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Plant-based phytotoxins play an important role in plant-plant interaction and are of great promise for the development of bioherbicide. In this study, screening of essential oils from six different Curcuma rhizomes identified black turmeric (Curcuma caesia Roxb.) oil as an efficient growth inhibitor in wheatgrass coleoptile bioassay (IC 50 57.1 µg/mL). The phytotoxic efficacy of this oil was further confirmed through the dose dependent (10.0–300.0 µg/mL) inhibition of germination, coleoptile and radicle growth of wheatgrass seeds in water medium (IC 50 176.7, 90.6 and 93.0 µg/mL respectively) and the pre-germinated seeds in agar medium. Activity-guided fractionation and purification of the crude oil identified curzerenone, a major furanosesquiterpene in this oil as the most active phytotoxin (IC 50 13.0 µg/mL in coleoptile bioassay; 188.3, 34.7 and 36.7 µg/mL respectively in water medium). Structure-activity relationship study indicated the importance of all the functional groups for its phytotoxicity. A significant contribution by the oxygenated monoterpenes towards oil phytotoxicity was also evidenced. Though inhibitory efficacy of the oil was comparatively weak in soil, a profound activity through aerial diffusion was observed against germination and/or growth of fresh and pre-germinated wheatgrass seeds (IC 50 1.4–6.2 mg/L air). The study also confirmed the uptake of active phytotoxins with no detectable transformation by the seeds in water and their persistence in the soil for at least one and half months. Further, its applicability was demonstrated through an efficient post-emergence growth inhibition (IC 50 37.0–81.4 µg/mL) of bermudagrass weed in water and agar medium. [Display omitted] • Screening: black turmeric (Curcuma caesia) essential oil is a potent phytotoxin. • Major phytotoxins: curzerenone (a furanosesquiterpene) and oxygenated monoterpenes. • Modes of transport: water, agar, soil and aerial diffusion. • Uptake of active phytotoxins by the seeds with no detectable transformation. • Efficient inhibitor of post-emergence growth in bermudagrass weed. [ABSTRACT FROM AUTHOR]

This study was carried out to determined the efficacy of freshly prepared pestal granules containing the wild and mutant strains of Pseudomonas aeruginosa and Lasiodiplodia pseudotheobromae in controlling weeds in a potted experiment. Six multi-combination formulations of the wild and mutant strains of Pseudomonas aeruginosa and Lasiodiplodia pseudotheobromae were combined with a semolina kaolin granular formulation which were represented as follows: BHI, BH2, BH3, BH4, BH5, and BH6. The effect of each formulated pesta granules were supplemented with an adjuvants (glycerol, glucose, sucrose, fructose, dextrose, lactose sugar, peptone) and they were evaluated on Tridax procumbens and sorghum plant. The efficacy of the bioherbicides were in the following orders: BH4>BH2>BH6>BH3>BH1>BH5. BH4 showed the highest activity compared to other formulations by reducing Tridax procumbens to the lowest dry weights and showing the highest percentage disease severity on Tridax procumbens compared to other formulations. BH4 among other formulations also lead to increase in the amount of grain yield and 100-grain weight of sorghum plants compared to uninoculated plants. Therefore, the use of pesta granules containing wild and mutant strains of Pseudomonas aeruginosa and Lasiodiplodia pseudotheobromae exposed to U.V for 1 hour 30 minutes against weeds using Tridax procumbens as a study case could help in achieving a sustainable agriculture through the application of bioherbicide produced during this study . [ABSTRACT FROM AUTHOR]

Abstract: Trichothecenes, a major class of mycotoxins produced by Fusarium, Myrothecium, and Stachybotrys species, are toxic to both plants and mammals. Simple trichothecenes, including type A (e.g., T-2 toxin) and type B (e.g., deoxynivalenol), are generally less toxic than macrocyclic trichothecenes. We sought to determine if simple trichothecenes are a potential source of candidates for development as bioherbicides, which require high phytotoxicity and low mammalian toxicity. We examined 28 simple trichothecenes in vitro for phytotoxicity using a small aquatic plant, Lemna pausicostata, and for mammalian toxicity using four cultured mammalian cell lines. Several structure–activity relationships were identified, including the following two, which may be relevant to bioherbicide development: peracetylation of type B trichothecenes and de-epoxidation of type A trichothecenes both substantially reduced mammalian toxicity with little effect on phytotoxicity. It was concluded that simple trichothecenes possessing strong phytotoxicity and minimal mammalian toxicity in vitro can be identified. [Copyright &y& Elsevier]

Abstract: The essential oil of Chrysanthemum coronarium (Garland) flowerheads was analyzed by gas chromatography–mass spectrometry and essayed for its in vitro scavenging activity on 1,1-diphenyl-2-picrylhydrazyl (DPPH) and its antimicrobial activities against Escherichia coli, Salmonella typhymurium, Candida albicans, Bacillus cereus and Staphylococcus aureus. The aqueous extracts were tested for their allelopathic properties on seed germination and seedling growth of two annual weeds (Sinapis arvensis and Phalaris canariensis) and two crops (Triticum durum and Zea mays) and the identity of the phenolic components was determined by using HPLC–PDA-MS. A total of 40 components, representing 96.58% of the total oil were identified, and the most plentiful constituents were found to be cis-chrysanthenyl acetate (21.82%), trans-chrysanthenyl acetate (12.78%), (E)-β-farnesene (8.97%), germacrene-D (8.92%) and camphor (6.03%). The oil was unable to reduce the DPPH radical, while it exhibited a good antimicrobial activity against the gram-positive bacteria B. aereus and S. aureus. The aqueous extracts suppress the germination and reduce the seedling growth of the target species. The phytotoxic effect was found to be selective towards weeds with the effects being more pronounced in S. arvensis and P. canariensis. HPLC–PDA-MS analysis allowed the identification of chlorogenic acid acid, di-cafeoylquinic acids isomers, rutin, luteolin, luteolin-7-O-glucoside, myricetin-3-O-galactoside and tricin. The latter components were reported in C. coronarium for the first time. It is suggested that the identified components may be at least, a key factors in the observed phytotoxic activity and the data presented may contribute to the development of naturally occurring herbicides. [Copyright &y& Elsevier]

