Integrated weed management strategies for delaying herbicide resistance in wild oats

Les biotypes de folle avoine (Avena fatua) résistants aux herbicides infestent les principales régions céréalières de l'Ouest américain et de l'Ouest canadien. Cet article passe en revue les stratégies de lutte intégrée contre les mauvaises herbes qui peuvent être utilisées pour empêcher ou retarder le développement de la résistance aux herbicides chez la folle avoine. Une stratégie de lutte intégrée contre la folle avoine, destinée à retarder ou à empêcher le développement de la résistance, devrait être basée sur la prévention de l'introduction des grains de folle avoine dans le sol. Deux façons d'y arriver sont d'empêcher l'immigration de graines dans le champ à partir de sources externes, et de réduire ou éliminer la production de graines par la folle avoine déjà présente au champ. Il est de plus en plus évident que le recours à l'utilisation continuelle d'herbicides comme seul moyen de lutte contre les mauvaises herbes n'éliminera pas la folle avoine ni les autres graines de mauvaises herbes de la banque de graines du sol. Au contraire, tout porte à croire que cette pratique va sélectionner des biotypes résistants aux herbicides utilisés, particulièrement là où des herbicides ayant le même mode d'action sont utilisés de façon continue. Il est essentiel, cependant, que les herbicides soient considérés seulement comme une composante d'un système intégré global incluant la lutte culturale et d'autres stratégies de gestion, et que les principes agronomiques soient considérés lors du développement de ce système.Herbicide-resistant biotypes of wild oats (Avena fatua) infest most major cereal producing regions in the western United States and Canada. This paper reviews potential integrated weed management strategies that can be used to prevent or delay selection of herbicide-resistant wild oats plants. An integrated wild oats management strategy to delay or prevent the development of herbicide resistance should be based on preventing the movement of wild oats seed into the soil. Two ways to achieve this are by preventing the immigration of seed into the field from external sources, and by reducing or eliminating seed production by wild oats already in the field. It is becoming increasingly clear that reliance on continuous herbicide useas the sole means of weed control will fail to eliminate wild oats and other weed seed from the soil seedbank. On the contrary, evidence is mounting that this practice will select for biotypes that are resistant to the herbicides used, especially where herbicides of the same mode of action are used continuously. It is essential, therefore, that herbicides be considered as just one component of an overall integrated System together with cultural control and other management strategies, and that agronomic principles be considered when developing this System

Clinical characteristics of women captured by extending the definition of severe postpartum haemorrhage with 'refractoriness to treatment': a cohort study

Background: The absence of a uniform and clinically relevant definition of severe postpartum haemorrhage hampers comparative studies and optimization of clinical management. The concept of persistent postpartum haemorrhage, based on refractoriness to initial first-line treatment, was proposed as an alternative to common definitions that are either based on estimations of blood loss or transfused units of packed red blood cells (RBC). We compared characteristics and outcomes of women with severe postpartum haemorrhage captured by these three types of definitions. Methods: In this large retrospective cohort study in 61 hospitals in the Netherlands we included 1391 consecutive women with postpartum haemorrhage who received either ≥4 units of RBC or a multicomponent transfusion. Clinical characteristics and outcomes of women with severe postpartum haemorrhage defined as persistent postpartum haemorrhage were compared to definitions based on estimated blood loss or transfused units of RBC within 24 h following birth. Adverse maternal outcome was a composite of maternal mortality, hysterectomy, arterial embolisation and intensive care unit admission. Results: One thousand two hundred sixty out of 1391 women (90.6%) with postpartum haemorrhage fulfilled the definition of persistent postpartum haemorrhage. The majority, 820/1260 (65.1%), fulfilled this definition within 1 h following birth, compared to 819/1391 (58.7%) applying the definition of ≥1 L blood loss and 37/845 (4.4%) applying the definition of ≥4 units of RBC. The definition persistent postpartum haemorrhage captured 430/471 adverse maternal outcomes (91.3%), compared to 471/471 (100%) for ≥1 L blood loss and 383/471 (81.3%) for ≥4 units of RBC. Persistent postpartum haemorrhage did not capture all adverse outcomes because of missing data on timing of initial, first-line treatment. Conclusion: The definition persistent postpartum haemo

