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Barley straw has been used around the world for decades as a simple, cost-effective and harmless phytoplankton growth inhibition method. Although the effect of this method on algal blooms is quite well depicted, it has not yet been tested what effect it has on submerged vascular plants and if it could be used to control the spread of alien macrophytes. In this study two highly invasive plant species: Cabomba caroliniana and Elodea nuttallii were exposed to different concentration of the barley straw extract (BSE) in laboratory conditions for a duration of four weeks. In the course of the investigations, responses of 8 traits associated with growth, biomass and chlorophyll concentration of specimens to three dosages (Low, Medium, High) of BSE corresponding to concentrations: 0.03, 0.30 and 1.50 ml l−1 were analysed. The result showed that although dry mass and total length of the plants did not differ significantly between the test groups, increase in tillering and internodes number was observed for certain concentrations of the extract. This shows that if BSE has any effect on submerged macrophytes it is a positive one and thus the method is not suitable for invasive submerged aquatic plant control. Furthermore, it is recommended that before using barley straw for algae bloom control one should make sure that there are no alien aquatic submerged plants in the area that could benefit from such a treatment. [ABSTRACT FROM AUTHOR]

This review aimed to show that bioherbicides are possible in organic agriculture as natural compounds from fungi and metabolites produced by them. It is discussed that new formulations must be developed to improve field stability and enable the commercialization of microbial herbicides. Due to these bottlenecks, it is crucial to advance the bioprocesses behind the formulation and fermentation of bio-based herbicides, scaling up, strategies for field application, and the potential of bioherbicides in the global market. In this sense, it proposed insights for modern agriculture based on sustainable development and circular economy, precisely the formulation, scale-up, and field application of microbial bioherbicides. [ABSTRACT FROM AUTHOR]

The sustainable management of the environment and crop production in modern agriculture involves dealing with challenges from climate change, environmental pollution, depletion of natural resources, as well as pressure to cope with dependence on agricultural inputs. Balancing crop productivity with environmental sustainability is one of the main challenges for agriculture worldwide. The emergence of weeds resistant to synthetic herbicides generates huge economic losses, so unconventional weed control strategies, especially those based on ecological principles, are very much needed in modern agriculture. Incorporating a natural eco-friendly approach—allelopathy—as a tool in an integrated weed control plan by growing specific crops or spraying fields with extracts containing allelopathic compounds can significantly reduce the use of herbicides. Allelopathy is considered a multi-dimensional phenomenon occurring constantly in natural and anthropogenic ecosystems, by which one organism produces biochemicals that influence the growth, survival, development, and reproduction of other organisms. The objective of this systematic literature review is to present a comprehensive overview of allelopathy, define this phenomenon, and classify allelochemicals. This paper also discusses and highlights recent advances, ongoing research, and prospects on plant allelopathy management practices applied in agriculture, and the underlying allelopathic mechanisms. The review suggested the holistic view of some allelochemicals as an ecological approach to integrated weed control and is an important contribution to future research directions of multidisciplinary programs, chemoinformatic tools, and novel biotechnology methods to plant breeding. [ABSTRACT FROM AUTHOR]

Weeds represent one of the most challenging biotic factors for the agricultural sector, responsible for causing significant losses in important agricultural crops. Traditional herbicides have managed to keep weeds at bay, but overuse has resulted in negative environmental and toxicological impacts, including the increase of herbicide-resistant species. Within this context, the use of biologically derived (bio-)herbicides represents a promising solution because they are able to provide the desired phytotoxic effects while causing less toxic environmental damage. In recent years, bioactive secondary metabolites, in particular those bio-synthesized by endophytic fungi, have been shown to be promising sources of novel compounds that can be exploited in agriculture, including their use in weed control. Endophytic fungi have the ability to produce volatile and nonvolatile compounds with broad phytotoxic activity. In addition, as a result of the beneficial relationships they establish with their host plants, they are part of the colonization mechanism and can provide protection for their hosts. As such, endophytic fungi can be exploited as bioherbicides and as research tools. In this review, we cover 100 nonvolatile secondary metabolites with phytotoxic activity and more than 20 volatile organic compounds in a mixture, produced by 28 isolates of endophytic fungi from 21 host plant families, collected in 8 countries. This information can form the basis for the application of endophytic fungal compounds in weed control. Key points: • Endophytic fungi produce a wide variety of secondary metabolites with unique and complex structures. • Fungal endophytes produce volatile and nonvolatile compounds with promising phytotoxic activity. • Endophytic fungi are a promising source of useful bioherbicides. [ABSTRACT FROM AUTHOR]

