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Background Tomato is one of the widely cultivated crops worldwide that is affected by several pests, such as fungi (Fusarium oxysoporum, Alternaria solani), bacteria (Pectobacterium carotovorum) and weeds (Cyperus iria L., Amaranthus spinosus). A growing interest has emerged for developing plant-derived pesticidal compounds to counteract these pests. One attractive alternative is to use barnyard grass (Echinochloa crus-galli), known to be widely resistant to synthetic herbicides, as a potential biopesticide compound source. Results Phytochemical screening of the crude extract showed that phenolic compounds were the most abundant component present in barnyard grass. The crude extract was evaluated for antifungal, antibacterial and herbicidal activities. Bioassays showed inhibition against F. oxysporum (10.73 ± 1.30%) and A. solani (20.47 ± 3.51%), the causative agent of Fusarium rot and early blight disease in tomato, respectively. Antibacterial activity against P. carotovorum gave a mean zone of inhibition (paper disc diffusion assay) of 17.00 ± 1.00 mm and an IC50 (dose-response assay) of 2.26 mg mL-1 was observed. Dose-responsive herbicidal activity on the lettuce seed germination bioassay produced an IC50 of 459.30 ppm. Selectivity studies showed inhibition towards C. iria and A. spinosus with no effect on tomato. Lastly, bioassay-guided fractionation coupled with untargeted metabolomics studies using ultra-performance liquid chromatography with diode array detection-tandem mass spectrometry mass analyses revealed loliolide and tricin as the putative metabolites present in barnyard grass. Conclusion To date, this is the first reported study on using barnyard grass as a potential alternative biopesticide against tomato pests such as fungi, bacteria and weeds. © 2021 Society of Chemical Industry.

Resistance to penoxsulam among barnyardgrass populations is prevalent in rice fields in China. Seeds of penoxsulam-resistant (AXXZ-2) and penoxsulam-susceptible (JLGY-3) barnyardgrass populations, as well as the seeds of two rice varieties, including Wuyungeng32 (WY) and Liangyou669 (LY), were planted in plastic pots and then treated with a rate titration of acetochlor, anilofos, butachlor, clomazone, oxadiazon, pendimethalin, pretilachlor, pyraclonil, or thiobencarb. The two barnyardgrass populations exhibited similar susceptibility to acetochlor, anilofos, butachlor, oxadiazon, pretilachlor, or pyraclonil. However, the susceptibility differed between the barnyardgrass populations in response to clomazone, pendimethalin, and thiobencarb. For AXXZ-2, herbicide rates that caused 50% reduction in shoot biomass from the nontreated control (GR50) were 179, >800, and 1,798 g ha−1 for clomazone, pendimethalin, and thiobencarb, respectively; whereas JLGY-3 GR50 values were 61, 166, and 552 g ha−1, respectively. Both rice varieties demonstrated excellent tolerance to acetochlor, butachlor, oxadiazon, pretilachlor, and thiobencarb. However, substantial rice damage was observed when anilofos and clomazone were used. Anilofos at 352 g ha−1 and clomazone at 448 g ha−1 reduced rice shoot biomass by 41% and 50% from the nontreated, respectively. Averaged across herbicide rates, clomazone use resulted in a reduction in rice shoot biomass from that of the nontreated control by 52% and 34% for WY and LY, respectively; and pendimethalin use resulted in a reduction in rice shoot biomass from the nontreated control by 25% and 9% for WY and LY, respectively.

Barnyardgrass [Echinochloa crus-galli (L.) P. Beauv.] is a problematic weed in rice (Oryza sativa L.) fields. Overapplication of herbicides causes environmental pollution and the emergence of resistant weeds, and integrated weed management methods can reduce dependence on herbicides. The growth of E. crus-galli and rice seedlings was shown to be significantly inhibited by high concentrations of fulvic acid (FA, C14H12O8) under flooding conditions (HF, 0.80 g L−1) (P < 0.05). In contrast, seedling growth was promoted by the application of very low concentrations of FA (LF, 0.02 g L−1). The activities of glutathione S-transferase (GST) and antioxidant enzymes, including total superoxide dismutase (T-SOD), peroxidase (POD), and catalase (CAT), in E. crus-galli seedlings were enhanced by the LF treatment; while POD activity decreased and GST, T-SOD, and CAT activity was not significantly altered by the HF treatment. The metabolomic and transcriptomic analyses showed that FA regulated E. crus-galli seedling growth by affecting the synthesis of indole derivatives and flavonoid compounds. Compared with the blank control (CK, 0 g L−1), the levels of four indole derivatives were upregulated under the HF treatment, and the indole derivatives were slightly downregulated under the LF treatment. The flavonoids, including naringenin, naringenin chalcone, eriodictyol, kaempferol, and epigallocatechin, were downregulated under HF treatment, and the growth of E. crus-galli was reduced. In contrast, the metabolism and transcription of flavonoids were not significantly altered by the LF treatment. The addition of 0.80 g L−1 FA obviously inhibited the growth of newly sprouted E. crus-galli, whereas rice growth was significantly promoted 8 d after rice planting (P < 0.05). The application of FA, therefore, might be a potential integrated weed management method to control the damage caused by E. crus-galli in paddy fields.

In this study, the phytoremediation potential of municipal sewage sludge was studied by Echinochloa crus galli and Hibiscus cannabinus plants with special reference to total organic carbon, total Kjeldahl nitrogen, total phosphorus, sodium uptake ratio, pH, electrical conductivity and lead and cadmium heavy metals. Design and construction of E. crus galli beds in Kermanshah and E. crus galli and H. cannabinus in Sarpol Zahab wastewater treatment plant was carried out at the outdoor. In Kermanshah wastewater treatment plant, the removal efficiency of total organic carbon in phytoremediation by E. crus galli increased with maturity and reached 62 ± 1.3% (P

Barnyardgrass [Echinochloa crus-galli(L.) P. Beauv] is the foremost weed in rice (Oryza sativaL.) systems, and its control is crucial to successful rice production. Quinclorac, a synthetic auxin herbicide, has been used effectively to manageE. crus-galli. However, occurrences of quinclorac-resistant genotypes are frequently reported, and its resistance evolution has led to questions about the continued utility of quinclorac for grass control. Identification of the resistance mechanism(s) of resistant genotypes will facilitate development of integrated weed management strategies that sustain quinclorac use for management ofE. crus-galli. We evaluated the responses to quinclorac of two contrasting genotypes: E7 (resistant, R) and LM04 (susceptible, S). Quinclorac induced ethylene and cyanide biosynthesis in the S-genotype. Both genotypes responded similarly to an increasing application of exogenous 1-carboxylic acid aminocyclopropane (ACC) and potassium cyanide, and their growth was inhibited at higher doses. The key mechanism for cyanide (HCN) detoxification in plants, β-cyanoalanine synthase (β-CAS) activity, was evaluated in both genotypes, and no significant difference was observed in the basal activity. However, quinclorac significantly induced β-CAS–like activity in the S-genotype, which is consistent with the increased synthesis of ethylene and cyanide. This work suggests that the resistance to quinclorac of the E7 R-genotype is likely related to an alteration in the auxin signal transduction pathway, causing a lower stimulation of ACC synthase and, therefore, limited synthesis of ethylene and HCN after quinclorac treatment.

