Fusarium fujikuroi : A novel source of metabolites with herbicidal activity

Herbicidal proteins from Bacillus wiedmannii isolate ZT selectively inhibit ryegrass (Lolium temulentum L.)

BACKGROUND

The widespread use of chemical herbicides and the growing issue of weed resistance pose significant challenges in agriculture. To address these problems, there is a pressing need to develop biological herbicides based on bacterial metabolites.

RESULTS

In this study, we investigated the impact of the cell-free culture filtrate (CFCF) from the ZT isolate, a bacilliform bacterium obtained from diseased wheat seeds, on the germination and seedling growth of various plant species, including wild oat, ryegrass, redroot, wheat, and chickpea. The results revealed that CFCF had a detrimental effect on the fresh and dry weight of stems and roots in most of the studied plants, except chickpeas. The CFCF was further subjected to separation into aqueous and organic phases using chloroform, followed by the division of the aqueous phase into 13 fractions using an alumina column. Notably, both the aqueous phase (20%) and all 13 fractions (ranging from 50% to 83%) displayed the ability to reduce the root length of ryegrass, a monocotyledonous weed. Liquid chromatography-mass spectrometry (LC-MS) analysis identified that fractions 3 and 7, which were effective against ryegrass but not redroot, contained Cry family proteins, including Cry10 Aa, Cry4 Ba, and Cry4 Aa. Additionally, 16s rRNA gene sequencing revealed that the ZT isolate is closely related (98.27%) to Bacillus wiedmannii.

CONCLUSION

Conclusively, metabolites from the ZT bacterium hold promise for monocotyledonous weed-targeted herbicides, providing a constructive strategy to confront agricultural issues tied to chemical herbicides and weed resistance. © 2024 Society of Chemical Industry.

Fungus-based bioherbicides on circular economy

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.

Injury and not the pathogen is the primary cause of corm rot in Crocus sativus (saffron)

Fusarium oxysporum has been reported to be the most devastating pathogen of Crocus sativus L., a commercially significant crop that yields the saffron spice. However, most of the pathogen isolations have been done from the diseased tissue, mostly from rotten corms, but no study has been conducted on diseased saffron fields. To fill the knowledge gap, the current study was carried out with the intention of recording the diversity of cultivable fungus species from saffron fields and screening them for pathogenicity towards saffron. The three study locations in Jammu and Kashmir, Srinagar (Pampore), Kishtwar, and Ramban, yielded a total of 45 fungal isolates. The internal transcribed spacer (ITS) of rDNA was used for the molecular identification. ITS rDNA-based sequence analysis classified all the operational taxonomic units (OTUs) into two phyla-Ascomycota (88.88%) and Mucoromycota (11.11%). Moreover, Fusarium (57.77%), Geotrichum (17.77%), Mucor (11.11%), Aspergillus (4.44%), Trichoderma (4.44%), Galactomyces (2.22%), and Colletotrichum (2.22%) all had different total abundances at the genus level. It was discovered that the saffron fields in Srinagar have fewer varied fungal species than the other two selected sites. All of the fungal isolates isolated including Fusarium solani, Aspergillus flavus, Trichoderma harzianum, Fusarium neocosmosporiellum, and Mucor circinelloides were pathogenic according to the pathogenicity test; however, injury to the saffron plant was found to be a must. These fungi were pathogenic in addition to F. oxysporum, which is well documented as a major cause of saffron corm rot diseases in Srinagar, but in the present study, injury was a must for F. oxysporum as well. The percentage disease severity index for both saffron roots and corms varied for each fungal isolate.

Parthenium hysterophorus's Endophytes: The Second Layer of Defense against Biotic and Abiotic Stresses

Parthenium hysterophorus L. is considered an obnoxious weed due to its rapid dispersal, fast multiplications, and agricultural and health hazards. In addition to its physio-molecular and phytotoxic allelochemical usage, this weed most probably uses endophytic flora as an additional line of defense to deal with stressful conditions and tolerate both biotic and abiotic stresses. The aim of this article is to report the diversity of endophytic flora (fungi and bacteria) in P. hysterophorus and their role in the stress mitigation (biotic and abiotic) of other important crops. Various endophytes were reported from P. hysterophorus and their roles in crops evaluated under biotic and abiotic stressed conditions. These endophytes have the potential to alleviate different stresses by improving crops/plants growth, development, biomass, and photosynthetic and other physiological traits. The beneficial role of the endophytes may be attributed to stress-modulating enzymes such as the antioxidants SOD, POD and APX and ACC deaminases. Additionally, the higher production of different classes of bioactive secondary metabolites, i.e., flavonoids, proline, and glutathione may also overcome tissue damage to plants under stressed conditions. Interestingly, a number of medicinally important phytochemicals such as anhydropseudo-phlegmcin-9, 10-quinone-3-amino-8-O methyl ether 'anhydropseudophlegmacin-9, 10-quinone-3-amino-8-Omethyl ether were reported from the endophytic flora of P. hysterophorus. Moreover, various reports revealed that fungal and bacterial endophytes of P. hysterophorus enhance plant growth-promoting attributes and could be added to the consortium of biofertilizers.

