Evaluation of Pre-Emergence and Post-Emergence Herbicides for Weed Management in Miscanthus sacchariflorus and Miscanthus sinensis

Miscanthus,is a promising bioenergy crop,considered superior to other bioenergy crops because of its higher water and nutrient use efficiency,cold tolerance,and higher production of biomass.Broadleaf weeds and grass weeds,cause major problems in the Miscanthus field.A field experiment was conducted in 2018 and 2019,to assess the effects of pre-emergence(alachlor and napropamide)and post-emergence herbicides(nicosulfuron,dicamba,bentazon,and glufosinate ammonium)on broadleaf and grass weeds in M.sinensis and M.sacchariflorus fields.The weed control efficiency and phytotoxicity of pre-and post-emergence herbicides were evaluated at 30 days after treatment(DAT)and compared to those of the control plots.The results showed wide variations in the susceptibility of the weed species to the treated herbicides.Treatment with nicosulfuron 40 g.a.i.ha^(-1) provided the most effective overall weed control(with 10%visual injury),without affecting the height and biomass of neither Miscanthus species in the field.Post-emergence herbicides such as glufosinate ammonium 400 g.a.i.ha^(-1) and dicamba 482 g.a.i.ha^(-1) were effective and inhibited the growth and density of the majority of weeds to a 100%;however,they showed significant phytotoxicity(toxicity scale of 1-10)to both species of Miscanthus.The application of glufosinate ammonium caused severe injuries to the foliar region(90%visual injury)of both Miscanthus sps.Comparatively,M.sinensis showed a slightly higher tolerance to the herbicides nicosulfuron,bentazon and napropamide with 10%visual injury at the recommended dose than M.sacchariflorus.The present study clearly showed that infestation of broadleaf and grass weeds in Miscanthus fields can cause significant damage to the growth and biomass of Miscanthus and applying pre-emergence and post-emergence herbicides effectively controls the high infestation of these weeds.

Effects of a glyphosate-based herbicide on the oestrous cycle of rats

Objective:To determine the effects of a glyphosate-based herbicide on the oestrous cycle of rats.Methods:Fifteen adult Wistar rats were randomly divided into three groups.Group A served as the control group,while groups B and C received 250 and 500 mg/kg of glyphosate-based herbicide orally for five oestrous cycles,respectively.Stages of oestrous cycle,oestrous cycle index,length of cycle,oestrous cycle ratio,serum estradiol and progesterone levels were determined.Results:The proestrus and oestrus stages of the glyphosate-based herbicide groups increased significantly(P<0.05),although proestrus in group C was not significantly different from the control group.There was a significant decrease in the metestrus and diestrus of the glyphosate-based herbicide groups(P<0.05).The oestrous cycle index of the glyphosate-based herbicide treated groups was altered;this was characterized by an increase in the oestrous index and a decrease in the metestrus and diestrus indexes.The proestrus index of group B increased,while that of group C decreased.The length of the cycle of the glyphosate-based herbicide groups significantly decreased from the 1st and 3rd week till the end of the study in groups B and C,respectively(P<0.05).There was a significant increase in the oestrous cycle ratio of the glyphosate-based herbicide groups compared to the control group(P<0.05).Though the estradiol and progesterone levels of the glyphosate-based herbicide groups increased and decreased,respectively,they were not significantly different from the control group.Conclusions:Glyphosate-based herbicide at the doses of 250 and 500 mg/kg can alter the pattern of the oestrous cycle in rats.

Effects of Different Herbicides on Weed Control in Alfalfa Field

[Objectives]The paper was to systematically study the technology of weed control in alfalfa field.[Methods]Reviving alfalfa field and newly sown alfalfa field after emergence were selected,and the effects of different herbicides on weed control and alfalfa yield were discussed.[Results]The optimal herbicides after alfalfa reviving were 5%imazethapyr and 10%imazethapyr,and the optimal dosages were 1.5 and 1.05 L/hm 2,respectively.The optimal herbicides after emergence of newly born alfalfa were 5%imazethapyr and 10%imazethapyr,and the optimal dosages were 1.5 and 0.75 L/hm 2,respectively.[Conclusions]This study will provide a technical support for high quality production of alfalfa.

