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BACKGROUND: 2,4‐Dichlorophenoxyacetic acid (2,4‐D) and other auxinic herbicides are important for weed control in cropping systems globally. Weeds with resistance to 2,4‐D and other auxinic herbicides have evolved, including several populations of Sonchus oleraceus from multiple sites in Australia. We report the underlying mechanism in these populations that gives rise to auxinic herbicide resistance. RESULTS: We studied a total of three susceptible and eight resistant Sonchus oleraceus populations. All resistant populations had a deletion of three amino acids flanking the degron sequence of an Aux/IAA gene, SoIAA20, which was not found in the three susceptible populations. The eight populations with the resistant allele were also resistant to dicamba, fluroxypyr and clopyralid. The resistant plants also had reduced movement of 2,4‐D out of the treated tissues compared to susceptible plants. CONCLUSION: The paired deletion flanking the degron region of SoIAA20 likely provides resistance to 2,4‐D by restricting the movement of 2,4‐D from the treated tissue to the rest of the plant. We hypothesise that this deletion keeps the 2,4‐D bound to the target site. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

SUMMARY: As a result of extensive selection, two polyploid grass weeds, Hordeum glaucum (northern barley grass; 2n = 4x = 28) and Bromus diandrus (ripgut brome; 2n = 8x = 56), have evolved resistance to glyphosate, in Australia. Previous research suggested amplification of 5‐enolpyruvylshikimate‐3‐Phosphate synthase (EPSPS) gene confers resistance in these two weed species. The objective of this research was to investigate the genomic organization of the EPSPS gene in these two species through molecular cytogenetic analyses of fluorescence in situ hybridization (FISH) to understand possible mechanism of amplification of this gene. EPSPS copy number of H. glaucum and B. diandrus plants was estimated via quantitative polymerase chain reaction. The susceptible plants of both species had one copy of EPSPS, whereas the resistant plants of H. glaucum and B. diandrus had 14–17 and 16–32 copies, respectively. FISH analysis of glyphosate‐susceptible (Hg‐RWS) H. glaucum, revealed four faint signals of the EPSPS gene in two pairs of homologous chromosomes, at the telomeric region. The glyphosate‐resistant H. glaucum (Hg‐YP1) also showed amplification of EPSPS gene at telomeric regions in two pairs of homologous chromosomes, but the signals were brighter and appeared as cluster of EPSPS genes. Similarly, the glyphosate‐susceptible B. diandrus (Bd‐S) plants showed faint signals of EPSPS gene on two homologous chromosomes, at the telomeric position. However, samples of two glyphosate‐resistant, B. diandrus, Bd‐SA988 and Bd‐Vic showed much brighter hybridization signals of EPSPS gene, located at the telomere on two homologous chromosomes, suggesting an increase in EPSPS gene copies at this position. Overall, unequal crossover during meiosis may have triggered the initial EPSPS gene duplication sparking the evolution of glyphosate resistance. [ABSTRACT FROM AUTHOR]

Background: Adrenal vein sampling (AVS), integral to identifying surgically remediable unilateral primary aldosteronism (PA), is technically challenging and subject to fluctuations in cortisol and aldosterone secretion. Intra‐procedural adrenocorticotropic hormone (ACTH), conventionally administered as a 250‐μg bolus and/or 50 μg per hour infusion, increases cortisol and aldosterone secretion and can improve AVS success, but may cause discordant lateralisation compared to unstimulated AVS. Aims: To assess if AVS performed with ultra‐low dose ACTH infusion causes discordant lateralisation. Methods: Here, we describe our preliminary experience using an ultra‐low dose ACTH infusion AVS protocol. We retrospectively reviewed the results of consecutive AVS procedures (n = 37) performed with and without ultra‐low dose ACTH (1‐μg bolus followed by 1.25 μg per hour infusion). Results: Bilateral AV cannulation was successful in 70% of procedures pre‐ACTH and 89% post‐ACTH (p < 0.01). Sixty‐nine percent of studies lateralised pre‐ACTH and 55% post‐ACTH, improving to 79% when both groups were combined. Lateralisation was discordant in 11 cases, including eight in which lateralisation was present only on basal sampling, and three in which lateralisation occurred only with ACTH stimulation. Discussion: Overall, the decrease in lateralisation rates with ACTH was higher than previously reported for some protocols utilising conventional doses of ACTH. Our results suggest that AVS performed with ultra‐low dose ACTH can cause discordant lateralisation similar to AVS performed with conventional doses of ACTH. Conclusion: Prospective studies directly comparing low and conventional dose ACTH AVS protocols and long‐term patient outcomes are needed to help define the optimal ACTH dose for accurate PA subtyping. [ABSTRACT FROM AUTHOR]

