Chemical control and herbicide resistance of hairy fleabane [Conyza bonariensis (L.) Cronquist] in Jordan

Two field experiments were conducted to evaluate the effectiveness of 12 herbicides in controlling hairy fleabane [ Conyza bonariensis (L.) Cronquist] in a date palm orchard located in the central Jordan valley during the spring of 2017. Results showed that C. bonariensis resists paraquat (2.5, 5 and 7.5kgha -1 ), oxadiazon (5kgha -1 ) and oxyflourfen (3.3kgha -1 ) herbicides applied at normal or higher than the recommended rates. None of the three herbicides was significantly effective against the weed and treated plants continued growing normally similar to those of untreated control. Higher rates (10-fold of the recommended rates) of the same herbicides failed to control the weed. The effect of other tested herbicides on the weed was varied with bromoxynil plus MCPA (buctril ® M), 2,4-D- iso-octyl ester, glyphosate, glyphosate trimesium and triclopyr were most effective and completely controlled the weed at recommended rates of application. Testing paraquat, oxadiazon and oxyflourfen using the normal recommended and 10-fold higher rates on two populations of C. bonariensis grown from seeds of the date palm and al-Twal (another site in the Jordan Valley) weed populations and grown in pots under glasshouse conditions showed that Date palm population was resistant to the three herbicides at both application rates while al-Twal site population was highly susceptible and completely controlled at normal and high rates of the three herbicides. It is concluded that certain populations of C . bonariensis developed resistance to paraquat, oxadiazon and oxyflourfen but control of this weed was possible using other herbicides of different mechanism of action. Herbicide rotation or other nonchemical weed control methods have been suggested to prevent or reduce the buildup and spread of resistant populations of this weed species. These results represent the first report on herbicide resistance of C. bonariensis in Jordan.

Morfoanatomía comparada del vástago adulto de Conyza bonariensis var. bonariensis y C. bonariensis var. angustifolia (Asteraceae)

Conyza bonariensis, una especie medicinal e importante maleza nativa de Argentina, está representada por las variedades C. bonariensis var. bonariensis y C. bonariensis var. angustifolia. El objetivo del trabajo es comparar morfológica y anatómicamente los vástagos de ambas variedades en su etapa adulta, con el fin de contribuir a su identificación. Se analizaron ejemplares en estado vegetativo y reproductivo recolectados de poblaciones naturales. Los vástagos fueron divididos en tres zonas, superior, media e inferior, para caracterizar su morfoanatomía por medio de técnicas convencionales para microscopía óptica y electrónica de barrido. Entre las características halladas con valor diagnóstico se describen el tamaño, forma y margen de las hojas, tipo de indumento, densidad de tricomas y de estomas, forma de las células del clorénquima en los tallos y tipo de mesófilo. Muchas de estas características no fueron constantes entre las distintas zonas del vástago analizado, particularmente en el vástago vegetativo. Estos resultados indican que existen caracteres morfoanatómicos cuali- y cuantitativos que permiten la identificación taxonómica de C. bonariensis a nivel infraespecífico, los cuales, a su vez, pueden variar según el tipo y zona del vástago adulto analizado.

Evaluation of Antimicrobial Activity of Conyza bonariensis Leaf Extracts against Clinically Isolated Fungi Causing Superficial Infection