A nonsynonymous mutation in an acetolactate synthase gene (Gh_D10G1253) is required for tolerance to imidazolinone herbicides in cotton

Background Herbicide tolerance in crops enables them to survive when lethal doses of herbicides are applied to surrounding weeds.Herbicide-tolerant crops can be developed through transgenic approaches or traditional mutagenesis approaches.At present,no transgenic herbicide tolerant cotton have been commercialized in China due to the genetically-modified organism(GMO)regulation law.We aim to develop a non-transgenic herbicide-tolerant cotton through ethyl methanesulfonate(EMS)mutagenesis,offering an alternative choice for weed management.Results Seeds of an elite cotton cultivar Lumianyan 37(Lu37)were treated with EMS,and a mutant Lu37-1 showed strong tolerance to imidazolinone(IMI)herbicides was identified.A novel nonsynonymous substitution mutation Ser642Asn at acetolactate synthase(ALS)(Gh_D10G1253)in Lu37-1 mutant line was found to be the potential cause to the IMI herbicides tolerance in cotton.The Ser642Asn mutation in ALS did not present among the genomes of natural Gossypium species.Cleaved amplified polymorphic sequence(CAPS)markers were developed to identify the ALS mutant allele.The Arabidopsis overexpressing the mutanted ALS also showed high tolerance to IMI herbicides.Conclusion The nonsynonymous substitution mutation Ser642Asn of the ALS gene Gh_D10G1253 is a novel identi-fied mutation in cotton.This substitution mutation has also been identified in the orthologous ALS genes in other crops.This mutant ALS allele can be used to develop IMI herbicide-tolerant crops via a non-transgenic or transgenic approach.

Pyramiding of multiple genes generates rapeseed introgression lines with clubroot and herbicide resistance, high oleic acid content, and early maturity

Clubroot and herbicide resistance,high oleic acid(OA)content,and early maturity are targets of rapeseed(Brassica napus L.)breeding.The objective of this study was to develop new male-fertility restorer lines by pyramiding favorable genes to improve these traits simultaneously.Seven elite alleles for the four traits were introduced into the restorer line 621R by speed breeding with marker-assisted and phenotypic selection.Six introgression lines(ILs)were developed with four-to seven-gene combinations and crossed with two elite parents to develop hybrids.All ILs and their corresponding hybrids displayed high resistance to both clubroot pathotype 4 and sulfonylurea herbicides.Three ILs and their hybrids showed large increases in OA contents and four showed earlier maturity.These new ILs may be useful in rapeseed hybrid breeding for the target traits.

Limiting Factors and Countermeasures for the Development of Biological Herbicides

This paper mainly analyzes the main limiting factors in the development of biological herbicides,such as narrow herbicidal spectrum,vulnerable to environmental impacts,difficulties in preparing dosage forms,difficult separation and low yield of active substances,biological safety,etc.Moreover,countermeasures and suggestions are put forward,including strengthening the study of biological screening of herbicidal activity,microbial metabolites and their use as lead compounds,dosage forms,fungi complex formulation,fungi and herbicide complex formulation,and fermentation technology.

Review and Analysis: Did the United States Transport, Off-Load and Use Commercial 2,4,5-T Herbicides with Unknown Amounts of Dioxin TCDD on Military Base Grounds in Panama Canal Zone between 1948 and 1999?