Abstract: Phoma macrostoma is registered as a bioherbicide in North America to control broadleaved weeds species in turfgrass. A study was conducted to examine the effect of nitrogen, phosphorus, potassium, lime, and commercial fertilizers with or without applications of the bioherbicide on the reduction of dandelion under greenhouse and field conditions. The bioherbicide provided 70–100% reduction of dandelion. The addition of nitrogen with the bioherbicide, in the form of urea (45-0-0), Scotts Turf Builder Pro (32-0-4 plus 2% Fe), and Scotts Lawn Pro (26-0-3, with no iron), significantly reduced dandelion more than in soil that was not amended with fertilizers in the greenhouse and field locations. Bioherbicide efficacy on dandelion was 10–20% better with these fertilizer treatments. Phosphate (0-46-0), potassium sulfate (0-0-42), and lime had either no effect or did not reduce dandelions under greenhouse conditions. This study showed that P. macrostoma retained bioherbicide efficacy on dandelion in conjunction with typical fertility practices and the combination of the bioherbicide with nitrogen fertilizers improved bioherbicide efficacy, especially in low nitrogen soils. [Copyright &y& Elsevier]

Several isolates of a previously unreported bacterial pathogen were discovered on common cocklebur seedlings in Chicot County, AR and Washington County, MS. Diseased plants in nature exhibited angular-shaped leaf spotting symptoms on leaf margins and central leaf areas. The isolates were cultured from diseased leaf tissue and tentatively identified as Xanthomonas spp., and their virulence on common cocklebur seedlings compared. The most virulent isolate (LVA987) was used in studies to define disease progression on cocklebur seedlings and to carry out a host range evaluation on various weeds and crop plants. High virulence was found on common cocklebur > marestail (Conyza canadensis) > giant ragweed {Ambrosia trifida) > and common ragweed (Ambrosia artemisifolia). These results suggest this pathogen may be useful for the biological control of these important species of weeds. This is also highly relevant since all of these weeds have evolved resistance to one or more synthetic herbicides and are thus becoming more difficult to control with conventional herbicides. [ABSTRACT FROM AUTHOR]

Cirsium arvense (Asteraceae) is known as creeping thistle in its native range in the UK and Canada thistle in its invasive North American range. Recently, the fungus Phoma macrostoma was registered in Canada as a bioherbicide in turfgrass, where it causes severe chlorosis (White Tip disease) and death of C. arvense and other broadleaved weeds. It was hypothesised that the disease originated in the UK on its thistle host and, therefore, that fungal isolates from both countries should be biologically and genetically similar. Twenty-six strains in the genus Phoma- isolated during surveys in the UK - were compared morphologically with the type culture of P. macrostoma, tested for bioherbicidal activity using the inoculum mat bioassay and genetically screened with bioherbicide-specific primers. White tip disease was found to be restricted to the eastern and southern counties of England. Phoma macrostoma was isolated consistently from diseased bleached tissues. Bioherbicidal isolates of P. macrostoma occupy a unique clade, which is phylogenetically distinct but morphologically indistinguishable from the type culture. Most isolates from the UK had the same bioherbicidal activity and similar genetic make-up as strain SRC 94-44B, the active ingredient in the registered Canadian product. The origin of all bioherbicidal strains found to date has a clear presence in both Canada and the UK, with strong genetic similarities, supporting the view of a common ancestry. Thus, on the evidence presented, the 'white tip' clade of P. macrostoma evolved in southern England. Therefore, the bioherbicide based on strain SRC 94-44B should also be eligible for registration in the UK, based on the pest risk assessment data already available. [ABSTRACT FROM AUTHOR]

Aim To develop an appropriate formulation of the deleterious rhizobacterium Pseudomonas trivialis X33d and to evaluate its effectiveness to reduce brome growth. Methods and Results Two formulations of Ps. trivialis X33d, a semolina-kaolin granular formulation ( Pesta) and talc-kaolin powder, were prepared and their effectiveness in reducing brome growth was evaluated. Both brome suppression and cell viability of X33d were higher in Pesta granular formulation than in talc-kaolin powder one. The impact of storage temperature and the addition of adjuvants (sucrose and oil) to the granular formulation of X33d were assessed in order to improve the shelf life of the formulation. The longest viability was found in formulated product supplemented with adjuvants and stored at 4°C. The effect of Pesta granules supplemented with adjuvants and stored for 6 months at 4°C on brome and wheat growth under controlled and greenhouse conditions was evaluated. The X33d formulation in Pesta increased the growth of wheat and reduced brome growth. Conclusion Our results indicate that Ps. trivialis X33d formulated in Pesta has potential as a bioherbicide to control brome. Significance and Impact of the Study Because of the impracticality of applying bacterial cell suspension on a large scale, the use of Pesta granules of X33d against brome could help in achieving a sustainable agriculture application of a bioherbicide. [ABSTRACT FROM AUTHOR]

Wheat crop has to compete with several weeds including Avena fatua , a noxious weed that alone is responsible for 30-70% losses in the yield annually. Because of the environmental concerns associated with conventional methods, researchers are on a continuous hunt to find clean alternatives in order to manage weeds. Fungi have shown promising weedicide potential in lab studies. The current study aimed to isolate endophytic fungi from wheat plants which can promote wheat growth and inhibit the growth of common weed, A. fatua . Of several isolates, GW (grayish white) was selected for its promising features, and the strain was identified as Fusarium oxisporum through ITS sequencing technique. This fungus released a number of compounds including Isovitexin, Calycosin, quercetagetin, and dihydroxy-dimethoxyisoflavone that inhibited the growth of A. fatua but did not influence the growth of wheat seedlings. Biomass of this fungus in the soil also reduced growth parameters of the weed and promoted the growth of wheat. For instance, the vigor index of A. fatua seedlings was reduced to only 6% of the control by this endophyte. In contrast, endophyte-associated wheat seedlings showed a higher vigor index than the control. Behind this differential response of the two plants were their contrasting physiological and biochemical status. Lower growth phenotypes of A. fatua seedlings had reduced levels of IAA, GAs, and SA and higher the levels of JA and ABA. Besides, their ROS scavenging ability was also compromised as evident from relatively lower activities of catalase, peroxidase, and ascorbic acid oxidase, as well as higher accumulation of ROS in their leaves. Wheat seedlings response to GW was opposite to the A. fatua . It may be concluded that F. oxysporum GW has the ability to differentially modulate physiology and biochemistry of the two hosts leading to contrasting phenotypic responses., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Asim, Hussain, Murad, Hamayun, Iqbal, Rehman, Tawab, Irshad, Alataway, Dewidar, Elansary and Lee.)

