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Introduction: Effective weed management tools are crucial for maintaining the profitable production of snap bean (Phaseolus vulgaris L.). Preemergence herbicides help the crop to gain a size advantage over the weeds, but the few preemergence herbicides registered in snap bean have poor waterhemp (Amaranthus tuberculatus) control, a major pest in snap bean production. Waterhemp and other difficult-to-control weeds can be managed by flumioxazin, an herbicide that inhibits protoporphyrinogen oxidase (PPO). However, there is limited knowledge about crop tolerance to this herbicide. We aimed to quantify the degree of snap bean tolerance to flumioxazin and explore the underlying mechanisms. Methods: We investigated the genetic basis of herbicide tolerance using genome-wide association mapping approach utilizing field-collected data from a snap bean diversity panel, combined with gene expression data of cultivars with contrasting response. The response to a preemergence application of flumioxazin was measured by assessing plant population density and shoot biomass variables. Results: Snap bean tolerance to flumioxazin is associated with a single genomic location in chromosome 02. Tolerance is influenced by several factors, including those that are indirectly affected by seed size/weight and those that directly impact the herbicide's metabolism and protect the cell from reactive oxygen species-induced damage. Transcriptional profiling and co-expression network analysis identified biological pathways likely involved in flumioxazin tolerance, including oxidoreductase processes and programmed cell death. Transcriptional regulation of genes involved in those processes is possibly orchestrated by a transcription factor located in the region identified in the GWAS analysis. Several entries belonging to the Romano class, including Bush Romano 350, Roma II, and Romano Purpiat presented high levels of tolerance in this study. The alleles identified in the diversity panel that condition snap bean tolerance to flumioxazin shed light on a novel mechanism of herbicide tolerance and can be used in crop improvement. [ABSTRACT FROM AUTHOR]

Glyphosate, widely used to manage weeds in cassava crops, simultaneously inhibits cassava growth, necessitating the development of herbicide-tolerant cassava varieties. In this study, screened 262 cassava varieties, identifying the glyphosate-resistant (GR) variety ZM8701 and the glyphosate-sensitive (GS) variety SC9. Transcriptomic analysis via Illumina sequencing revealed differentially expressed genes associated with resistance, including Cytochrome P450, GST, GT, ABC transporters, and others such as MIOX1, LHCA1, PPH, HSP26, HSP83A, and UGT73C5. Notably, the EMB3004 gene, involved in the biosynthesis of aromatic amino acids, was significantly upregulated in resistant varieties, suggesting a key role in countering glyphosate's inhibition of the shikimic acid pathway. These genes are pivotal in enhancing cell wall biosynthesis, optimizing photosynthesis, and improving detoxification processes. This research elucidated the molecular mechanisms underlying cassava's resistance to glyphosate, thereby laying the groundwork for breeding programs aimed at developing herbicide-resistant varieties. [ABSTRACT FROM AUTHOR]

Incorporation of red clover (Trifolium pratense L.) into grass pastures can reduce the need for nitrogen fertilizer applications and increase the nutritional value of the forage. However, red clover cultivars available for Kentucky producers are highly susceptible to herbicides, such as 2,4-D (2,4-dichlorophenoxy acetic acid), used for pasture broadleaf weed control. To overcome this problem, 'UK2014' red clover was selected for increased tolerance to 2,4-D. We employed a transcriptome analysis approach to compare the gene expression response following 2,4-D treatment of 'UK2014' to that of 'Kenland', a 2,4-D sensitive red clover and one of the parents of 'UK2014'. The objectives were to first determine if the increased 2,4-D tolerance in 'UK2014' is reflected in a change of transcription response and/or a quicker recovery of a transcriptional response following 2,4-D treatment, and second, to identify genes, whether constitutively expressed or induced by 2,4-D, which could be the basis for the increased 2,4-D tolerance. Leaf tissue from the two red clovers grown in the field was collected at 4, 24, and 72 h after 2,4-D (1.12 kg 2,4-amine a.e. ha−1) treatment from both untreated and treated plants. Global gene expression was determined with reads from Illumina Hiseq 2500 mapped against the red clover draft genome, Tpv2.1 (GenBank Accession GCA_900079335.1). Genes that displayed differential expression (DEGs) following 2,4-D treatment were selected for further analysis. The number of DEGs was higher for 'Kenland' than for 'UK2014', suggesting that a lower transcriptional response corresponds with the higher 2,4-D tolerance in the 'UK2014' line. Similarly, gene ontology enrichment analysis revealed that expression of photosynthesis-related genes was less affected by 2,4-D in the 'UK2014' line than 'Kenland'. Although we were not able to identify any specific genes that are the basis for the increased 2,4-D tolerance of 'UK2014', we concluded that the increased 2,4-D tolerance of 'UK2014' correlates with a decreased transcription response to 2,4-D. Additionally, expression of several cytochrome P450 genes that had different isoforms between 'UK2014' and 'Kenland' increased significantly in both following 2,4-D treatment, one or more of these P450s could be mediators of 2,4-D metabolism and tolerance in red clover. [ABSTRACT FROM AUTHOR]

The post‐emergent herbicide options to control grasses in sorghum have historically been limited. Therefore, a mass selection program was implemented to increase the tolerance of sorghum to the broad‐spectrum herbicide tembotrione. The objectives of this study are to determine (i) which observation timing and vegetative indices are most effective in assessing sorghum injury to tembotrione using unoccupied aerial system imagery and (ii) if mass selection can be used to increase the tolerance of sorghum to tembotrione. Using an unoccupied aerial system, several vegetative indices, collected at either 14 or 21 days after tembotrione application, accurately measured sorghum injury. Over four cycles of selection, tembotrione tolerance increased in a linear and consistent manner. This demonstrates that mass selection can be used as a strategy for developing herbicide tolerance in crops. The modest, but steady genetic gain indicates both the quantitative nature of the trait and sufficient heritability to improve it. Given further development, tembotrione‐resistant sorghum hybrids could provide an effective means of post‐emergent weed control for a range of common weeds. [ABSTRACT FROM AUTHOR]

BACKGROUND: Tolpyralate, a relatively new inhibitor of 4‐hydroxyphenylpyruvate dioxygenase (HPPD), is registered for postemergence use in all types of corn (Zea mays L.) and has a record of excellent crop tolerance. A report of severe crop injury to sweet corn inbred (XSEN187) led to the following objectives: (i) determine whether sensitivity to tolpyralate in XSEN187 exists, and if confirmed, (ii) determine the genetic basis of tolpyralate sensitivity, and (iii) screen other corn germplasm for sensitivity to tolpyralate. RESULTS: Inbred XSEN187 was confirmed sensitive to tolpyralate. Inclusion of methylated seed oil or nonionic surfactant in the spray volume was necessary for severe crop injury. Tolpyralate sensitivity in XSEN187 is not conferred by alleles at Nsf1, a cytochrome P450‐encoding gene (CYP81A9) conferring tolerance to many corn herbicides. Evidence suggests that tolpyralate sensitivity in XSEN187 is conferred by a single gene mapped to the Chr05: 283 240–1 222 909 bp interval. Moreover, tolpyralate sensitivity was observed in 48 other sweet corn and field corn inbreds. CONCLUSIONS: Severe sensitivity to tolpyralate exists in sweet corn and field corn germplasm when the herbicide is applied according to label directions. Whereas the corn response to several other herbicides, including HPPD‐inhibitors, is conferred by the Nsf1 locus, corn sensitivity to tolpyralate is the result of a different locus. The use of tolpyralate should consider herbicide tolerance in inbred lines from which corn hybrids were derived, whereas alleles that render corn germplasm sensitive to tolpyralate should be eliminated from breeding populations, inbreds, and commercial cultivars. © 2023 Illinois Foundation Seeds, Inc and The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA. [ABSTRACT FROM AUTHOR]