Measurement of the gamma ray background in the Davis Cavern at the Sanford Underground Research Facility

Deep underground environments are ideal for low background searches due to the attenuation of cosmic rays by passage through the earth. However, they are affected by backgrounds from γ-rays emitted by 40K and the 238U and 232Th decay chains in the surrounding rock. The LUX-ZEPLIN (LZ) experiment will search for dark matter particle interactions with a liquid xenon TPC located within the Davis campus at the Sanford Underground Research Facility, Lead, South Dakota, at the 4,850-foot level. In order to characterise the cavern background, in-situ γ-ray measurements were taken with a sodium iodide detector in various locations and with lead shielding. The integral count rates (0--3300~keV) varied from 596~Hz to 1355~Hz for unshielded measurements, corresponding to a total flux in the cavern of 1.9±0.4~γ cm−2s−1. The resulting activity in the walls of the cavern can be characterised as 220±60~Bq/kg of 40K, 29±15~Bq/kg of 238U, and 13±3~Bq/kg of 232Th

Bioensaio rápido de determinação da sensibilidade da acetolactato sintase (ALS) a herbicidas inibidores Rapid bioassay to determine the sensitivity of acetolactate synthase (ALS) to inhibitor herbicides

Foi avaliada a atividade da acetolactato sintase (ALS), em plantas resistentes e suscetíveis de B. pilosa e A. quitensis após a aplicação de herbicidas inibidores da ALS. O método baseia-se na utilização do ácido ciclopropanodicarboxílico (CPCA) para inibir a cetoácido reductoisomerase (KARI), enzima que catalisa a reação seguinte do acetolactato na cadeia de biossíntese dos aminoácidos valina, leucina e isoleucina, provocando assim, o acúmulo de acetolactato, que na presença de um ácido forte forma acetoína. A base para a distinção entre os biotipos resistentes e suscetíveis é a quantidade de acetoína formada, que será maior nos biotipos em que a enzima ALS não sofreu inibição, ou seja, nos biotipos resistentes. A quantificação da acetoína acumulada ocorreu através da formação de um complexo colorido vermelho, devido a reação entre acetoína, creatina e naftol, cuja densidade ótica a 530 nm é proporcional à concentração do acetolactato formado na reação. Sendo assim, foi desenvolvido um ensaio utilizando este método após a aplicação dos herbicidas chlorimuron-ethyl e imazethapyr nos biotipos R e S de Bidens pilosa, Amaranthus quitensis no estádio de dois pares de folhas. O bioensaio demonstrou que a enzima ALS dos biotipos resistentes é insensível aos herbicidas inibidores da ALS e que este tipo de bioensaio é uma forma rápida e eficaz de diferenciação entre biotipos resistentes e suscetíveis.<br>In order to compare the acetolactate synthase (ALS) activity of resistant and susceptible biotypes of Bidens pilosa and Amaranthus quitensis to ALS inhibitor herbicides, a method based on ciclopronocarboxilic acid (CPCA) to inhibit the enzyme ketoacidredutoisomerase (KARI) is used. This enzyme catalyzes the reaction after acetolactate in the biosynthesis reaction chain of the aminoacids valine, leucine and isoleucine. In the presence of a KARI inhibitor, carbon from pyruvate flows through the branched chain aminoacid biosynthetic pathway and accumulates in acetolactate, which in the presence of sulfuric acid can be converted to acetoin. The base to distinguish between the resistant and susceptible biotypes is the amount of acetoin formed, which will be much higher in the biotype where the ALS was not inhibited by the herbicide. If acetoin is mixed with naphtol and creatine the solution will develop a reddish color, so that it is possible to quantify indirectly the sensitivity of the ALS to the herbicide by the color of the solution formed. An experiment was carried out with suspected resistant biotypes of Bidens pilosa and Amaranthus quitensis using this method after spraying the plants at the two pair leaf stage with chlorimuron-ethyl and imazethapyr. The ALS of the resistant biotype has insensitivity to ALS inhibitor herbicides