The study aims at investigating the allelopathic effects of twelve weed species including Anagallis arvensis, Plantago lanceolata, Medicago polymorpha, Ammi visnaga, Phragmites australis, Silybum marianum, Emex spinosa, Malcolmia africana, Calendula arvensis, Rumex crispus, Fumaria indica and Cirsium arvense on seed germination, seed inhibition, seed germination time, seed germination index and seed vigor index of the test crops (wheat, maize and sunflower). A laboratory experiment was laid out in a completely randomized design in March 2010 in the Department of Weed Science, The University of Agriculture, Peshawar, Pakistan. Rumex crispus inhibited the seed germination up to 80% and 70% in both wheat and sunflower, respectively while the seed of maize showed high tolerance against all extracts except Fumaria indica extract that inhibited the maize seed germination up to 40%. In the present study, sunflower proved more susceptible to all extracts and maize was more tolerant to the phytotoxicity of all the weeds. [ABSTRACT FROM AUTHOR]

The fungus Phoma macrostoma Mont. isolate 94-44B was registered as a bioherbicide for control of broadleaved weeds in Canada and the USA in 2011 and 2012, respectively. To obtain the registrations, the fungus had to be characterised both biologically and genetically. The objectives of this study were to demonstrate that bioherbicidal activity was associated with specific genetic markers and to determine whether bioherbicidal activity was a general trait of the species or only selected isolates. A collection of 64 isolates of P. macrostoma was established. A greenhouse bioassay and bioherbicidal-specific primers were used to determine bioherbicidal activity of all isolates. Only isolates originating from Canada thistle demonstrated the ability to reduce dandelion seedlings and display the 853 bp amplicon for the bioherbicidal-specific primer. Bioherbicidal isolates were consistently differentiated from all other isolates with two main genotypic groupings (I and II) arising from internal transcribed spacer (ITS) and amplified fragment length polymorphisms (AFLP) sequence analyses. Using AFLP, two biotypes of bioherbicidal isolates were also differentiated by the presence or absence of an AFLP marker at a single polymorphic locus. The genetic divergence among the bioherbicidal and nonbioherbicidal isolates of P. macrostoma was only 2.21% which was lower than that reported for other related Phoma sp. Other than the bioherbicidal trait, there was no apparent affiliation of the genetics with known varietal types, host or geographic origin. ITS sequence analysis and AFLP fingerprinting may be used as tools to detect bioherbicidal isolates of P. macrostoma. [ABSTRACT FROM AUTHOR]

The fungal plant pathogen, Myrothecium verrucaria, is highly virulent to several important weed species and has potential utility as a bioherbicide. However the production of macrocyclic trichothecene mycotoxins by this fungus presents significant safety concerns. It was discovered that trichothecenes are removed from M. verrucaria spores by repeated washes with water. These washed spores retained bioherbicidal efficacy against kudzu when tested in field trials and on sicklepod when tested under greenhouse conditions. Changes in the growth medium combined with washing spores with water resulted in greater than 95% reduction in roridin A and verrucarin A. Washing spores reduced trichothecene concentrations in spore preparations with no significant effect on plant biomass reduction, thus demonstrating the possibility of M. verrucaria formulations with improved safety to researchers, producers and applicators. [ABSTRACT FROM AUTHOR]

The taxonomic characteristics of weeds such as morphology of shoot, leaves, flowers, stem, fruits and seeds were recorded as Gynandropsis pentaphylla, DC, Amarantus spinosus Linn, Cyperus rotundus, Amarantus viridis Linn, Cassia occidentalis, Linn and Echinochilora orygicola. Totally 20 actinobacteria isolates were screened for herbicidal activity against the weed. Among the 20 isolates, only four actinobacterial isolates KA1-3, KA1-4, KA1-7 and KA23A showed significant herbicidal activity against C. rotundus. The herbicidal effect of actinobacterial culture filtrates on germination and seedling growth of C. rotundus was tested. The shoot and root growth of C. rotundus was severely affected when compared to control. The potent actinobacterial isolates KA1-4 and KA1-7 were characterised based on their morphological and molecular phylogenetic property and were identified as Streptomyces sp. The present study concludes that actinobacterial isolates will be used as bioherbicide against C. rotundus. Further studies are required to confirm the activity of actinobacterial isolates against C. rotundus under field conditions. [ABSTRACT FROM AUTHOR]

Pseudomonas fluorescens BRG100 produces secondary metabolites with herbicidal activity on green foxtail ( Setaria viridis), an important weed pest in Canadian agriculture. Five gfp transformants of P. fluorescens BRG100 were compared with the wild-type isolate for green foxtail root herbicide activity, i.e., root growth suppression, doubling time, carbon utilization, and colonization of green foxtail root (proximal and distal regions). The most revealing comparison between the wild type and its gfp transformants was herbicidal activity on green foxtail. Herbicidal activity of transformant gfp-7 was not significantly different from the uninoculated control, suggesting that insertion of the gfp gene may have interfered with a gene, or genes, vital to the bioherbicide process. Doubling time, carbon utilization, and colonization of green foxtail did not differ to a great extent between the wild type and the gfp transformants, indicating their suitability as conservatively tagged organisms for subsequent colonization-herbicidal activity studies. Accordingly, a pesta granule formulation delivered transformant gfp-2 to the seed coat and roots of green foxtail. Epifluorescent and confocal laser scanning microscopy revealed the transformant gfp-2 colonized the ventral portion of the seed coat, root hairs, and all areas of the root except the root cap region, where gfp-2 presumably exerted herbicidal effects. These results suggest that P. fluorescens BRG100 has considerable potential as a bioherbicide because of its successful colonization and suppressive activity on green foxtail root growth. [ABSTRACT FROM AUTHOR]