Using glyphosate is easier than manually controlling the invasive plant Carpobrotus in dune ecosystems. However, before it is used its effect on native species in this ecosystem needs to be determined. This study reports the effects in the laboratory of different concentrations of glyphosate (1.0, 0.5, 0.3, 0.1, 0.05, 0.01, and 0.005 g/m2 ) on germination and seedling emergence of four species of Mediterranean dune plants, Lotus creticus, Medicago marina, Ononis ramosissima and Ammophila arenaria, used in the restoration of this natural ecosystem. Germination was completely inhibited when glyphosate was applied at 0.5, and 1.0 g/m². The recommended dose (0.3 g/m²) also inhibited the germination of L. creticus and M. marina. The percentage germination of O. ramosissima and A. arenaria was around 40% and 30% respectively when a dose of glyphosate of 0.1 g/m² was used, whereas for seeds of L. creticus and M. marina it was lower than 5%. The T50 at germination of seed incubated with glyphosate increased in all species independently of the dose of glyphosate. Seedling emergence from seeds previously germinated in the presence of glyphosate was only recorded for O. ramosissima and A. arenaria. The results indicate that seeds of O. ramosissima are more tolerant of glyphosate, followed by those of A. arenaria and those of L. creticus and M. marina are the most sensitive. [ABSTRACT FROM AUTHOR]

The clustered regularly interspaced short palindromic repeats/CRISPR-associated protein (CRISPR/Cas) genome editing technology, derived from the adaptive immune system of bacteria, has now been recognized as one of the most useful genetic tools in genome engineering. Short stretch of RNA guides the Cas enzyme to precise locations within the target genome of living organisms to accurately modify and control the functions of genes with high accuracy. Cas-mediated genome editing is scalable, practically feasible, and permits the research community to expound the functional organization of the hereditary material and helps to understand the relationship between genetic variations and biological phenotypes. Although CRISPR/Cas system has opened many possibilities in the field of genetic engineering, it still has some shortcomings, such as constraints of the protospacer-adjacent motif (PAM) sequence, relatively larger size of the Cas9 gene and higher chances of off-targeting. To overcome these shortcomings, many new Cas9 variants have been engineered with improved features such as specificity and editing efficacy. Anticipated traits can be developed in plants with high utility in agriculture. For the past decade, this editing system has made significant progress and has been widely used in genome editing to create gene knock-ins and knock-outs. Genome editing is mediated either by non-homologous end joining (NHEJ) or homology-directed repair (HDR) mechanism, consequently resulting in desired mutations that directly enhance plant performance. This paper summarizes the new variants of the CRISPR/Cas system and applications of the CRISPR system in plant science for the enhancement of various attributes such as yield, quality, nutritional factors, stress tolerance, and herbicide tolerance through knock-in and knock-out strategies. [ABSTRACT FROM AUTHOR]

The research was carried out on newly planted bare-root plants at an early stage of their cultivation. The scope of the growth responses of woody plants was verified in relation to the recommended herbicide rate, namely for herbicide solution application rates of 0.825% and 1.025%. The new increment of the longest shoot and the mortality rate were evaluated. The selective efficacy on weeds was observed. Data collection took place at 2, 4, 8, 12 and 24 weeks after application. The experiment followed the manufacturer's recommendations for application. It was conducted on an experimental area of loamy sand soil in 2019 and it was not affected by extreme weather conditions. The application of the herbicide to privet (Ligustrum vulgare) showed a small inhibitory effect, reducing the average increment of the longest plant shoot by 4.7% and 8.3%, respectively, by the end of the study period compared to the control. By contrast, in the case of the European Bladdernut (Staphylea pinnata), the application was found to have an adverse effect. The role of the application rate was secondary. The average increment of the longest shoot was reduced by 45.68% and 50.13%, respectively, and the mortality rate of the treated woody plants reached 10% at the end of the study period. The highest inhibitory effect of the herbicide on the ornamental woody plants that had been treated was observed in the first 2 and 4 weeks after treatment, respectively. The application of the herbicide proved ineffective against horseweed (Conyza canadensis) and groundsel (Senecio vulgaris). [ABSTRACT FROM AUTHOR]

BACKGROUND: The potential of weed species to respond to selection forces affecting the evolution of weedy traits such as competitive ability is poorly understood. This research characterized evolutionary growth changes in a single Abutilon theophrasti Medik. population comparing multiple generations collected from 1988 to 2016. A competition study was performed to understand changes in competitive ability, and a herbicide dose–response study was carried out to assess changes in sensitivity to acetolactate synthase‐inhibiting herbicides and glyphosate over time. RESULTS: When grown in monoculture, A. theophrasti biomass production per plant increased steadily across year‐lines while leaf number decreased. In replacement experiments, A. theophrasti plants from newer year‐lines were more competitive and produced more biomass and leaf area than the oldest year‐line. No clear differences in sensitivity to imazamox were observed among year‐lines. However, starting in 1995, this A. theophrasti population exhibited a progressive increase in growth in response to a sublethal dose of glyphosate (52 g a.e. ha−1), with the 2009 and 2016 year‐lines having more than 50% higher biomass than the nontreated control. CONCLUSION: This study demonstrates that weeds can rapidly evolve increased competitive ability. Furthermore, the results indicate the possibility of changes in glyphosate hormesis over time. These results highlight the importance of the role that rapid (i.e., subdecadal) evolution of growth traits might have on the sustainability of weed management strategies. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Crop wild relatives (CWRs) belonging to the Brassicaceae family possess extensive genetic diversity and have frequently been utilized in the enhancement of cultivated Brassica species. However, their tolerance to glyphosate, a widely used herbicide, has remained unknown. Our study examined the glyphosate response of 20 genotypes from the Brassicaceae family, which included genotypes within the U triangle and their wild relatives. We evaluated their behaviour based on morpho-biochemical responses, specifically focusing on the traits of germination percentage, root length, and survival percentage. By calculating the mean membership function value (MFV) for each genotype's response to these traits, we classified them into three distinct groups: susceptible, moderately tolerant, and tolerant. Among these genotypes, Brassica rapa (NRCPB rapa 8) demonstrated tolerance to glyphosate, as indicated by their mean MFV value of 0.68. Moderate tolerance to glyphosate was observed in Brassica juncea (Pusa Jaikisan) with a mean MFV of 0.52. Conversely, Diplotaxis catholica, Diplotaxis muralis, and Enarthrocarpus lyratus were susceptible, with mean MFV values of 0.37, 0.35, and 0.34, respectively. These findings revealed varying levels of response to glyphosate among these genotypes, with some displaying significant tolerance. The study provides valuable insights into the herbicide tolerance of Brassica CWRs and emphasizes the potential use of phenotypic and biochemical markers in evaluating herbicide tolerance. [ABSTRACT FROM AUTHOR]

Weeds that usually grow in non-agricultural areas have become increasingly common invading perennial crops. Species of the genus Filago, in addition to invading Spanish olive groves, have developed certain levels of natural tolerance to the acetolactate synthase (ALS) inhibiting herbicide flazasulfuron. The objective of this study was to determine the level and the mechanism involved in the tolerance to flazasulfuron in Filago pyramidata L., which occurs in olive groves of southern Spain, as well as to identify possible cross- or multiple-tolerances by evaluating alternative herbicides for its control. A population resistant (R) to flazasulfuron and a susceptible (S) one of Conyza canadensis were used as references. The accessions of F. pyramidata presented LD50 values (from 72 to 81 g active ingredient (ai) ha−1) higher than the field dose of flazasulfuron (50 g ai ha−1), being 11–12.5 times more tolerant than the S population of C. canadensis, but less than half the R population (170 g ai ha−1). Enzymatically, F. pyramidata was as sensitive to flazasulfuron (I50 = 17.3 μM) as the S population of C. canadensis. Filago pyramidata plants treated with flazasulfuron, combined with 4-chloro-7-nitro-2,1,3-benzoxadiazole, had a growth reduction of up to 85%, revealing the participation of glutathione-S-transferases in herbicide metabolism. Filago pyramidata presented cross-tolerance to the different chemical groups of ALS inhibitors, except triazolinones (florasulam). Synthetic auxins (2,4-D and fluroxypyr) presented good control, but some individuals survived (low multiple resistance). Cellulose synthesis, 5-enolpyruvylshikimate-3-phosphate, 4-hydroxyphenylpyruvate dioxygenase, protoporphyrinogen oxidase, photosystem I, and photosystem II inhibitor herbicides, applied in PRE or POST-emergence, presented excellent levels of control of F. pyramidata. These results confirmed the natural tolerance of F. pyramidata to flazasulfuron and cross-tolerance to most ALS-inhibiting herbicides. The mechanism involved was enhanced metabolism mediated by glutathione-S-transferases, which also conferred low multiple tolerance to synthetic auxins. Even so, herbicides with other mechanisms of action still offer excellent levels of control of F. pyramidata. [ABSTRACT FROM AUTHOR]