Plants have been used since long time ago to treat infectious diseases and are considered as important sources of new antimicrobial agents. In this study, crude extracts from leaves of Conyza bonariensis were prepared using methanol, ethyl acetate, hexane, and chloroform. Antimicrobial activity of the extracts was evaluated against pathogenic fungi causing superficial infection (Candida albicans, Malassezia globosa, and Malassezia furfur). Results demonstrated that all extracts had different effects against all the tested fungi with the exception of crude extract using hexane which did not show any effect against M. furfur. A strong effect was observed with chloroform and hexane extracts on C. albicans (32.60 ± 4.69 mm and 27.00 ± 1.00 mm), respectively. While, ethyl acetate and methanol extracts showed the best effect against M. furfur (30.80 ± 1.71 mm and 27.00 ± 1.00 mm), respectively. Moreover, the ethyl acetate showed a considerable effect on M. globosa (25.03 ± 1.05 mm). Minimum inhibitory concentration (MIC) of the fractions was also determined by the microbroth dilution method. The results recorded as the MIC values of the tested extracts against fungi varied from 0.19 ± 0.00 to 66.66 ± 2.86 mg/mL. Ethyl acetate was the best and powerful extract with the lowest MIC value of 0.190.19 ± 0.00 mg/mL for all tested fungi followed by chloroform and methanol extracts with the MIC values ranging from 0.19 ± 0.00 to 0.78 ± 0.00 mg/mL and 0.84 ± 0.68 to 1.56 mg/mL, respectively. Concerning minimum bactericidal concentration (MFC), ethyl acetate was the most potent extract with a MFC value of 0.190.19 ± 0.00 mg/mL for C. albicans and M. furfur. Higher (0.39 mg/mL) MFC was recorded against M. globosa by this extract. In conclusion, solvent extracts of some C. bonariensis can be used to treat infections with pathogenic fungi such as C. albicans, M. furfur, and M. globosa. Further studies should consider this plant as one of the best candidates for the discovery of potent antimicrobial compounds that treat superficial infections.

Effect of Soil Moisture Regimes on the Glyphosate Sensitivity and Morpho-Physiological Traits of Windmill Grass (Chloris truncata R.Br.), Common Sowthistle (Sonchus oleraceus L.), and Flaxleaf Fleabane [Conyza bonariensis (L.) Cronq.]

The glasshouse study was conducted with the objectives of (i) investigating the effect of soil moisture variations on the control efficiency of glyphosate on windmill grass (Chloris truncata R.Br.), common sowthistle (Sonchus oleraceus L.), and flaxleaf fleabane [Conyza bonariensis (L.) Cronq.], (ii) evaluating the tolerance of tested weed species under soil moisture variations, and (iii) determining the morphological and physiological characteristics of these species to partially explain herbicide tolerance under periods of reduced soil moisture availability (RSM). The species’ tolerance to glyphosate increased significantly under reduced soil moisture availability (p < 0.001). The lethal dose to cause herbicide injury or biomass reduction by 50% (LD50) and 80% (LD80) in relation to untreated control for water-stressed plants [i.e., moderate soil moisture availability (MSM) and RSM] was significantly higher than that of plants grown under high soil moisture availability (HSM). The tolerance factor (TF) for C. truncata, S. oleraceus, and C. bonariensis, in terms of biomass reduction under RSM, was 2.6, 2.4, and 2.6, respectively, as compared to HSM. The results showed that the glyphosate sensitivity, especially at the sub-lethal rates, of the three weed species under study decreased as soil moisture availability reduced (p < 0.01). Overall glyphosate efficacy, in relation to the recommended rate, was unaffected, except for C. truncata; the weed survived the highest tested glyphosate rate [750 g active ingredient (a.i.) ha−1] under RSM. There was significant interaction between weed species and soil moisture regimes for weed morpho-physiological traits (p < 0.001), with reduced soil moisture having a more influential impact on the growth of C. bonariensis and S. oleraceus compared to C. truncata. Changes in the leaf characteristics, such as increased leaf thickness, higher leaf chlorophyll content, reduced leaf area, and limited stomatal activity for all the tested weed species under MSM and RSM in relation to HSM, partially explain the tolerance of species to glyphosate at sublethal rates.

Predictive phytotoxic value of water-soluble allelochemicals in plant extracts for choosing a cover crop or mulch for specific weed control