In greenhouse and field experiments, an invert emulsion (MSG 8.25) was tested with dried, formulated spores of the bioherbicidal fungus Colletotrichum gloeosporioides f. sp. aeschynomene, a highly virulent pathogen of the leguminous weed Aeschynomene virginica (northern jointvetch), but considered ‘immune’ against another more serious leguminous weed, Sesbania exaltata (hemp sesbania). A 1:1 (v/v) fungus/invert emulsion mixture resulted in 100% infection and mortality of inoculated hemp sesbania seedlings over a 21-day period under greenhouse conditions. In replicated field tests of the fungus/invert formulation conducted in Stuttgart, AR, and Stoneville, MS, hemp sesbania was controlled 85 and 90%, respectively. These results suggest that this invert emulsion expands the host range of C. gloeosporioides f. sp. aeschynomene, with a concomitant improvement of the bioherbicidal potential of this pathogen. [ABSTRACT FROM PUBLISHER]

The present study investigated the chemical composition and allelopathic potential of volatile oil from Eucalyptus tereticornis on growth and establishment of Amaranthus viridis, a wasteland weed. The volatile oil was rich in monoterpenoids and a total of 34 components were identified by gas chromatography/gas chromatography–mass spectroscopy analyses, constituting 98.52%. α-Pinene (32.5%) and 1,8-cineole (22.4%) were the two major constituents. The volatile oil and two major components were evaluated for their allelopathic potential against A. viridis. A significant reduction in early seedling growth and seedling vigor of A. viridis was observed in response to volatile oil or its major monoterpenes. Further, the contents of photosynthetic pigments, i.e. chlorophylls a and b, and carotenoids, and cellular respiration in oil-/monoterpene-treated seedlings were significantly reduced thereby indicating adverse effects of the oil on photosynthetic machinery and energy metabolism. Based on the study, it can be concluded volatile oil of E. tereticornis possess allelopathic potential and could be explored as bioherbicide for future weed management programs. [ABSTRACT FROM PUBLISHER]

Cirsium arvense is one of the worst weeds in agriculture. As herbicides are not very effective and not accepted by organic farming and special habitats, possible biocontrol agents have been investigated since many decades. In particular plant pathogens of C. arvense have received considerable interest and have been promoted as "mycoherbicides" or "bioherbicides". A total of 10 fungi and one bacterium have been proposed and tested as biocontrol agents against C. arvense. A variety of experiments analysed the noxious influence of spores or other parts of living fungi or bacteria on plants while others used fungal or bacterial products, usually toxins. Also combinations of spores with herbicides and combinations of several pathogens were tested. All approaches turned out to be inappropriate with regard to target plant specificity, effectiveness and application possibilities. As yet, none of the tested species or substances has achieved marketability, despite two patents on the use of Septoria cirsii and Phomopsis cirsii. We conclude that the potential of pathogens for biocontrol of C. arvense has largely been overestimated. [ABSTRACT FROM AUTHOR]

Abstract: Isolates of the fungus Phoma macrostoma cause intense photobleaching and mortality of Canada thistle (Cirsium arvense), dandelion (Taraxacum officinale) and other broadleaved weeds when applied to the soil. The symptoms are caused by the production of macrocidins which have been extracted from cultured mycelium and the growth medium broth. The objective of this study was to determine the pathway of infection that leads to plant damage resulting in bioherbicidal activity. This was accomplished by first determining which infective unit (i.e., conidia and/or mycelium) resulted in plant damage when applied to a host. Then the infection process was microscopically observed from infested granules placed in the soil through the various stages of colonization and penetration in a resistant and a susceptible host. Conidia were ineffective as infective units because there was no plant damage when target weeds were inoculated using either a foliar spray of a conidial suspension or granules containing conidia placed in the soil. Only mycelium of the fungus applied either pre-emergently to soil ahead of weed seed emergence or post-emergently to soil containing established weeds resulted in significant plant damage. Microscopic observations showed that P. macrostoma 94-44B mycelium germinated from formulated granules in soil, colonizing roots of dandelion (susceptible) and barley (resistant) within 7days of application. The fungus entered the hosts at sites proximal to root hairs where wounding of the cells was most likely, and growing intercellularly towards the root core. In dandelion, the mycelium proliferated around the vascular trachea disrupting the competence of neighboring cells. In barley, proliferation was less obvious being restricted to the outer layers and there was no disruption of the internal cell structure. P. macrostoma boasts potential as a bioherbicide to control susceptible broadleaved weeds but not harm resistant nontarget hosts. [Copyright &y& Elsevier]

The fungal pathogen Colletotrichum truncatum is a potential bioherbicide agent for management of the noxious weed scentless chamomile (Metricaria perforate) in western Canada. Isolates of the potential biocontrol agent from scentless chamomile cannot be separated morphologically from the pathogen that causes anthracnose on lentil and field pea, raising questions about crop safety for its use as a bioherbicide agent in the region. Internal transcribed spacer (ITS) regions of ribosomal DNA (rDNA) of C. truncatum from scentless chamomile and several crop species were examined for genetic differences. ITS-rDNA fragments of 63 isolates were amplified using the universal primers Its4 and Its5 and sequenced. The rDNA fragment was 571 bp in size for isolates from scentless chamomile, 566 bp from lentil, 558 or 559 bp from field pea isolates and 555 bp from soybean. Phylogenetic analysis using parsimony and neighbour-joining methods separated these putative C. truncatum isolates into four groups that coincided with host origin. All of the isolates of scentless chamomile fell within a single cluster regardless of their geographic origins, and were most closely related to C. truncatum isolates from lentil. Morphologically, the isolates from scentless chamomile, lentil and field pea were similar in conidial shape and dimension, whereas soybean isolates had substantially longer and more falcate conidia and slightly bigger appressoria. Based on the sequence information, strain-specific PCR primers were designed for isolates of C. truncatum from each host and used to amplify specific rDNA fragments (markers). This molecular technique was sensitive and strain-specific for detection and differentiation of Colletotrichum isolates from scentless chamomile, lentil, field pea and soybean, and may be used as a tracking and monitoring tool in environmental risk assessment for the bioherbicide agent. [ABSTRACT FROM AUTHOR]