DOR: 98.1000/2383-1251.1398.6.151.12.2.1575.41 Extended abstract Introduction: Due to their aggressive and competitive habits, weeds inhibit the growth of valuable plants. Interference in plants includes environmental competition and allelopathy (Autotoxicity and hetrotoxicity). In hetrotoxicity, chemical compounds released from plants are able to effect the neighboring plants. Proper management of weeds and the exploitation of their hetrotoxicity potential can reduce losses caused by weeds. This could also represent an effective step towards the reduction of the use of herbicides. Therefore, the purpose of this study was to evaluate the effect of hetrotoxicity potential of aqueous extract of various organs of Malva sylvestris L. weed on traits of germination and photosynthetic pigments of Echinochloa crus-galli L. Material and Methods: An experiment was conducted to evaluate the effect of hetrotoxicity potential of aqueous extract of Malva sylvestris L. weed including the stem, leaf and flower as well as their mixture on traits of germination and photosynthetic pigments of Echinochloa crus-galli L. as a completely randomized design in three replications in Weeds Science Laboratory of Gonbad Kavous University in 2017. For this experiment, aerial parts of M. sylvestris were first collected at the flowering stage from Ramian field. They were subsequently separated with great care and were powdered. Then from them, 5% suspensions (weight/volume) were prepared, using distilled water. Finally, the extract of each organ of M. sylvestris was added to Petri dishes containing E. crus-galli seeds. After the 7th day, traits such as rate and percentage of germination, radical and shoot elongation, vigor index, total content of chlorophyll a and b and carotenoids were measured. Results: The results showed that various organs of M. sylvestris and their mixture had different inhibitory effects on traits of germination and seedling length of E. crus-galli weed. The highest inhibition effects on rate and germination percentage and elongation of radical and shoot of E. crus-galli were obtained using leaf extract of M. sylvestris about 64.04, 64.37, 87.69, 62.81%. In this study, radical length is more affected under hetrotoxic compounds of various organs of M. sylvestris, as compared with shoot length. Based on the results, various organs of M. sylvestris and their mixture also have different inhibitory effects on chlorophyll and carotenoid content of E. crus-galli weed. It seems that the differential effects among different organs of M. sylvestris are a function of the threshold concentration of allelochemicals to hetrotoxic compounds of the organs, which causes various response by E. crus-galli. Conclusion: Given the evidence for the effect of hetrotoxicity potential of various organs of M. sylvestris on traits of germination and pigments of chlorophyll and carotenoid of E. crus-galli and huge biomass generated, it is advisable to exploit allelochemical compounds of this plant as bio-herbicides. Highlights: 1- Study of the the effect of hetrotoxic potential of Malva sylvestris weed on germination characteristics and photosynthetic pigments of Echinochloa crus-galli in Ramian field. 2- E. crus-galli weed exhibits great sensitivity to hetrotoxic compounds of various organs of M. sylvestris, especially the leaves. 3- Allelopathic characteristics of M. sylvestris weed have huge potentials for the production of bio-herbicides.

Expression of genes involved in diterpene biosynthesis, especially momilactone and gibberellins (GAs), in rice plants (Oryza sativa L.) in response to barnyard grass (Echinochloa crus-galli) stress was examined. The three analyzed class II diterpene synthases had the highest fold change expression. Transcription patterns of genes for two homologs of momilactone synthases, OsMAS and OsMAS2, suggests their distinct roles in response to the presence of barnyard grass.

Weeds infest rice causing high yield losses, leading to the increasing use of herbicides for weed control. However, many weeds have evolved resistance to common commercial herbicides, including penoxsulam, metamifop and quinclorac. This study investigated the weed control effect and the phytotoxicity mechanism of florpyrauxifen-benzyl, a novel synthetic auxin herbicide registered for weed management in rice fields in China. The greenhouse study showed that florpyrauxifen-benzyl was highly efficient (GR50

The present study was aimed at investigating the allelopathic effects of a crude extract from Chromolaena odorata (L.) R.M.King and H.Rob. (Siam weed). The effects of 70% crude ethanol extract from the whole plant, leaf, stem, and root on the germination and growth of Echinochloa crus-galli and Amaranthus viridis seedlings were evaluated using Petri-dish tests under laboratory conditions. Crude extracts from the leaf showed the highest inhibitory activity. The leaf extract (OR) was further separated by sequential solvent extraction to provide hexane (HX), ethyl acetate (ET), and butanol (BU) fractions, which were also evaluated using Petri-dish tests. The hexane fraction was significantly the most active, therefore, it was selected for formulation in a concentrated suspension and tested for its herbicidal characteristics. The formulation showed greater early post-emergence than post- and pre-emergence activities, respectively. The physiological mechanism of the formulation was tested against E. crus-galli and showed that chlorophyll a and b and the carotenoid contents of the leaf dramatically decreased when the concentration was increased, suggesting its ability to disrupt the process of photosynthesis. As thiobarbituric acid reactive substances also occurred in the leaf of E. crus-galli, this suggests lipid peroxidation and cell disruption. These results represent the possibility that C. odorata extract contains inhibitory compounds with herbicidal activity and could be used as an early post-emergence herbicide for weed control.

Echinochloa crus-galli is a major weed in rice fields in China, and quinclorac has been long used for its control. Over-reliance of quinclorac has resulted in quinclorac resistance in E. crus-galli. Two resistant (R) E. crus-galli populations from Hunan, China were confirmed to be at least 78-fold more resistant to quinclorac than the susceptible (S) population. No difference in foliar uptake of 14C-labelled quinclorac was detected between the R and S plants. However, a higher level of 14C translocation and a lower level of quinclorac metabolism were found in the R plants. Basal and induced expression levels of β-cyanoalanine synthase (β-CAS) gene and β-CAS activity were not significantly different between the R and S plants. However, the induction expression of 1-aminocyclopropane-1-carboxylic acid oxidase (ACO1) gene by quinclorac treatment was evident in the S plants but not in the R plants. Quinclorac resistance in the two resistant E. crus-galli populations was not likely to be related to foliar uptake, translocation or metabolism of quinclorac, nor to cyanide detoxification via β-CAS. Thus, target-site based quinclorac signal reception and transduction and regulation of the ethylene synthesis pathway should be the focus for further research. Keywords: Echinochloa crus-galli, Quinclorac resistance, Quinclorac metabolism, β-cyanoalanine synthase, 1-aminocyclopropane-1-carboxylic acid synthase, 1-aminocyclopropane-1-carboxylic acid oxidase, Rice

Herbicide resistance identification is essential for effective chemical weed control. In this study, we quantified the differences in growth response between penoxsulam resistant (R) and sensitive (S) Echinochloa crus-galli populations, explored the changes in ALS, and performed genetic analyses to identify metabolic genes that are up-regulated by the application of penoxsulam and other common herbicides. The R population showed a 26.0-fold higher resistance to penoxsulam and varied resistance to most tested herbicides with indices ranging from 4.9 to 145.9. A Trp-574-Arg amino acid mutation in ALS and low penoxsulam ALS sensitivity were the main mechanisms underlying herbicide resistance. The penoxsulam resistance can be significantly reversed by two P450s inhibitors and one GST inhibitor. By RNA-Seq, thirty-six highly expressed contigs were selected, and 30 of them were up-regulated in the R population treated by penoxsulam. Many of these genes were significantly expressed when treated with pyroxsulam, metamifop, and quinclorac. These upregulated genes appear to be complementary for plant resistance to penoxsulam and other common herbicides.

Competition for shared above-ground (e.g. light) and below-ground (e.g. water and nutrients) resources among neighbouring plants is one of the main processes that affect cropping systems. This study aimed to evaluate the effects of weed shading on growth and yield production of bean plants when grown in weedy condition without below-ground competition. The experiments were organized as a split plot design with three replications. The main plots consisted of the nitrogen application rates including of 0, 70, 140 and 280 kg N ha−1 and the sub plots consisted of barnyardgrass densities including 0 (D0), 2 (D2) and 20 (D20) plants m−2. The N application rates were 0 (N0), 25 (N25), 50 (N50), 100% (N100) and 200% (N200) of the recommended N rate on the basis of seed yield goal. Biomass of common bean decreased by 30% for N0, 41% for N50, 35% for N100 and 38% for N200, as weed pressure increased from D0 to D20.. Mean reduction in 100-seed weight, seed number and seed yield caused by high weed pressure was 11, 20 and 41% compared with weed free, respectively. The weed biomass and N uptake increased by 66 and 159% as the nitrogen dose increased from N0 to N200. The highest biomass and N uptake was obtained from N200 treatment. We conclude that agronomically optimum N rates for seed yield was obtained at 140 kg N ha−1 within the range of N fertilization rates used across all weed pressure levels.

Alternative irrigation systems are viable options to reduce water footprint in rice; however, it could increase the difficulty of controlling weeds, as the water layer prevent weed emergence. Despite the environmental importance, there is no knowledge regarding effective chemical control of Echinochloa crus-galli (L.) P. Beauv. under contrasting field layouts and irrigation systems in dry-seeded rice. In this study, we quantified the efficacy of some pre-emergence (PRE) and post-emergence (POST) herbicide sequences and tank mixtures to control E. crus-galli under continuous and intermittent irrigation at two different field layouts. The experiment was conducted during three growing seasons between 2012 and 2014, in two edaphoclimatic regions of Uruguay. The rice yield was directly related to the efficacy of controlling of E. crus-galli at flowering (R2 ≈ 0.60). The efficacy of chemical options to control E. crus-galli was not affected by the irrigation or the field layout system. Clomazone PRE followed by penoxsulam was the most effective option (80% weed control). The results suggest that chemical options are available to control E. crus-galli when applying alternative field layout and irrigation systems that promote improved water efficacy in rice. We expect this new approach to control E. crus-galli be useful in reducing water needs, and hence making rice production more sustainable.