A case of recurrent insulinoma spanning 4 decades is described. Following a delayed diagnosis, hyperinsulinemic hypoglycemia was confirmed in a 24-year-old woman during early pregnancy. Initial surgery, culminating in subtotal pancreatectomy, was noncurative. A 1-cm insulinoma was subsequently resected from the head of the pancreas postpartum, with postoperative resolution of hypoglycemia. However, 32 years later, the patient experienced a recurrence of hypoglycemic symptoms. Eventually, a subcentimeter extrapancreatic lesion was identified anterior to the pancreatic head on gallium-68 DOTA-Exendin-4 positron emission tomography/computed tomography. In 2022, a third operation was performed, with excision of a 4 × 3 mm tumor adjacent to the pancreatic head, and histology confirming insulinoma. She was again cured of symptoms. [ABSTRACT FROM AUTHOR]

BACKGROUND: Control of prickly lettuce has become increasingly difficult for lentil growers in southern Australia because of widespread resistance to common herbicides, a lack of alternative herbicide options and the prolific production of highly mobile seed. This study aimed to quantify acetolactate synthase (ALS)‐inhibiting herbicide resistance in the Mid North (MN) and Yorke Peninsula (YP) of South Australia, characterize the resistance mutations present and investigate population structure and gene flow in this species. RESULTS: Resistance was identified in all populations tested, with average survival of 92% to chlorsulfuron and 95% to imazamox + imazapyr. Five different amino acid substitutions were identified at proline 197 of the ALS gene. There was no significant difference in the median lethal dose (LD50) between plants with these five different substitutions when treated with metsulfuron‐methyl; however, the imidazolinone resistance level was higher in plants with a phenylalanine substitution and lower in plants with a serine. Population structure based on 701 single nucleotide polymorphisms and 271 individuals provided evidence for both independent evolution of the same mutation in different populations, as well as frequent short‐ to medium‐distance dispersal accompanied by occasional long‐distance dispersal events. The overall inbreeding coefficient (FIS) was calculated at 0.5174, indicating an intermediate level of outcrossing despite the cross‐pollination experiment showing only low outcrossing. In the structure analyses, most individuals from YP were assigned to a single cluster, whereas most individuals from MN were assigned 50% to each of two clusters, indicating some genetic differences between these two regions, but also evidence for dispersal between them. CONCLUSIONS: Use of imidazolinone herbicides has selected for mutations conferring higher levels of resistance, such as the Pro‐197‐Phe mutation, and resulted in further spread of resistance in this species. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Context: Wild oats (Avena spp.), brome grass (Bromus spp.) and barley grass (Hordeum spp.) are significant grass weeds of crop production in south-eastern Australia. The presence of herbicide resistance in these weed species is a major limiting factor on both productivity and profitability. Aims: We aimed to determine the distribution of herbicide resistance in these weed species across south-eastern Australia. Methods: Several surveys were conducted in randomly selected fields across four states in south-eastern Australia over a 5-year period, collecting 663 wild oats, 366 brome grass and 262 barley grass samples that were screened for resistance with up to five different herbicide groups or subgroups. Key results: In wild oats, resistance was most common to clodinafop-propargyl ('fop' ACCase inhibitor), with 22% of samples resistant and resistance detected in all regions except Tasmania. Resistance to sulfonylurea herbicides (ALS inhibitors) was less common with 7% of samples resistant, but regionally more variable. For both brome grass and barley grass, a greater proportion of samples was resistant to the sulfonylurea mesosulfuron-methyl, at 24% and 19%, respectively, than to quizalofop-ethyl ('fop' ACCase inhibitor). Conclusions: Resistance was recorded in all three species, with differences in the extent of resistance among herbicide groups and regions. Overall, a higher than average frequency of wild oats resistance to clodinafop-propargyl was found in regions of New South Wales and of brome grass and barley grass resistance to mesosulfuron-methyl in regions of South Australia. However, for all species some herbicides were still effective on all samples. Implications: The presence of significant herbicide resistance in these weed species indicates that management decisions need to include consideration of resistance to enable successful control measures. Herbicide-resistant weeds are a major threat to crop production, with wild oats, brome grass and barley grass being species of concern in Australia. Surveys of south-eastern Australia conducted over a 5-year period found >20% of wild oats samples to be resistant to Group 1 'fop' herbicides. For both brome grass and barley grass, resistance was highest to the Group 2 sulfonylurea herbicides, at 24% and 19%, respectively. [ABSTRACT FROM AUTHOR]