The 84 km Panama Canal connecting the Atlantic and Pacific oceans has historically been a strategic waterway for shipping and the location of United States (US) military bases. Since the construction of Lake Gatun reservoir, canal locks and navigation channel through the Isthmus of Panama tropical forests in the 1910s, chemicals, pesticides, and herbicides have been essential for controlling upland and wetland vegetation as well as managing mosquito-borne diseases. Chemicals and pesticides flowed into Lake Gatun via land surface runoff and subsurface drainage either attached to the sediment or in solution during the rainy season. Lake Gatun and the Panama Canal was the drinking water source for most of the civilian and military population living in the Panama Canal Zone. Between 1948 and 1999, US military base commanders had the ability to order, from the Federal Supply Catalog, commercially available herbicide 2,4,5-T with unknown amounts of dioxin TCDD for use on the military base grounds in the Panama Canal Zone. The herbicide 2,4,5-T was transported to Panama Canal Zone ports, including the ports Cristobal on the Caribbean and Balboa on the Pacific, and distributed to the US military bases in Panama by rail or truck. The US National Toxicology Program and the International Agency for the Research on Cancer listed dioxin and TCDD as known human carcinogens. Dioxins are endocrine disrupters and can cause certain chloracne, cancers, developmental and reproductive effects. In 1985, the United States government banned the manufacture of the herbicide 2,4,5-T, with unknown amounts of dioxin TCDD, after it was shown to cause cancer in animals. The objectives of this study are to determine: 1) the fate of dioxin TCDD, a contaminant in the herbicide 2,4,5-T, sprayed on the US military base vegetation in the Panama Canal Zone from 1948 to 1999, 2) the transport of dioxin TCDD rich sediment via soil erosion and overland flow into Lake Gatun and Panama Canal waterways and 3) the human health impacts of dioxin TCDD, a known carcinogen, on US military and Panamanian civilians exposed to dioxin TCDD in the Panama Canal Zone.

Characterization of a strain of Sphingobacterium sp. and its degradation to herbicide mefenacet

A bacterium(designated strain Y1) degrading acetanilide herbicide mefenacet was isolated from aerobic sludge. Based on the analyses of partial 16S rRNA gene, cellular fatty acid and BIOLOG-GN, and general physiological and biochemical characteristics, strain Y1 was identified as Sphingobacterium multivolum. Strain Y1 was able to degrade mefenacet used as sources of carbon and energy. Degradation of mefenacet was accompanied by producing the metabolites N-methylaniline and an unidentified compound with molecular weight 205, indicating a metabolic pathway of mefenacet initiated by hydrolysis of amido bond.

Inheritance and molecular characterization of resistance to AHAS- inhibiting herbicides in rapeseed

Rapeseed is a very important oil crop in China; however, its production is challenging due to the absence of effective weed management strategies. This is predominantly because of a shortage of herbicide resistance genes. Acetohydroxyacid synthase （AHAS） herbicides inhibit AHAS, a key enzyme involved in branched-chain amino acid synthesis that is required for plant growth. A rapeseed line designated M342 with AHAS herbicide resistance was developed through seed muta- genesis and was studied to assess the level and mode of inheritance of the resistance and to identify the molecular basis of resistance. M342 possessed a high level of cross-resistance to sulfonylureas （SUs） and imidazolinones （IMIs）. This resistance was due to AHAS insensitivity to these herbicides and was inherited as a dominant trait conferred by a single nuclear-encoded gene. Molecular analysis revealed the presence of a Trp574Leu mutation in M342, and an allele-specific cleaved amplified polymorphic sequence （AS-CAPS） marker was developed and cosegregated with herbicide resistance in the F2, BC1, and BC2 populations. This mutation altered the transcript levels of BnAHAS1 and BnAHAS3 in M342 compared with those in the wild type, but it did not affect the agronomic or quality traits. The simple genetic inheritance of this mutation and the availability of the cleaved amplified polymorphic sequence （CAPS） marker and herbicide resistance gene should facilitate the development of herbicide-resistant rapeseed cultivars for effective weed control in China.

Isolation and Structural Speculation of Herbicide-Active Compounds from the Metabolites of Pythium aphanidermatum

Natural herbicides, or environment-friendly bioherbicides have been attracted more and more attentions. Isolation and structural identification of natural herbicide-active compounds from plant pathogens has been proved to be an effective approach for novel lead discovery of the pesticide development. In this study, the metabolites of the mutant strain PAM1, which obtained from PA1 of Pythium aphanidermatum （Eds.） Fitzp by ultraviolet radiation were separated and identified by HPLC, NMR, and IR. The results revealed that three active compounds including 4-hydroxy-3-methoxycinnamic acid and two indole derivatives, exhibited inhibition activity on the elongation of radical and coleoptile of Digtaria sanguinalis （L.） Scop.