Abstract: Phoma macrostoma 94-44B was evaluated against 94 plant species in 34 botanical families, of economically important agricultural, horticultural and ornamental species, as well as target and nontarget weeds. Fifty-seven species from 28 families were found to be resistant to P. macrostoma, while 38 species from 12 families, six of which also contained resistant species, were found to be susceptible. Those families comprising both susceptible and resistant species included the Asteraceae, Brassicaceae, Fabaceae, Lamiaceae, Plantaginaceae and Rosaceae with the foremost three containing the largest numbers of susceptible species. P. macrostoma was pathogenic to many dicotyledonous plant species, but nonpathogenic to monocots. Commercial applications for weed management in turfgrass, agriculture, horticulture and forestry seem probable, while domestically management of weeds in lawns, transplanted ornamental and annual flowering species may provide alternative markets. [Copyright &y& Elsevier]

The essential oils from the aerial parts of catmint ( Nepeta meyeri Benth.) were analyzed by hydrodistillation with GC-MS. Fourteen compounds were identified in the yellowish essential oil of the plant, representing more than 99.07% of the oil, of which the major components were found to be 4aα,7α,7aβ-nepetalactone (83.4%) and 4aα,7α,7aα-nepetalactone (8.83%). The oils were characterized by relatively high content of oxygenated monoterpenes, and were tested on the germination and antioxidative systems in early seedlings of seven weed species ( Amaranthus retroflexus L., Bromus danthoniae Trin., Bromus intermedius Guss., Chenopodium album L., Cynodon dactylon L., Lactuca serriola L., and Portulaca oleracea L.) and autotoxicity. The essential oil of N. meyeri inhibited seed germination by more than 50% in three weed species ( B. danthoniae, B. intermedius, and L. serriola) when applied at a concentration of 0.01%. When the same oils were applied at 0.02% concentration, the inhibition of germination was more than 70% in two weeds ( C. album and C. dactylon) and was 100% in four weeds ( A. retroflexus, B. danthoniae, B. intermedius, and L. serriola). The essential oils increased CAT activity in all the weed species and decreased SOD activity, except in A. retroflexus. POX activity did not exhibit a revealing situation in the weed species tested. The essential oils increased the level of lipid peroxidation and hydrogen peroxide (HO) concentration in all the weeds studied. Our results show that the essential oils of N. meyeri have an important phytotoxic effect on seed germination and, consequently, seedling growth by exhausting antioxidative system of the weeds. The phytotoxic activity of the essential oils may be attributed to their relatively high content of oxygenated monoterpenes, especially 4aα,7α,7aβ-nepetalactone. It can be suggest that the essential oils of N. meyeri have the potential to be used as a bioherbicide. [ABSTRACT FROM AUTHOR]

• Premise of the study: Fungal plant pathogens exert much of their effect on plant cells through alterations in the host cell walls. However, obtaining biochemical proof for this change is difficult because of the relatively small number of cells that are affected by the pathogen relative to the bulk of host tissue. In this study, we examined the differences in host wall composition between infected and uninfected areas of seedlings of the weed hemp sesbania (Sesbania exaltata) that were treated with the biocontrol agent Colletotrichum gloeosporioides. • Methods: To determine the changes in cell wall composition, we used semi-thin sections and a battery of antibody probes that recognize components of the cell wall and immunogold-silver cytochemistry to visualize the probes. • Key results: A loss of specific plant cell wall polysaccharides in the region surrounding the primary fungal infection and the creation of a defensive layer by the plant to limit the fungal invasion were the two most obvious changes noted in this study. At the invasion site, there was significant loss of rhamnogalacturon-1 (RGI) and esterified and de-esterified homogalacturonan (HG)-reactive epitopes from the cell walls. In contrast, boundary tissue between the vascular tissue and the fungal lesion reacted more strongly with antibodies that recognize arabinogalactan proteins (AGPs) and xyloglucans than in unaffected areas. • Conclusions: These data strongly indicate a role of pectinases in the invasion of the biocontrol agent and the importance of extensins, AGPs, and xyloglucans as defense by the host. [ABSTRACT FROM AUTHOR]

Abstract: The fungal pathogen, Microsphaeropsis amaranthi, is under consideration as a bioherbicide for the control of weeds in the genus Amaranthus. This organism has been shown to be virulent against a number of important Amaranthus species but has not yet demonstrated sufficient aggressiveness or reliability in the field to be commercially developed. We report a sequence of experiments evaluating a range of solid media for the production of high quality inoculum, methodologies for the enhancement of aggressiveness in culture, and the effects of a variety of spray adjuvants. Additionally, we report preliminary results testing the efficacy of the bioherbicide applied as granules, prior to weed emergence. The fungus grew well and sporulated profusely on a range of different solid substrates. Conidia produced on corn stover were larger than those produced on other substrates, had thicker cell walls, and exhibited particularly high aggressiveness. Repeated inoculation and re-isolation of the fungus from Amaranthus tuberculatus plants increased its aggressiveness. In addition, application in Sunspray oils resulted in improved disease impact under low moisture conditions. Preemergence application of granular formulations, especially where the fungus was grown and applied in ground barley grains, resulted in good control of emerging A. tuberculatus. Further progress has been made in improving the M. amaranthi bioherbicide by refining the conditions for the production and deployment of quality inoculum. [ABSTRACT FROM AUTHOR]

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Abstract: Two soil microorganisms have been shown to negatively affect the invasive species cheatgrass (Bromus tectorum) and have the potential to serve as biological control agents. The fungal pathogen Pyrenophora semeniperda kills mostly slow-germinating cheatgrass seeds and reduces the cheatgrass seedbank. It is naturally occurring within the western United States. The deleterious rhizobacterium Pseudomonas fluorescens D7 inhibits cheatgrass root elongation and seedling vigor. This paper characterized the interaction between the two microorganisms in order to determine if dual inoculations would provide more effective cheatgrass control. First, to determine the effect of P. fluorescens D7 on P. semeniperda activity, dormant cheatgrass seeds were exposed to the microorganisms in combination and alone. We found a slight increase in fungal infection with dual inoculations but a decrease in fungal-caused seed mortality. Second, to study the effect of P. semeniperda on P. fluorescens D7, non-dormant cheatgrass seeds were exposed to one or both microorganisms. We observed no increase in the inhibitory effect of P. fluorescens D7 with dual inoculations and in some cases saw less growth inhibition in the presence of both microorganisms. Overall, our findings suggest that there is no beneficial interaction between P. semeniperda and P. fluorescens D7 that provides improved cheatgrass control. Possible explanations include the production of antifungal metabolites by P. fluorescens D7, the production of antibiotics by P. semeniperda, or competition within the seed zone (i.e. spermosphere) for space or limited resources. [Copyright &y& Elsevier]

