing high concentrations of terpinen-4-ol, lavandulol or linalyl acetate could be useful for the production of natural herbicides. These essential oil components combined with selected oregano or clove essential oil components, increase phytotoxicity and weed control due to the synergistic effect observed when in mixture.

Large quantities of chemical herbicides are used in agroecosystems every year, which not only imposes a significant financial burden on farmers but also leads to environmental pollution. To address this challenge, the present study aimed to replace Treflan with Fedaleh essential oils (EO). Treflan is a commonly used chemical herbicide for spring-summer crops, and Chenopodium album has been chosen as a prevalent and abundant weed in many agricultural ecosystems. Four types of inhibitors, including Treflan herbicide and essential oils extracted from the leaf, stem, and flower of Fedaleh, were used in this experiment. These inhibitors were tested at five different concentrations: 0, 0.5, 1, 2, and 5 μL/mL. Based on GC-MS results, the key compounds found in Fedaleh EO were α-pinene, α-phellandrene, γ-terpinene, linalool, sabinol, β-myrcene, neric acid, carvacrol, β-phellandrene, thymol, and spathulenol. A dose-dependent increase in hydrogen peroxide, malondialdehyde, electrolyte leakage, and proline content was observed with Fedaleh EO or Treflan. However, a decline in cell viability, germination, radicle length, radicle weight, plumule length, plumule weight, and seedling vigor index was observed in a dose-dependent manner with Fedaleh EO or Treflan. The weight of the radicle and plumule was noticeably decreased by 27 %, 28 %, and 14 %, 19 % respectively when treated with essential oils derived from the stem and flower of the Fedaleh, as compared to Treflan. Interestingly, at concentrations of 5 μL/mL EO, the germination, radicle length, plumule length, and seedling vigor index significantly decreased by 64-72 %, 56-56 %, 41-44 % and 90-93 % % as compared with control, respectively. The essential oils extracted from different parts of Fedaleh showed no significant difference in terms of hydrogen peroxide, electrolyte leakage, cell viability, and proline content, compared to Treflan ( P  > 0.05). Compared to the control, Treflan did not affect germination ( P  > 0.05), but the EO of Fedaleh's different parts significantly inhibited germination ( P  < 0.05). The growth inhibitors at a concentration of ≥1 μL/mL significantly reduced the length of the radicle and plumule in Chenopodium album . Overall, Fedaleh EO has significant potential as a growth inhibitor and oxidative stress inducer to prevent weed interference. This makes it a suitable option for the commercial production of a natural herbicide., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

Wood vinegar, a by-product of wood pyrolysis, is mostly discarded. Wood vinegar has a phytotoxic effect and could be potentially used as a naturally derived herbicide for weed control. The objective of this research was to evaluate the efficacy of wood vinegar from the pyrolysis of apple (Malus × domestica Borkh.) tree branch wastes to control weeds. The wood vinegar concentrations required to inhibit 50% motherwort (Leonurus cardiaca L.), redroot pigweed (Amaranthus retroflexus L.), Spanish needles (Bidens pilosa L.), and tall fescue (Festuca arundinacea L.) seed germination measured 0.51%, 0.48%, 0.16%, and 1.1%, respectively. The wood vinegar application rates (spray volume) required to provide 50% control of motherwort and Spanish needles measured 1911 L ha−1 and 653 L ha−1, respectively, while the highest evaluated rate at 4000 L ha−1 controlled 35% tall fescue by 10 days after treatment (DAT). Common purslane (Portulaca oleracea L.) control increased as the wood vinegar application rate increased from 500 L ha−1 to 2000 L ha−1. Wood vinegar was more effective in dark than light conditions for controlling common purslane. By 5 DAT, averaged over application rates, wood vinegar provided 95% and 87% control of common purslane in dark and light conditions, respectively. These findings suggest that wood vinegar obtained from the pyrolysis of apple tree branches could be used for weed management.

Natural herbicide is considered as a sustainable approach for weed management in agriculture. Here, allelopathic activities of Piper betle L. extract (BE) and known allelochemical eugenol (EU) were studied against rice and associated weeds in terms of germination and seedling growth. Five plant species including a rice crop (Oryza sativa L.); a dicot weed, false daisy (Eclipta prostrata (L.) L.); and three monocot weeds, barnyard grass (Echinochloa crus-galli (L.) P. Beauv.), swollen fingergrass (Chloris barbata Sw.), and weedy rice (Oryza sativa f. spontanea Roshev.) were studied. The paper-based results demonstrated that BE and EU had inhibitory effects on seed germination and seedling growth. The IC50 values of BE and EU for seed germination were ranked from swollen fingergrass, to false daisy, barnyard grass, rice, and weedy rice, respectively. The ratio of root to shoot length of the seedlings indicated that the roots were more affected by the treatments than the shoots. In addition, the gel-based results showed the reduction of the rice seedling root system, especially on lateral root length and the numbers upon the treatments. Taken together, BE had an allelopathic activity similar to that of EU. Interestingly, the major paddy weed, barnyard grass, was more sensitive to BE than rice, underlining BE as a natural herbicide in rice agriculture.