This study was designed to evaluate the inhibitory potential of plant extract and essential oils (EOs) extracted from Artemisia abyssinica, Cinnamomum verum, Cymbopogon citratus, C. martinii, C. winterianus, Curcuma longa, Cupressus lusitanica, Eucalyptus citriodora, E. globules, Lantana camara, Rosmarinus officinalis, and Thymus schimperi against some of the most troublesome weed species in the coffee field via a series of lath-house and field conditions using various application frequencies at the rate of 5% (v/v) arranged in RCBD with three replications. Our result showed that EOs significantly reduced the shoot height (58 to 100%) and root length (52 to 100%) as well as total biomass of G. parviflora seedlings compared to untreated control. The inhibitory effects were measured to be varied among EOs of the tested plants followed application frequencies dependent manner. The potential herbicidal properties of EOs from selected plants based on their efficacy in the lath-house experiments were further tested against weeds of coffee under the field. Except for EO from E. citriodora, all the tested materials showed strong inhibitory effects (ranging from 23.22 to 46.27%) on all weed species compared to untreated control. In conclusion, the application of EOs from Cymbopogon species had the potential to retard the growth of weeds in coffee and may be used as a component of integrated weed management options. However, further study needs to be done to investigate the mechanism of inhibition and the exact active ingredient responsible for the inhibitory effects. [ABSTRACT FROM AUTHOR]

The sorption of the allelochemical scopoletin (7-hydroxy-6-methoxycoumarin) was studied in eight agricultural soils and different model sorbents. We also determined its degradation in selected soils and related sorption and degradation results to the expression of scopoletin phytotoxicity in soil towards two model plant species, Eruca vesicaria and Hordeum vulgaris. Scopoletin was sorbed to a greater extent in acid soils than in alkaline soils. Correlations with soil properties indicated that the soil pH and fine (silt/clay) fraction played a primary role in the sorption of scopoletin by soils. Weak interactions controlled its sorption in acid soils, whereas stronger interactions, probably with mineral clay constituents, became more relevant in alkaline clay soils. Dissipation of scopoletin in the soils was microbial-mediated and occurred more slowly in acid than alkaline soils. As a result, the phytotoxic activity of scopoletin was expressed in acid but not in alkaline soil. The results point to the influence that soil properties are expected to exert on the expression of the phytotoxicity of scopoletin in natural and agricultural ecosystems. [ABSTRACT FROM AUTHOR]

In this study, the active metabolites from both the wild strain of Lasiodiplodia pseudotheobromae C1136 and three genetically enhanced strains of C1136 were obtained through random mutagenesis. The effect of the active metabolites from these strains was evaluated in relation to physiological, biochemical, and ultrastructural changes on the leaves of two weeds (Amaranthus hybridus and Echinochloa crus-galli). The phytotoxic metabolites secreted by the genetically enhanced strains showed a decrease in the pigments (chl a, chl b, and carotenoids), carbohydrate content, and the amino acid profile. On the other hand, an increase in total phenols of the tested leaves was observed when compared with the untreated leaves. The scanning electron microscopy showed the presence of damages, necrosis, degradation, and ultrastructural changes on the tested leaf tissues of the weeds. Also, increased lipid peroxidation and electrolyte leakage were also observed on the tested weeds treated with phytotoxic metabolites secreted by the genetically enhanced strains. We also showed that the phytotoxins from the strains of C1136 are biocompatible and that it improved soil CO2 evolution, organic carbon content, and enzymatic activity (acidic and alkaline phosphatase, dehydrogenases, cellulase, catalase). The study validates the severe pathological effects of phytotoxic metabolites from the strains of C1136 on the leaves of the weeds presented in this study. The mode of action of the phytotoxic metabolites produced from this bioherbicidal isolates will go a long way in preventing environmental hazards. [ABSTRACT FROM AUTHOR]