Laboratory analyses using the 1st generation bioassay were conducted in the years 2013-2014 to investigate the allelopathic potential of wateralcoholic and aqueous extracts from dry weight of rhizomes and roots as well as stems and leaves of Solidago gigantea. Analysed acceptors were two weed species, i.e. monocotyledonous Echinochloa crus-galli and dicotyledonous Amaranthus retroflexus. When the acceptors (E. crus-galli and A. retroflexus) reached the 2-leaf stage (BBCH 12) they were sprayed with wateralcoholic and aqueous extracts (at concentrations of 12.5%, 10%, 5% and 2.5%) obtained from the donor, i.e. S. gigantea. Results indicate an inhibitory effect of wateralcoholic extracts from aboveground parts (leaves and stems) of S. gigantea in relation to dry weight of E. crus-galli and A. retroflexus. The volume of dry weight reduction in acceptors was dependent on the concentration of extracts produced from the donor plant S. gigantea. Dry weight of E. crus-galli and A. retroflexus was reduced most effectively by two concentrations: 12.5% and 10%. In turn, aqueous extracts from rhizomes and roots of S. gigantea, irrespective of the applied concentration, caused an increase in dry weight of E. crus-galli and A. retroflexus. Only aqueous extracts produced from leaves and stems of S. gigantea, irrespective of their concentration, reduced dry weight in only E. crus-galli., W badaniach laboratoryjnych przeprowadzonych z użyciem biotestu I generacji w latach 2013-2014, porównywano potencjał allelopatyczny wyciągów wodnoalkoholowych oraz wodnych uzyskanych z suchej masy kłączy i korzeni oraz łodyg i liści Solidago gigantea. Akceptorami były dwa gatunki chwastów: jednoliścienny Echinochloa crus-galli oraz dwuliścienny Amaranthus retroflexus. W monecie uzyskania przez akceptory (E. crus-galli i A. retroflexus), fazy 2 liści właściwych wykonano oprysk wyciągiem wodno-alkoholowym oraz wodnym, o stężeniu 12,5%, 10%, 5% i 2,5%, otrzymanym z donora, którym było S. gigantea. Uzyskane wyniki badań wskazują na efekt inhibicyjnego odziaływania wyciągów wodno-alkoholowych sporządzonych z nadziemnych części roślin (liści i łodyg) S. gigantea w odniesieniu do suchej masy E. crus-galli oraz A. retroflexus. Wielkość redukcji suchej masy akceptorów uzależniona była od stężenia wyciągów sporządzonych z rośliny donorowej S. gigantea. Najefektywniej suchą masę E. crus-galli oraz A. retroflexus redukowały dwa stężenia: 12,5% oraz 10%. Natomiast wyciągi wodne sporządzone z kłączy i korzeni S. gigantea, niezależnie od zastosowanego stężenia, powodowały zwiększenie suchej masy E. crus-galli oraz A. retroflexus. Jedynie wyciągi wodne otrzymane z liści i łodyg S. gigantea, niezależnie od stężenia, powodowały redukcję suchej masy E. crus-galli.

Field and greenhouse studies were conducted to evaluate the antagonism potential of glufosinate applied sequentially or mixed with graminicides on barnyardgrass control. Applications of glufosinate alone provided variable control throughout the growing season in both field and greenhouse experiments. In the field, barnyardgrass control was not adversely affected by glufosinate- and clethodim-mix applications or sequential applications of glufosinate before or after clethodim. Soybean yield was not affected by application timing or clethodim rate, with yield ranging from 1,748 to 2,733 kg ha−1. In the greenhouse, glufosinate applied 1 and 3 d before graminicides generally reduced barnyardgrass control compared with the graminicides applied alone. The response with quizalofop-P was not as dramatic as with the other graminicides. Although significant visual barnyardgrass control differences were detected due to application timing of glufosinate, barnyardgrass biomass with fluazifop-P and quizalofop-P did not differ between the application timings of glufosinate. However, glufosinate applied 1 and 3 d before clethodim had significantly greater biomass compared with glufosinate applied 1 and 3 d after clethodim. The differences in environmental conditions and growth stages at the time of application may have contributed to barnyardgrass control response differences between the field and greenhouse experiments. Although barnyardgrass control in the field was not affected by glufosinate application timing, data from the greenhouse indicate potential exists for reduced control if glufosinate is applied 1 or 3 d before graminicides.

Six different ortho-disubstituted disulfides were synthesized and evaluated in wheat coleoptiles bioassays. The most active ones were evaluated on seeds of four different plant species (Solanum lycopersicum L., Lolium rigidum Gaudin, Echinochloa crus-galli (L.) Beauvois, and Urochloa decumbens (Stapf) R. D. Webster) to evaluate their effects on the germination and plant growth, presenting, in general, higher activity than the model herbicide Logran. The results shown in this study indicate that these compounds are potential candidates as herbicide leads for weed control in agriculture.

Amino acids have a wide range of biological activities, which usually rely on the stereoisomer presented. In this study, glycine and 21 common α-amino acids were investigated for their herbicidal property against Chinese amaranth (Amaranthus tricolor L.) and barnyard grass (Echinochloa crus-galli (L.) Beauv.). Both d- and l-isomers, as well as a racemic mixture, were tested and found that most compounds barely inhibited germination but moderately suppressed seedling growth. Various ratios of d:l-mixture were studied and synergy between enantiomers was found. For Chinese amaranth, the most toxic d:l-mixtures were at 3:7 (for glutamine), 8:2 (for methionine), and 5:5 (for tryptophan). For barnyard grass, rac-glutamine was more toxic than the pure forms, however, d-tryptophan exhibited greater activity than racemate and l-isomer, indicating the sign of enantioselective toxicity. The mode of action was unclear, but d-tryptophan caused bleaching of leaves, indicating pigment synthesis of the grass was inhibited. The results highlighted the enantioselective and synergistic toxicity of some amino acids, which relied upon plant species, chemical structures, and concentrations. Overall, our finding clarifies the effect of stereoisomers, and provides a chemical clue of amino acid herbicides, which may be useful in the development of herbicides from natural substances.

Herbicide resistance is frequently reported in E. crus-galli globally with target and non-target site resistance mechanism to acetolactate synthase (ALS)-inhibiting herbicides. However, resistance to certain herbicides can result in increased sensitivity to other herbicides, a phenomenon called negative cross-resistance. The objective of this study is to identify the occurrence of negative cross-resistance (NCR) to the pro-herbicide clomazone in populations of E. crus-galli resistant to ALS inhibitors due to increased metabolization. Clomazone dose-response curves, with and without malathion, were performed in imazethapyr-resistant and -susceptible E. crus-galli biotypes. CYPs genes expression and antioxidant enzymes activity were also evaluated. The effective dose to reduce 50% (ED50) of dry shoot weight obtained in the clomazone dose-response curves of the metabolic based imazethapyr-resistant and -susceptible biotypes groups were 22.712 and 58.745 g ha−1, respectively, resulting in a resistance factor (RF) of 0.37, indicating the occurrence of NCR. The application of malathion prior to clomazone increased the resistance factor from 0.60 to 1.05, which indicate the reversion of the NCR. Some CYP genes evaluated were expressed in a higher level, ranging from 2.6–9.1 times according to the biotype and the gene, in the imazethapyr-resistant than in -susceptible biotypes following clomazone application. Antioxidant enzyme activity was not associated with NCR. This study is the first report of NCR directly related to the mechanism of resistance increased metabolization in plants. The occurrence of NCR to clomazone in E. crus-galli can help delay the evolution of herbicide resistance.

The levels of resistance to glyphosate of 13 barnyard grass (Echinochloa crus-galli) populations harvested across different agriculture areas in the Southern Iberian Peninsula were determined in greenhouse and laboratory experiments. Shikimate accumulation fast screening separated the populations regarding resistance to glyphosate: susceptible (S) E2, E3, E4, and E6 and resistant (R) E1, E5, E7, E8, E9, E10, E11, E12, and E13. However, resistance factor (GR50 E1–E13/GR50 E6) values separated these populations into three groups: (S) E2, E3, E4, and E6, (R) E1, E5, E7, E8, and E9, and very resistant (VR) E10, E11, E12, and E13. 14C-glyphosate assays performed on two S populations (E2 and E6) showed greater absorption and translocation than those found for R (E7 and E9) and VR (E10 and E12) populations. No previous population metabolized glyphosate to amino methyl phosphonic acid (AMPA) and glyoxylate, except for the E10 population that metabolized 51% to non-toxic products. The VR populations showed two times more 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) activity without herbicide than the rest, while the inhibition of the EPSPS activity by 50% (I50) required much higher glyphosate in R and VR populations than in S populations. These results indicated that different target-site and non-target-site resistance mechanisms were implicated in the resistance to glyphosate in E. crus-galli. Our results conclude that resistance is independent of climate, type of crop, and geographic region and that the level of glyphosate resistance was mainly due to the selection pressure made by the herbicide on the different populations of E. crus-galli studied. This work was funded by the Asociacion de Agroquímicos y Medioambiente and by national funds through the Fundação para a Ciência e Tecnologia, I.P. by the project UIDB/05064/2020 (VALORIZA).

