Study of extremophile plant extracts as botanical herbicides

peer reviewedWeeds are defined as harmful plant pests affecting agriculture worldwide. They cause huge economic losses which can rise up to 34% in major crops by lowering yields and competing with crops for nutrients, light, and water. For these reasons, a great interest has been shown on plant extracts as sources of allelochemicals used for weed management. In this context, our study aimed to assess, for the first time, the herbicidal effect of ten extremophile plant extracts in order to develop botanical herbicides. Aerial plant materials were grounded and macerated with methanol for 24H. Methanol was then eliminated using a rotavapor. The yield of plant extracts varied between 5.29% and 29.71% following the species. Cynara cardunculus crude extract exhibited the best activity in terms of visual effect after spraying on weeds. Moreover, a formulation was carried out to improve their efficiency. The results showed that formulated C. cardunculus has completely punctured Trifolium incanatum and has inhibited growth of Phalaris minor and Sylibum marianum. We have observed that C. cardunculus crude extract induced oxidative stress in the treated plants and consequently disturbed the physiological and biochemical functions of the plant cells. A fractionation of C. cardunculus crude extract was then carried out. Five fractions were obtained and tested on T. incanatum. Among these fractions, F2 formulated at 20 g/L showed a very similar effect to a commercial bioherbicide. It caused the total death of T. incanatum 9 days after spraying. Based on bioassay-guided fractionation, five compounds were identified which can be employed in developing new types of bioherbicides for controlling weeds on crops. The strong weed suppressive ability of F2 formulated therefore offers interesting possibilities as an effective natural environment-friendly approach for weed management. Trials are ongoing in order to optimize the acclimatization and the growth of extremophile plants

Etude du potentiel herbicide des extraits végétaux des espèces xero-halophytes Tunisiennes et détermination de leurs modes d’action.

Les adventices constituent une contrainte majeure pour l’agriculture. En effet, connues par leur pouvoir allélopathique important, ces adventices peuvent causer des dommages économiques sévères atteignant 34% dans les grandes cultures. Dans cette optique, suite à la forte limitation des herbicides chimiques sur le marché et plus spécifiquement le retrait progressif du glyphosate, la demande du public pour des herbicides alternatifs d'origine biologique et davantage respectueux de l’environnement, est croissante. Cette thèse s’inscrit dans la politique de minimiser l’utilisation des herbicides chimiques principalement le glyphosate. Les travaux de recherche effectué dans le cadre de cette thèse ont permis de sélectionner 2 extraits végétaux à forte activité herbicide à savoir, l’extrait phénoliques de Cynara cardunculus et l’huile essentielle de Rosmarinus officinalis. Par la suite nous avons procédé à un fractionnement bio-guidé afin de déterminer les composés bioactifs majoritaires. Ainsi, la myricitrine extraite de C. cardunculus a été identifiée pour la première fois comme molécule à potentiel herbicide. Ensuite, nous avons élaboré une nouvelle formulation à base de ces deux extraits végétaux sélectionnés qui pour la première fois améliore en même temps leurs efficacités et leurs stabilités. Finalement, l’étude des modes d’action de l’extrait phénolique de C. cardunculus a été réalisé par l’analyse des paramètres physiologiques et biochimiques de la plante cible traitée par nos deux extraits végétaux et en même temps par l’étude de l’interaction des molécules bioactives avec la membrane lipidique de Arabidopsis thaliana