A temperature-controlled glasshouse study was conducted to evaluate the influence of elevated temperature (eT – 34/24 ± 2°C) on the growth and glyphosate susceptibility of windmill grass (Chloris truncata R.Br.), common sowthistle (Sonchus oleraceus L.), and flaxleaf fleabane [Conyza bonariensis (L.) Cronquist]; and to determine the morpho-physiological factors involved in differential glyphosate tolerance under eT. Results showed that elevation of temperature from ambient temperature (aT – 28/20 ± 2°C) to 34/24 ± 2°C increased growth and biomass production of C. truncata. In contrast, eT suppressed growth of S. oleraceus and C. bonariensis, resulting in fewer, thicker, and smaller leaves with reduced stomatal conductivity and less total plant biomass. In terms of herbicide susceptibility, the responses to glyphosate under different temperature regimes were species- and rate-specific. Slight variations in glyphosate susceptibility were observed when sprayed at sub-lethal rates at eT. Under eT, C. truncata, S. oleraceus, and C. bonariensis required 1.5, 2.0-, and 1.6-times higher glyphosate rates, respectively, to suppress biomass by 50% compared with plants grown at aT. Depending upon the species and glyphosate rate, differences in leaf characteristics (i.e. leaf chlorophyll content, leaf area/thickness, and stomatal conductance) could have promoted or delayed glyphosate activity under eT over the period, especially at sub-lethal rates. Overall, the glyphosate efficacy was unaffected since herbicide within the recommended rates completely controlled all tested weed species under both temperatures. [ABSTRACT FROM AUTHOR]

Assessing the adaptability and stability of herbicide-tolerant lentil accessions to two broad-spectrum post-emergence herbicides in multi-environment trials has become a must in a breeding program to improve its selection. The adaptability and stability of 42 herbicide-tolerant lentil accessions were investigated using five stability parameters under eight different environments. Significant Genotype–Environment (GE) interaction was found for days to flowering (DFLR), days to maturity (DMAT), and seed yield per plant (SY). The analyzed stability parameters such as Cultivar superiority, Finlay–Wilkinson, Shukla, Static Stability, and Wricke's Ecovalence ranked the tested accessions differently, confirming the importance of using a combination of stability parameters when evaluating the performance of a group of accessions. GGE biplot of the SY trait accounted for 60.79% of sums of squares of the GE interaction and showed that cool and high rainfall environments are ideal for testing the agronomic performance of tolerant accessions. The GGE biplot of SY showed that IG4605(19), IG195(6), and IG156635(12) were specifically adapted to one mega environment, whereas IG70056(38) was identified as a superior line having a high and stable yield. These lines should be included in lentil crossing programs to develop herbicide-tolerant cultivars adapted to diverse environments. [ABSTRACT FROM AUTHOR]

Insect infestation and weed interference have a seriously negative impact on the growth, yield, and grain quality of maize. In this study, transgenic maize plants harboring three exogenous genes, cry2Ab, vip3A, and cp4epsps, that were constructed into a single T-DNA were developed for protection against insects and weeds. The transgene integration sites on the chromosomes in two transgenic maize events, CVC-1 and CVC-2, were determined using whole genome sequencing and specific PCR detection. As revealed by laboratory insect bioassays, these two transgenic events exhibited strong insecticidal toxicity against three major species of Lepidoptera insects, including Mythimna separata, Helicoverpa armigera, and Spodoptera frugiperda, with mortality rates exceeding 96%, 100%, and 100%, respectively, after six days of infestation. In addition, CVC-1 exhibited a high tolerance to glyphosate under field conditions. The successful expressions of cry2Ab, vip3A, and cp4epsps in various tissues at different developmental stages of CVC-1 were validated at the transcriptional and translational levels using quantitative real-time reverse transcription PCR (qRT-PCR) and enzyme-linked immunosorbent assay (ELISA), respectively. These findings demonstrated that the transgenic maize CVC-1 developed using this triple gene construct has excellent insect resistance and herbicide tolerance, which may provide a valuable germplasm resource and data support for future maize breeding of insect and weed control. [ABSTRACT FROM AUTHOR]

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Context: Yield losses in lentil (Lens culinaris ssp. culinaris Medik.) caused by weeds are estimated at 20–80%. In the absence of effective broad-spectrum herbicides, the menace of weed has emerged as a serious yield constraint in lentil. Aims: Identification of tolerance to two broad-spectrum post-emergence herbicides, imazethapyr and metribuzin. Methods: 221 lentil accessions were screened at the experimental research station of the International Center for Agricultural Research in the Dry Areas, Terbol (Lebanon) over four crop seasons (2014/15–2018/19). During the 2014/15 season, a preliminary screening experiment was conducted with 221 lentil accessions in an alpha lattice design with two replications, where accessions were treated at the pre-flowering stage at 150% of the recommended dose of imazethapyr (112.5 g active ingredient/ha) or metribuzin (315 g active ingredient/ha). Based on the preliminary results, 38 accessions were selected for further evaluation. In subsequent testing, the selected accessions were screened at 100% and 150% of the recommended doses of imazethapyr or metribuzin. Key results: Herbicide treatments delayed the flowering time and maturation of tested lentil accessions. The plant height of selected tolerant accessions was reduced by 15% and 8% in the plots treated by imazethapyr and metribuzin, respectively. Reduction index (RIsy) was an effective tool to select for herbicide tolerance. Stability analysis indicated that two accessions (IG4400 and IG5722) performed under high rainfall environments while two other accessions (IG323 and IG4605) were adapted to low rainfall environments. Conclusions: Four accessions (IG323, IG5722, IG4400, IG4605) were identified as independently tolerant to metribuzin and imazethapyr. Implications: The identified herbicide-tolerant accessions can be used to develop herbicide-tolerant cultivars. The integration of herbicide-tolerant lentil in the cropping system increases its sustainability and soil fertility in West Asian and North African regions. Therefore the identified sources for herbicide tolerance combined with other traits can be used to develop new cultivars that can be adapted to modern cropping systems in the region. The cultivars can decrease the cost of the production by reducing the cost of laborious hand weeding. [ABSTRACT FROM AUTHOR]