Abstract Background Plant extracts could turn out to be natural herbicides to be used in weed control. This study was conducted to study the phytotoxic effects of methanol extracts obtained from Tamarix mannifera, Alhagi maurorum, Echinops spinosissimus, Haloxylon salicornicum, Lactuca virosa, Neurada procumbens, Ochradenus bacctus, and Cyperus conglomerates plants on germination and growth of Phalaris minor, Echinochloa crusgalli, Portulaca oleracea, and Lactuca sativa. Results In laboratory trial, extracts of eight plants at 0, 5, 10, 20, and 40 g/L were evaluated on germination of seeds of four target species. The inhibitory effect of tested extracts varied among the examined seeds, and P. minor was the most sensitive. Extracts of T. mannifera and L. virosa showed the greatest effect on seed germination and seedling growth of studied seeds. Using the extract of T. mannifera at 40 g/L completely inhibited the germination and seedling growth of P. minor and shoot length of P. oleracea as well as root length of E. crusgalli and L. sativa. At this concentration, L. virosa nearly had a complete inhibition effect on germination and seedling growth of P. minor and P. oleracea. In the greenhouse trial, extracts from tested plants at four concentrations (0, 30, 60, and 90 g/L) were used in a phytotoxic bioassay against 6-week-old L. sativa and three target weeds. The growth of 6-week-old weeds tended to be less sensitive to the tested extracts than the weed germination. The significant injury effect was observed only when T. mannifera extract at 60 and 90 g/L was sprayed on P. minor, E. crusgalli, and L. sativa plants. Conclusions Among tested species, T. mannifera and L. virosa could be used for developing new natural herbicide.

BACKGROUND: Berberine is a herbicidal chemical that we isolated from Coptis chinensis. In continuation of our program aimed at discovering and developing natural botanical herbicides, we evaluated the herbicidal activities of 39 berberine analogues and developed a three-dimensional quantitative structure–activity relationship (3D-QSAR) model. RESULTS: Among these 39 analogs, the most active compounds were determined to be worenine chloride and coptisine chloride, with median inhibitory concentration (IC50) values on all eight tested weed species of < 10 mg L−1. As a reference, the IC50 values of berberine on six weed species were < 10 mg L−1. Furthermore, the results of a greenhouse experiment showed that at 10 mg L−1, and 7 days after treatment, the effects of worenine chloride and coptisine chloride on Lemna minor and Ageratum conyzoides were significantly higher than those of glyphosate and sulcotrione. In the 3D-QSAR analysis, the electrostatic field contour map indicated that introducing an electropositive group in the N-7, C-9 and C-10 positions would potentially improve the inhibition rate. A positively charged nitrogen atom at the N-7 position was important for activity. Replacement of -OCH3 by -OH at the C-9 and C-10 positions could decrease the inhibitory activity, while the hydrophobic field contour map revealed that the hydrophobicity of the C-10 position was associated with high activity. Moreover, the hydrogen bond acceptor field contour map suggested that the existence of a hydrogen bond acceptor at the C-3 and C-9 positions might affect the inhibition rate. CONCLUSIONS: 3D-QSAR provided meaningful clues to the structural features of berberine analogues that will assist the design of more potent herbicidal compounds in the future. [ABSTRACT FROM AUTHOR]

This study was conducted as a plot experiment to investigate the phytotoxicity effects of nano-encapsulated savory essential oil (EO) when it is incorporated separately into carbohydrate and protein natural polymers (Arabic gum-gelatin, apple pectin and gelatin) and two cross-linkers including one poly acid and one enzyme (citric acid and transglutaminase enzyme). Each product was tested as a pre-emergence herbicide against amaranth and tomato. The evaluations also involved determining the stability, morphology, encapsulation efficiency and release properties of the prepared formulations. Coating the savory EO with cross-linked biopolymers enhanced its stability and herbicidal activity, compared to the EO nano-emulsion without any polymer or cross-linker. Among the tested formulations, the strongest inhibitory effect against amaranth germination and growth was caused by Arabic gum-gelatin and apple pectin biopolymers at the concentration of 3 ml/L of EO, when cross-linked with citric acid. These two treatments had slight effects on tomato seedlings, however. The suppressive ability of the formulations was almost similar and comparable to the chemical herbicide metribuzin (1.75 g/L). In conclusion, Arabic gum-gelatin and apple pectin cross-linked by citric acid containing savory EO can be considered as potential, green and safe replacements for metribuzin in organic tomato production. Unlabelled Image • Nano-encapsulation of essential oil by cross linked polymer increased its stability. • Principal component analysis was applied to choose the best herbicidal treatment. • Arabic gum/gelatin cross-linked by citric acid had the highest herbicidal activity. • The applied formulations can be considered as green alternatives to metribuzin. [ABSTRACT FROM AUTHOR]

Radicinin is a phytotoxic fungal dihydropyranopyran-4,5-dione under evaluation for the development of a target-specific bioherbicide for invasive buffelgrass (Cenchrus ciliaris) control. It has already demonstrated high toxicity on host plants, low toxicity to native plants and no negative effects on zebrafish embryos. To continue these studies at the whole-plant level there is a need to obtain much larger quantities of radicinin, either by optimizing its large-scale production by fungal fermentation or through its total stereoselective synthesis. A rapid and sensitive HPLC method for quantification of radicinin in complex mixtures has been developed in order to evaluate its production by different Cochliobolus australiensis strains and in different cultural conditions. The analysis proved that radicinin is not produced by all the strains tested and its synthesis is strongly affected by cultural conditions. The HPLC method could be useful in selecting the best fungal source for the production of this promising potential bioherbicide. [ABSTRACT FROM AUTHOR]