In greenhouse experiments, an invert emulsion (MSG 8.25) was tested with spores of the mycoherbicidal fungus Colletotrichum gloeosporioides f. sp. aeschynomene, a highly virulent pathogen of the leguminous weed Aeschynomene virginica (northern jointvetch), but considered “immune” against another leguminous weed, Sesbania exaltata (hemp sesbania). A 1:1 (v/v) fungus/invert emulsion mixture resulted in 100% infection and mortality of inoculated hemp sesbania seedlings over a 21 day period. Microscopic examinations revealed that the fungus proliferated within the cells of hemp sesbania and produced anthracnose lesions containing acervuli on infected stems. The fungus was reisolated and found to infect and kill northern jointvetch seedlings, thus fulfilling Koch’s postulates for disease identification. These results suggest that this invert emulsion expands the host range of C. gloeosporioides f. sp. aeschynomene, and possibly improves the bioherbicidal potential of this pathogen. [ABSTRACT FROM AUTHOR]

Abstract: The vigorous vegetative reproduction of intolerant deciduous competition limits the efficacy of mechanical release operations in young softwood plantations. Applying bioherbicides such as the fungus Chondrostereum purpureum (Pers. ex Fr.) Pouzar could improve the effectiveness of release by reducing stump sprouting while gaining public acceptance. A field experiment was conducted in Québec (Canada) in two white spruce (Picea glauca [Moench] Voss) plantations invaded by intolerant hardwoods. This study compared four-year response of traditional mechanical release and mechanical release with an application of C. purpureum under the commercial formulation Myco-Tech™. The general objective of the project was to measure the silvicultural efficacy and worker productivity related to applying C. purpureum to control intolerant hardwoods in young white spruce plantations. The potential of C. purpureum was somewhat expressed four years after treatment by reducing paper birch (Betula papyrifera Marsh.) competition. However, because of the slight effect of the treatment on pin cherry (Prunus pensylvanica L.f.), red maple (Acer rubrum L.) and trembling aspen (Populus tremuloïdes Michx.), the addition of the biological treatment did not significantly improve light availability and morphological parameters (height, diameter) of white spruce seedlings. A 2.6-fold reduction in worker productivity compared to traditional mechanical release was caused by the additional operations and weight of the equipment used for the application of the Myco-Tech™ paste. The conditions that facilitate the operational application and effectiveness of C. purpureum applied in the form of the Myco-Tech™ paste do not seem to be present in young conifer plantations with a high density of intolerant hardwood competition. [Copyright &y& Elsevier]

Abstract: Herbicides and spray adjuvants were evaluated for compatibility with the bioherbicidal fungus, Myrothecium verrucaria. Several commercial formulations of glyphosate were found to be compatible for tank mixing with M. verrucaria, including Touchdown® and RoundUp HiTech®. Others, such as Accord XRT II® and RoundUp WeatherMAX® killed all the spores of M. verrucaria immediately after mixing at only 10% the maximum labeled application rate. Many herbicides, which were not suitable for co-application with M. verrucaria, did not inhibit the growth of the fungus when added directly to media at up to 1% concentration, indicating that these products could be compatible with M. verrucaria as sequential applications in an integrated weed management system. Several commercially available spray adjuvants and polyoxyethylene tridecyl ether (TDA) formulations were tested in vitro for their efficiency in dispersing spores and in a plant bioassay for bioherbicidal activity. All of the products improved the activity of M. verrucaria over the water-only treatments and TDA formulations with a hydrophilic–lipophilic balance (HLB) number of 8 or 10 had the highest activity. The mechanism for improved bioherbicidal activity with these adjuvants was investigated in vitro, and TDA HLB 8 and 10 did not significantly improve conidia dispersal or accelerate spore germination relative to other surfactants. It is possible that the role of the surfactant is in the alteration of the plant cuticle or otherwise preparing the infection court. Better adjuvant selection and integration with affordable synthetic herbicides should aid in the development of more cost-effective biological control of weeds. [Copyright &y& Elsevier]

The article discusses the study that investigates the host specificity of Colletotrichum truncatum (CT) from weed scentless chamomile in western Canada. The study was conducted by understanding the risk, potential infection strategy and biocontrol agents of chamomiles, and their cross infection was observed through inoculation. The study reveals the absence of infection structures from the lentil leaves which depict the absence of endophytic colonization and infection during incubation.

The article presents a study which examines the capability of NEP1 gene to improve the pathogenicity of Orobanche aegyptiaca when the gene is transformed into two Fusarium species. It states that NEP1 gene transformants can quickly kill Orobanche compared to other wild type of transformants. It mentions that the transformed gene eliminates minute amounts of NEP1-like protein which is immunologically and bioassay-detectable. It also notes that the sequence of the NEP1 transformants differs depending on the Fusarium species.

The article presents a research that assesses the agronomic potential of the seed coating and pesta techniques of three isolates of Fusarium oxysporum f. sp. strigae on Striga-resistant and Striga-susceptible varieties of sorghum and maize. It uses Striga-susceptible and Striga-resistant sorghum varieties Korboula and sarias-o14 which originate from Burkina Faso. Results show that the amount of inoculum used in maize was the same for both varieties. Meanwhile, striga plants emerge in Burkina Faso and other uninfested control plots. It also discovers that fungi application is more beneficial in maize than in sorghum for the varieties examined. It concludes that 90 % reduction in Striga emergence was due to synergistic effects between the Striga-resistant maize line and F. oxysporum.