Background and Objectives: Quinoa (Chenpodium quinoa Willd.) is an herbaceous flowering annual plant from amaranth family grown as a crop primarily for its valuable seeds; the seeds are rich in protein, fibers, vitamins, and minerals in amounts greater than in many grains. Because of drought and salt tolerance, Quinoa can be cultivated in the areas affected by drought and salt stress conditions in the country. Weeds are the major obstacles in increasing the productivity of Quinoa. Since now, there has been no remarkable research and suitable herbicides available for weed control in Quinoa fields during the post-emergence stage. The aim of the present study was to screening the herbicides already registered for weed control in different crops rather than quinoa, and to test the possible tolerance of quinoa to the applied herbicides for secure and safe herbicide recommendations. Materials and Methods: A field study was conducted for screening and selection of possible herbicides to be used for chemical weed control in quinoa fields of Astan Ghods Razavi, in Anabad, located in Bardascan in Khorasan Razavi province, Iran, in during 2019. Herbicides were sprayed as post emergence (foliar applied) at 4-6 leafy stage of quinoa by Matabi® rechargeable sprayer calibrated to deliver 350 l ha-1 of spray solution. The layout was a completely randomized blocks design with three replicates. Treatments were post emergence application of atrazine (800 g a i ha-1 ), metribuzin (525 g a i ha-¹ ), phenmedipham+ desmedipham+ ethofumesate (822 g a i ha-1 ), quizalofop tefuryl (60 g a i ha-1 ), clethodim (96 g a i ha-1 ), haloxyfop methyl (104 g a i ha-1 ), acetochlor (228 g a i ha-1 ), bensulfuron methyl (30 g a i ha-1 ), bentazon (1440 g a i ha-1 ), queen merak+ metazachlor (1040 g a i ha-1 ), clopyralid (225 g a i ha-1 ), 2, 4-D + dicamba (698 g a i ha-1 ), imazethapyr (100 g a i ha-1 ), isoxaflutole+ thiencarbazone methyl (232.5 g a i ha-1 ), ethofumesate (1250 g a i ha-1 ), oxadiazone (360 g a i ha-1 ), oxyfluorfen (360 g a i ha-1 ), pendimethalin (Prol® ) (675 and 1350 g a i ha-1 ), sethoxydim (375 g a i ha-1 ), sulfosulfuron (19.95 g a i ha-1 ), clodinafop (192 g a i ha-1 ), tribenuron methyl (15 g a i ha-1 ), rimsulfuron+ nicosulfuron (131.25 g a i ha-1 ) plus hand weeding and untreated control. Results: Two weeks after herbicide spray, no visual injury were observed on quinoa when sprayed with clethodim, quizalofop tefuryl, clodinafop, haloxyfop methyl, sethoxydim and pendimethalin (675 g a i ha-1 ). Severe visual damage (100% injury) however, observed on quinoa when sprayed with atrazine, metribuzin, phenmedipham+ desmedipham+ ethofumesate, oxyfluorfen, bentazon and oxadiazone. The rest of the herbicides were rated in between. Quinoa grain yield when sprayed with clethodim (3190.7kg ha-1 ) and quizalofop tefuryl (2674.7 kg ha-1 ) were not significantly different from hand weeding (3346.7 kg ha-1 ). But application of atrazine, metribuzin, phenmedipham+ desmedipham+ ethofumesate, oxyfluorfen, bentazon and 2, 4-D + dicamba yielded to complete quinoa death. Quinoa grain yield when sprayed with bensulfuron methyl (1402.7 kg ha-1 ), imazethapyr (1184 kg ha -1 ), clopyralid (1402.7 kg ha-1 ) and pendimethalin (784 and 964 kg ha-1 at doses of 675 and 1350 g a i ha-¹, respectively) were promising results while still significantly lower than that of hand weeding control. Conclusion: Application of quizalofop-tefuryl and clotidim can be recommended to be used for weed control in quinoa. Besides application of haloxyfop methyl, sethoxydim, clodinafop, bensulfuron methyl, imazethapyr, clopyralid, pendimethalin and queen merak+ metazachlor showed promising results but still more experimentation need to be done for final recommendation. [ABSTRACT FROM AUTHOR]

BACKGROUND: CYP81A cytochrome P450s (CYP81As) play a key role in herbicide detoxification in Poaceae plants. Crop CYP81As confer natural tolerance to multiple herbicides, whereas CYP81As in weeds disrupt herbicide action. Identifying differences in CYP81A herbicide specificity between crops and weeds could provide valuable information for controlling weeds. In this study, we quantitatively compared herbicide specificity between CYP81A6 from rice (Oryza sativa) and CYP81A12 and CYP81A21 from a weed, Echinochloa phyllopogon, using transgenic Escherichia coli and Arabidopsis. RESULTS: All three CYP81As metabolized the five tested herbicides and formed similar metabolites, with the highest relative activities of 400 to 580% toward bentazone compared to their activity on bensulfuron‐methyl (defined as 100%). However, they showed differing activity toward propyrisulfuron. The relative activities of Echinochloa phyllopogon CYP81A12 (12.2%) and CYP81A21 (34.4%) toward propyrisulfuron were lower than that of rice CYP81A6 (98.5%). Additionally, rice CYP81A6 produced O‐demethylated propyrisulfuron and hydroxylated products, whereas Echinochloa phyllopogon CYP81As produced only hydroxylated products. Arabidopsis expressing CYP81A12 and CYP81A21 exhibited lower levels of resistance against propyrisulfuron compared to that in Arabidopsis expressing CYP81A6. Homology modeling and in silico docking revealed that bensulfuron‐methyl docked well into the active centers of all three CYP81As, whereas propyrisulfuron docked into rice CYP81A6 but not into Echinochloa phyllopogon CYP81As. CONCLUSION: The differing herbicide specificity displayed by rice CYP81A6 and Echinochloa phyllopogon CYP81A12 and CYP81A21 will help design inhibitors (synergists) of weed CYP81As, as well as develop novel herbicide ingredients that are selectively metabolized by crop CYP81As, to overcome the problem of herbicide resistance. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Weed interference in the crop field is one of the major biotic stresses causing dramatic crop yield losses, and the development of herbicide-resistant crops is critical for weed control in the application of herbicide technologies. To identify herbicide-resistant germplasms, we screened 854 maize inbreed lines and 25,620 seedlings by spraying them with 1 g/L glufosinate. One plant (L336R), possibly derived from a natural variation of line L336, was identified to have the potential for glufosinate tolerance. Genetic analysis validated that the glufosinate tolerance of L336R is conferred by a single locus, which was tentatively designated as ZmGHT1. By constructing a bi-parental population derived from L336R, and a glufosinate sensitive line L312, ZmGHT1 was mapped between molecular markers M9 and M10. Interestingly, genomic comparation between the two sequenced reference genomes showed that large scale structural variations (SVs) occurred within the mapped region, resulting in 2.16 Mb in the inbreed line B73, and 11.5 kb in CML277, respectively. During the fine mapping process, we did not detect any additional recombinant, even by using more than 9500 F2 and F3 plants, suspecting that SVs should also have occurred between L336R and L312 in this region, which inhibited recombination. By evaluating the expression of the genes within the mapped interval and using functional annotation, we predict that the gene Zm00001eb361930, encoding an aminotransferase, is the most likely causative gene. After glufosinate treatment, lower levels of ammonia content and a higher activity of glutamine synthetase (GS) in L336R were detected compared with those of L336 and L312, suggesting that the target gene may participate in ammonia elimination involving GS activity. Collectively, our study can provide a material resource for maize herbicide resistant breeding, with the potential to reveal a new mechanism for herbicide resistance. [ABSTRACT FROM AUTHOR]

Understanding the genetics of metribuzin (a group C herbicide) tolerance in wheat is vital in developing tolerant cultivars to improve wheat productivity in dryland farming systems. This study investigated metribuzin tolerance in wheat by conducting a Genome-wide Association Studies (GWAS) with a panel of 150 wheat genotypes of diverse genetic backgrounds and genotyped them with the wheat 90 K SNP genotyping assay. The phenotyping was conducted in a temperature-controlled glasshouse at the University of Western Australia (UWA). Genotypes were sprayed with a metribuzin dose of 400 grams of active ingredient (g. a.i.) ha−1 as pre-emergent in a specialized spraying cabinet and transferred to the glasshouse where the tolerance level of the genotypes was assessed by measuring the relative reduction in chlorophyll content of the leaves. The decrease in chlorophyll content of the treated plants compared to the control was regarded as the phytotoxic effects of metribuzin. GWAS analysis following a mixed linear model revealed 19 genomic regions with significant marker-trait associations (MTAs), including ten on chromosome 6A, three on chromosome 2B, and one on chromosomes 3A, 5B, 6B 6D, 7A, and 7B, respectively. Sequences of the significant markers were blasted against the wheat genome, IWGSC RefSeq V1.0, and candidate genes having annotations related to herbicide tolerance in wheat, especially in pathways reported to be involved in metribuzin tolerance, such as cytochrome P450 pathways and ATP Binding Cassette (ABC) superfamilies, were identified in these genomic regions. These included TraesCS6A01G028800, TraesCS6A02G353700, TraesCS6A01G326200, TraesCS7A02G331000, and TraesCS2B01G465200. These genomic regions were validated on 30 top tolerant and 30 most susceptible genotypes using the five closest SSR makers to the flanked SNPs. Sufficient polymorphism was detected on two markers (wms193 and barc1036) that were found to differentiate between the susceptible and tolerant alleles and a t-test analysis of the phenotypic data shows a significant (value of p < 0.001) difference suggesting that these markers can be used for marker-assisted selection (MAS) in metribuzin studies and wheat breeding programs. [ABSTRACT FROM AUTHOR]