Cover crops and mulches have become an alternative for soil management in vineyards due to the agronomic, environmental, and economic advantages, especially the possibility of weed control. Implicitly to this objective lies the idea of assessing the potential herbicide effect of the allelochemicals released by different cover crop and mulch species. With this objective, the present work evaluated the phytotoxic effects of 12 aqueous extracts of selected species with potential use as a cover crop or mulch: a Bromus species mixture (B. hordeaceus L. and B. rubens L.), Festuca arundinacea Schreb., Hordeum murinum L., H. vulgare L., Vulpia ciliata Dumort., Medicago rugosa Desr., M. sativa L., Trifolium subterraneum L., T. incarnatum L., Phacelia tanacetifolia Benth., Sinapis alba L., and Pinus sylvestris L.,on the germination and early growth of three troublesome weeds (Conyza bonariensis (L.) Cronquist, Aster squamatus (Spreng.) Hieron, and Bassia scoparia (L.) A. J.). The different in vitro bioassays showed that aqueous extracts of some species significantly inhibited or reduced germination and root and shoot growth of the target weed species in a dose-response manner. Germination of A. squamatus and C. bonariensis was reduced by 100-80% by the different extracts applied at 50% concentration, and completely blocked at 100% concentration, except for M rugosa extract to which both species showed less sensitivity. Root elongation of A. squamatus was absolutely inhibited under every extract and concentration, whereas C. bonariensis root growth showed only some tolerance to the crude extracts of F. arundinaceaand P. sylvestris. Bassia scoparia was relatively tolerant to the aqueous plant extracts, except for T. subterraneum crude extract, which reduced total germination by 80%; otherwise, B. scoparia showed higher general sensitivity of shoot growth than the other two weed species. The chemical profiles of phenolic compounds of the aqueous extracts were obtained and identified by HPLC-DAD, the phenolic profiles of H. murinum, V. ciliata, and M. rugosa being reported in this work for the first time. Using stepwise regression, the influence of certain phenolic compounds from the aqueous extracts on the germination and early growth of weeds was predicted. Among other significant compounds, the flavonoid naringenin identified in T. subterraneumaqueous extract at 8.09 µg·mL-1 was predicted to underlie its specific phytotoxicity on B. scoparia germination. These results support the use of cover crops and mulches in weed management and can help to select the most suitable species to adopt according to the target weed species. Highlights The phytotoxic nature of the aqueous extracts of twelve conventional and novel cover crops and mulch species was demonstrated on three troublesome weed species in vineyards. Phenolic acids and flavonoids of the twelve aqueous extracts were identified and quantified by HPLC-DAD, and, by regression analysis, some allelochemicals were postulated as responsible for the phytotoxic effects. The water-soluble phenolic profiles of three potential cover crops, namely Hordeum murinum, Vulpia ciliata, and Medicago rugosa, are reported for the first time. In vitro germination and early root growth of Conyza bonariensis and Aster squamatus were almost entirely restricted by any of the twelve plants' aqueous extracts and presumably by the joint action of their particular allelopathic compounds. Bassia scoparia germination was relatively much less sensitive to the extracts, except for Trifolium subterraneum, for which the flavonoid naringenin was predicted to underlie its specific phytotoxicity.

Molecular Mechanisms Responsible for In Vitro Cytotoxic Attributes of Conyza bonariensis Extract against Lymphoblastic Leukaemia Jurkat Cells

Background: Conyza bonariensis is known to have anti-cancer properties. Objective: The study investigated the in vitro pro-apoptotic properties of Conyza bonariensis (C. bonariensis) towards human lymphoblastic leukemia Jurkat cells. Methods: C. bonariensis are extracted with non-polar solvent by maceration. MTS cell viability assay was employed to determine the cytotoxic activity of the extract towards human leukemia Jurket cells and normal Peripheral Blood Mononuclear Cells (PBMCs) cells. The phytochemical composition of the extract was chemically characterized using HPLC. Flow cytometric studies (FACS) were conducted to explore the pro-apoptotic potential of the extract. Western blot studies were employed to identify the molecular targets involved in the induction of apoptosis. Results: The n-hexane extract showed selective cytotoxic activity towards Jurkat cells. FACS analysis indicated that the extract induced early and late apoptosis in Jurkat cells. Western blot studies revealed that the extract down-regulated the expression of DNMT1, SIRT1, and UHRF1 with a simultaneous up-regulation of the expression of p73 and caspases-3 proteins. HPLC characterization of the extract revealed the presence of phenolic compounds. Conclusion: Overall these findings demonstrate that the anticancer effects of a Conyza bonariensis extract towards human lymphoblastic leukemiais due to the modulation of the activity of multiple oncogenic and tumor suppressor proteins and that its phenolic content is involved are proposed to be responsible for these activities.