Background: Annual sowthistle is a weed that is difficult to control in lentil crops in southern Australia due to a lack of herbicide options, widespread herbicide resistance and prolific production of highly mobile seed. This study investigates herbicide resistance in annual sowthistle in the Mid‐North (MN) and Yorke Peninsula (YP) regions of South Australia, identifies and characterizes the mechanisms of acetolactate‐synthase (ALS)‐inhibitor resistance in this amphidiploid species, and combines this with analyses of population structure and gene flow. Results: ALS‐inhibitor‐resistant annual sowthistle is widespread across the YP and MN of South Australia and is associated with a variety of Proline‐197 mutations of the ALS gene, including leucine, alanine, arginine, serine, threonine and histidine. These mutations were found in different combinations on either of the two copies of the ALS gene. An additional 200 tissue samples were collected from across a single field on the YP and the ALS gene was sequenced for all these individuals. Different ALS‐inhibitor resistance profiles were evident between mutation combinations and within mutation combinations, possibly mediated by differing subgenome assortment of the mutations, or altered gene experession of the two ALS homeologs. Population genetics analysis showed evidence of long‐distance dispersal, resulting in highly mobile resistance genes, and multiple instances of resistance mutation evolution. Conclusions: Continuing selection of Sonchus oleraceus populations with ALS‐inhibiting herbicides has resulted in the accumulation of additional mutations within the ALS gene. New practices to control herbicide‐resistant S. oleraceus should be examined, and control should focus on reducing seed set and dispersal to prevent the spread of emerging cases of resistance. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Context: Bromus diandrus Roth is a serious weed of cereal-based cropping systems in South Australia. Its adaptation to local climate and production systems, prolific seed production and evolution of herbicide resistance have made this weed difficult to manage. Aims: Studies were undertaken to determine genetic variation in seed dormancy within B. diandrus populations and its association with genes involved with gibberellic acid and abscisic acid synthesis. Methodology: Seeds from five B. diandrus populations were sampled during 2017 from commercial fields and planted during 2018 in pots. Protracted seedling emergence in these populations allowed selection of low and high dormancy cohorts. Seeds produced by these cohorts from each population were evaluated for variation in seed dormancy in the following year. The process of cohort selection and seed dormancy evaluation was repeated. The mechanism regulating seed dormancy was investigated in 2020 by assessing seeds of low and high dormancy cohorts concurrently for dormancy and for expression of ABA1 and GA20ox genes, using quantitative real-time PCR. Results: There was at least a two-fold difference in seed dormancy among populations collected from different farms. Low and high dormancy cohorts within each population maintained consistent differences in seed dormancy in both years of assessment, suggesting genetic control over this trait. Differences in seed dormancy between low and high dormancy cohorts were significantly correlated with ABA1 and GA20ox gene expression. Conclusions: Large differences in seed dormancy exist between individuals in B. diandrus populations. The study has provided evidence of genetic variation for seed dormancy within B. diandrus populations, which was associated with ABA1 and GA20ox gene expression. Implications: Presence of genetic variation for seed dormancy could play an important role in adaptation to escape pre-sowing weed-control tactics, meaning that B. diandrus could become an even greater problem in field crops grown in this region. Bromus diandrus is a serious weed of cereal crops in South Australia and is responsible for significant yield decline in wheat. Seed dormancy of different B. diandrus populations analysed for 3 years revealed genetic variation, and genes responsible for the control of seed dormancy were identified. The findings improve understanding of the genes involved in regulating seed dormancy, their expression over time, and how loss of dormancy is associated with changes in the gene expression. [ABSTRACT FROM AUTHOR]