Common wheat (Triticum aestivum L.) is one of the most important agricultural crop, which provides direct source of food for humans. Besides abiotic stresses, weeds pose a significant challenge to successful crop production. Avena fatua (wild oat) is one of the most common damaging grass weed, which causes 17–62% losses in yield of winter wheat. Excessive use of herbicides to control wild oat has resulted in serious environmental and human health hazards. Therefore, biological control of weeds is required to cope up with the increasing food demand and to attain self-sustainability. In this study, eighty eight rhizobacterial isolates were isolated from rhizosphere soil samples collected from Rewari and Hisar districts. After screening of the isolates, only thirty isolates showed in vitro antagonistic and herbicidal activities. The selected antagonistic isolates were further tested for production of IAA and ALA, and utilization of ACC. Bacterial isolates BWA18 and RWA52 produced 53.80 and 19.18 ug ml−1 IAA, respectively and high ALA production was shown by isolates HCA3 and RCA3. Five isolates i.e., BWA20, BWA23, BWA29, BWA38 and RCA3 showed significant ACC utilization. Inoculation of selected bacterial isolates BWA18, RWA69 and SYB101 showed significant increase in root dry weight (RDW) and shoot dry weight (SDW) of wheat plants under pot house conditions, and decreased RDW and SDW of A. fatua weed as compared to RDF-amended uninoculated soil at 25 DAS (days after sowing). Bacterial isolates RWA69 and SYB101 caused significant increase in RDW and SDW of wheat growth at 50 DAS, whereas their inoculation decreased RDW and SDW of A. fatua. Thus, seed bacterization with bacterial isolates RWA52, RWA69 and SYB101 caused significant increase in RDW and SDW of wheat, whereas their inoculation caused significant decrease in RDW and SDW of A. fatua. The best performing bacterial isolates RWA52 and RWA69 were identified as Bacillus siamensis and Bacillus endophyticus using 16S rRNA analysis. The promising rhizobacterial isolates could further be tested for the bioherbicidal activity and plant growth promotion effects under field conditions before their use as bioherbicides. [ABSTRACT FROM AUTHOR]

Bioherbicides appear as an ecofriendly alternative to synthetic herbicides, generally used for weed management, because they are supposed to have low side on human health and ecosystems. In this context, our work aims to study abiotic (i.e., photolysis) and biotic (i.e,. biodegradation) processes involved in the fate of leptospermone, a natural β-triketone herbicide, by combining chemical and microbiological approaches. Under controlled conditions, the photolysis of leptospermone was sensitive to pH. Leptospermone has a half-life of 72 h under simulated solar light irradiations. Several transformation products, including hydroxy-leptospermone, were identified. For the first time, a bacterial strain able to degrade leptospermone was isolated from an arable soil. Based on its 16S ribosomal RNA (rRNA) gene sequence, it was affiliated to the Methylophilus group and was accordingly named as Methylophilus sp. LS1. Interestingly, we report that the abundance of OTUs, similar to the 16S rRNA gene sequence of Methylophilus sp. LS1, was strongly increased in soil treated with leptospermone. The leptospermone was completely dissipated by this bacteria, with a half-life time of 6 days, allowing concomitantly its growth. Hydroxy-leptospermone was identified in the bacterial culture as a major transformation product, allowing us to propose a pathway of transformation of leptospermone including both abiotic and biotic processes. [ABSTRACT FROM AUTHOR]

A recent greenhouse study revealed a significant reduction of germination and growth of redroot pigweed ( Amaranthus retroflexus) and common purslane ( Portulaca oleracea) by rye mulch, whereas velvetleaf ( Abutilon theophrasti) and common lambsquarters ( Chenopodium album) were not suppressed. Since BOA detoxification by metabolic alteration may influence the relation between the benzoxazinoid content of the soil mulch and weed suppression, we tested the dynamics in BOA detoxification in different plant organs of three and 10-day-old seedlings of four warm season weeds incubated with five BOA concentrations (4, 20, 40, 80, and 200 μmol g fresh weight). In addition, germination and length of 3-day-old seedlings were measured after exposure to 0, 0.3, 1.5, 3, 6, and 15 μmol BOA. Finally, we tested the influence of the MDR translocator inhibitors verapamil, nifedipine, and the GST inhibitor ethycrynic acid on BOA accumulation and detoxification activity. Due to BOA-detoxification, all weeds were able to grow in environments with low BOA contents. At higher contents, Abutilon theophrasti and Chenopodium album had a better chance to survive because of highly active mechanisms that avoided the uptake of BOA ( A. theophrasti) and of efficient detoxification activities in youngest seedlings ( C. album). The interpretation of all of the data gave the following sequence of increasing sensitivity: A. theophrasti <<< C. album << P. oleracea ≤ A. retroflexus. The results were in agreement with recent findings of the suppression of these weeds by rye mulches and their benzoxazinoid contents. Our studies demonstrate for the first time that the detoxification of BOA influences the survival of certain weeds in environments enriched with this allelochemical. Therefore, detoxification processes affect the potential for weed suppression by soil allelochemicals in sustainable weed management. [ABSTRACT FROM AUTHOR]

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