Senna garrettiana (Craib) Irwin & Barneby (Fabaceae) is a medicinal plant known to be rich in biologically active compounds that could be exploited to produce bioherbicides. The present study was conducted to explore the allelopathic potential and phytotoxic substances of S. garrettiana. Extracts of S. garrettiana leaves were found to significantly inhibit the growth of Lepidium sativum L. and Echinochloa crus-galli (L.) P. Beauv. (p ≤ 0.05). The phytotoxic substances were isolated and identified as vanillic acid and ferulic acid by bioassay-directed fractionation and spectral data analysis. The two compounds were shown to significantly inhibit the seed germination, seedling growth, and dry biomass of L. sativum. Based on the concentration required for 50% growth inhibition (defined as IC50), the roots of L. sativum were the most sensitive to the compounds, and the inhibitory effect of ferulic acid (IC50 = 0.62 mM) was >1.3 times more potent than that of vanillic acid (IC50 = 0.82 mM). In addition, a mixture of the two compounds (0.3 mM) resulted in synergistic inhibitory activity against the L. sativum roots compared with the individual compounds. These results suggest that the extracts of S. garrettiana leaves and their phytotoxic compounds have potential as candidate natural herbicides. [ABSTRACT FROM AUTHOR]

A rapid technique for trichothecene detection was needed in screening tests of the potential bioherbicide Myrothecium verrucaria (MV), in order to select strains, mutants, or formulations that were void of or that possessed low amounts of these undesirable mycotoxin compounds. Commercially available enzyme-linked immunosorbent assay (ELISA) plates for trichothecene detection, possessing cross-reactivity with several trichothecene mycotoxins (e.g., verrucarin A, and J, roridin A, L-2, E, and H), were tested for their ability to detect trichothecenes produced by a strain of Myrothecium verrucaria (MV) in cell cultures, in plant tissues (hemp sesbania and kudzu) treated with purified roridin A, or ethyl acetate fractions of MV cultures. Evaluations of ELISA assays showed linear responses for standards of verrucarin A and roridin A over a concentration range of 0.2 to 20 ppb. Ethyl acetate or aqueous extractions were used to obtain samples from MV cultures and plant tissues for testing. Trichothecenes were detected in conidia and mycelia of MV, and in agar upon which wild-type MV was grown, indicating secretion into the growth media. Two MV sectors (morphological variants of wild type) also tested positive for trichothecenes. Purified roridin A and concentrated extracts containing trichothecenes from MV spore cultures exhibited phytotoxicity (growth inhibition or necrosis) when applied to excised shoots of hemp sesbania seedlings and intact kudzu leaf tissues. Evidence of some translocation of trichothecenes from the application point in kudzu was found, but translocation to the upper shoot portion of hemp sesbania was not detected at the lowest limit of detection in this assay (0.14 ppb). This assay is also being employed to identify induced mutants and/or other naturally occurring sectors deficient in trichothecene mycotoxin production. Results indicated that ELISA is a sensitive and rapid assay method to quantify trichothecenes produced by this bioherbicidal fungus and in certain plant tissues treated with trichothecenes. [ABSTRACT FROM AUTHOR]

The extent of variation in aggressiveness, growth and pigmentation in culture, phytotoxin production and fatty acid profile were determined in a population of 55 isolates of Cercospora piaropi, a fungus used as a biocontrol agent of the aquatic weed water hyacinth ( Eichhornia crassipes). Besides differences in the colour of mycelium and diffusible pigments in culture, isolates of C. piaropi grown under standard conditions differed significantly in their ability to produce the phytotoxin cercosporin, as well as in aggressiveness and growth rate. A positive correlation existed between the ability of the isolates to produce cercosporin and their aggressiveness, and a negative correlation between growth rate and cercosporin production or growth rate and aggressiveness. Based on thin-layer chromatographic separation of extracts and comparison with beticolin-1, used as a standard, there was no evidence of production of beticolins. In discriminant analysis, fatty acid methyl ester (FAME) profiles had low resolution for differentiating populations among isolates of the fungus, and the level of resolution was influenced by the age of the colonies. Diffusible pigments in culture and cercosporin production are useful adjuncts to aggressiveness screening for choosing the most effective isolate of C. piaropi for biological control. [ABSTRACT FROM AUTHOR]

Abstract: Molecular genetic tools and concepts are in relentless and continuous development, affecting every field of biology. Biological control of weeds, an applied science with over a century of history, is no exception. There are many examples of successful biocontrol of weeds, in some cases quite spectacular. However, biocontrol is not applicable to every weed challenge, in large part due to the limitations of available biocontrol agents. Indeed, one cannot realistically expect that naturally occurring agents have serendipitously evolved to meet all of man''s weed control needs. In cases where agents are lacking, molecular biology may be able to improve biocontrol, reduce dependence on chemical herbicides, and control intractable weed species. In theory, any biological weed control strategy could be improved through molecular biology, whether by improvement to a biocontrol agent (e.g. increased lethality, improved specificity, ability to work in concert with other pest management tactics), improvement of the crop (e.g. improved weed-inhibiting properties), by increasing knowledge about the evolution of the target and its natural enemies to assist the search for and selection of classical biocontrol agents, or even by genetic manipulation of the target weed itself. Molecular genetic technology can enable novel strategies that would not be possible in its absence, as well as allow weed researchers to adapt molecular solutions from other fields, including biocontrol of other pests or fields only remotely connected to weed biocontrol. This paper will review concepts of weed biocontrol and molecular biology applications to weed control, as well as propose novel weed-control strategies. [Copyright &y& Elsevier]

The bioherbicidal fungus, Colletotrichum truncatum (Schwein.) Andrus & Moore, was tested at different inoculum concentrations alone and in combination with, prior to or following treatment with different rates of glyphosate ( N-[phosphonomethyl]glycine) (Roundup Ultra) for the control of hemp sesbania ( Sesbania exaltata[Raf.] Rydb. ex A.W. Hill) in Roundup Ready soybean field plots. Colletotrichum truncatum and glyphosate were applied in all pair-wise combinations of 0, 1.25, 2.5, 5.0, and 10.0 × 106 spores mL−1 (i.e. 3.125, 6.25, 12.5, and 25 × 1011 spores ha−1), and 0.15, 0.30, 0.60, and 1.2 kg ha−1, respectively. Weed control and disease incidence were enhanced at the two lowest fungal and herbicidal rates when the fungal spores were applied after glyphosate treatment. The application of the fungus in combination with or prior to glyphosate application at 0.30 kg ha−1 resulted in reduced disease incidence and weed control regardless of the inoculum's concentration. At the highest glyphosate rates, the weeds were controlled by the herbicide alone. These results suggest that it might be possible to utilize additive or synergistic herbicide and pathogen interactions to enhance hemp sesbania control. [ABSTRACT FROM AUTHOR]