Context: Lolium rigidum Gaudin (annual ryegrass) has remained the most problematic weed of crop production in Australia for more than 20 years. There is some evidence that this weed species can rapidly adapt to management practices including delayed crop sowing. Aims: Studies were undertaken to determine genetic variation for seed dormancy within L. rigidum populations and its association with genes involved with gibberellic acid and abscisic acid synthesis. Methodology: Populations of L. rigidum were grown in pots to select low and high dormancy cohorts. Seeds produced by these cohorts from each population were assessed for variation in seed dormancy. Seeds of high and low dormancy cohorts were concurrently assessed for seed dormancy and expression of LrABA1 and LrGA20ox genes, using quantitative real-time PCR. Results: Presence of differences greater than two-fold in seed dormancy between populations from the same farm indicated in situ selection for seed dormancy, most likely in response to management. Low and high dormancy cohorts of all populations maintained clear differences in seed dormancy in both years of assessment. Differences in seed dormancy between low and high dormancy cohorts were significantly correlated with LrABA1 and LrGA20ox gene expression. Conclusions: This investigation has provided clear evidence of the presence of genetic variation for seed dormancy within L. rigidum populations. Implications: The presence of genetic variation for seed dormancy in L. rigidum populations will allow this weed to adapt rapidly to changes in weed management practices such as delayed sowing of crops. Lolium rigidum is one of the most problematic weeds of cereal crops in southern Australia. Seed dormancy of different L. rigidum populations was analysed, and genes responsible for the control of seed dormancy were identified. Findings from our research enhance understanding of the genes involved in regulating seed dormancy, their expression over time, and how loss of dormancy is associated with changes in gene expression. [ABSTRACT FROM AUTHOR]

Extinction is usually associated with the death of the last remaining individual of a species, taxon, or population of organisms. Here I ask the question of whether extinction might also be applied to cases where individuals of the relevant category remain alive. Global impacts in the Anthropocene suggest extinction may be broader than typically thought. Technologies available in the emerging 'synthetic age' alter taxa in ways that may appropriately be characterized as extinction. The core of the more traditional account of extinction remains valuable. Losing the last few individuals of a taxon matters. But emerging types of loss may demand a broader understanding of extinction. This broader understanding could capture more of what humans are doing to the biosphere. [ABSTRACT FROM AUTHOR]

Context: Annual ryegrass (Lolium rigidum) is a major weed of crop production in southern Australia that readily develops resistance to herbicides. Resistance increases both yield losses and control costs associated with this species. Aims: This study aimed to gauge the extent and distribution of resistance to herbicides in L. rigidum across south-eastern Australian grain production systems by collecting seed from randomly selected fields. Methods: A total of 1441 weed populations were collected through random surveys conducted over 5 years across 13 agricultural regions of four states with these samples then tested for resistance to eight herbicides from six modes of action. Key results: Resistance to diclofop-methyl and sulfometuron-methyl was most common, being present in 64% and 63% of populations respectively. Glyphosate resistance was present in 4% of populations collected. Only 15% of populations collected were susceptible to all herbicides tested. Large differences in resistance occurred between the 13 regions surveyed with resistance to diclofop-methyl ranging from 15% to 86% of populations and sulfometuron-methyl from 12% to 96%. Resistance to post-emergent herbicides tended to be higher than pre-emergent herbicides. Multiple resistance was common with 60% of populations collected having resistance to two or more herbicide modes of action. Conclusions: There were significant differences in the extent of multiple resistance in L. rigidum populations collected from individual regions suggesting that the rates of resistance evolution have differed between regions. Implications : The high incidence of herbicide resistance in L. rigidum populations randomly collected from south-eastern Australian cropping fields highlights the need for the adoption of additional weed control practices to mitigate the impact of this species on grain production systems. Herbicide resistant weeds are a major threat to crop production, with annual ryegrass being the major species of concern in Australia. Surveys of south-eastern Australia conducted over a 5 year period found over 60% of populations were resistant to two or more herbicide groups and only 15% of ryegrass populations were susceptible to all tested herbicides. The high level of resistance found across south-eastern Australia highlights the need for farmers to adopt non-herbicide practices, in conjunction with herbicides, to control this species. [ABSTRACT FROM AUTHOR]