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Thymol is a natural phenolic monoterpene widely produced by different species belonging to the Labiateae family. Although the thymol phytotoxicity is well known, the knowledge of its potential toxic mechanism is still limited. In this regard, the model species Arabidopsis thaliana was treated for 16 days by sub-irrigation with 300 μM of thymol. The results confirmed the high phytotoxic potential of this phenolic compound, which caused a reduction in plant growth and development. Thymol induced a water status alteration accompanied by an increase in ABA content and stomatal closure. Furthermore, leaves appeared necrotic in the margins and their temperature rinsed. The increase in H 2 O 2 content suggested an oxidative stress experienced by treated plants. Both metabolomic and proteomic analysis confirmed this hypothesis showing a strong increase in osmoprotectants content, such as galactinol and proline, and a significant up-accumulation of proteins involved in ROS detoxification. Furthermore, the down-accumulation of proteins and pigments involved in the photosynthetic machinery, the increase in light sensitivity and the lower PSII efficiency well indicated a reduction in photosynthetic activity. Overall, we can postulate that thymol-induced phytotoxicity could be related to a combined osmotic and oxidative stress that resulted in reduced plant development. Image 1 • The phytotoxic potential of thymol on Arabidopsis adult plants was assayed. • Thymol induced oxidative stress and stimulated the production of osmoprotectants. • Proteins involved in ROS scavenging activity were induced by thymol. • Photosystem II as well as photosynthesis were significantly altered by thymol. • Thymol is a good candidate as natural bioherbicide. [ABSTRACT FROM AUTHOR]

Pyroligneous acids can be used in herbicides, but the dosage used often more than 1000 kg ha−1. Five treatments including the application of bamboo, wood, straw vinegar, acetic acid and sulphuric acid at high dosages sprayed once every 6 days, for a total of 3 times. We then continuously monitored the changes in soil pH, moisture content and the activities of three soil hydrolase enzymes involving in urease, protease and sucrase. We found that after 1~3 days of spraying with all 5 kinds of acid, the soil pH was not immediately reduced, but from 3 days after application onward it was reduced by a maximum of 1.54~1.75, which showed that the soil had some buffering capacity. Over time, the pH began to return to the water control pH value, which showed that the soil also had good restorative capacity. After the second and third times of spraying, the pH change measured showed no cumulative effect, which demonstrated that the soil had adaptive capacity. We accidentally found that bamboo vinegar could improve the soil pH by a maximum of 0.65~1.02, while the other four acids reduced its pH. Bamboo vinegar was found to contain the 6 compounds while wood and straw vinegar contained none of these compounds. These compounds may be a new potential reagent(s) for improving the pH. Three soil sample processing methods tested for determining pH, including the moist soil test, oven-dry soil test and air-dried soil test, all produced extremely and significantly different pH values. Five acids were unable to significantly improve the water holding capacity of the soil; they had adverse effects on the activity of the urease enzymes while beneficial effects on the protease and sucrase enzymes. Therefore, pyroligneous acid and acetic acid have no effects on soil health as herbicides. [ABSTRACT FROM AUTHOR]

To date, synthetic herbicides are the main tools used for weed control, with consequent damage to both the environment and human health. In this respect, searching for new natural molecules and understanding their mode of action could represent an alternative strategy or support to traditional management methods for sustainable agriculture. Protodioscin is a natural molecule belonging to the class of steroid saponins, mainly produced by monocotyledons. In the present paper, protodioscin’s phytotoxic potential was assessed to identify its target and the potential mode of action in the model plant Arabidopsis thaliana. The results highlighted that the root system was the main target of protodioscin, which caused a high inhibitory effect on the primary root length (ED50 50 μM) with morphological alteration, accompanied by a significant increase in the lateral root number and root hair density. Through a pharmacological and microscopic approach, it was underlined that this saponin modified both auxin distribution and transport, causing an auxin accumulation in the region of root maturation and an alteration of proteins responsible for the auxin efflux (PIN2). In conclusion, the saponin protodioscin can modulate the root system of A. thaliana by interfering with the auxin transport (PAT).

The present study was aimed at investigating the allelopathic effects of a crude extract from Chromolaena odorata (L.) R.M.King and H.Rob. (Siam weed). The effects of 70% crude ethanol extract from the whole plant, leaf, stem, and root on the germination and growth of Echinochloa crus-galli and Amaranthus viridis seedlings were evaluated using Petri-dish tests under laboratory conditions. Crude extracts from the leaf showed the highest inhibitory activity. The leaf extract (OR) was further separated by sequential solvent extraction to provide hexane (HX), ethyl acetate (ET), and butanol (BU) fractions, which were also evaluated using Petri-dish tests. The hexane fraction was significantly the most active; therefore, it was selected for formulation in a concentrated suspension and tested for its herbicidal characteristics. The formulation showed greater early post-emergence than post- and pre-emergence activities, respectively. The physiological mechanism of the formulation was tested against E. crus-galli and showed that chlorophyll a and b and the carotenoid contents of the leaf dramatically decreased when the concentration was increased, suggesting its ability to disrupt the process of photosynthesis. As thiobarbituric acid reactive substances also occurred in the leaf of E. crus-galli, this suggests lipid peroxidation and cell disruption. These results represent the possibility that C. odorata extract contains inhibitory compounds with herbicidal activity and could be used as an early post-emergence herbicide for weed control.

Weeds pose a serious threat to farmers. Using allopathic properties of the plants, especially those of the medicinal plants, has an important role in controlling weeds. This study was conducted to examine the allelopathic potential of Achillea wilhelmsii in germination of Hirshfeldia incana and Hordeum glaucum. A factorial experiment was conducted, adopting a completely randomized design with three replicates in both libratory and pot cultivation. Organ extracts (flower, leaf and root) of Achillea wilhelmsii in four concentrations were used, namely: 1, 2 and 5%. In addition, distilled water was used as a control. The result showed that the greatest percentages of the germination of Hordeum glaucum and Hirshfeldia incana were in the distilled water, which were 100 and 91%, respectively and that their germination reached zero percent under extraction of leaf and flower with a concentration of 5%. The concentration higher than 2% of the extraction of Achillea wilhelmsii significantly decreased germination, length of radicle and aerial part, fresh and dry weight of shoot and root, leaf area index and amount of chlorophyll in Hordeum glaucum and Hirshfeldia incana, in contrast with distilled water. The results showed that leaf and flower extraction of Achillea wilhelmsii had allopathic effects. In addition, it had impacts on germination and growth of the seeds of Hordeum glaucum and Hirshfeldia incana, which could be used in the production of natural herbicides. Highlights: Aqueous extrac of Achillea wilhelmsii significantly decreases germination and growth of Hordeum glaucum and Hirshfeldia incana. Aqueous extrac of Achillea wilhelmsii can be used to produce the natural herbicides.