Effect of Cadmium and Herbicides on the Growth, Chlorophyll and Soluble Sugar Content in Rice Seedlings

To investigate the combined effects of Cd^2＋ （ 0,10,100,500 μmol/L） , acetochlor （AC） （0,1.6,4.0,8.0μmol/L）, and bensulfuronmethyl （BSM） （ 0,0.16,0.40,0.80 μmol/L） on the biomass,leaf soluble sugar, total chlorophyll （chl） content, chl a/b ratio, and Cd content in roots and shoots in the rice seedlings, pot culture experiments were conducted with rice （Oryza sativa L. ） cultivar Jinyou 402. The results showed that the Cd and AC combined treatment （Cd＋ AC treatment） significantly inhibited the growth of the roots and shoots. The root dry weight/shoot dry weight （RDW/SDW） ratio, total chlorophyll content and chl a/b ratio decreased by 41%, 50%, 56% , respectively, in comparison with the control, as well as the leaf soluble sugar content, plant dry weight /plant fresh weight （PDW/PFW） ratio increased by 284% and 44% , respectively. Cd content in the roots and shoots had a decreasing tendency with the increasing concentration of AC under the Cd＋AC treatment. The Cd and BSM combined treatment （Cd＋BSM treatment） had a similar result to the Cd＋AC treatment. The results suggest that the toxicity of Cd to rice seedlings has been enhanced due to its combination with herbicides.

Recent Advances in Development of Herbicide Resistant Transgenic Hybrid Rice in China

In addition to weed control in direct seeding field of hybrid rice, herbicide resistance genes were used by Chinese scientists to increase and identify the purity of hybrid seeds, and to realize the mechanization of hybrid seed production. The elite restorer lines, such as Minghui 63, R752, T461, R402, D68 and E32 were transformed directly with herbicide resistance genes, in which D68 and E32 are restorer lines of two-line system and the others are of three-line system. Because almost all of important restorer lines are indica varieties and are recalcitrant in transformation, many herbicide resistant near-isogenic restorer lines were developed by sexual hybridization of indica and japonica varieties and backcross with indica restorer lines later, such as Ce 64, Minghui 63, Teqing, Milyang 46, R402 and 9311, in which 9311 is a restorer line of two-line system. The elite photoperiod-sensitive/thermo-sensitive genic male sterile lines, such as Pei＇ai 64S, P88S, 4008S and 7001S, were transformed with herbicide resistance genes. A few herbicide resistant male sterile lines were developed through sexual hybridization and subsequently systemic selection, such as Bar1259S, Bar2172S, 05Z221A and 05Z227A. With the employment of herbicide resistant male sterile lines or herbicide resistant restorer lines, a few herbicide resistant hybrid rice combinations were developed, such as Xiang 125S/Bar 68-1 and Pei＇ai 64S/Bar 9311. Based on herbicide resistance, the research was marching on to investigate the parental lines of hybrid rice with insect resistance, drought tolerance, etc.

Herbicide resistance: Development of wheat production systems and current status of resistant weeds in wheat cropping systems

Herbicide resistance in crops has extended the scope of herbicide applications to control weeds. The introduction of herbicide resistant crops resulted in a major shift in the way that herbicides are used in many crops, but not necessarily increased the prevalence of herbicide use, especially in wheat. Wheat is one of the most widely grown crops in the world and currently only two major herbicide-resistant wheat groups have been commercialized to manage weeds in a cost-effective manner. However, sustainable wheat production is threatened by the expanding occurrence of herbicide-resistant weed populations with limited efforts to discover new herbicide molecules. Selective control of certain problematic weeds in wheat was impossible until development and introduction of the technologies, Clearfield and Co AXium Production Systems. However, the current limitations of reliance on specific herbicides and evolution of resistant weeds mandate precautions and considerations when using these systems to prevent the loss of existing herbicide resources and continue sustainable wheat production. The focus of this review is to provide an overview of natural pre-existing herbicide resistance and development of herbicide-resistant technologies in wheat. The mechanisms of resistance to herbicides in wheat as well as the weed populations in wheat cropping systems, and implications for weed management are discussed.