BACKGROUND: In initial screening, glyphosate was ineffective in controlling five Poa annua populations. These populations were tested for resistance, and studies undertaken to determine resistance mechanisms and inheritance pattern. RESULTS: Dose–response studies conducted at 16/12°C and 27/20°C on the five putative resistant populations showed low‐level resistance (1.4‐ to 2.5‐fold) to glyphosate. Shikimic acid accumulation in response to glyphosate confirmed differences among the populations, with greater shikimic acid accumulation in the susceptible population. The EPSPS gene copy number was 0.5‐ to 5.2‐fold greater in one resistant population (HT) than in the susceptible (S) population, but not in the others. EPSPS gene expression was five‐ to tenfold higher in HT compared with the susceptible population. Target site mutations, differences in glyphosate absorption or translocation or altered expression of aldo‐keto reductase (AKR) were not identified in any of the resistant populations. Crosses were successful between one resistant population and the susceptible population (P262‐16♂ ✕ S♀) and inheritance of glyphosate resistance appears to be controlled by a single, nuclear dominant gene in this population. CONCLUSION: Our study identified EPSPS gene amplification in a South Australian glyphosate‐resistant P. annua population (HT). This mechanism of resistance was not identified in the other four glyphosate‐resistant populations, and other common mechanisms were excluded. Although the resistance mechanism in some P. annua populations remains unknown, inheritance studies with one population suggest the involvement of a single dominant gene. © 2021 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

The natural auxin indole-3-acetic acid (IAA) is a key regulator of many aspects of plant growth and development. Synthetic auxin herbicides such as 2,4-Dmimic the effects of IAA by inducing strong auxinic-signaling responses in plants. To determine the mechanism of 2,4-D resistance in a Sisymbrium orientale (Indian hedge mustard) weed population, we performed a transcriptome analysis of 2,4-D-resistant (R) and -susceptible (S) genotypes that revealed an in-frame 27-nucleotide deletion removing nine amino acids in the degron tail (DT) of the auxin coreceptor Aux/IAA2 (SoIAA2). The deletion allele cosegregated with 2,4-D resistance in recombinant inbred lines. Further, this deletion was also detected in several 2,4- D-resistant field populations of this species. Arabidopsis transgenic lines expressing the SoIAA2 mutant allele were resistant to 2,4-D and dicamba. The IAA2-DT deletion reduced binding to TIR1 in vitro with both natural and synthetic auxins, causing reduced association and increased dissociation rates. This mechanism of synthetic auxin herbicide resistance assigns an in planta function to the DT region of this Aux/IAA coreceptor for its role in synthetic auxin binding kinetics and reveals a potential biotechnological approach to produce synthetic auxin-resistant crops using gene-editing. [ABSTRACT FROM AUTHOR]

Accelerating genetic gain in crop improvement is required to ensure improved yield and yield stability under increasingly challenging climatic conditions. This case study demonstrates the effective confluence of innovative breeding technologies within a collaborative breeding framework to develop and rapidly introgress imidazolinone Group 2 herbicide tolerance into an adapted Australian chickpea genetic background. A well-adapted, high-yielding desi cultivar PBA HatTrick was treated with ethyl methanesulfonate to generate mutations in the ACETOHYDROXYACID SYNTHASE 1 (CaAHAS1) gene. After 2 years of field screening with imidazolinone herbicide across >20 ha and controlled environment progeny screening, two selections were identified which exhibited putative herbicide tolerance. Both selections contained the same single amino acid substitution, from alanine to valine at position 205 (A205V) in the AHAS1 protein, and KASP™ markers were developed to discriminate between tolerant and intolerant genotypes. A pipeline combining conventional crossing and F2 production with accelerated single seed descent from F2:4 and marker-assisted selection at F2 rapidly introgressed the herbicide tolerance trait from one of the mutant selections, D15PAHI002, into PBA Seamer, a desi cultivar adapted to Australian cropping areas. Field evaluation of the derivatives of the D15PAHI002 × PBA Seamer cross was analyzed using a factor analytic mixed model statistical approach designed to accommodate low seed numbers resulting from accelerated single seed descent. To further accelerate trait introgression, field evaluation trials were undertaken concurrent with crop safety testing trials. In 2020, 4 years after the initial cross, an advanced line selection CBA2061, bearing acetohydroxyacid synthase (AHAS) inhibitor tolerance and agronomic and disease resistance traits comparable to parent PBA Seamer, was entered into Australian National Variety Trials as a precursor to cultivar registration. The combination of cross-institutional collaboration and the application of novel pre-breeding platforms and statistical technologies facilitated a 3-year saving compared to a traditional breeding approach. This breeding pipeline can be used as a model to accelerate genetic gain in other self-pollinating species, particularly food legumes. [ABSTRACT FROM AUTHOR]