Understanding the genetics of metribuzin (a group C herbicide) tolerance in wheat is vital in developing tolerant cultivars to improve wheat productivity in dryland farming systems. This study investigated metribuzin tolerance in wheat by conducting a Genome-wide Association Studies (GWAS) with a panel of 150 wheat genotypes of diverse genetic backgrounds and genotyped them with the wheat 90 K SNP genotyping assay. The phenotyping was conducted in a temperature-controlled glasshouse at the University of Western Australia (UWA). Genotypes were sprayed with a metribuzin dose of 400 grams of active ingredient (g. a.i.) ha−1 as pre-emergent in a specialized spraying cabinet and transferred to the glasshouse where the tolerance level of the genotypes was assessed by measuring the relative reduction in chlorophyll content of the leaves. The decrease in chlorophyll content of the treated plants compared to the control was regarded as the phytotoxic effects of metribuzin. GWAS analysis following a mixed linear model revealed 19 genomic regions with significant marker-trait associations (MTAs), including ten on chromosome 6A, three on chromosome 2B, and one on chromosomes 3A, 5B, 6B 6D, 7A, and 7B, respectively. Sequences of the significant markers were blasted against the wheat genome, IWGSC RefSeq V1.0, and candidate genes having annotations related to herbicide tolerance in wheat, especially in pathways reported to be involved in metribuzin tolerance, such as cytochrome P450 pathways and ATP Binding Cassette (ABC) superfamilies, were identified in these genomic regions. These included TraesCS6A01G028800, TraesCS6A02G353700, TraesCS6A01G326200, TraesCS7A02G331000, and TraesCS2B01G465200. These genomic regions were validated on 30 top tolerant and 30 most susceptible genotypes using the five closest SSR makers to the flanked SNPs. Sufficient polymorphism was detected on two markers (wms193 and barc1036) that were found to differentiate between the susceptible and tolerant alleles and a t-test analysis of the phenotypic data shows a significant (value of p < 0.001) difference suggesting that these markers can be used for marker-assisted selection (MAS) in metribuzin studies and wheat breeding programs. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Agricultural Science & Technology (1008-0864) is the property of Journal of Agricultural Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Thirty-one sugarcane genotypes were planted in the experiment and post-emergence application of Halosulfuron Methyl 75% WG and Metribuzin 70% WP was carried out at the rate of 67.5 g and 1000 g a.i. per hectare on 42 days after planting (DAP). Lower leaves of some of the genotypes were found to show injuries on 5 days after spraying (DAS). Phytotoxicity was recorded in visual scoring scale of 0 to 10 at 7, 15, 21 and 30 DAS. Phytotoxicity rating of the 31 genotypes studied ranged between 0 and 4. Nine genotypes showed no visual injury and found tolerant, while eight genotypes showed moderate toxic effect (rating 4). All the genotypes (14 nos.) that showed phytotoxicity rating of 1 to 3 recovered visually (leaf injuries) except Co 06027 at 30 DAS, while all the genotypes that showed moderate phytotoxicity did not recover completely except Co 94008. The genotypes with Co 7201 and Co 775 as one of the parents showed phytotoxicity rating ranging from 1 to 4. The genotypes, Co 06030, Co 86032, Co 11015, Co 92005 and Co 09004 did not exhibit phytotoxicity symptoms, while their parent, CoC 671 exhibited phytotoxicity. Seven parental genotypes showed 100% probability of no herbicidal injury in their progenies and exhibited herbicidal tolerance from initial stage. Cane yield reduction (> 5%) was observed only in Co 8021, Co 94008 and Co 99006 with herbicide treatment over no herbicide application. The present study provides a preliminary information on the genetic variation among sugarcane genotypes for herbicide tolerance and their parental relationship, which could be utilized for the development of herbicide tolerant varieties for effective weed management in sugarcane agriculture. [ABSTRACT FROM AUTHOR]

Rimsulfuron is commonly used to control common lambsquarters (Chenopodium album L.) and redroot pigweed (Amaranthus retroflexus L.) in potato (Solanum tuberosum L.) fields. Comparing rimsulfuron absorption and metabolism patterns in these two weed species with potato could provide crucial information to optimise herbicide application in the field. Hence, an experiment was conducted in Denmark and Iran to evaluate the absorption and metabolism of rimsulfuron at the application rate of 30 g ha−1 in potato, common lambsquarters and redroot pigweed. Seedlings at the 2- to 4-leaf stage were foliar treated with rimsulfluron and plant tissues were harvested at 0, 1, 4, 8, 24 and 48 h after treatment (HAT) to measure the rate of herbicide absorption and metabolism using HPLC. Absorption and metabolism of rimsulfuron differed between potato and weed seedlings. This explains the different susceptibility to rimsulfuron in potato, redroot pigweed and common lambsquarters. Redroot pigweed, the most sensitive species in this study, showed the highest rate of absorption and lowest rate of the herbicide metabolism. Common lambsquarters, a species with an intermediate sensitivity, revealed moderate rimsulfuron absorption and metabolism levels. Potato, the tolerant crop species to rimsulfuron, showed the lowest and highest rate, respectively, of absorption and metabolism. [ABSTRACT FROM AUTHOR]

The immediate impact of prevailing environmental conditions on sensitivity of weeds to herbicides is well documented but little is known about the effects of parental environments on the responses of progeny to herbicides. It has been suggested that parental plants subjected to abiotic stress may result in progeny with increased tolerance to stresses. We tested this hypothesis by growing two populations of Palmer amaranth (Amaranthus palmeri) from California and Kansas under well‐watered (WW) and water‐deficit (25% of WW treatment) conditions to obtain F1 seeds. We then tested the responses of F1 seedlings to various doses of five herbicides with different modes of action. Dose‐response analysis of visual plant injury, aboveground biomass, and chlorophyll content showed that in 16 out of 30 comparisons, sensitivity to herbicides in A. palmeri progeny originated from a maternally water stressed environment was significantly lower than those obtained from WW plants. Only in one case the progeny from stressed plants was significantly more sensitive to herbicide (saflufenacil) than that from non‐stressed plants, and no differences were observed between the two types of progeny in all other (13) comparisons. The reduced sensitivity in progeny from stressed plants was consistent in terms of the evaluated response variables in population from California with the application of S‐metolachlor, rimsulfuron, and simazine; and in population from Kansas with the application of S‐metolachlor and rimsulfuron. Our study suggests that A. palmeri plants experiencing drought during the season may produce progeny that might be more difficult to control because of an increase in herbicide tolerance endowed through transgenerational effects of water stress. [ABSTRACT FROM AUTHOR]

Currently, genetically modified (GM) crops are an important part of world agriculture, offering numerous benefits to farmers. This study investigates the dynamics of the cultivated area with GM crops, especially with genetically modified (GM) soybean, for the period 2014-2018, by country and by transgenic trait, using ISAAA and FAOSTAT databases. In the studied period, the top 5 GM crops countries were USA, Brazil, Argentina, Canada and India which totalled 166.1 million hectares or 89.5% of the global area. Regarding GM soybean, the top 5 countries were USA, Brazil, Argentina, Paraguay and Canada which cultivated 89.9 million hectares or 96.8% of the global area with this crop. The linear regression and the Pearson correlation coefficient have pointed out a general increasing trend for both cultivated areas. The USA and Brazil occupied the leading position in world with 32.93 and 32.55 million hectares of GM soybean, respectively. Herbicide tolerance (HT) has been consistently the dominant transgenic trait for GM soybean in USA, Argentina, Paraguay and Canada. In Brazil, the cultivated areas with stacked HT/IR traits have been larger than the areas cultivated with a single HT trait, in the last 3 years. As a conclusion, the global area of GM soybean will continue to increase due to its important economic role in the agriculture development and environmental benefits. [ABSTRACT FROM AUTHOR]

Herbicide-tolerant rice varieties generated by genome editing are highly desirable for weed control. We have used a cytosine base editor to create a series of missense mutations in the P171 and/or G628 codons of the acetolactate synthase (ALS) gene to confer herbicide tolerance in rice. The four different missense mutations in the P171 codon, P171S, P171A, P171Y and P171F, exhibited different patterns of tolerance towards five representative herbicides from five chemical families of ALS inhibitors. For example, P171S and P171A had lower levels of tolerance than P171Y and P171F to bispyribac but not to the other herbicides. Interestingly, a novel triple mutant (P171F/G628E/G629S) had the highest tolerance to all five tested herbicides. Field trials showed that both P171F and P171F/G628E/G629S could potentially be used with nicosulfuron. Our work illustrates an effective way of using base editing to generate herbicide tolerance in elite rice varieties. [ABSTRACT FROM AUTHOR]