ABSTRACT: The phytotoxic composition of Achyranthes aspera was identified through HPLC, and its herbicidal potential was investigated against two narrow leaf weeds viz., Phalaris minor Retz. and Avena fatua L.; and four broad leaf weeds viz. Lathyrus aphaca L., Vicia sativa L., Convolvolus arvensis L. and Asphodelus tenuifolius L. through bioassays. Weed seeds were grown in the aqueous extracts of various plant parts (roots, leaf, stem, fruit and whole plant) of A. aspera at 5% (w/v) concentration. The extracts of all plant parts caused significant reductions with differential degree in germination percentage and mean germination time. Phalaris minor, A. fatua, L. aphaca, V. sativa and A. tenuifolius completely failed to germinate whereas C. arvensis showed the lowest GP (20%) in response to 5% fruit extract of A. aspera. Inhibition of seed germination of all weeds was higher with the fruit extract than with the root, stem, leaf and whole plant extracts of A. aspera. Seed germination of all narrow leaf weeds was completely inhibited at the 5% fruit extract of A. aspera. The highest phytotoxic inhibitory effect of A. aspera fruit extract was proved to be due to the presence of gallic acid (88.4 mg kg-1), caffeic acid (519.2 mg g-1) and m-coumaric acid (51.4 mg kg-1) as assessed by their HPLC analyses. The study, therefore, showed that A. aspera exerts an inhibitory effect on germination of weeds and can be further explored as a pre- or post-emergence herbicide to provide natural alternative to chemical herbicides in the future.

Eucalyptus globulus Labill. (Tasmanian blue gum), one of the most widespread wood species, is broadly grown in forestry exploitations for timber production, giving rise to abundant harvest residues devoted to obtaining bioenergy or essential oils. However, considering the need for searching new environmentally friendly strategies for weed control, a question arises: 'would remnants of pruning and logging from eucalyptus plantations be processed and used as a green manure with herbicidal potential in agricultural fields?' After the evident allelopathic nature of E. globulus and the phytotoxic effects observed from our previous in vitro and greenhouse studies, it is time to address the actual ability of eucalyptus residues for weed control under field conditions. In this study, the potential of E. globulus leaves for weed control was approached by field experiments conducted in weed-infested maize fields, during two growing seasons and at two different locations. Significant reductions were observed on the biomass of the dominant problematic weed species Digitaria sanguinalis (L.) Scop. and Chenopodium album L. up to 69.5 and 88.5% relative to control plots, respectively, together with general effectiveness for weed control throughout the experiments. Concomitantly, maize was not negatively affected by eucalyptus green manure. The phytotoxic effects on weeds were more significant at early stages of maize establishment since weed biomass was reduced from ca. 38–80% relative to control plots, thus alleviating weed-crop competition. Additionally, eucalyptus green manure increased pH, CECe, exchangeable cations Ca2+, Mg2+, and K+, and microbial biomass carbon, as symptoms of enhanced soil quality. Our results demonstrate that the incorporation of E. globulus harvest residues into the soil as a green manure can be a feasible and environmentally friendly practice for field weed control in organic maize-based cropping systems. Image 1 • Eucalyptus green manure reduced Chenopodium album and Digitaria sanguinalis biomass. • Maize was not negatively affected. • Weed control lasted for the entire growing seasons. • Soil pH, CECe and microbial biomass carbon were increased. [ABSTRACT FROM AUTHOR]

Abstract In the present study, the essential oil (EO) of Hyptis suaveolens has been explored for the first time for its phytotoxic and cytotoxic activities. The phytotoxic activity was assessed against rice (Oryza sativa) and its major troublesome weed, Echinochloa crus-galli , under laboratory and screenhouse conditions. GC-MS analysis revealed EO to be monoterpenoid (~ 79% monoterpenes) in nature with α -phellandrene (22.8%), α -pinene (10.1%) and limonene (8.5%) as the major chemical constituents. The laboratory bioassay showed a complete growth inhibitory effect of EO (≥ 2 mg mL−1) towards the germination and seedling growth of E. crus-galli. However, the inhibitory effect on rice was much less (~40% inhibition). EO caused visible injury, reduction in chlorophyll content, cell viability and ultimately led to complete wilting of E. crus-galli plants. In addition, EO altered the cell division in the meristematic cells of Allium cepa as depicted by ~63% decrease in mitotic index. EO exposure induced several aberrations at chromosomal (c -mitosis, anaphase bridges, chromosomal breakage, vagrant chromosomes, and sticky chromosomes) and cytological level (cytoplasm destruction, peripheral nuclei, and bi-nucleate cells). The present study concludes that H. suaveolens EO possesses phytotoxic activity due to its mito-depressive activity, and could serve as a natural herbicide under sustainable agricultural practices. Highlights • Essential oil (EO) of H. suaveolens was phytotoxic towards the germination, and seedling growth. • Inhibitory effect was more pronounced on the root growth than on shoot growth. • Post-emergent application of EO caused visible injury, chlorosis and necrotic patches, leading to wilting. • EO altered the cell division and induced several cytological and chromosomal aberrations in root meristems. • EO could be utilized as a natural herbicide. [ABSTRACT FROM AUTHOR]