Predicting herbicides concentrations in paddy water and runoff to the river basin

This study was conducted to investigate the dissipation pattern and runoff of herbicides to the river basin from the paddy fields. Pesticide paddy field model(PADDY) was applied to predict herbicide concentration in paddy fields. A field study was conducted in a paddy farm of Higashi Hiroshima City, Hiroshima Prefecture, Japan in the year of 2003 paddy season. The herbicides were mefenacet, thiobencarb, and bensulfuron methyl. The sample water was analyzed by using gas chromatography and HPLC after solid phase extraction. Predicted dissipation rate of thiobencarb in paddy water was higher(DT_ 50 = 4 36) than that measured, with a lower k value(-0 069). Two weeks after application no thiobencarb was detected in the drainage channel and down stream. In the down stream, thiobencarb was detected until 3 d after application, with a range of 0 02% to 0 08% of applied herbicide. The predicted dissipation rate(k) and half-life(DT_ 50 ) of mefenacet was not significantly different from that of measured. In the drainage channel, upstream and downstream mefenacet was found during the whole study period. In downstream, the maximum concentration of mefenacet was present 0 61% of applied in the paddy field on 3DAH. The dissipation rate(k) of BSM varied from -0 0860 to -0 1059 to with half-life(DT_ 50 ) 3 5 and 2 84 d. In upstream water, no BSM was detected except trace amounts(0 01 μg/L) at 3 d after application. However, in the drainage channel 8%, 6% and 1 58% of applied BSM was present at 0, 1 and 3 d after application respectively. In the down stream, the highest concentration was 1 06%, shortly after application.

Phytotoxicity of four herbicides on Ceratophyllum demersum,Vallisneria natans and Elodea nuttallii

The physiological effects of 4 herbicides （butachlor, quinclorac, bensulfuron-methyl and atrazine） on 3 submerged macrophytes （Ceratophyllum demersum, Vallisneria natans and Elodea nuttallii） were tested in laboratory. The variables of the relative growth rate and the photosynthetic pigment content showed that all of the tested herbicides affected the growth of the plants obviously, even at the lowest concentration （0.0001 mg/L）. Except for the C. demersum treated with quinclorac at 0.005 and 0.01 mg/L, the relative growth rates of the plants were inhibited significantly （p 〈 0.01）. Statistical analysis of chlorophyll a （Chl-a） contents was carded out with both the t-test and one-way ANOVA to determine the difference between the treatment and control. The results showed that Chl-a contents of the plants in all treatment groups were affected by herbicides significantly, except for the C. demersum treated with bensulfuron-methyl at 0.0005 mg/L. The decrease in Chl-a content was positively correlated to the dosage of the herbicides in most treatment groups. It was suggested that herbicides in water bodies might potentially affect the growth of aquatic macrophytes. Since the Chl-a content of submerged macrophytes responded to the stress of herbicides sensitively and directly, it could be used as a biomaker in environmental monitoring or in the ecological risk assessment of herbicide contamination.

Adsorption and correlation with their thermodynamic properties of triazine herbicides on soils

Adsorption of atrazine, prometryne and prometon was determined on six soils with different physical and chemical properties. The adsorption isotherms of three herbicides could well fit Freundlich equation. On all of six soils, adsorption of herbicides increased in the order: atrazine ≈prometon<prometryne. This order is quite the same to the calculation result of by means of excess thermodynamic properties of triazine. The Freundlich adsorption constants, K f, showed to have good correlation with organic matter(OM%) of soils for each of these herbicides, suggesting that OM is the main factor, which dominates in the adsorption process of these triazine herbicides.