Background Clausena lansium (Lour.) Skeels, belonging to the genus Clausena of the family Rutaceae, has a wide range of medical and agricultural activities. Previous studies on agricultural activities have shown that C. lansium extracts and some components have obvious herbicidal activities. In order to study systematically herbicidal activity of this plant, we studied the herbicidal effect of ethyl acetate (EtOAc) extract from the stems and leaves of this plant and further isolated the active compounds. Results The EtOAc extract inhibited the growth of roots and shoots of Echinochloa crus-galli (L.) Beauv., and the inhibitory effect of the EtOAc extract on roots were stronger than those on shoots with half maximal inhibitory concentration (IC50 ) values of 420.45 and 585.05 mg L-1 , respectively. Fifteen compounds were subsequently isolated and identified from the stems and leaves of C. lansium, including nine O-monoterpenoid furanocoumarins and six cinnamamides. Our results showed that most compounds exhibited varying degrees of herbicidal activities to E. crus-galli. Among them, compounds 3, 8, and 13-15 showed the best inhibitory activities on the growth of E. crus-galli roots, with inhibition rate values ranging from 70% to 83% at a concentration of 300 mg L-1 . Compounds 1 and 2 are two new compounds, and their structures were established as 5-O-monoterpenoid furanocoumarin and 8-O-monoterpenoid furanocoumarin, and named as claulansicoumarin-A and -B, respectively. Conclusion The EtOAc extract and pure compounds showed noticeable herbicidal activities against E. crus-galli and indicated a great potential for these natural compounds to be developed as a herbicide. © 2020 Society of Chemical Industry.

Echinochloa crus-galli var. mitis has rarely been reported for herbicide resistance, and no case of quinclorac resistance has been reported so far. Synthetic auxin-type herbicide quinclorac is used extensively to control rice weeds worldwide. A long history of using quinclorac in Chinese rice fields escalated the resistance in E. crus-galli var. mitis against this herbicide. Bioassays in Petri plates and pots exhibited four biotypes that evolved into resistance to quinclorac ranking as JS01-R &gt, AH01-R &gt, JS02-R &gt, JX01-R from three provinces of China. Ethylene production in these biotypes was negatively correlated with resistance level and positively correlated with growth inhibition. Determination of the related ethylene response pathway exhibited resistance in biotypes that recorded a decline in 1-aminocyclopropane-1-carboxylic acid (ACC) content, ACC synthase oxidase activities, and less inducible ACS and ACO genes expressions than the susceptible biotype, suggesting that there was a positive correlation between quinclorac resistance and ethylene biosynthesis inhibition. Cyanides produced during the ethylene biosynthesis pathway mainly degraded by the activity of &beta, cyanoalanine synthase (&beta, CAS). Resistant biotypes exhibited higher &beta, CAS activity than the susceptible ones. Nucleotide changes were found in the EcCAS gene of resistant biotypes as compared to sensitive ones that caused three amino acid substitutions (Asn-105-Lys, Gln-195-Glu, and Gly-298-Val), resulting in alteration of enzyme structure, increased binding residues in the active site with its cofactor, and decreased binding free energy, hence, its activity was higher in resistant biotypes. Moreover, these mutations increased the structural stability of the enzyme. In view of the positive correlation between ethylene biosynthesis inhibition and cyanide degradation with resistance level, it is concluded that the alteration in ethylene response pathway or at least variation in ACC synthase and ACC oxidase enzyme activities&mdash, due to less relative expression of ACS and ACO genes and enhanced &beta, CAS activity, as well as mutation and increased relative expression of EcCAS gene&mdash, can be considered as a probable mechanism of quinclorac resistance in E. crus-galli var. mitis.

Dose-response experiments were conducted to assess the sensitivity of one susceptible and three putative resistant (R1, R2, and R3) barnyardgrass [Echinochloa crus-galli (L.) P. Beauv.] biotypes to florpyrauxifen-benzyl and cyhalofop-butyl alone and as a formulated premix. Subsequently, potential resistance mechanisms of the barnyardgrass were evaluated. Based on biomass reduction results, resistant/susceptible ratios were calculated for R1 (7.0–50), R2 (7.0–150), and R3 (18–214) biotypes. Absorption and translocation of [14C]-florpyrauxifen-benzyl decreased in R1 and R3 biotypes, but not for [14C]-cyhalofop-butyl. The metabolism of [14C]-florpyrauxifen-benzyl to [14C]-florpyrauxifen-acid was >2-fold less in resistant biotypes (9–11%) than in the susceptible biotype (23%). Moreover, the production of [14C]-florpyrauxifen-acid in susceptible barnyardgrass (not in the R biotypes) increased 3-fold when florpyrauxifen-benzyl and cyhalofop-butyl were applied in mixture compared to florpyrauxifen-benzyl applied alone. The tested barnyardgrass biotypes had no mutation in the Transport Inhibitor Response1, auxin-signaling F-box, and acetyl coenzyme A carboxylase genes. Although further studies on cyhalofop-butyl resistance with respect to analysis of specific metabolites are needed, our findings in this study demonstrates that the evolution of florpyrauxifen-benzyl resistance in multiple resistant barnyardgrass can be related to non-target-site resistance mechanisms reducing absorption and translocation of the herbicide and causing reduced conversion or rapid degradation of florpyrauxifen-acid.

The phytotoxic effects of two allelochemicals (trans-cinnamic acid and syringaldehyde) at different concentrations (1000, 100, 10, and 1 µM) on seed germination, seedling growth, and physiological and biochemical changes of Echinochloa crus-galli L. were tested by comparison to a commercial herbicide ‘Nominee’ (that is, 100 g/L bispyribac-sodium). trans-Cinnamic acid and the herbicide inhibited seed germination completely at 100 µM, whereas for syringaldehyde, complete inhibition required 1000 µM. However, with 100 µM syringaldehyde, the seed germination of the test species was 53% of the control. Allelochemicals and the herbicide delayed seed germination and significantly affected the speed of germination index (S), speed of cumulative germination index (AS), and coefficient of germination rate (CRG). The roots were more affected when nutrients were not added to the growth bioassay. In general, with the increasing concentration of allelochemicals from 100 to 1000 µM, the inhibitory effects increased. Via microscopy analysis, we found leaf blade wilting and necrosis at concentrations above 100 µM in allelochemical-treated plants. Roots of E. crus-galli treated with 1000 µM allelochemicals had black points on root nodes but had no root hairs. The anatomy of roots treated with allelochemicals (1000 µM) showed contraction or reduction of root pith cells as well as fewer and larger vacuoles compared to the control. The allelochemicals also showed remarkable effects on seedling growth, SPAD index, chlorophyll content, and free proline content in a pot culture bioassay, indicating that trans-cinnamic acid and syringaldehyde are potent inhibitors of E. crus-galli growth and can be developed as herbicides for future weed management strategies.

We previously reported that the mechanism of quinclorac resistance in Echinochloa crus-galli var. zelayensis may be closely related to ethylene biosynthesis and the detoxification of cyanide. Differences in EcCAS gene sequences and expression levels may result in higher capacity to detoxify cyanide in resistant biotypes, which may avoid cyanide accumulation and avoid more ethylene and cyanide production and then avoid damage. In the present study, we focused on the mechanism of resistance related to ethylene biosynthesis in E. crus-galli var. zelayensis. The fresh weight of susceptible and moderately resistant biotypes were significantly reduced after treatment with quinclorac. However, AOA, an ethylene biosynthesis inhibitor, reduced the impact of quinclorac. On pretreatment with AOA, ethylene production was significantly reduced in the three biotypes. The highly resistant biotype produced less ethylene compared to the other two biotypes. Three ACS and seven ACO genes, which are the key genes in ethylene biosynthesis, were obtained. The expression levels of EcACS-like, EcACS7, and EcACO1 varied in the three biotypes upon treatment with quinclorac, which could be manipulated by AOA. In summary, it is inferred that the expression of EcACS-like, EcACS7, and EcACO1 can be stimulated to varying extent after quinclorac treatment in three E. crus-galli var. zelayensis biotypes, which consequently results in varying levels of ethylene production. Lower expression of these three genes results in more resistance to quinclorac, which may also be related to quinclorac resistance in E. crus-galli var. zelayensis.