Pseudomonas fluorescens WH6 produces the non-proteinogenic amino acid 4-formylaminooxyvinylglycine (FVG), a secondary metabolite with antibacterial and pre-emergent herbicidal activities. The gvg operon necessary for FVG production encodes eight required genes: one regulatory (gvgR), two of unknown functional potential (gvgA and C), three with putative biosynthetic function (gvgF, H, and I), and two small ORFs (gvgB and G). To gain insight into the role of GvgA and C in FVG production, we compared the transcriptome of knockout (KO) mutants of gvgR, A, and C to wild type (WT) to test two hypotheses: (1) GvgA and GvgC play a regulatory role in FVG production and (2) non-gvg cluster genes are regulated by GvgA and GvgC. Our analyses show that, collectively, 687 genes, including the gvg operon, are differentially expressed in all KO strains versus WT, representing >10% of the genome. Fifty-one percent of these genes were similarly regulated in all KO strains with GvgC having the greatest number of uniquely regulated genes. Additional transcriptome data suggest cluster regulation through feedback of a cluster product. We also discovered that FVG biosynthesis is regulated by L-glu, L-asp, L-gln, and L-asn and that resources are reallocated in KO strains to increase phenotypes involved in rhizocompetence including motility, biofilm formation, and denitrification. Altogether, differential transcriptome analyses of mutants suggest that regulation of the cluster is multifaceted and the absence of FVG production or its downregulation can dramatically shift the lifestyle of WH6.

The elimination of broadleaf weeds from agricultural fields has become an urgent task in plant and environment protection. Allelopathic control is considered a potential approach because of its exclusive and ecological safety measures. Plant secondary metabolites also called allelochemicals are released from plant leaves, roots, stem, bark, flowers and play significant roles in soil rhizosphere signaling, chemical ecology, and plant defense. The present study was carried out to evaluate the impact of two allelochemicals; ferulic acid (FA) and p-hydroxybenzoic acid (pHBA) on photosynthetic characteristics; Fv/Fm: efficiency of photosystem II photochemistry in the dark-adapted state; ΦPSII: photosynthetic quantum yield; NPQ, non-photochemical quenching; qP, photochemical quenching, and photon energy dissipation (1−qP)/NPQ in Rumex acetosa following 6 days exposure. R. acetosa seedlings were grown in perlite culture, irrigated with Hoagland solution and treated with allelopathic compounds FA and pHBA and were evaluated against the photosynthetic attributes. Both compounds behaved as potent inhibitors of photosynthetic traits such as Fv/Fm, ΦPSII, qP, and NPQ in R. acetosa. Photon energy dissipation (1−qP)/NPQ increased significantly from days 3 to 6. Higher dissipation of absorbed energy indicates the inactivation state of reaction centers and their inability to effectively use the absorbed energy in photosynthesis. These results indicated the potential allelopathic application of FA and pHBA for control of broadleaf weed, Rumex acetosa.

The study was conducted to evaluate the responses of rice and rice weed seedlings (barnyardgrass and weedy rice) at the three-leaf stage to Tinospora tuberculata leaf methanol extract (3.12, 6.25 and 12.5 g L−1) under hydroponic culture. It shows that the leaf methanol extract had various degrees effects depending on target plant species and each tested index (biomass, root length, shoot length, transpiration volume, chlorophyll a, chlorophyll b and carotenoid contents). The effective concentration of the leaf extract capable of reducing 50% of rice growth was higher than those of target weed species. Moreover, the root length was more tolerant to leaf methanol extract in comparison to the other plant parameters measured. A greater reduction was observed in chlorophyll a content compared to chlorophyll b and carotenoid. The results revealed that the reduction of transpiration volume closely coincided with the magnitude of growth inhibition of tested plants. Ultra-fast liquid chromatography analysis revealed 11 of 32 peaks in chemical profile, including benzoic acid, caffeic acid, chlorogenic acid, isoorientin, isovitexin, orientin, p-anisic acid, syringic acid, trans-cinnamic acid, trans-ferulic acid, and vitexin have the same retention time with those peaks of the extract. The amount of compounds was present in the range of between 4 817 and 115.5 mg kg−1 dry weight (DW). The concentration-response bioassay of all 11 individual compounds and their equimolar mixture against the seeds of barnyardgrass revealed their contribution in the allelopahic activity of T. tuberculata leaf extract. The examined compounds and their combination exhibited various degrees of growth inhibitory effects on the early growth of barnyardgrass. Therefore, the specific number, concentration, combination and inhibitory activity of bioactive compounds leads to allelopathy activity of T. tuberculata leaves which could be employable directly as a natural herbicide and its growth inhibitor compounds can be used as a template for producing new herbicides.

The allelopathic plant extracts can be applied as soil or foliar bioherbicides and are capable of suppressing germination and growth of several weeds, some of which are herbicide resistant. This study evaluated the allelopathic activity of the aqueous extract of aerial biomass of mugwort (Artemisia vulgaris L.) on seed germination and seedling growth of redroot pigweed (Amaranthus retroflexus L.) and maize (Zea mays L.), in order to be applied as a potential bioherbicide. The aqueous extract of mugwort was qualitatively examined for the presence of bioactive compounds and it was applied in a Petri dish and pot bioassays quantifying its effects on redroot pigweed and maize by non-linear regression analyses according the log-logistic model. The aqueous extract of mugwort showed the presence of several bioactive compounds with allelopathic activity, such as polysaccharides, organic acids, flavonoids and terpenoids. The aqueous extract of mugwort, at the concentrations from 7.5% to 10% w/v, were found to be the optimal concentration range since it is able to inhibit seed germination, seedling emergence and plant growth of redroot pigweed, without affecting seed germination and seedling emergence of maize, or rather, stimulating its radicle, mesocotyl and plant’s growth. EC90 values for the seed germination, radicle and hypocotyl length of redroot pigweed were in the order: 6.1% and 8.1%, 3.2% and 6.2%, 3.8% and 5.7% w/v of aqueous extract in the two repeated bioassays, respectively. Due to potential herbicidal activity against weeds and biostimulant action on the crops, this extract could be the ideal solution in an integrated weed management program, in order to suppress weeds, increasing competitive ability of crops.