Genes of tolerance for herbicide has become one of the options more used in world level for the weed control. This study had as objective to evaluated crosses between tolerant irrigated rice plants and sensitive to herbicides of the imidazolinone chemical group, through the evaluation of F2 populations. Five genotypes of irrigated rice were crossed. Three of these parents are sensitive to the herbicide: BRS Querência, BRS Fronteira and BRS Pampa and two genotypes, BRS Sinuelo CL and Puitá INTA CL, tolerant to the herbicide. F1 seeds were obtained in greenhouse, and generation advance was performed in Embrapa Rice and Beans, resulting in the F2 population. F2 plants in the stage V4 received herbicide applications of (Only®) at a dose of 75 and 25 g a.i. L−1, and Dash® in dose of 0.5% v/v. A second application was performed after one week. The degree of phytotoxicity was scored as dead leaves and phytotoxicity intensity, percent survival of leaves and the relative growth. The results showed that the F2 hybrids, resulting of the crosses between the cultivars carriers of the gene of herbicide tolerance of the imidazolinone (Only®) class and conventional irrigated rice cultivars, are viable, thus enabling the establishment of herbicide-tolerant irrigated rice populations, with greater capacity to fight the red rice and with characteristics of agronomic interest. F2 progenies descending from crosses with the cultivar Puitá INTA CL presented more tolerance when compared with progenies descending from crosses with the cultivar BRS Sinuelo CL. [ABSTRACT FROM AUTHOR]

The genome of Brassica napus L. is the result of several polyploidization events that occurred during the history of B. napus. Due to its relatively short domestication history, diversity is relatively limited. An increasing number of loci in this crop's genome have been gene-edited using various technologies and reagent delivery methods for basic research as well as for trait development. New alleles have been developed as edits in single, 2, 4, or more homologous loci in this important oilseed crop. This comprehensive review will summarize new alleles that have been developed as they relate to weed control, flowering, self-incompatibility, plant hormone biology, disease resistance, grain composition, and pod shatter reduction. These new alleles have significantly augmented our understanding of both plant growth and development for basic research as well as for their potential commercial impacts. [ABSTRACT FROM AUTHOR]

Herbicides are one of the most widely used chemicals in agriculture. While they are known to be harmful to nontarget organisms, the effects of herbicides on the composition and functioning of soil microbial communities remain unclear. Here we show that application of three widely used herbicides—glyphosate, glufosinate, and dicamba—increase the prevalence of antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs) in soil microbiomes without clear changes in the abundance, diversity and composition of bacterial communities. Mechanistically, these results could be explained by a positive selection for more tolerant genotypes that acquired several mutations in previously well-characterized herbicide and ARGs. Moreover, herbicide exposure increased cell membrane permeability and conjugation frequency of multidrug resistance plasmids, promoting ARG movement between bacteria. A similar pattern was found in agricultural soils across 11 provinces in China, where herbicide application, and the levels of glyphosate residues in soils, were associated with increased ARG and MGE abundances relative to herbicide-free control sites. Together, our results show that herbicide application can enrich ARGs and MGEs by changing the genetic composition of soil microbiomes, potentially contributing to the global antimicrobial resistance problem in agricultural environments. [ABSTRACT FROM AUTHOR]

BACKGROUND: Clomazone is a potent herbicide for controlling weeds that have evolved resistance to other herbicides due to its unique mode of action. Clomazone is used in rice cultivation, but is limited to long‐grain cultivars because other cultivars are highly sensitive to it. In this study, we investigated the mechanism of clomazone tolerance in a long‐grain cultivar. RESULTS: The long‐grain cultivar Kasalath tolerated approximately five‐fold higher doses of clomazone compared to two short‐grain cultivars, Nipponbare and Koshihikari. While Arabidopsis thaliana transformed with a rice cytochrome P450, CYP81A6, showed resistance to clomazone, the cyp81a6 knockout Kasalath was unchanged in its clomazone sensitivity. The inheritance of clomazone sensitivity in the F1 and F2 of Kasalath and Nipponbare indicated the involvement of multiple loci for clomazone tolerance. Four chromosome segment substitution lines of Nipponbare/Kasalath and Koshihikari/Kasalath exhibited partial tolerance to clomazone. The overlapping DNA region among the four lines is on chromosome 5 within 11.5 Mb. CONCLUSION: Multiple loci are involved in clomazone tolerance in Kasalath, one of which is located on chromosome 5. This information will help develop short‐grain cultivars tolerant to clomazone. © 2021 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

We investigated changes in plant morphology, anatomy and physiology in a commonly occurring weed, Euphorbia helioscopia L. due to exposure to post‐emergence herbicides. Weed plants were sprayed with one of the following herbicides: pyrimidinyl sulphonylharnstoffe (PS), tribenuron‐methyl (TM), fluroxypyr‐methyl tribenuron‐methyl (FMTM) and bromoxynil (Br). The PS treatment significantly decreased plant height, promoted initiation of side branches and induced a prostrate habit. A specific response of root anatomy to PS and Br treatments was the high proportion of storage parenchyma. The Br‐treated plants showed thickest roots with a significantly large storage parenchyma, not only in the central portion of roots, but also in the cortical parenchyma outside the vascular tissue. A high proportion of xylem in the central portion of roots in the TM or FMTM‐treated plants provides a strong survival response in E. helioscopia. Disintegration of stem cortical parenchyma is the most prominent response of E. helioscopia when treated with a herbicide like PS or FMTM. Survival against these herbicides relates to a complete ring of vascular bundles and intact cortical parenchyma outside the vascular tissue. Increased leaf thickness was recorded in most of the cases except in the FMTM‐treated plants. The PS‐treated plants showed midrib thickness with two distinct vascular bundles. The cortical region, however, was found to be damaged by tissue collapse forming a large lysigenous aerenchyma. Euphorbia helioscopia had altered morphology, anatomy and physiology in response to herbicide application, which changed its growth in the field. To achieve control of this weed species, alternative strategies or higher doses of herbicide should be applied. Further research is required to determine the interaction of surviving weed plants with the crop. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Plant Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study assessed the farm-level economic and environmental impacts from the use of genetically modified (GM) corn in Vietnam (resistant to Lepidopteran pests of corn and tolerant to the herbicide glyphosate). It was largely based on a farmer survey conducted in 2018–19. The GM varieties out-performed conventional varieties in terms of yield by +30.4% (+15.2% if the yield comparison is with only the nearest performing equivalent conventional varieties) and reduced the cost of production by between US $26.47 per ha and US $31.30 per ha. For every extra US $1 spent on GM seed relative to conventional seed, farmers gained between an additional US $6.84 and US $12.55 in extra income. The GM maize technology also reduced insecticide and herbicide use. The average amount of herbicide active ingredient applied to the GM crop area was 26% lower (1.66 kg per ha) than the average value for the conventional corn area (2.26 kg/ai per ha) and in terms of the associated environmental impact of the herbicide use, as measured by the Environmental Impact Quotient (EIQ) indicator, it was lower by 36% than the average value applicable to the conventional corn area. Insecticides were used on a significantly lower GM crop area and, when used, in smaller amounts. The average amount of insecticide applied to the GM corn crop was significantly lower by 78% (0.08 kg/ai per ha) than the average value for the conventional corn area (0.36 kg/ai per ha) and in terms of the associated environmental impact of the insecticide use, as measured by the EIQ indicator, it was also lower by 77% than the average value for conventional corn (14.06 per ha). [ABSTRACT FROM AUTHOR]

Genetically modified (GM) plants can be created by adding specific DNA sequences obtained from the same plant species or different species. Which aims to achieve higher yields, disease and pest resistance, herbicide tolerance, production of antibodies, and other pharmaceutical molecules by manipulating gene expression to alter the protein properties. Insect resistant plants reduce the damage caused by pests and diseases. Herbicide glyphosate or glufosinate-tolerant GM plants gave promising results in combating weed. The properties of plants such as metal uptake, transport, accumulation, and detoxification of organic pollutants can be enhanced by genetically manipulating the fast-grown and introducing the responsible gene from the hyper accumulative species. GM plants can be used to produce cost-efficient and manageable drugs, vaccine, and biopharmaceuticals, if certain limitations are to be considered such as quality of final products, techniques for extraction and processing of biopharmaceuticals, and biosafety. Despite all these benefits, its adverse effects on the environment and human health have always been a matter of concern. The main limitation includes a horizontal transfer of the transgene to other species which may code for the specific antibiotic and herbicide resistance. It might be the possible transmission of resistance from the food products to the whole human population via intestinal bacteria. To address this several methods, need to be adopted to either keep away or eliminate marker genes from the transformed plants before growing in the field. Many scientists have come up with strategies to generate marker-free transgenic plants to give us safe and reliable GM technology. [ABSTRACT FROM AUTHOR]