BACKGROUND: Hordeum glaucum Steud. is an important grass weed species in South Australia that has evolved resistance to glyphosate. This study investigated the mode of inheritance of glyphosate resistance in this species. RESULTS: Hand‐pollination of glyphosate susceptible and resistant populations generated two F1 individuals, selfed to yield F2 progenies. In dose–response experiments, the F2 progenies showed intermediate response between the two parent populations. High variation in EPSPS gene copies was observed among F2 individuals, with some individuals possessing more gene copies than the resistant parent population. No evidence of a Mendelian single‐gene pattern of inheritance was observed. CONCLUSION: Inheritance of gene amplification in H. glaucum is non‐Mendelian. © 2021 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

The scale of herbicide resistance within a cropping region can be estimated and monitored using surveys of weed populations. The current approach to herbicide resistance surveys is time‐consuming, logistically challenging and costly. Here we review past and current approaches used in herbicide resistance surveys with the aims of (i) defining effective survey methodologies, (ii) highlighting opportunities for improving efficiencies through the use of new technologies and (iii) identifying the value of repeated region‐wide herbicide resistance surveys. One of the most extensively surveyed areas of the world's cropping regions is the Australian grain production region, with >2900 fields randomly surveyed in each of three surveys conducted over the past 15 years. Consequently, recommended methodologies are based on what has been learned from the Australian experience. Traditional seedling‐based herbicide screening assays remain the most reliable and widely applicable method for characterizing resistance in weed populations. The use of satellite or aerial imagery to plan collections and image analysis to rapidly quantify screening results could complement traditional resistance assays by increasing survey efficiency and sampling accuracy. Global management of herbicide‐resistant weeds would benefit from repeated and standardized surveys that track herbicide resistance evolution within and across cropping regions. © 2021 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

BACKGROUND: Gene amplification has been shown to provide resistance to glyphosate in several weed species, including Hordeum glaucum populations in South Australia. The stability of 5‐enolpyruvylshikimate‐3‐phosphate synthase (EPSPS) gene copies in resistant populations in the presence or absence of glyphosate selection has not been determined. RESULTS: Applying glyphosate to a cloned plant resulted in an increase in resistance and EPSPS copy number in the progeny of that plant compared to the untreated clone. The LD50 (herbicide concentration required for 50% mortality) increased by 75% to 79% in the progeny of the treated clones compared to the untreated in both populations (YP‐17 and YP‐16). EPSPS copy number estimates were higher in treated individuals compared to untreated individuals with an average of seven copies compared to six in YP‐16 and 11 compared to six in YP‐17. There was a positive correlation (R2 = 0.78) between EPSPS copy number and LD50 of all populations. CONCLUSION: EPSPS gene copy number and resistance to glyphosate increased in H. glaucum populations under glyphosate selection, suggesting the number of EPSPS gene copies present is dependent on glyphosate selection. © 2021 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Reciprocal F1, F2 and F3 populations of lentil (Lens culinaris Medik.) were developed by crossing between lines, with a chloroplastic psbA gene mutation conferring tolerance to the photosystem II inhibitor herbicide metribuzin, and sensitive parent PBA Flash, to understand the genetic control of the herbicide tolerance. Additionally, reciprocal BC1F2 populations were developed to identify any fitness penalty associated with the metribuzin tolerance. Phenotyping and genotyping results of the F1, F2, and F3 populations identified a predominantly maternal inheritance pattern, but with a level of paternal leakage. Paternal leakage occurred in approximately 20% of F1 phenotypes, when including lines showing heteroplasmy (the existence of maternal and paternal chloroplasts within an individual). Field experiments with BC1F2 and BC1F3 lines confirmed this biparental inheritance pattern. Grain yield was reduced by 20–40% in metribuzin tolerant backcrossed lines compared with sensitive lines. Net assimilation rate at the onset of anthesis and plant dry weight at mid anthesis and maturity were also reduced in the tolerant lines suggesting reduced photosynthetic efficiency associated with the metribuzin tolerance results in lower dry weight and grain yield in the tolerant lines. The mode of inheritance and associated yield penalty of the tolerance trait will complicate its introgression in lentil breeding programs. However, the high level of tolerance and unique weed control benefits of this trait suggest that this form of metribuzin tolerance in lentil, which is similar to triazine tolerant canola (Brassica napus L.), could be adopted. [ABSTRACT FROM AUTHOR]