Saffron (Crocus sativus L.) is a highly valuable plant. Iran provides nearly 90% of the world’s total saffron and is the biggest global producer. The allelopathic effects of saffron corm (SC) and saffron field soil (SFS) have been hypothesized to play an important role in replanting. Recently, adsorbent materials have been used to neutralize the effects of allelochemicals. These materials, including activated carbon and zeolite, have large surface areas, pore volumes, as well as tremendous adsorptive capacity and complex chemical and physical properties. In this study, three independent experiments were conducted. In the first test, the allelopathic effects of aqueous and methanolic extracts of SC remnant and 9-year-old SFS as well as filtered aqueous extract of soil were investigated. In the second assay, the effects of SC remnants and SFS with different ages (i.e., 4, 6, and 9 years old) in combination with adsorbents were examined on the germination and growth of lettuce (Lactuca sativa L.) seedlings by the sandwich method. In the third experiment, we examined the effects of SC remnants combined with adsorbents on lettuce growth parameters. Our results showed that the allelopathic effects of aqueous and methanolic extracts of SC remnant were significantly superior to those of 9-year-old SFS. The aqueous extract of SC remnant reduced the root length of lettuce by 50%. The use of activated carbon and zeolites significantly decreased the observed allelopathic effect. Moreover, lettuce growth in rhizosphere soil was significantly inhibited by SC remnant and SFS extracts. The allelopathic effects of SC remnants caused a growth imbalance between the shoot and roots. Based on biochemical analyses, using the adsorbents increased the carotenoid content and chlorophyll index of lettuce by 23.33% and 5.25%, respectively. Adsorbents may play a role in treating soils contaminated by allelochemicals.

This study aimed to compare the herbicidal activity of solid formulas obtained by spray drying with conventional liquid formulas containing biomolecules produced by submerged cultivation of the fungus Diaporthe sp. in a stirred-tank bioreactor. The solid formula presented the highest phytotoxicity on plant control (96.7%) and the phytotoxicity was directly related to the concentration of fermented broth in the formula. The use of adjuvant improved the efficiency of the bioherbicide. Dry matters of treatments were lower than the control and this was correlated with an increase in oxidative stress, since the activity of the antioxidant enzymes such as superoxide dismutase and guaiacol peroxidase increased in the treatment with a high level of phytotoxicity. Spray drying technology is a promising tool to concentrate bioherbicide without the loss of bioactive compounds since one of the major challenges in the production of bioherbicides is the low concentration of active ingredients in the fermented broth.

ABSTRACT: Metabolites of Aspergillus niger, prepared in malt extract (ME) broth and potato dextrose (PD) broth, were evaluated for their herbicidal activity against a noxious parthenium weed (Parthenium hysterophorus). In laboratory assays, original (X) and diluted (½ X) fungal metabolites significantly reduced germination and seedling growth of weed. However, metabolites prepared in ME broth proved to have greater herbicidal activity than metabolites prepared in other growth medium. Original metabolites prepared in ME broth have completely hinder the germination of parthenium seeds; while those prepared in PD broth have reduced germination by 89% over control. In pot trials, one-week, two-week and three-week-old parthenium seedlings were sprayed three times with original and concentrated (2X) metabolites of A. niger prepared in ME broth. Plants were harvested after 40 days of sowing. One-week treatment plants were most susceptible to fungal metabolites spray, followed by two-week and three-week treatment plants, respectively. Original and concentrated metabolites have significantly reduced shoot biomass of one-week-old plants by 57% and 68%, and root biomass by 50% and 75%, respectively. The present study has come to the conclusion that A. niger metabolites prepared in ME broth can effectively control germination and growth of parthenium.

Aqueous extract of celery (2.5-20 g l-1, w/v) was evaluated for its phytotoxicity against three weed species, under laboratory and greenhouse conditions. Celery extract had a strong inhibitory effect on germination and seedling growth of Corchorus olitorius, Echinochloa crusgalli and Portulaca oleracea seeds. From dose response curves of tested seeds, LC50 were calculated to be in the range from 6.3 to 8.3 g l-1 for germination percent, from 7.2 to 8.0 g l-1 for shoot length and from 1.7 to 3.6 g l-1 for root length. Completely inhibition of root growth was exhibited C. olitorius and P. oleracea at 7.5 g l-1 corresponded with 15 g l-1 for E. crusgalli seed. Total phenolics in celery extract at 20 g l-1 constituted 201 mg l-1. Ten phenolic acids were identified in extract by HPLC, among of them p-coumaric acid and p-hydroxybenzoic acid were presented in high amounts. Aqueous extract was partitioning between three solvents, hexane, methylene chloride, ethyl acetate. Generally, water residue after partitioning aqueous extract with the three solvents had the most phytotoxic effect on seedling growth of target seeds. In greenhouse trial, foliar spray of aqueous extract of celery (30, 60 and 90 g l-1) and its fractions did not produce any significant effect on growth of two-weeks-old C. olitorius, or E. crusgalli or P. oleracea weeds.