Barnyardgrass (Echinochloa crus-galli) seed samples were collected in rice fields in different locations at Mekong delta in Vietnam for herbicide resistance tests. The ALS-resistant and synthetic auxin-resistant E. crus-galli were confirmed at several locations in the Mekong Delta. The average LD90 value of bispyribac, penoxsulam and quinclorac for assessed weed populations was 33.1, 15.1 and 550.2 g a.i.ha−1 respectively. There were cross resistant barnyardgrass populations to bispyribac and penoxsulam, the LD90 value of the two ALS inhibitors for E. crus-galli was positively correlated at R2=0.39, the cross resistant population was 33.3% of total sample. The correlation analysis was not useful to evaluate the multiple resistance between quinclorac and the two ALS inhibitors, the R2 value was lower than 0.05, however, the percentage of multiple resistance weed was 36.2% of population. There was no cross resistance or multiple resistance among the 3 tested herbicides and the new synthetic auxin herbicide Rinskor™. All tested weed samples, including quinclorac-resistant populations, were effectively controlled by Rinskor™. There was no difference between control from Rinskor™ in the different herbicide resistant populations. Average LD90 value of Rinskor™ in all tested barnyardgrass was 17.1 g a.i ha−1.

Summary The genus Echinochloa (Poaceae) includes numerous problematic weeds over a wide range of ecoregions in the world. To date, molecular markers for species identification and assessing phylogenetic relationship are still limited in the genus Echinochloa. In this study, we developed seven chloroplast molecular markers based on divergent chloroplast regions of E. crus-galli and E. oryzicola. Furthermore, Marker #1 (psbA) was examined in more than 200 Echinochloa accessions and a phylogenetic tree grouped these Echinochloa accessions into four clades. Additionally, two different E. crus-galli varieties (E. crus-galli var. crus-galli, E. crus-galli var. praticola) and E. colona were successfully distinguished by this marker. The developed molecular markers contribute to better identification of Echinochloa taxa.

Harvest weed seed control is an alternative non-chemical approach to weed management that targets escaped weed seeds at the time of crop harvest. Relatively little is known on how these methods will work on species in the US. Two of the most prominent weeds in soybean production in the midsouthern US are Palmer amaranth and barnyardgrass. Typically, when crop harvesting occurs the weed seed has already either shattered or is taken into the combine and may be redistributed in the soil seedbank. This causes further weed seed spread and may contribute to the addition of resistant seeds in the seedbank. There is little research on how much seed is retained on different weed species at or beyond harvest time. Thus, the objective of this study was to determine the percentage of total Palmer amaranth and barnyardgrass seed production that was retained on the plant during delayed soybean harvest. Retained seed over time was similar between 2015 and 2016, but was significantly different between years for only Palmer amaranth. Seed retention did not differ between years for either weed species. Palmer amaranth and barnyardgrass retained 98 and 41% of their seed at soybean maturity and 95 and 32% of their seed one month after soybean maturity, respectively. Thus, this research indicates that if there are escaped Palmer amaranth plants and soybean is harvested in a timely manner, most seed will enter the combine and offer potential for capture or destruction of these seeds using harvest weed seed control tactics. While there would be some benefit to using HWSC for barnyardgrass, the utility of this practice on mitigating herbicide resistance would be less pronounced than that of Palmer amaranth because of the reduced seed retention or early seed shatter.

Two major weeds in rice in the Philippines, Sphenochlea zeylanica Gaertn. and Echinochloa crus-galli (L.) Beauv., are controlled with chemical and cultural methods. In the 1980s, after >10 years of continuous use of 2,4-D, S. zeylanica evolved resistance to the chemical in those rice fields that had been treated with 2,4-D once or twice every cropping season. In the 1990s, E. crus-galli evolved resistance to butachlor and propanil in rice monocrop areas where both herbicides were used continuously for 7–9 years. Rice farmers continue to use 2,4-D, butachlor and propanil extensively and are often unaware of herbicide resistance or the potential for cross-resistance, its causes or its implications. In order to control herbicide-resistant E. crus-galli, farmers are shifting to locally available herbicides with different modes of action, such as bispyribac, an acetolactate synthase inhibitor, and cyhalofop, an acetyl coenzyme A carboxylase inhibitor. Follow-up manual weeding or rotary weeding after herbicide spraying, a common farmers’ practice, removes the susceptible and resistant biotypes and could help to delay or prevent the evolution of resistance. Although the resistance mechanisms of both weeds are not determined yet, they could be related to enhanced degradation that is similar to the mechanisms that are shown by the resistant biotypes in other countries.

Rhamnolipid (Rh) is a biosurfactant produced by the bacterial Pseudomonas aeruginosa. This present study investigates rhizospheric strain C1501 of P. aeruginosa with an accession number KF976394 with the best production of rhamnolipid: a biosurfactant. The partially purified rhamnolipid from strain C1501 and Tween 80 was tested on mycelial growth of wild strain C1136. The enzyme activities involved in biodegradation, as well as necrosis induction on the tested weeds, were performed using scanning electron microscopy. It was observed that the different concentrations of rhamnolipid tested enhanced the dry mycelia weight yield of Lasiodiplodia pseudotheobromae which has been established to be producing a phytotoxic metabolite for killing weeds. It was observed that strain C1136 had a high level of cellulase and xylanase enzyme activities during this study. The scanning electron microscopy showed that the mutant strain of C1136 combined with 0.003% v/v of rhamnolipid enhances biodegradability and a high level of necrosis on the tested weeds compared with that on the untreated weeds. The highest CMCase activities and xylanase activities were obtained on the fourth day from the phytotoxic metabolite produced from the mutant strain of L. pseudotheobromae when combined with 0.003% v/v of rhamnolipid. This study has shown that rhamnolipid can serve as an adjuvant in order to enhance the penetrability of bioherbicide active ingredient for controlling weeds.

Until recently, Digitaria aequiglumis var. aequiglumis, native to South America, and Digitaria ciliaris subsp. nubica, native to Northeast Africa, were completely overlooked in Belgium due to their close morphological resemblance to Digitaria sanguinalis and Digitaria ischaemum. One of the possible reasons for their expansion in maize fields, besides for example the lack of crop rotation, might be a lower sensitivity to post-emergence herbicides acting against panicoid grasses. Dose-response pot experiments were conducted in the glasshouse to evaluate the effectiveness of four foliar-applied HPPD-inhibiting herbicides (mesotrione, sulcotrione, tembotrione, topramezone) and two foliar-applied ALS-inhibiting herbicides (foramsulfuron, nicosulfuron) for controlling Belgian populations of D. aequiglumis and D. ciliaris subsp. Nubica, as well as local D. sanguinalis and D. ischaemum populations. In another dose-response pot experiment, the influence of growth stage at time of herbicide application on efficacy of topramezone and nicosulfuron for Digitaria spp. control was evaluated. In general, D. aequiglumis and D. ciliaris subsp. nubica populations were less sensitive to HPPD inhibitors than D. ischaemum and D. sanguinalis populations, except for D. aequiglumis treated with topramezone. Contrary to other herbicides tested, topramezone adequately controlled all D. aequiglumis populations at doses well below maximum authorised field dose. All species tested showed a progressive decrease in sensitivity to topramezone and nicosulfuron with seedling age. A satisfactory post-emergence control of Digitaria species in the field will require appropriate choice of herbicide and dose, as well as more timely application.

Barnyardgrass (Echinochloa crus-galli) is one of the top 15 herbicide-resistant weeds around the world that interferes with rice growth, resulting in major losses of rice yield. Thus, multi-herbicide resistance in barnyardgrass presents a major threat, with the underlying mechanisms that contribute to resistance requiring elucidation. In an attempt to characterize this multi-herbicide resistance at the proteomic level, comparative analysis of resistant and susceptible barnyardgrasses was performed using iTRAQ, both with and without quinclorac, bispyribac-sodium and penoxsulam herbicidal treatment. A total of 1342 protein species were identified from 2248 unique peptides by searching the UniProt database and conducting data analysis. Approximately 904 protein species with 4774 Gene Ontology (GO) terms were grouped into the categories of biological process, cellular component and molecular function. Among these, 688 protein species were annotated into 1583 KEGG pathways, with 980 protein species relating to metabolism and 93 relating to environmental information processing. A total of 292 protein species showed more than a 1.2-fold change in abundance in the resistant biotype relative to the susceptible biotype. Furthermore, herbicide treatment resulted in 157 protein species that showed more than a 1.2-fold change in the resistant biotype. Moreover, physiological analyses demonstrated an ecological fitness cost in the resistant biotype. Significance While some studies have shown a fitness cost to be associated with an altered ecological interaction, our understanding of the fitness costs associated with herbicide resistance are limited. Herein, physiological and proteomic analysis demonstrates herbicide resistance associated ecological fitness cost and potential mechanisms of herbicide-resistance in resistant biotypes of E. crus-galli. The results presented herein have revealed differences in ecological adaptation between resistant and susceptible biotypes in E. crus-galli and provide a fundamental basis enabling the development of new strategies for weed control. Lastly, this is the first large-scale proteomics study to examine herbicide stress responses in different barnyardgrass biotypes.