Ipomoea species are troublesome weeds in crop systems through Brazil. Drought stress typically reduces glyphosate efficacy by reducing the foliar uptake of herbicides and their translocation. Using both glyphosate tolerant (GT) and sensitive (GS) plants from Ipomoea grandifolia, I. indivisa and I. purpurea species, this research aimed to (a) correlate amounts of epicuticular wax and tolerance to glyphosate in plants and (b) determine the effect of drought stress (DStress) on changes in the quantity and chemical composition of plant epicuticular waxes. The dose that causes 50% inhibition of growth (GR50) of the biotypes varied between 62 and 1208 (I. grandifolia), 159 and 913 (I. indivisa), and 389 and 1925 g a.e. ha−1 of glyphosate (I. purpurea). There was low inverse correlation (–0.46) between the amount of epicuticular wax and the sensitivity to glyphosate. GT biotypes of the species presented greater plastic capacities than GS biotypes for increasing the amount of epicuticular wax under DStress. The three Ipomoea species exhibited different chemical profiles of waxes supported by IR spectra, which allows for their differentiation. For I. grandifolia and I. purpurea, there was an increase in the polar components in the state without DStress, while for the species I. indivisa, no differences in infrared spectra were detected between the two water conditions. [ABSTRACT FROM AUTHOR]

Weeds burden plant growth as they compete for space, sunlight, and soil nutrients leading to 25–80% yield losses. Glyphosate [ N -(phosphonomethyl)glycine] is a widely used broad spectrum non-selective herbicide that controls weeds by inhibiting 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) enzyme and interfering with the shikimate biosynthesis pathway. Cotton (Gossypium hirsutum L.) is one of the most important commercial crops grown worldwide for its fiber. We have developed herbicide tolerant transgenic cotton (cv. P8-6) by introgression of a codon-optimized and modified EPSPS gene (CP4-EPSPS) possessing an N-terminal chloroplast targeting peptide from Petunia hybrida. Because of the recalcitrant nature of cotton, a genotype-independent non-tissue culture-based apical meristem-targeted in planta transformation approach was used to develop transformants. Although in planta transformation methodologies are advantageous in developing a large number of transgenic plants, effective screening strategies are essential for initial identification of transformants. In the present study, the use of a two-level rigorous screening strategy identified 2.27% of T1 generation plants as tolerant to 800 and 1,500 mg/L of commercially available glyphosate (Roundup). Precise molecular characterization revealed stable integration, expression, and inheritance of CP4-EPSPS in advanced generations of the promising transgenic events. Further, superiority of selected transgenic plants in tolerating increasing levels of glyphosate (500–4,000 mg/L) was ascertained through reduced accumulation of shikimate. This report is the first of its kind where cotton transformants tolerating high levels of glyphosate (up to 4,000 mg/L) and accumulating low levels of shikimate have been identified. This study not only reiterated the genotype-independent nature of the transformation strategy but also reiterated the translational utility of the CP4-EPSPS gene in management of weeds. [ABSTRACT FROM AUTHOR]

This study assesses the economic and environmental impacts that have arisen from the adoption and use of genetically modified (GM) cotton and maize in Colombia in the fifteen years since GM cotton was first planted in Colombia in 2003. A total of 1.07 million hectares have been planted to cotton and maize containing GM traits since 2003, with farmers benefiting from an increase in income of US $301.7 million. For every extra US $1 spent on this seed relative to conventional seed, farmers have gained an additional US $3.09 in extra income from growing GM cotton and an extra US $5.25 in extra income from growing GM maize. These income gains have mostly arisen from higher yields (+30.2% from using stacked (herbicide tolerant and insect resistant cotton and +17.4% from using stacked maize). The cotton and maize seed technology have reduced insecticide and herbicide spraying by 779,400 kg of active ingredient (−19%) and, as a result, decreased the environmental impact associated with herbicide and insecticide use on these crops (as measured by the indicator, the Environmental Impact Quotient (EIQ)) by 26%. The technology has also facilitated cuts in fuel use, resulting in a reduction in the release of greenhouse gas emissions from the GM cotton and maize cropping area and contributed to saving scarce land resources. [ABSTRACT FROM AUTHOR]

Auxin-like herbicides such as dicamba, in low concentration, plays a role close to phytohormones in promoting plant growth. On the other hand, with an increase in auxin compound concentration, their activity is gradually changed to an abiotic stressor, thus disrupting normal plant processes. From our previous study, we identified three wild tomato accessions to be tolerant of the simulated drift rate of dicamba. Understanding the mechanism of tolerance in these accessions to dicamba will, therefore, be crucial in breeding for auxin tolerant tomato. This information will also shed light on auxin tolerance/resistance mechanisms in plants since much of this is unknown. The objective of this study was, therefore, to investigate the molecular and biochemical basis of dicamba tolerance in three wild tomato accessions. We conducted gene expression analysis to determine the potential role of F-boxTIR1/AFB in dicamba tolerance. Besides, levels of H2O2 and HCN in response to dicamba application were measured and compared between dicamba-tolerant and susceptible tomato accessions. Based on the greenhouse study, all wild accessions were confirmed tolerant to dicamba at the simulated drift rate (0.001X; 2.8 g ae ha-1). Association analysis using SSR markers revealed that dicamba tolerance trait might be associated with drought stressinduced gene, 1e16. Expression study of TIR1, AFB1, and AFB2 genes using qPCR showed relative differential expression of TIR1 between tolerant accessions and susceptible cultivars. No difference was observed between tolerant accessions and cultivars in the relative expression of AFB1 and AFB2 genes. Biochemical compounds quantified were related to auxin herbicide activity and correlated with gene expression data; the levels of H2O2 and HCN were increased in susceptible cultivars over time, but not in tolerant accessions. [ABSTRACT FROM AUTHOR]

Copyright of Agronomía Colombiana is the property of Universidad Nacional de Colombia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Hybrid rice breeding offers an important strategy to improve rice production, and therefore is crucial for ensuring worldwide food security. Purity of hybrids is a key factor in keeping the high production of hybrid rice. While another important thing is mechanical weeding of hybrid rice, which could greatly release labor from laborious work and cut the production cost. Both of these two problems could be partly resolved by developing glyphosate-tolerant restorer lines. In this study, a novel glyphosate-tolerant gene I.variabilis-EPSPS* was transferred into elite indica restorer line Minghui 86 (MH86) by Agrobacterium-mediated transformation. By Southern blot and inverse PCR analysis, 3 transgenic restorer lines (MY28, MY50, and MY51) with a single copy of I.variabilis-EPSPS* integrated into the intergenic regions were selected from 72 regenerated transgenic plants. The inheritance of I.variabilis-EPSPS* in the 3 transgenic restorer lines was proved to follow Mendelian inheritance by germinating test. In the following generations, according to Southern blot, Northern blot, 3'RACE, and Western blot, I.variabilis-EPSPS* were proved to stably inherit and express in the candidate transgenic restorer lines. At the same time, glyphosate tolerance assay was performed in the field, in which the candidate transgenic restorer lines kept normal agronomic traits under glyphosate treatments with a dosage as high as 8400 g/ha. Therefore, the candidate transgenic restorer lines were highly tolerant to glyphosate. The 3 candidate transgenic restorer lines were respectively hybridized with the male sterile line II-32A, and their hybrids were respectively named as MY28H, MY50H, and MY51H. According to Southern blot and Western blot analysis, I.variabilis-EPSPS* could stably inherit to F1 hybrids and express in these hybrids, which indicated that the true hybrids could be distinguished by I.variabilis-EPSPS*. In the field test, the transgenic hybrids with I.variabilis-EPSPS* could suffer 3360 g/ha glyphosate without the damage of agronomic traits, which indicated the application potential of these hybrids in direct seeding. Collectively, the transgenic glyphosate-tolerant restore lines developed in this study were highly tolerant to glyphosate, and they had potential to be used in commercial production of hybrid rice. [ABSTRACT FROM AUTHOR]