Development of herbicide resistance genes and their application in rice

Rice is one of the most important food crops in the world.Weeds seriously affect the rice yield and grain quality.In recent years,there are tremendous progresses in the research and application of herbicideresistant genes in rice worldwide.This article reviews the working mechanisms of six herbicides(glyphosate,glufosinate,acetolactate synthase inhibitor herbicides,acetyl-Co A carboxylase inhibitor herbicides,hydroxyhenylpyruvate dioxygenase(HPPD)inhibitor herbicides and dinitroaniline herbicides),the resistance mutations of the corresponding herbicide-target genes,and the herbicide detoxification mechanisms by non-target genes.Examples are provided on herbicide-resistant rice materials obtained by transformation of exogenous resistance genes,by artificial mutagenesis and mutant screening,and by modifying the target genes through gene editing.This paper also introduces the current application of herbicide-resistant rice,points out problems that may be caused by utilization of herbicide resistant rice and solutions to the problems,and discusses the future prospects for the development of herbicideresistant rice.

Adsorption of chloroacetanilide herbicides on soil and its components III. Influence of clay acidity, humic acid coating and herbicide structure on acetanilide herbicide adsorption on homoionic clays

Adsorption of chloroacetanilide herbicides on homoionic montmorillonite, soil humic acid, and their mixtures was studied by coupling batch equilibration and FT IR analysis. Adsorption isotherms of acetochlor, alachlor, metolachlor and propachlor on Ca 2+ \|, Mg 2+ \|, Al 3+ \| and Fe 3+ \| saturated clays were well described by the Freundlich equation. Regardless of the type of exchange cations, K f decreased in the order of metolachlor > acetolachlor > alachlor > propachlor on the same clay. FT IR spectra showed that the carbonyl group of the herbicide molecule was involved in binding, probably via H bond with water molecules in the clay interlayer. The type and position of substitutions around the carbonyl group may have affected the electronegativity of oxygen, thus influencing the relative adsorption of these herbicides. For the same herbicide, adsorption on clay increased in the order of Mg 2+ <Ca 2+ <Al 3+ ≤Fe 3+ which coincided with the increasing acidity of homoionic clays. Acidity of cations may have affected the protonation of water, and thus the strength of H bond between the clay water and herbicide. Complexation of clay and humic acid resulted in less adsorption than that expected from independent adsorption by the individual constituents. The effect varied with herbicides, but the greatest decrease in adsorption occurred at a 60:40 clay to humic acid ratio for all the herbicides. Causes for the decreased adsorption need to be characterized to better understand adsorption mechanisms and predict adsorption from soil compositions.

Simultaneous Voltammetric Determination of Three Herbicides in Food and Water Samples with the Aid of Chemometrics

Differential pulse stripping voltammetry method（DPSV） was applied to the determination of three herbicides, ametryn, cyanatryn, and dimethametryn. It was found that their voltammograms overlapped strongly, and it is difficult to determine these compounds individually from their mixtures. With the aid of chemometrics, classical least squares（CLS）, principal component regression（PCR） and partial least squares（PLS）, voltammogram resolution and quantitative analysis of the synthetic mixtures of the three compounds were successfully performed. The proposed method was also applied to the analysis of some real samples with satisfactory results.

Determination of triazine herbicide residues in water samples by on-line sweeping concentration in micellar electrokinetic chromatography

A new method for the determination of atrazine, simazine and prometryn in water samples by on-line sweeping concentration technique in micellar electrokinetic chromatography （MEKC） was developed. Various parameters affecting sample enrichment and separation efficiency were systematically studied. Compared with the conventional MEKC method, up to 60-200-fold improvement in concentration sensitivity was achieved in terms of peak height by using this sweeping injection technique. The compound strychnine was used as the internal standard for the improvement of the experimental reproducibility. The limits of detection （S/ N = 3：1） for atrazine, simazine and prometryn were 9, 10 and 0.5 ng mL-1, respectively. This method has been successfully applied to the analysis of atrazine, simazine and prometryn in lake, steam and ground water.