Echinochloa crus-galli is the main weed in direct dry-seeded rice systems worldwide and is the target of most herbicide applications. Numerous cases of E. crus-galli biotypes with resistance to herbicides have been reported in different regions of the world, however, to date, no cases have been reported in Uruguay. The purpose of this research is to assess the presence of herbicide-resistant E. crus-galli in the rice fields of Uruguay. More than 40 E. crus-galli biotypes were sampled from eastern to northern regions in different years and assessed following the Herbicide Resistance Action Committee (HRAC) protocols of confirmation, using the herbicides propanil, quinclorac, clomazone, bispyribac&ndash, sodium, penoxsulam, imazapyr + imazapic, profoxidim and cyhalofop. Herbicides rates included 0, 0.125, 0.25, 0.50, 1, 2, 4 and 8 times the label rate. Most E. crus-galli biotypes (35) resulted as resistant to quinclorac. Furthermore, resistance was confirmed to propanil in at least seven biotypes, 12 to imazapyr + imazapic, and three to penoxsulam. Five biotypes showed multiple resistance to propanil and quinclorac, and one biotype was resistant to quinclorac, penoxsulam and imazapyr + imazapic. No biotype showed confirmed resistance to clomazone, bispyribac-sodium, cyhalofop or profoxidim&mdash, herbicides that ensure satisfactory control. The presence of E. crus-galli herbicide resistant-biotypes reduces herbicide options, threatening rice production in Uruguay. In this context, a redesign of the productive systems would represent an opportunity to complement the chemical control, integrating larger-scale cultural and management practices.

Background Echinochloa crus-galli (L.) Beauv. and Amaranthus palmeri S. Wats are two common and problematic weeds prevalent across the Midsouth of the USA. Herbicide absorption, translocation, and metabolism were investigated as potential sources of herbicide antagonism on A. palmeri and E. crus-galli using 14 C-labeled herbicides. Three 14 C-labeled herbicides, glyphosate, glufosinate, and dicamba, were utilized individually in separate experiments. Results Uptake of 14 C-glyphosate in E. crus-galli was 15% of the total applied radioactivity for glyphosate/glufosinate (897 + 595 g a.i./a.e. ha-1 ) compared to 25% for glyphosate alone. Similarly, uptake of 14 C-glyphosate in A. palmeri reduced by 10% when applied with glufosinate. Applying glyphosate/dicamba (897/560 g a.e. ha-1 ) reduced 14 C-glyphosate uptake in both species. In the 14 C-glufosinate experiment, both species absorbed less 14 C-glufosinate when mixed with glyphosate compared to glufosinate alone. No metabolic degradation of glyphosate was observed in either species. E. crus-galli metabolized dicamba 23 times faster than A. palmeri. When glufosinate was applied with dicamba, metabolic degradation of 14 C-dicamba was limited in both species. For example, 99.9% of the applied radioactivity was recovered in A. palmeri as the parent compound when 14 C-glufosinate dicamba was applied with glufosinate, compared to 95.7% for dicamba alone. Conclusion These findings demonstrate absorption, translocation, or metabolism of dicamba, glufosinate, and glyphosate can be affected by mixing with another herbicide. As mixing two herbicides is often a critical component of resistance management, careful investigation into the performance of these mixtures in the field is needed. © 2020 Society of Chemical Industry.

Napropamide is a chiral acetamide herbicide commonly applied to control Echinochloa crus-galli in maize. The inhibition effect may be enantioselective for Echinochloa crus-galli and maize. It may also be affected by the potential allelopathy at field condition. To investigate this, we have examined the inhibition effect of napropamide on Echinochloa crus-galli mono-cultured or co-cultured with maize at field conditions. Our results on morphology, physiology, chlorophyll content and chlorophyll fluorescence suggest that R-napropamide has stronger inhibitory effect than Rac-napropamide and S-napropamide on Echinochloa crus-galli, while none of them affects maize. We found that both glutathione-S-transferase (GST) genes and oxidative enzymes (superoxide dismutase, malondialdehyde) played roles in the inhibition. Accumulations of napropamide in Echinochloa crus-galli were more prominent in roots than in shoots, and no enantioselectivity was found in medium dissipation. We have observed relative allelopathy when applying napropamide to Echinochloa crus-galli co-cultured with maize. The results warrant further field studies on the enantioselectivity and allelopathy of herbicides.

The objective of this research was to confirm the resistance of a barnyardgrass biotype (Echinochloa crus-galli) to herbicides quinclorac (synthetic auxin), penoxsulam (ALS inhibitor) and cyhalofop-butyl (ACCase inhibitor). Two experiments were carried out in a greenhouse located in Itajaí, State of Santa Catarina, Brazil. One experiment evaluating the biotype ECH 18 (known as susceptible) and one with the ECH 141 biotype (suspected to be multiple resistant). The experimental design used was completely randomized, in a 4 x 7 factorial arrangement with four replications. The first factor was the herbicide: cyhalofop-butyl (Clincher(r)), penoxsulam (Ricer(r)), quinclorac (Facet(r)) and propanil (Grassaid(r)) and the second factor consisting of seven rates of each herbicide (0.00; 0.25; 0.50; 1; 2; 4 and 8 times the label rate). The evaluations of percentage of control, plant density per pot and dry mass of shoots were performed 35 days after treatments. The rates to control 50% and 80% and the dose to provide 50% and 80% of the weed biomass accumulation and the resistance factor were estimated based on data analysis. The initial hypothesis was confirmed; the biotype ECH 141 presented multiple resistance (synthetic auxin, ALS and ACCase inhibitor). However, the herbicide propanil controlled biotype ECH 141 adequate. RESUMO Este estudo teve como objetivo confirmar a resistência múltipla de um biótipo de capim-arroz (Echinochloa crus-galli) aos herbicidas auxínicos (quinclorac), inibidores da ALS (penoxsulam) e ACCase (cyhalofop-butyl). Foram conduzidos dois experimentos em casa de vegetação localizada no município de Itajaí/SC: um com o biótipo ECH 18 (sabidamente suscetível) e outro com o biótipo ECH 141 (com suspeita de resistência múltipla). O delineamento experimental utilizado foi o inteiramente casualizado (DIC), organizado em arranjo fatorial 4 x 7, com quatro repetições. O primeiro fator avaliado foram os herbicidas: cyhalofop-butyl, penoxsulam, quinclorac e propanil (Clincher(r), Ricer(r), Facet(r) e Grassaid(r), respectivamente). O segundo fator consistiu de sete doses de cada herbicida (0,00, 0,25, 0,50, 1,00, 2,00, 4,00 e 8,00 vezes a dose de registro). Aos 35 dias após a aplicação dos tratamentos, foram realizadas as avaliações de porcentagem de controle, densidade de plantas por vaso e massa seca da parte aérea. Após a análise dos dados, estimou-se a dose para proporcionar controle de 50% e 80%, a dose para proporcionar redução de 50% e 80% no acúmulo de biomassa e o fator de resistência. A hipótese inicial foi confirmada, pois o biótipo ECH 141 apresentou resistência múltipla aos herbicidas quinclorac (auxina sintética), penoxsulam (inibidor da ALS) e cyhalofop-butyl (inibidor de ACCase). Contudo, o herbicida propanil o controlou com eficiência.

Monoterpenes, the major constituents of essential oils, are known for their diverse biological activities. This study was conducted to assess the herbicidal effect of six monoterpenes viz. (R)-carvone, 1,8-cineole, cuminaldehyde, (S)-fenchone, geraniol, (S)-limonene, and (R)-linalool on barnyardgrass under laboratory and glasshouse conditions with a view to explore the possibility of their utilization for future weed management. The effect of monoterpenes on chlorophyll contents and total phenolic compounds was also evaluated. The inhibitory effects of monoterpenes on seed germination and seedling growth were tested at concentrations of 1, 2, 4, 6, and 8 mM. The results showed that geraniol and (R)-carvone caused greatest reduction of seed germination with complete inhibition at the concentrations > 2 mM. Similarly, these two compounds were the most potent inhibiters for root and shoot growth. In general, monoterpenes were less effective against seed germination than seedling growth. Furthermore, the inhibition of root growth by all compounds was greater than that of shoot growth. In foliar application treatments under glasshouse conditions, the monoterpenes reduced the fresh and dry weights, and shoot length of two-leaf stage barnyardgrass at concentrations of 1 and 2%. In addition, the tested monoterpenes caused phytotoxicity symptoms, mainly chlorosis and necrosis, followed by weed death. Complete weed control was observed in the treatments with 1 and 2% of geraniol, and 2% of cuminaldehyde. Further, a reduction of chlorophyll contents and total phenolic compounds of barnyardgrass leaves was noticed, indicating that the monoterpenes cause adverse effect on photosynthesis and weed metabolism. Based on the results of this study, it can be concluded that the monoterpenes, particularly geraniol, (R)-carvone, and cuminaldehyde, can be used as potential natural herbicides.