Fundaments and Concepts on Screening of Microorganisms for Biotechnological Applications. Mini Review

Microbial biotechnology uses microorganisms and their derivatives to generate industrial and/or environmental products that impact daily life. Modern biotechnology uses proteomics, metabolomics, quantum processors, and massive sequencing methods to yield promising results with microorganisms. However, the fundamental concepts of microbial biotechnology focus on the specific search for microorganisms from natural sources and their correct analysis to implement large-scale processes. This mini-review focuses on the methods used for the isolation and selection of microorganisms with biotechnological potential to empathize the importance of these concepts in microbial biotechnology. In this work, a review of the state of the art in recent years on the selection and characterization of microorganisms with a basic approach to understanding the importance of fundamental concepts in the field of biotechnology was carried out. The proper selection of isolation sources and the design of suitable selection criteria according to the desired activity have generated substantial changes in the development of biotechnology for more than three decades. Some examples include Taq polymerase in the PCR method and CRISPR technology. The objective of this mini review is to establish general ideas for the screening of microorganisms based on basic concepts of biotechnology that are left aside in several articles and maintain the importance of the basic concepts that this implies in the development of modern biotechnology.

Herbicidal characteristics and structural identification of a potential active compound produced by Streptomyces sp. KRA18-249

The KRA18-249 strain, isolated from a natural recreational forest near Jeongseon, Gangwon-do, when applied to plants induced signs of wilting within 24 h, leading to plant death. The isolated actinomycete was identified as Streptomyces gardneri based on 16S rRNA gene homogeneity analysis. The culture filtrate was solvent fractionated to obtain the active substance, and the active compound 249-Y1 was isolated from the purified fractions via a herbicide activity test using Digitaria ciliaris. NMR and ESI-MS analyses revealed that the molecular formula of 249-Y1 is C₂₀H₁₆O₆ [MW = 352.0947] and is an anthraquinone (rubiginone D2) produce by polyketide synthetase system. The active compound 249-Y1 showed strong (100%) herbicidal activity against several weeds at 500 μg mL^-1 concentration. Twisting symptoms began to appear within 24 h of treatment and intensified over time. The KRA18-249 strain produced the herbicidal compound under specific culture conditions, that is, at 200 rpm, 35 °C, for eight days at an initial pH of 10. We also found that 249-Y1 inhibited chlorophyll, but was not a radical generator. Overall, the secondary metabolite 249-Y1, produced by KRA18-249, can be used as a new biological agent for weed control.

Achievements, Developments and Future Challenges in the Field of Bioherbicides for Weed Control: A Global Review

The intrusion of weeds into fertile areas has resulted in significant global economic and environmental impacts on agricultural production systems and native ecosystems, hence without ongoing and repeated management actions, the maintenance or restoration of these systems will become increasingly challenging. The establishment of herbicide resistance in many species and unwanted pollution caused by synthetic herbicides has ushered in the need for alternative, eco-friendly sustainable management strategies, such as the use of bioherbicides. Of the array of bioherbicides currently available, the most successful products appear to be sourced from fungi (mycoherbicides), with at least 16 products being developed for commercial use globally. Over the last few decades, bioherbicides sourced from bacteria and plant extracts (such as allelochemicals and essential oils), together with viruses, have also shown marked success in controlling various weeds. Despite this encouraging trend, ongoing research is still required for these compounds to be economically viable and successful in the long term. It is apparent that more focused research is required for (i) the improvement of the commercialisation processes, including the cost-effectiveness and scale of production of these materials; (ii) the discovery of new production sources, such as bacteria, fungi, plants or viruses and (iii) the understanding of the environmental influence on the efficacy of these compounds, such as atmospheric CO₂, humidity, soil water stress, temperature and UV radiation.