Essential oil of Tunisian plant: biopesticide applied in agricultural system

The use of plant-derived products in postharvest disease management may be a valid alternative to conventional chemical treatments (Pane et al., 2016). Unfavorable environmental conditions (such as salt and drought) increase production and accumulation of reactive oxygen species (ROS). Consequently, Tunisian plants have developed adaptive responses including the synthesis of specific bioactive molecules used for medical and nutritional purposes (Ksouri et al., 2012). In that context, the main objective of the present study was the identification of essential oils from Tunisian plants against the important plant pathogens, particularly in Europe. The study began with the selection of endemic medicinal plant suspected to present antimicrobial properties. The essential oil was extracted by hydrodistillation using a Clevenger type apparatus (with a yield of 1.2%). The chemical composition of the essential oil obtained by hydro-distillation from the aerial parts was analyzed by GC/MS. Therefore, antifungal activity was evaluated against Fusarium culmorum, Fusarium oxysporum and Penicillium italicum, using ELISA microplates with a blocked randomized design, as described previously (Kouassi et al., 2012). In addition, the essential oil was then tested for their herbicidal activities in pre-emergence and post-emergence assays against three weeds species. The chromatographic analysis showed a complex mixture where twenty compounds were identified accounting for 98.75 % of the total oil. Monoterpenes was represented by 71.73 %. The dominant monoterpenes are α Pinene (7.09%), 1,8-Cineole (54.6%) and Camphor (12.27%). Essential oil reduced significantly spores germination in a dose-dependent manner. Their fungistatic activity reached 100% at 0.6% against Fusarium oxysporum . In the dose response bioassay, the essential oil reduced seed germination rate of Phalaris minor, Sylibum marianum and Trifolium incanatum. Seedling growth was measured by shoot and root lengths at day 7. At 0.5%, essential oil reduced 100% seed germination. Post-emergence bioassays consisted in spraying essential oil at 3 concentrations (0.75, 2 and 3.4 %) at 2 leaves stage of three weeds species. Pelargonic acid was used as commercial positive control at 3.4%. At 0.75% and 2%, the essential oil do not show any sign of injury. However, only at 3.4 %, the spraying of essential oil showed visible injury ranging from wilting (after 1 day) and chlorosis (after 3 day) on Trifolium incanatum and Phalaris minor. After formulation, to enhance the distribution, the coverage and the penetration of the active molecules, the essential oil presented a high herbicidal activity. In conclusion, this work allowed to open new perspectives on the application of Tunisian essential oil as Novel biocontrol strategies against damageable plant pathogens and weeds

Les huiles essentielles : de vraies alternatives à l'utilisation des produits agrochimiques

Afin de réduire l'utilisation des produits agrochimiques, une attention particulière est portée ces dernières années sur les applications des huiles essentielles (HEs) extraites de plantes aromatiques et médicinales dans les secteurs de la protection des plantes et de l’emballage des denrées alimentaires. Dans ce contexte, cet article décrit quatre applications concrètes des HEs en tant qu’herbicide, fongicide ou bactéricide dans le traitement post-récolte de certains fruits, insecticide dans le stockage de denrées en silos et antimicrobien dans le packaging alimentaire. Plusieurs études en laboratoire (voire en conditions pratiques) ont montré une efficacité des HEs contre les micro-organismes contaminant les denrées ou pathogènes des plantes, mais également contre les insectes et les adventices. Cependant, à ce jour, peu de produits sont commercialisés. Afin de stimuler l’accès au marché, les défis techniques, scientifiques et réglementaires rencontrés pour le développement sont soulevés. Il est également nécessaire d’assurer une meilleure collaboration entre la recherche, les jeunes entreprises innovantes et les fabricants d'HEs, tel est le cas de la collaboration étroite entre Gembloux Agro Bio Tech et la jeune spinoff APEO, développant des bioherbicides à base d’huiles essentielles

Herbicidal activity of Tunisian plant extracts against various weeds

In agricultural systems, weeds can dramatically reduce crop yields (by the constant competition for water and nutrients) and interfere with plant functions to suppress their growth causing huge economic losses.Yield losses can reach up to 34% in crops. Plant extracts are known since a long time to have phytotoxicity potentialities and could be used as new natural compounds with bioherbicide activities. The study began with the selection of ten plant species suspected to be phytotoxic due to their wealth of phenolic, terpene and alcaloid compounds, such as flavonoids and phenolic acids coumarins. Then, three weeds were selected from Maghreb and European weeds as models (Phalaris minor, Sylibum marianum and Trifolium incanatum). Aerial plant materials were grounded and macerated with methanol for 24H. Methanol was then eliminated along rotavapor. The yield of plant extract varied between 5.29% and 29.71 % following the species. The essential oil was extracted by hydrodistillation using a Clevenger type apparatus (with a yield of 1.2%). Methanol extracts and the essential oil were then tested for their herbicidal activity in post-emergence assays against the three weeds species.The most active extracts were selected and formulated to increase their efficiency. Post-emergence bioassays consisted in spraying each extract at 3 concentrations (7500, 20000 and 340000 ppm) at 2 leaves stage . Pelargonic acid was used as commercial positive control at 34000 ppm. After 7 days on incubation in greenhouses, results showed that E6, presented poor phytotoxicity against three weeds at 7500 and 20000 ppm. However, E6 caused total wilting and several leaf blight against Phalaris minor and Trifolium incanatum and sever necrosis against Sylibum marianum. At that higher concentration of 34000 ppm. , the extracts E3 and E8 and the essential oil appeared also phytotoxic. The three extracts and the essential oil were selected for the formulation. After formulation to enhance the distribution, the coverage and the penetration of the active molecules at 34000 ppm, E3, E6, E8 and essential oil presented a high herbicidal activity compared with the extracts without formulation. E6 with the formulation has completely punctured Trifolium incanatum and suppressed growth of Phalaris minor and Sylibum marianum. The results of this study reveal that plant extracts, after formulation, are more effective in inhibiting weed growth. The strong weed suppressive ability of formulated E6 therefore offers interesting possibilities as an effective natural environment-friendly approach for weed management.Lutte Biologiqu