BACKGROUND: Protoporphyrinogen IX oxidase (PPO)‐inhibiting herbicides act by inhibiting a key enzyme in the heme and chlorophyll biosynthetic pathways in plants. This enzyme, the PPO enzyme, is conserved across plant species. However, some microbes are known to utilize a unique family of PPO enzymes, the HemG family. This enzyme family carries out the same enzymatic step as the plant PPO enzymes, but does not share sequence homology with the plant PPO enzymes. RESULTS: Bioinformatic analysis was used to identify putative HemG PPO enzyme variants from microbial sources. A subset of these variants was cloned and characterized. HemG PPO variants were characterized for functionality and tolerance to PPO‐inhibiting herbicides. HemG PPO variants that exhibited insensitivity to PPO‐inhibiting herbicides were identified for further characterization. Expression of selected variants in maize, soybean, cotton and canola resulted in plants that displayed tolerance to applications of PPO‐inhibiting herbicides. CONCLUSION: Selected microbial‐sourced HemG PPO enzyme variants present an opportunity for building new herbicide tolerance biotechnology traits. These traits provide tolerance to PPO‐inhibiting herbicides and, therefore, could provide additional tools for farmers to employ in their weed management systems. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Under rice-rapeseed rotation in the Yangzi River Basin, risk of rice herbicide residues on rapeseed production should be evaluate for selection of herbicide-tolerant rapeseed. Thus 19 rapeseed varieties were evaluated under pyrazosulfuron, pretilachlor, bentazone and cyhalofop herbicides stresses. Rapeseed traits were investigated on seed germination rate, plant height, maximum root length, fresh weight aboveground, fresh weight of roots, dry weight aboveground and root dry weight. Results showed that, under herbicide stresses, the tolerance coefficients of different genotype were significantly different. By cluster analysis, varieties were selected with relatively strong tolerance to different herbicides. It showed that comprehensive evaluation of herbicide tolerance was effective on rapeseed by integration of principal component analysis, subordinative function value and clustering analysis, which could avoid bias and instability of single index analysis. It suggested a practical selecting method for rapeseed as succession crop after rice according to actual use of herbicides in rice plantation. [ABSTRACT FROM AUTHOR]

The study was to identify the potential tolerance of Crotalaria juncea to diclosulam uptake and translocation and its effects on the physiological metabolism of plants. Two experiments were carried out; I—Evaluation of uptake and translocation of 14C-diclosulam (35 g a.i. ha−1) in C. juncea, at seven and 14 days after emergence. II—Evaluation of chlorophyll a transient fluorescence of dark-adapted C. juncea leaves when applied diclosulam in pre-emergence. Plants of C. juncea presented an anatomical/metabolic barrier to diclosulam translocation in the stem, which may confer tolerance to this herbicidal, besides reduced translocation due to low accumulation in the cotyledons. In addition, plants can maintain photosynthetic metabolism active when growing in soil with diclosulam by not changing the dynamics of energy dissipation. Thus, when cultivated in soil with residual of diclosulam, C. juncea can tolerate the herbicide to maintain plant growth. [ABSTRACT FROM AUTHOR]

The introduction of herbicide-tolerant (HT) genetically engineered (GE) soybeans has raised new challenges for the European risk assessment of imported food and feed. Food and feed products derived from these plants may show specific patterns of chemical residues and altered nutritional composition. Furthermore, there has been a substantial increase in the usage of herbicides in soybean production due to the emergence of resistant weeds. This concerns particular glyphosate-based herbicides and also other herbicides. In this review, we give an overview of available data regarding glyphosate application on HT GE soybeans in North and South America. We have further compared this data with herbicide applications in experimental field trials conducted by the industry. We conclude that field trials carried out for risk assessment purposes do not generally represent the real agronomic conditions in commercial HT GE plant cultivation. In most cases, neither the applied dose nor the number of applications match real conditions. This finding is especially relevant for risk assessment since a review of relevant publications shows that the amount and timing of spraying glyphosate as a complementary herbicide onto HT GE plants can impact their composition; this is relevant to EFSA comparative risk assessment of GMOs. Further, closely related issues were identified that overlap with EU GMO and pesticide regulation, but are not currently considered. These issues concern indirect, cumulative and combinatorial effects as well as the assessment of mixed toxicity. Consequently, current risk assessment practice for HT GE plants cannot be considered to fulfil EU regulatory standards which require the safety of food and feed to be demonstrated. It is much more likely that concerns about the health risks of HT GE plant material used for food and feed have been underestimated. We therefore conclude that the EU risk assessment of food and feed derived from HT GE plants needs substantial improvement. [ABSTRACT FROM AUTHOR]

Herbicide resistance is one of the most important traits for plant biotechnology, which is widely used to improve agricultural efficiency by controlling weeds and also used as a selectable marker during genetic engineering by the transformation. For these reasons, new technologies for conferring herbicide resistance to plants are continuously developing, in which CRISPR/Cas9-mediated gene editing methods enable precise modifications of DNA sequences and offer a great promise for the improvement of crops. Here, we review recent advances in developing herbicide-resistant plants by the CRISPR/Cas9-mediated gene editing technology, targeting on endogenous genes such as acetolactate synthase (ALS), 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), cellulose synthase A catalytic subunit 3 (CESA3), and splicing factor 3B subunit 1 (SF3B1). In addition, we also introduce possible candidate genes to develop herbicide-resistant plants by generating loss-of-function mutations using the CRISPR/Cas9 system. [ABSTRACT FROM AUTHOR]

Copyright of Acta Prataculturae Sinica is the property of Acta Prataculturae Sinica Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

4‐Hydroxyphenylpyruvate dioxygenase (HPPD) catalyzes the second reaction in the tyrosine catabolism and is linked to the production of cofactors plastoquinone and tocopherol in plants. This important biological role has put HPPD in the focus of current herbicide design efforts including the development of herbicide‐tolerant mutants. However, the molecular mechanisms of substrate binding and herbicide tolerance have yet to be elucidated. In this work, we performed molecular dynamics simulations and free energy calculations to characterize active site gating by the C‐terminal helix H11 in HPPD. We compared gating equilibria in Arabidopsis thaliana (At) and Zea mays (Zm) wild‐type proteins retrieving the experimentally observed preferred orientations from the simulations. We investigated the influence of substrate and product binding on the open–closed transition and discovered a ligand‐mediated conformational switch in H11 that mediates rapid substrate access followed by active site closing and efficient product release through H11 opening. We further studied H11 gating in At mutant HPPD, and found large differences with correlation to experimentally measured herbicide tolerance. The computational findings were then used to design a new At mutant HPPD protein that showed increased tolerance to six commercially available HPPD inhibitors in biochemical in vitro experiments. Our results underline the importance of protein flexibility and conformational transitions in substrate recognition and enzyme inhibition by herbicides. [ABSTRACT FROM AUTHOR]

The Hawaii Statewide Noxious Invasive Pest Program (SNIPP) and associated storm water management plans provide statutory justification for increased use of native plants along the State of Hawaii transportation corridors. The demand for native plants exceeds the availability of plant materials or seed. To produce seed stock and ensure seed lot purity, establishment protocols for weed control must first be defined. Uhaloa (Waltheria indica), a native Hawaiian broadleaf shrub has been identified for increased roadside usage, thus will be the focus of this research. Weed control during the establishment phase of uhaloa is essential for optimising establishment success. In this study, the efficacy and phytotoxicity of the pre-emergence herbicides oxadiazon and indaziflam, applied over uhaloa transplants, were evaluated. Crop and weed response to granular oxadiazon at 2.24 kg ai ha-1 and 4.48 kg ai ha-1 and flowable indaziflam at 24 g ai ha-1 and 49 g ai ha-1 were determined. Unacceptable uhaloa injury with both rates of indaziflam was recorded. Oxadiazon provided excellent broad-spectrum weed control with acceptable injury to uhaloa. [ABSTRACT FROM AUTHOR]