Diversity, Antimicrobial Activity, and Antibiotic Susceptibility Pattern of Endophytic Bacteria Sourced From Cordia dichotoma L

Endophytic bacteria isolated from medicinal plants are crucial for the production of antimicrobial agents since they are capable of possessing bioactive compounds with diverse structures and activities. Cordia dichotoma, a plant of medicinal importance native to the Jammu region of India, was selected for the isolation and characterization of culturable endophytic bacteria and evaluation of their antimicrobial activities. Standardized surface sterilization methods were employed to isolate thirty-three phenotypically distinguishable endophytic bacteria from the root, stem, and leaf parts of the plant. Shannon Wiener diversity index clearly divulged diverse endophytes in roots (0.85), stem (0.61), and leaf (0.54) tissues. Physio-biochemical features of the isolates differentiated the distinct variations in their carbohydrate utilization profile and NaCl tolerance. The endophytes produced an array of enzymes, namely, catalase, oxidase, amylase, cellulase, nitrate reductase, and lipase. The bacterial isolates belong to the genera Bacillus, Pseudomonas, Paenibacillus, Acidomonas, Streptococcus, Ralstonia, Micrococcus, Staphylococcus, and Alcalignes predominantly. However, the antibiotic susceptibility pattern indicated that the isolates were mostly sensitive to erythromycin and streptomycin, while they were resistant to rifampicin, amoxicillin, and bacitracin. Interestingly, majority of the bacterial endophytes of C. dichotoma showed antimicrobial activity against Bacillus subtilis followed by Klebsiella pneumoniae. The 16S rRNA sequence of Bacillus thuringiensis has been deposited in the NCBI GenBank database under accession number OM320575. The major compounds of the crude extract derived from endophytic B. thuringiensis OM320575, according to the metabolic profile examination by GC-MS, are dibutyl phthalate, eicosane, tetrapentacontane, heneicosane, and hexadecane, which possessed antibacterial activities. In conclusion, results indicated the potential of C. dichotoma to host a plethora of bacterial endophytes that produce therapeutic bioactive metabolites.

Evaluation of the herbicidal potential of some fungal species against Bidens pilosa, the coffee farming weeds

Weeds are the most productive limiting factor, especially in organic farming systems where the uses of synthetic herbicides are not allowed due to their negative impacts. Hence, synthetic herbicides need to be replaced with biological herbicides for weed management. Thus, the present study was designed to evaluate the herbicidal activity of conidia suspensions from Aspergillus niger, Trichoderma asperlium, Trichoderma atroviride, Trichoderma hamatum, Trichoderma harzanium, Trichoderma longibrachatum and Trichoderma viride against Bidens pilosa weed via a series of laboratory and lath-house conditions that laid out in a CRD and RCBD, respectively, with three replications for each bioassay. The results revealed that all fungi, except T. longibrachatum, had significantly reduced seed germination as well as early growth of the target weed compared to the untreated control. The inhibitory effects were measured to be varied among the types of conidia suspensions of fungal species and their level of concentration. The highest rate of inhibition was observed for conidia suspension from A. niger which suppressed with the maximum seed germination inhibitory level (65%) over control. Likewise, the plumule and radicle growth length of the target weed also significantly inhibited by the tested fungi (ranging from 10 to 85% and 34 to 97%) compared to the control, respectively. Based on their efficacy in the laboratory bioassay, the herbicidal potential of selected fungi was further evaluated in pot experiments. In contrarily to laboratory observations, the effect of different fungal conidia suspensions on various growth parameters of the targeted weed was insignificant in the lath-house experiments. In conclusion, the application of A. niger displayed some potential green light to be investigated as a biocontrol agent with promising retarding in the germination and early growth of B. pilosa. Hence, we recommend further investigation of those fungi under field conditions on different coffee weed species.

Bioherbicides: An Eco-Friendly Tool for Sustainable Weed Management

Weed management is an arduous undertaking in crop production. Integrated weed management, inclusive of the application of bioherbicides, is an emerging weed control strategy toward sustainable agriculture. In general, bioherbicides are derived either from plants containing phytotoxic allelochemicals or certain disease-carrying microbes that can suppress weed populations. While bioherbicides have exhibited great promise in deterring weed seed germination and growth, only a few in vitro studies have been conducted on the physiological responses they evoke in weeds. This review discusses bioherbicide products that are currently available on the market, bioherbicide impact on weed physiology, and potential factors influencing bioherbicide efficacy. A new promising bioherbicide product is introduced at the end of this paper. When absorbed, phytotoxic plant extracts or metabolites disrupt cell membrane integrity and important biochemical processes in weeds. The phytotoxic impact on weed growth is reflected in low levels of root cell division, nutrient absorption, and growth hormone and pigment synthesis, as well as in the development of reactive oxygen species (ROS), stress-related hormones, and abnormal antioxidant activity. The inconsistency of bioherbicide efficacy is a primary factor restricting their widespread use, which is influenced by factors such as bioactive compound content, weed control spectrum, formulation, and application method.