Les huiles essentielles comme alternatives aux herbicides synthétiques dans les cultures horticoles

peer reviewedAs the controversy behind synthetic herbicides grow, the search for efficient, sustainable and environmentally-friendly herbicides becomes more and more pressing. This need is all the more present for horticultural crop where the number of herbicides is limited and their efficiency limited. In this context, our study aimed to evaluate the post-emergence phytotoxicity of the formulated EO1 in greenhouse and field trials. The two trials were realised at different dose against the weeds Lolium perenne and Trifolium incarnatum for the greenhouse trials and against several monocotyledonous and dicotyledonous weeds for two consecutive years for field trials. The herbicidal activity of EO1 was first confirmed in controlled conditions were the EO1 sprayed twice at highest concentration 2N showed a phytotoxicity of 100% against dicotyledons and 89% against monocotyledons. The high efficiency against dicotyledons was supported by the field trials where at concentration 2N sprayed twice, the phytotoxicity was comparable to the positive control with 98% and 100% phytotoxicity in 2019 and 2020 respectively. The efficiency against monocotyledons in the field trials was more dependent on the dose and the year. Overall, EO1 can be suggested as a potential environmentally-friendly alternative to synthetic post-emergence herbicides

Extremophile plants as source of biopesticides against European damageable plant pathogens

The use of plant-derived products in postharvest disease management may be a valid alternative to conventional chemical treatments (Pane et al., 2016). Unfavorable environmental conditions (such as salt and drought) increase production and accumulation of reactive oxygen species (ROS). Consequently, extremophile plants have developed adaptive responses including the synthesis of specific bioactive molecules used for medical and nutritional purposes (Ksouri et al., 2012). In that context, the main objective of the present study was the identification of effective plant extracts and essential oils from extremophile plants against the most important plant pathogens in Europe (in term of loss, treatment necessity and/or cost). The study began with the selection of four endemic medicinal species suspected to be antimicrobial due to their wealth of phenolic and terpene compounds, such as flavonoids, phenolic acids, and coumarins (Ksouri et al., 2012). Each of the aerial plant materials was grounded and macerated with solvent (methanol or chloroform) for 24 h. The solvent was then eliminated along rotavapor. The yield of plant extract varied between 1.56 and 6.7%. Kinetics of growth of the 3 pathogens cultivable in liquid medium was determined before testing the impact of plant extracts and essential oils. Methanolic and chloroform plant extracts (EM1, EM2, EC1 and EC2) and essential oils (EO1, EO2) were compared for their antifungal potential. The chemical composition of the essential oils obtained by hydrodistillation from the aerial parts was analyzed by GC/MS. Yield of essential oil varied between 0.7 and 1.2%. Therefore, antifungal activity of plant extracts and essential oils was evaluated using ELISA microplates with a blocked randomized design, as described previously (Parisi et al., 2013). The results obtained showed that EM2 at 7 mg/ml has a very high fungistatic activity against Fusarium culmorum, F. oxysporum and Penicillium italicum. It was characterized with a high amount of polyphenols, flavonoids and condensed tannins. Statistical analysis showed that the efficiency of methanol extracts significantly differed from those of the chloroform extracts. In addition, essential oils significantly reduced spores germination in a dose-dependent manner. Their fungistatic activity reached 100% at 6000 ppm. In conclusion, this work allowed us to open new perspectives on the application of extremophile plant extracts as novel biocontrol strategy against plant pathogens

HERBICIDAL COMPOSITION COMPRISING AT LEAST ONE PHENOLIC ACTIVE COMPOUND

publication date: 2019; filing date: 2019-11-07Herbicidal composition comprising at least one phenolic active compound The present invention relates to a herbicidal composition comprising at least one phenolic active compound being myricitrin. The invention also relates to the use of such a herbicidal composition