Aqueous extract of celery (2.5-20 g l-1, w/v) was evaluated for its phytotoxicity against three weed species, under laboratory and greenhouse conditions. Celery extract had a strong inhibitory effect on germination and seedling growth of Corchorus olitorius, Echinochloa crusgalli and Portulaca oleracea seeds. From dose response curves of tested seeds, LC50 were calculated to be in the range from 6.3 to 8.3 g l-1 for germination percent, from 7.2 to 8.0 g l-1 for shoot length and from 1.7 to 3.6 g l-1 for root length. Completely inhibition of root growth was exhibited C. olitorius and P. oleracea at 7.5 g l-1 corresponded with 15 g l-1 for E. crusgalli seed. Total phenolics in celery extract at 20 g l-1 constituted 201 mg l-1. Ten phenolic acids were identified in extract by HPLC, among of them p-coumaric acid and p-hydroxybenzoic acid were presented in high amounts. Aqueous extract was partitioning between three solvents, hexane, methylene chloride, ethyl acetate. Generally, water residue after partitioning aqueous extract with the three solvents had the most phytotoxic effect on seedling growth of target seeds. In greenhouse trial, foliar spray of aqueous extract of celery (30, 60 and 90 g l-1) and its fractions did not produce any significant effect on growth of two-weeks-old C. olitorius, or E. crusgalli or P. oleracea weeds. [ABSTRACT FROM AUTHOR]

ABSTRACT In agriculture, weeds have inevitable importance because of reducing the crop growth and also affecting food quality. Although, synthetic herbicides are available to combat these weeds but during recent years there is a trend of using ecofriendly herbicides extracted from natural resources. Present investigation is a continuity of the research, which reported a natural herbicidal compound named as Ophiobolin A from a fungus, Drechslera rostrata. The fungus was incubated in a growth medium of known composition (minimal medium) up to 28 days and its metabolites were extracted with organic solvents. The compound showing bioactivity was purified with the help of Reversed Phase High Performance Liquid Chromatography (RPHPLC) and identified with the help of Spectroscopic techniques viz. Mass Spectroscopy (MS) (LRESIMS and HRESIMS) and Nuclear Magnetic Resonance Spectroscopy (NMR). The purified compound caused death of superficial leaf cells of Chenopodium album, a noxious weed of wheat. Present investigation concludes that the identified compound could be used as structural analogue alternative to synthetic herbicides to synthesize natural herbicides.

The essential oils are fast emerging as the source of natural herbicides owing to their environmentally benign properties. The focus of the present study, thus, was to investigate the phytotoxicity and cytotoxicity of Citrus aurantiifolia oil, and its major constituents-citral and limonene. C. aurantiifolia oil was selected due to its extreme commercialisation and safe nature. GC–MS analysis revealed that C. aurantiifolia oil is rich in monoterpenes (83.93%), with limonene (40.92%) and citral (27.46%) as the major compounds. Phytotoxicity was assessed against three agricultural weeds, Avena fatua, Echinochloa crus-galli and Phalaris minor , at concentration ranging from 0.10–1.50 mg/ml. Percent germination, IC 50 value and seedling growth (root and coleoptile length) were significantly reduced in a dose-response manner. C. aurantiifolia oil, citral and limonene caused alteration in the cell cycle of Allium cepa root meristematic cells as evidenced by decrease in mitotic index (MI) and increase in chromosomal aberrations at progressive concentrations (0.01–0.10 mg/ml) and time periods (3 h and 24 h). Cytotoxic evaluation confirmed mitodepressive effect of the tested volatiles though the intensity was variable. Overall, citral was the most toxic followed by C. aurantiifolia oil and limonene. The significant phytotoxic activity of C. aurantiifolia oil and citral suggests the possibility of being developed into eco-friendly and acceptable products for weed management in agriculture system. [ABSTRACT FROM AUTHOR]

Weeds constitute the largest biotic threat affecting the yield of cultivated plants. While conventional agriculture relies principally on chemicals for weed control, alternative biological methods may be important tools to reduce weed pressure in agroecosystems. Furthermore, as the problem of excessive residue of plant protection agents in agroecosystems and the growing number of herbicide resistant weed biotypes continue to increase, new solutions that have smaller impacts on the environment are becoming increasingly desirable. One promising such method is the use of crops that exert a negative phytotoxic influence on weeds. This natural phenomenon describing the ability of certain plant species to produce compounds that affect the growth of other plants in their surroundings is called allelopathy. Managing weed infestations in cultivated fields by planting allelopathic crops is a sustainable, economic, and environmentally friendly approach that has been strongly articulated in the international arena. Among cultivated crops, sorghum (Sorghum bicolor (L.) Moench) has been intensively studied because of demonstrated allelopathic potential. This report provides a comprehensive literature review of the applications of sorghum allelopathy in agriculture. A critical analysis of the allelopathic properties of sorghum identified the following areas contributing to its ability to reduce weed infestation in agroecosystems: 1. a large number of compounds produced by sorghum have allelopathic properties, 2. allelopathic compounds can be applied in the form of mixed plant extracts or in combination with herbicides, 3. sorghum extracts have a broad spectrum of activity, 4. sorghum may be used to produce bioherbicides. [ABSTRACT FROM AUTHOR]