In field experiments conducted near Stoneville, MS, USA, in 2000 and 2001, the bioherbicidal fungus, Myrothecium verrucaria (Alb. & Schwein.) Ditmar: Fr., was tested alone and in combination with a glyphosate ( N-[phosphonomethyl]glycine) product for controlling natural infestations of the invasive vines, redvine ( Brunnichia ovata[Walt.] Shinners) and trumpetcreeper ( Campsis radicans[L.] Seem. ex Bureau). After 12 days, redvine and trumpetcreeper were controlled by 88% and 90%, respectively, through a synergistic interaction between the fungus and the herbicide, glyphosate. The disease symptomatology was characterized by rapid necrosis of the leaf and stem tissues, with mortality occurring within 72 h. Neither glyphosate alone, nor M. verrucaria alone, controlled these weeds at commercially acceptable levels (≥80%). No visual disease or herbicide damage occurred to the soybean in the treated test plots 12 days after planting. These results suggest that some formulations of glyphosate, mixed with M. verrucaria, can effectively control redvine and trumpetcreeper. [ABSTRACT FROM AUTHOR]

Copyright of Biotechnologie, Agronomie, Societe et Environnement is the property of Les Presses Agronomiques de Gembloux 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.)

In field experiments conducted over 3 years, the mycoherbicidal fungus Colletotrichum gloeosporioides, formulated either in 20% (v/v) unrefined corn oil and 0.2% Silwet L-77 surfactant or with an invert emulsion, provided season-long control of Senna obtusifolia in narrow (51 cm) rows of soybean. However, in wide (102 cm) rows, one application of either formulation failed to provide season-long control of S. obtusifolia, and two applications were required to achieve season-long weed control. In narrow (51 cm) rows, one application of the fungus either in unrefined corn oil or an invert emulsion controlled S. obtusifolia an average of >90%, and a second application was not required for season long weed control. Soybean yields in wide-row plots treated with two applications of either the fungus/corn oil or fungus/invert emulsion, or with a single application of the fungal treatments in narrow-row soybean plots, were not significantly different from weed-free control plots, or from plots treated with the herbicide chlorimuron. These results suggest that row spacing can affect mycoherbicidal efficacy of this fungus for controlling S. obtusifolia. [ABSTRACT FROM AUTHOR]

Many microbes have bioherbicidal activity, and several phytopathogenic fungi and bacteria have been patented as weed-control agents. The phytotoxic components of most agents have not been elucidated, but some phytotoxins and other secondary compounds produced by such microbes may be toxic to mammalian systems. Furthermore, few rigorous assessments have addressed uptake, translocation, metabolism, and persistence of these phytotoxins (some of which have not been identified), or the environmental effects of repeated augmentative applications of these microorganisms on long-term impact, environmental fate, or interactions with other microbial communities. Generally, there is a lack of definitive research on the overall toxicological risk of bioherbicidal microorganisms to the degree achieved or required for synthetic herbicides. This article presents a brief overview of bioherbicides (microorganisms and/or their phytotoxins), with emphasis on the toxicity of certain bioherbicides, and general considerations of risks associated with bioherbicidal use. A subsequent article presents some of our research results and future research directions on efforts to develop the bioherbicidal fungus Myrothecium verrucaria as a safe and efficacious bioherbicide have been published elsewhere. [ABSTRACT FROM AUTHOR]

Starfruit, Damasonium minus (R. Br.) Buch, is a herbicide-resistant, aquatic-weed occurring in Australian rice fields. The fungal pathogen Plectosporium alismatis (Oudem) W.M. Pitt, W. Gams & U. Braun is a potential mycoherbicide for the control of this weed. Previous work showed that the fungus can suppress the growth of starfruit juvenile plants. This paper reports the effect of environmental factors on the disease development on starfruit at the floating-leaf stage. Fungal inoculation of plants in advanced phases of floating leaf stage reduced significantly (P<0.05) the green leaf area, but only when the percentages of diseased areas were deducted. However, inoculation when the first floating leaf was emerging reduced significantly (P<0.001) both, plant dry above-ground biomass and leaf area. [ABSTRACT FROM AUTHOR]

The fungus Myrothecium verrucaria (MV) has previously been shown to have potential as a bioherbicide for kudzu (Pueraria lobata) control. It has also been shown that MV wild-type (MV-wt) often forms sectors, when grown on various nutrient media. Experiments compared MV-wt and MV sector efficacy when grown on agar or on rice grains. In greenhouse evaluations of sectors, applied as foliar sprays in water or in other formulations (corn oil, surfactant, and corn oil plus surfactant) for efficacy against kudzu seedlings, some sectors possessed bioherbicidal activity equal that of MV-wt, but others exhibited lower activity. Without a dew period, aqueous formulations of MV-wt, a yellow sector, and a white sector provided zero control, but all three isolates were active without a dew period when formulated in corn oil, Silwet L-77 surfactant, and in surfactant plus corn oil. Generally, the yellow sector was less effective than the other two isolates in any formulations, and the MV-wt and white sector provided approximately 100% mortality of the test plants. Dew (10 h) increased weed control to 100, 33, and 65%, respectively, for MV-wt, the yellow sector and the white sector. All isolates provided nearly 100% control in the oil and surfactant formulations with a dew period compared to treatments receiving no dew. Soil incorporation studies were also performed to compare MV-wt efficacy of preparations grown on agar versus growth on rice grains. Higher efficacies (1.75-3.3-fold increase) were obtained from rice grain preparations compared to preparations grown on agar, when preparations were incorporated at several rates into soil prior to planting. Cell-free extracts of the MV-rice cultures were also phytotoxic to kudzu seedlings up to the eight- to 10-leaf growth stage. Thus, formulation, growth media, and the application method are important determinants in the efficacy of MV and MV sectors on kudzu seedlings. [ABSTRACT FROM AUTHOR]