Concentration of exopolysaccharides produced by Fusarium fujikuroi and application of bioproduct as an effective bioherbicide

Exopolysaccharides are secondary metabolites produced by microorganisms and are a subject of research in many fields of science and industry due to some of their confirmed properties, especially in the pharmaceutical and agrochemical areas. In this context, the objectives of this work were to evaluate the potential of Fusarium fujikuroi for producing exopolysaccharides and to concentrate such compounds in order to increase the herbicidal activity. Exopolysaccharides were produced by submerged fermentation and different concentration methods (membranes, lyophilization, and evaporation) were evaluated. The phytotoxic effects were assessed through absorption assays in detached leaves of Cucumis sativus and evaluated on the seventh day after application. The surface tension was evaluated for each concentration method. The production of exopolysaccharides in the crude broth without concentration was 5.94 g/L. When using the lyophilization method, a maximum yield of exopolysaccharides of 10.64 g/L was obtained. The membranes also presented satisfactory results of exopolysaccharides: 9.60 g/L. The increase of bioherbicidal activity and the lower surface tension are proportionally related to the increase of the concentration of exopolysaccharides.

Isolation, identification and characterization of Streptomyces metabolites as a potential bioherbicide

Bioactive herbicidal compounds produced by soil microorganisms might be used to creating a bioherbicide for biological weed control. A total of 1,300 bacterial strains were isolated and screened for herbicidal activity against grass and broadleaf weeds. Among primarily selected 102 strains, the herbicidal activity of bacterial fermentation broths from the following three isolates strain-101, strain-128, and strain-329 reduced the growth of D. sanguinalis by 66.7%, 78.3%, and 100%, respectively as compared with control. Phylogenetic analysis of 16S rRNA gene sequencing determined that the strain-329 has 99% similarity to Streptomyces anulatus (HBUM 174206). The potential bioherbicidal efficacy of Streptomyces strain-329 was tested on grass and broadleaf weeds for phytotoxic activity through pre- and post-emergence applications. At pre-emergence application, the phytotoxic efficacy to D. sanguinalis and S. bicolor on seed germination were 90.4% and 81.3%, respectively at the 2x concentration, whereas in the case of Solanum nigrum, 85.2% phytotoxic efficacy was observed at the 4x concentration. The efficacy of Streptomyces strain-329 was substantially higher at post-emergence application, presenting 100% control of grass and broadleaf weeds at the 1x concentration. Two herbicidal compounds coded as 329-C1 and 329-C3 were extracted and purified by column chromatography and high-performance liquid chromatography methods. The active compound 329-C3 slightly increased leaf electrolytic leakage and MDA production as concentration-dependent manner. These results suggest that new Streptomyces sp. strain-329 produced bioherbicidal metabolites and may provide a new lead molecule for production an efficient bioherbicide to regulate grass and broadleaf weeds.

Antioxidant compounds extracted from Diaporthe schini using supercritical CO2 plus cosolvent

Endophytic fungi have been highlight in the production of secondary metabolites with different bioactive properties, such as in the production of the antioxidant compounds. Therefore, the objective of this work was the extraction of the antioxidant compounds from the biomass of Diaporthe schini using supercritical carbon dioxide (CO₂) without and with ethanol as cosolvent. The biomass was produced by submerged fermentation and the parameters evaluated in the extraction process were: pressure (150-250 bar), temperature (40-60 ºC) and cosolvent [biomass: cosolvent ratio, 1:0, 1:0.75 and 1:1.5 (w/v)]. Extraction yield, antioxidant activity and chemical composition of the extracts were determined. The highest extraction yield (3.24 wt.%) and the best antioxidant activity against the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical (96.62%) were obtained at 40 ºC, 250 bar and biomass:cosolvent ratio of 1:1.5 (w/v). The chemical compounds 1,4-diaza-2,5-dioxo-3-isobutyl bicyclo[4.3.0]nonane and benzeneethanol identified in GC/MS could be responsible for the antioxidant activity found in this study.