Some plant GH3 genes are specifically induced by auxin within minutes and play important roles in plant growth and development. A GH3 cDNA was isolated from barnyardgrass. The gene, designated EcGH3.1 (Genebank Number: JN241678 ), has a full-length 1839 bp open reading frame predicted to encode a 67.82 kDa protein. Sequence alignment showed that EcGH3.1 is a GH3 homolog. Its transcript level in leaves and roots of quinclorac-susceptible (S) biotypes was higher than that in quinclorac-resistant (R) biotypes. After exposure to quinclorac in 30 min, EcGH3.1 expression was obviously decreased in leaves of S biotypes, but markedly increased in leaves of the R plants. EcGH3.1 with its different expression patterns can be considered a marker and applied to distinguish R and S biotypes. The results of this study also provide basic information for further research of the function of EcGH3 in barnyardgrass under herbicide stress .

Nine field trials (4 in corn and 5 in soybean) were conducted over 2 years (2014 and 2015) to determine if there is greater benefit of adding ammonium sulfate (AMS) (2.5 L·haˉ1) or an equal dollar value of glyphosate (406 g·ae·haˉ1) to glyphosate applied at 450, 675 or 900 g·ae·haˉ1 for weed control in corn and soybean. Glyphosate applied at 450 g·ae·haˉ1 controlled velvetleaf 90% to 98%, common ragweed 80% - 97%, common lambsquarters 91% - 99%, Eastern black nightshade 83% - 100% and barnyardgrass 73% - 97% in corn and common ragweed 37% - 89%, common lambsquarters 39% - 98%, barnyardgrass 90% - 98% and green foxtail 91% - 98% in soybean. The addition of AMS to glyphosate applied at 450, 675 or 900 g·ae·haˉ1 provided little to no added benefit for the control of velvetleaf, common ragweed, common lambsquarters, Eastern black nightshade, barnyardgrass and green foxtail in corn and soybean. There was a greater benefit in weed control efficacy by simply adding and equal dollar value of glyphosate (406 g·ae·haˉ1) than AMS (2.5 L·haˉ1) to glyphosate. There was no difference in corn or soybean yield among the herbicide treatments evaluated. Based on these results, addition of AMS to glyphosate at rates evaluated had little benefit on weed control efficacy or yield of corn and soybean.

Multiple-herbicide resistance (MHR) in barnyardgrass (Echinochloa crus-galli) is a threat to rice production. The Ala-205-Val mutation in acetolactate synthase (ALS) conferred resistance to several ALS inhibitors in the E. crus-galli population AXXZ-2; consequently, ALS-inhibitors were unable to control this noxious weed species. In the present study, the sensitivity to acetyl-coenzyme A carboxylase (ACCase) herbicides and other herbicides having different modes of action was evaluated to determine an effective strategy for chemical weed control. Compared with that of the reportedly sensitive population JLGY-3, the AXXZ-2 population showed differential resistance to three ACCase-inhibitors (cyhalofop-butyl, fenoxaprop-P-ethyl, and pinoxaden), in addition to quinclorac and pretilachlor. A novel substitution (Asp-2078-Glu) in ACCase was detected as the main target-site resistance mechanisms in the AXXZ-2 population. Structural modeling of the mutant ACCase protein predicted that Asp-2078-Glu confers resistance to three ACCase inhibitors by reducing the binding affinity between them and the ACCase protein. To the best of our knowledge, this is the first study to report that the novel Asp-2078-Glu mutation confers resistance to several ACCase inhibitors. Target-site mutations in ALS and ACCase were detected in this MHR population. Except for quinclorac, pretilachlor, ALS inhibitors, and the three ACCase inhibitors, a number of herbicides remain effective in controlling this MHR E. crus-galli population.

A resistência não relacionada ao local de ação (NRLA) pelo incremento da degradação de herbicidas é um problema crescente em várias espécies ao redor do mundo. Neste estudo foi avaliada a ocorrência de incremento da degradação por enzimas citocromo P450 monoxigenases (cytP450) como mecanismo de resistência ao imazethapyr em capim-arroz. Os inibidores de cytP450 malathion e butóxido de piperonila (PBO) e o indutor anidrido naftálico (AN), aplicados em mistura ou sequencialmente ao imazethapyr, foram avaliados sobre biótipos de capim-arroz suscetíveis e resistentes às imidazolinonasàs imidazolinonas . Além disso, a degradação de imazethapyr foi analisada em plantas tratadas com esse herbicida, aplicado isoladamente ou duas horas após malathion ou AN. A pulverização de malathion e PBO reduziu o fator de resistência (FR) de 15,92 para 3,44 e 4,99, respectivamente, na população resistente PALMS01. Inversamente, o indutor de cytP450 AN aumentou o FR de 4,45 para 8,32. A pulverização prévia de malathion aumentou a concentração de imazethapyr em plantas de capimarroz resistentes, em comparação com plantas que receberam apenas o herbicida, indicando a inibição da degradação de imazethapyr. A pulverização simultânea de malathion e imazethapyr foi menos eficiente que a aplicação prévia deste inibidor de cytP450. Esses resultados indicam que o incremento de metabolização causado por enzimas cytP450 está envolvido no mecanismo de resistência de capim-arroz ao imazethapyr, e medidas apropriadas devem ser tomadas para manejar essas populações. Non-target site (NTS) herbicide resistance by degradation enhancement is an increasing problem in several weeds around the world. In this study, the occurrence of degradation enhancement by cytochrome P450 monooxygenases (cytP450) was evaluated as the mechanism of resistance to imazethapyr in barnyardgrass. The cytP450 inhibitors malathion and piperonyl butoxide (PBO) and the inducer naphthalic anhydride (NA), applied in mixture or sequentially with imazethapyr, were evaluated on imidazolinone-susceptible and – resistant barnyardgrass byotipes. In addition, the degradation of imazethapyr was analyzed in plants treated with imazethapyr applied alone or two hours after malathion or NA. The spraying of malathion and PBO reduced the resistance factor (RF) from 15.92 to 3.44 and 4.99, respectively, in the resistant population PALMS01. Conversely, the cytP450 inducer NA increased the RF from 4.45 to 8.32. Malathion increased imazethapyr concentrations in resistant barnyardgrass in comparison with plants sprayed with the herbicide alone, indicating the inhibition of imazethapyr degradation. The simultaneous spraying of malathion and imazethapyr was less efficient than the previous application of this cytP450 inhibitor. These results indicate that degradation enhancement caused by cytP450 enzymes is involved in the resistance mechanism of barnyardgrass to imazethapyr, and appropriate measures should be taken to manage these populations.

Echinochloa crus-galli var. zelayensis, a variety of E. crus-galli (L.) Beauv. has evolved resistance to quinclorac, but the mechanism of resistance remains unclear. Treatments with quinclorac, cause rapid leaf chlorosis, continuous decrease in the chlorophyll content to about 0.4 times, and rapid decline in biomass by about 20% in sensitive E. crus-galli var. zelayensis within 72 h. Then transcriptome sequencing for quinclorac-sensitive and -resistant E. crus-galli var. zelayensis biotypes was performed, and more differentially expressed genes (DEGs) were observed in the sensitive biotype (1115 DEGs, including 548 up-regulated and 567 down-regulated) than that in the resistant biotype (901 DEGs, including 373 up-regulated and 528 down-regulated). Thirty-four photosynthesis-related candidate genes were screened, in which twenty-nine genes were more affected by quinclorac in the sensitive biotype than that in the resistant biotype. The qPCR verification involving more sampling time-points revealed that on continuous treatment with 50 μ mol/L quinclorac, expression levels of 34 photosynthesis-related genes dropped significantly by 2–1000 times within 12 h in the sensitive biotype. Following significant or marginal decline in expression at 6 h after quinclorac treatment, recovery of the expression levels of 21 genes was observed after 12 h and the expression levels of another 13 genes remained unaltered in the resistant biotype. It is hypothesized that the sustained sharp decrease in the expression of photosynthesis-related genes is a major cause of death in the sensitive biotype. Further, it is inferred that there may be a regulatory mechanism in the resistant biotype that allowed the expression of these genes to be significantly unaffected or to rapidly recover, in turn preventing severe damage to the plants caused by quinclorac.