Synthesis of maternal transfer of mercury in birds: Implications for altered toxicity risk

Maternal transfer is a predominant route of methylmercury (MeHg) exposure to offspring. We reviewed and synthesized published and unpublished data on maternal transfer of MeHg in birds. Using paired samples of females' blood (n = 564) and their eggs (n = 1814) from 26 bird species in 6 taxonomic orders, we conducted a meta-Analysis to evaluate whether maternal transfer of MeHg to eggs differed among species and caused differential toxicity risk to embryos. Total mercury (THg) concentrations in eggs increased with maternal blood THg concentrations; however, the proportion of THg transferred from females to their eggs differed among bird taxa and with maternal THg exposure. Specifically, a smaller proportion of maternal THg was transferred to eggs with increasing female THg concentrations. Additionally, the proportion of THg that was transferred to eggs at the same maternal blood THg concentration differed among taxonomic orders, with waterfowl (Anseriformes) transferring up to 382% more THg into their eggs than songbirds (Passeriformes). We provide equations to predict THg concentrations in eggs using female blood THg concentrations, and vice versa, which may help translate toxicity benchmarks across tissues and life stages. Our results indicate that toxicity risk of MeHg can vary among bird taxa due to differences in maternal transfer of MeHg to offspring

Development of herbicide-tolerant irrigated rice cultivars Desenvolvimento de cultivares de arroz irrigado tolerantes a herbicida

The objective of this work was to develop new irrigated rice lines tolerant to imidazolinone herbicides. The backcross breeding procedure was used to transfer the imidazolinone tolerance allele from mutant 93AS3510 to the recurrent parents 'BRS 7 Taim' and 'BRS Pelota'. Individual herbicide-tolerant plants were selected in each generation, for three backcrossings (RC1 to RC3), followed by three selfing generations (RC3F1 to RC3F3). The best four RC3F3 lines for agronomic traits were genotyped with 44 microsatellite markers. The observed conversion index of the new imidazolinone-tolerant lines varied from 91.86 to 97.67%. Pairwise genetic distance analysis between these lines and 22 accessions from the Embrapa's Rice Germplasm Bank clustered the new lines with their respective recurrent parents, but not with 'IRGA 417', which was originally used as recurrent parent to derive IRGA 422 CL, the only imidazolinone-tolerant irrigated rice cultivar recommended for cultivation in Brazil. Therefore, these lines represent new options of genetically diverse imidazolinone-tolerant rice accessions. Lines CNA10756 ('BRS Sinuelo CL') and CNA10757 will be released for cultivation in the Clearfield irrigated rice production system in Rio Grande do Sul, Brazil.<br>O objetivo deste trabalho foi desenvolver novas linhagens de arroz irrigado tolerantes ao herbicida imidazolinona. O método de retrocruzamento foi usado para transferir o alelo de tolerância à imidazolinona do mutante 93AS3510 para os genitores recorrentes 'BRS 7 Taim' e 'BRS Pelota'. Indivíduos tolerantes ao herbicida foram selecionados em cada geração, por três gerações de retrocruzamento (RC1 a RC3), seguidas por três gerações de autofecundação (RC3F1 a RC3F3). As quatro melhores linhagens RC3F3 quanto às características agronômicas foram genotipadas com 44 marcadores microssatélites. O índice de conversão observado nas novas linhagens tolerantes à imidazolinona variou de 91,86 a 97,67%. A análise de distância genética par-a-par, entre estas linhagens e 22 acessos do banco de germoplasma de arroz da Embrapa, agrupou-as com os seus respectivos genitores recorrentes, mas não com 'IRGA 417', que foi originalmente usada como genitor para derivar a IRGA 422 CL, única cultivar tolerante ao herbicida imidazolinona recomendada para cultivo no Brasil. Portanto, estas linhagens representam novas opções de acessos geneticamente diversos de arroz irrigado com tolerância ao herbicida imidazolinona. As linhagens CNA10756 ('BRS Sinuelo' CL) e CNA10757 serão lançadas para cultivo no sistema de produção "Clearfield" no Rio Grande do Sul, Brasil