The aim of the present study was to obtain an oil/water (O/W) nanoemulsion (NE) containing garden savory ( Satureja hortensis ) essential oil (EO) and evaluating its herbicidal activity against Amaranthus retroflexus and Chenopodium album . Gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) were employed to determine the chemical composition of the EO. Carvacrol (55.6%) and γ-terpinene (31.9%) were the major EO components. Low energy method was applied, allowing achievement of EO nanodroplets. The NE also presented low polydispersity, and the mean droplet was below 130 nm even after storage for 30 d. Laboratory tests showed that the NE at different concentrations (100, 200, 400, 800, and 1000 μ L . L − 1 ) significantly (P≤0.05) reduced the germination indices and the seedling's growth in dose-response. The inhibitory effect was the greatest at 800 μ L . L − 1 NE. Overall, root length was more inhibited as compared to shoot length. Post-emergence application of NE at different concentrations (1000, 2000, 3000, 4000 and 5000 μ L . L − 1 of EO) on 2–4 true leaves' stage of the weeds caused significant (P≤0.05) decrease in the growth factors in dose-dependent manner. Complete lethality was observed by 4000 μ L . L − 1 NE sprayed on the weeds. Spraying of NE significantly (P≤0.05) reduced chlorophyll content in the tested weeds. Increasing in relative electrolyte leakage (REL) 1 and 5 d after treatment represented significant cell membrane disruption and increased cell membrane permeability. Transmission electron microscope (TEM) pictures confirmed NE droplet size and demonstrated membrane destruction. The study approved that the NE of S. hortensis EO has herbicidal properties as it has high phytotoxic effect, and interferes with the germination, growth and physiological processes of the weeds. The production of NE from S. hortensis EO is a low energy method that offers a promising practical natural herbicide for weed control in organic agricultural systems. [ABSTRACT FROM AUTHOR]

Ferulic (FA) and p-hydroxybenzoic acid (pHBA) are commonly found as phenolic compounds (PHC) in many forage and cereal crops. Although the effects of these PHC on seedling growth are relatively explored, not many information is available regarding the phytotoxicity on ecophysiological processes of perennial ryegrass adult plants. The experiment was conducted with the aim to evaluate the phytotoxic potential of PHC on the seedling growth, leaf water relation, chlorophyll fluorescence attributes and carbon isotope discrimination adult plants of perennial ryegrass ( Lolium perenne L.). The results clearly indicated that PHC behaved as potent inhibitors of chlorophyll fluorescence yield (F/F) in leaves of L. perenne and plants showed poor tolerance against allelochemicals stress. Quantum yield (ΦPSII), chlorophyll fluorescence quenching (qP) and non-photochemical quenching (NPQ) were decreased following exposure to FA and pHBA. The portion of absorbed photon energy that was thermally dissipated ( D) in L. perenne was decreased. Exposure of the L. perenne seedlings to FA and pHBA stress led to a decrease in fresh/dry weight, relative water content and leaf osmotic potential. Carbon isotope composition ratio (δC) was significantly less negative than the control following treatment with FA or pHBA. The results suggested that PHC uptake was a key step for the effectiveness of these secondary metabolites and their phytotoxicity on L. perenne adult plants was mainly due to the alteration of leaf water status accompanied by photosystem II damage. Acquisition of such knowledge may ultimately provide a better understanding about the mode of action of the tested compounds. [ABSTRACT FROM AUTHOR]

trans-Caryophyllene (TC) is a sesquiterpene commonly found as volatile component in many different aromatic plants. Although the phytotoxic effects of trans-caryophyllene on seedling growth are relatively explored, not many information is available regarding the phytotoxicity of this sesquiterpenes on weed germination and on adult plants. The phytotoxic potential of TC was assayed in vitro on weed germination and seedling growth to validate its phytotoxic potential on weed species. Moreover, it was assayed on the metabolism of Arabidopsis thaliana adult plants, through two different application ways, spraying and watering, in order to establish the primary affected organ and to deal with the unknown mobility of the compound. The results clearly indicated that TC inhibited both seed germination and root growth, as demonstrated by comparison of the ED50 values. Moreover, although trans-caryophyllene-sprayed adult Arabidopsis plants did not show any effect, trans-caryophyllene-watered plants became strongly affected. The results suggested that root uptake was a key step for the effectiveness of this natural compound and its phytotoxicity on adult plants was mainly due to the alteration of plant water status accompanied by oxidative damage. [ABSTRACT FROM AUTHOR]

The aim of this study was to identify bioactive compounds from leaves of the invasive plant Xanthium spinosum and assess their phytotoxic activity. Activity-guided fractionation led to the isolation of 6 bioactive compounds: xanthatin (1), 1α,5α-epoxyxanthatin (2), 4-epiisoxanthanol (3), 4-epixanthanol (4), loliolide (5) and dehydrovomifoliol (6). Of them, compounds 2⁻6 were isolated from the X. spinosum for the first time. The structures of 1⁻6 were elucidated on the basis of extensive NMR studies and ESI-MS measurements as well as comparison with literature data. All of compounds were evaluated for their phytotoxic activity. Among them, compounds 1⁻4 exhibited stronger activity on 2 receiver plants compared with the other 2 compounds, with xanthatin (1) being the most potent compound, which suppressed root growth of the dicot plant Amaranthus retroflexus by 32.5%, 39.4%, 84.7% when treated xanthatin (1) at 5, 20, and 100 µg/mL, while for the monocot plant, root growth was inhibited by 14.7%, 28.0%, and 40.0%, respectively. Seedling growth was nearly completely inhibited when the concentration of xanthanolides increased to 500 µg/mL, whereas there was still some seedling growth when loliolide (5) and dehydrovomifoliol (6) were applied at the same concentration. Dehydrovomifoliol (6) did not negatively affect seedling growth of P. annua at all tested concentrations, and root length was still 42.0% of the control when the highest concentration 500 µg/mL was used. This is the first report of the phytotoxicity of 1α,5α-epoxyxanthatin (2), 4-epiisxanthanol (3) and 4-epixanthanol (4). These compounds have the potential to be utilized as natural herbicides, especially 4-epiisoxanthanol (3), which exhibited significant selective activity between the dicot and monocot plants. On the other hand, whether these bioactive substances serve as allelochemicals to facilitate the invasion success of X. spinosum needs to be further studied.