Thirty-seven commercial aldehydes containing aliphatic chains and aromatic rings as well as heteroaromatic rings were evaluated for their inhibitory activities against Chinese amaranth (Amaranthus tricolor L.) and barnyardgrass (Echinochloa crus-galli (L.) Beauv). Polysorbate 80 (Tween® 80) was used as a surfactant and the research was preliminarily conducted at 400 μM of all aldehydes. Among these aldehydes, (E)-cinnamaldehyde (7) showed the greatest inhibitory effect on seed germination, shoot and root growth of Chinese amaranth by 54.55%, 75.53%, and 85.13% respectively. Similarly, (E)-crotonaldehyde (5), a related α,β-unsaturated aldehyde, inhibited the germination and seedling growth of the tested species at a high percentage. Apart from these two unsaturated aldehydes, no other aliphatic aldehydes had a harmful effect on Chinese amaranth. In terms of benzaldehyde (6), it had no effect on the tested plant; however, many of its derivatives displayed some inhibitory activity. Furthermore, for the ten common heteroaromatic aldehydes, picolinaldehyde (32) had a high inhibitory effect on Chinese amaranth which closely related to the effect of (E)-crotonaldehyde (5) and (E)-cinnamaldehyde (7), whereas, other heteroaromatic aldehydes showed lower effects. In the case of a monocot plant, barnyardgrass, no tested aldehydes reduced seed germination, however, (E)-cinnamaldehyde (7), 2,4,6-trimethoxybenzaldehyde (16) and 4-(dimethylamino)benzaldehyde (24) could inhibit the seedling growth of the plant with low to moderate levels. The herbicidal effects of the most active aldehydes were then further investigated in order to find the minimum concentration of these aldehydes suppressing the germination and growth of the tested plants. At concentrations as low as 50-100 μM some aldehydes could inhibit the seedling growth of the tested species. The structure-activity relationship (SAR) study reported here demonstrates the chemical clues governing the inhibitory activity of aldehydes which could be utilized in the development of highly effective herbicides in the near future.

Echinochloa crus-galli and Echinochloa colona mostly grown as weeds in different economic crops and cause losses in their yield. Flooding and Crop rotation ca not suppress these weeds. Herbicides are widely applied to control barnyard grasses. Bisbyric-sodium was applied at FRD (Field Recommended Dose) on both species, the results of preliminary experiment indicated that E. crus-galli was susceptible to bispyribac-sodium but E. colona was resistance. The Confirmation experiment for E. colona resistance indicated that herbicide effect on the biomass of plants which caused reduction in fresh and dry weight. The photosynthetic pigments were affected by herbicide, which decreased by increasing the herbicide concentration. While anthocyanins content were increased to protect the leaves from the stress of photoinhibitory light fluxes by absorbing the excess photons. The soluble and insoluble sugar content was increased by increasing the concentration of herbicide. The transcript level of ALS in E. colona was modified by different concentrations of herbicide. The present study indicated that ALS expression level was responsive to herbicide treatment. This suggests that ALS is a target site of bispyric-sodium. But 50% FRD can be considered as sub-lethal dose which upregulated the expression of ALS by 4 folds.

Barnyardgrass (Echinochloa crus-galli) proliferation seriously threatens rice production worldwide. Whole-plant bioassays were conducted in order to test the sensitivity to penoxsulam of 52 barnyardgrass populations and the resistance of six penoxsulam-resistant populations to 12 other herbicides that are commonly used in rice fields. Among the 48 populations that had escaped penoxsulam control in the rice fields, 8.3% showed a very high level of resistance, 58.3% showed a high level of resistance and 10.4% showed a moderate level of resistance. Multiple resistance was confirmed in all six penoxsulam-resistant populations that were tested further. They exhibited at least a moderate level of resistance; that is, to 6–10 of the total of 13 herbicides that was tested. Most of the six penoxsulam-resistant populations showed at least a moderate level of resistance to bispyribac-sodium, quinclorac, metamifop, cyhalofop-butyl and oxadiazon, three populations held at least a moderate level of resistance to oxyfluorfen and pretilachlor, two populations also held at least a moderate level of resistance to pyrazosulfuron-ethyl, pyribenzoxim and fenoxaprop-P-ethyl, but the resistance indices of the six populations to pendimethalin were all low. This study has confirmed resistance to pretilachlor and oxadiazon in weeds for the first time.

Coumarin is a natural compound well known for its phytotoxic potential. In the search for new herbicidal compounds to manage weeds, three synthetic derivatives bearing the coumarin scaffold (1–3), synthesized by a carbonylative organometallic approach, were in vitro assayed on germination and root growth of two noxious weeds, Amaranthus retroflexus and Echinochloa crus-galli. Moreover, the synthetic coumarins 1–3 were also in vitro assayed on seedlings growth of the model species Arabidopsis thaliana to identify the possible physiological targets. All molecules strongly affected seed germination and root growth of both weeds. Interestingly, the effects of synthetic coumarins on weed germination were higher than template natural coumarin, pointing out ED50 values ranging from 50–115 µM. Moreover, all synthetic coumarins showed a strong phytotoxic potential on both Arabidopsis shoot and root growth, causing a strong reduction in shoot fresh weight (ED50 values ≤ 60 µM), accompanied by leaf development and a decrease in pigment content. Furthermore, they caused a strong alteration in root growth (ED50 values ≤ 170 µM) and morphology with evident alterations in root tip anatomy. Taken together, our results highlight the promising potential herbicidal activity of these compounds.

Herbicides mixtures are used in many situations without the adequate knowledge related with the effect on major target weeds. The objective of this study was to evaluate the effects of different herbicides mixtures used in irrigated rice in order to establish the adequate combinations for the prevention and management of herbicide resistance in barnyardgrass (Echinochloa crus-galli). Three experiments were performed at field conditions with all major post-emergent herbicides used in irrigated rice in Brazil. The first experiment was performed with barnyardgrass resistant to imidazolinone herbicides and herbicides applied at label rates. The second and third experiments were performed with barnyardgrass resistant and susceptible to imidazolinone herbicides applied at doses of 50 or 75% of the label rates. The occurrence of additive, synergistic and antagonistic effects was identified at 18, 18 and 64%, respectively, among the total of 50 different associations of herbicide and rates evaluated. In general, the mixture of ACCase inhibitors with ALS inhibitors, quinclorac, clomazone + propanil or thiobencarb resulted in antagonism. Sinergic mixtures were found in clomazone with propanil + thiobencarb, profoxydim with cyhalofop-butyl or clomazone, and quinclorac with imazapyr + imazapic, bispyribac-sodium or cyhalofop-butyl. The mixtures of quinclorac with profoxydim were antagonic. Rice grain yield varied according to the efficiency of weed control. Seveveral mixtures were effective for imidazolinone resistant barnyardgrass control. RESUMOEm diversas situações as associações de herbicidas são realizadas sem o conhecimento do efeito sobre as principais plantas alvo da aplicação. O objetivo deste trabalho foi avaliar o efeito da associação de herbicidas utilizados na cultura do arroz irrigado, de forma a estabelecer opções de combinações de herbicidas que possam ser utilizadas na prevenção e manejo da resistência de capim-arroz. Foram realizados três experimentos em condições de campo, com os principais herbicidas utilizados em pós-emergência na cultura do arroz irrigado no Brasil. O primeiro experimento foi realizado com capim-arroz resistente a imidazolinonas e herbicidas em doses recomendadas. O segundo e o terceiro experimentos foram realizados com capim-arroz suscetível a imidazolinonas e herbicidas em doses de 50 ou 75% da dose máxima recomendada. A ocorrência de aditividade, sinergismo e antagonismo foi observada em 18, 18 e 64%, respectivamente, em um total de 50 diferentes misturas avaliadas. De forma geral, a mistura de inibidores da ACCase com inibidores de ALS, quinclorac, clomazone ou propanil + thiobencarb, resultaram em antagonismo. Associações sinérgicas foram encontradas em clomazone com propanil + thiobencarb, profoxydim com cyhalofop-butyl ou clomazone, e quinclorac com imazapyr + imazapic, bispyribac-sodium ou cyhalofop-butyl. A associação de quinclorac com profoxydim foi antagônica. O rendimento de grãos variou conforme a eficiência de controle de plantas daninhas, uma vez que nos tratamentos em que a mistura foi sinérgica, obteve-se maior produtividade de grãos. Várias misturas foram eficientes para o controle de capim-arroz resistente a imidazolinonas.