The genus Lolium comprises many species, of which L. perenne ssp. multiflorum, L. perenne ssp. perenne, and L. rigidum are of worldwide agricultural importance as both pasture crops and as weeds. These three species are inter‐fertile, obligate out‐crossers with a self‐incompatible reproduction system. This combination contributes to high genetic diversity that supplies new variants during expansion to new natural areas and agricultural environments. Human dispersal, de‐domestication and crop‐weed hybridization events between Lolium spp., or with others such as Festuca spp., are likely associated with their distinct weediness abilities. Furthermore, new introductions followed by introgression may hasten adaptation to new environments. Most Lolium‐related weed science studies have focused on adaptation leading to herbicide resistance, but other forms of adaptation may also occur. In this review, we explore how the wide genetic variation among Lolium species and hybridization with other species may contribute to range expansion, and adaptation to both new agricultural practices and future predicted climate change scenarios. © 2020 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Calls for public participation in climate engineering research and governance have appeared in numerous scientific and policy reports on the topic, indicating a desire for transparency and public oversight. But meaningful public engagement can require more of scientists and regulatory agencies than many realize. Over the past several decades, researchers and practitioners have developed many different methodologies to enable citizens to productively engage with experts and policy makers about emerging scientific and technological issues such as climate engineering. In fact, the United Kingdom has already convened several public participation exercises on climate engineering. Now is the time for federal agencies in the United States to start similar processes. The public is ready to discuss climate engineering. Are American scientists and decision makers ready to reciprocate? [ABSTRACT FROM PUBLISHER]

New techniques for modifying the genomes of agricultural organisms create difficult ethical challenges. We provide a novel framework to replace worn-out ethical lenses relying on 'naturalness' and 'crossing species lines.' Thinking of agricultural intervention as a 'negotiation' of 'integrity' and 'agency' provides a flexible framework for considering techniques such as genome editing with CRISPR/Cas systems. We lay out the framework by highlighting some existing uses of integrity in environmental ethics. We also provide an example of our lens at work by looking at the creation of 'cisgenic' (as opposed to 'transgenic') potatoes to resist late potato blight. We conclude by highlighting three distinct advantages offered by the integrity framework. These include a more fitting way to look at the practice of scientific researchers, a more inclusive way to consider ethics around agriculture, and a more flexible way to provide the ethical grounds for regulation in different cultural contexts. [ABSTRACT FROM AUTHOR]

BACKGROUND Resistance to the dinitroaniline herbicide trifluralin in Lolium rigidum (annual ryegrass) often is mediated by the enhanced capacity to metabolize the herbicide to less toxic polar conjugates and/or by functionally recessive target‐site mutations in α‐tubulin. RESULTS: In two L. rigidum populations possessing enhanced trifluralin metabolism, resistance was largely reversed by recurrent selection with the thiocarbamate herbicide prosulfocarb (i.e. plant survival was two‐ to >20‐fold lower). Their ability to metabolize trifluralin was significantly decreased (by ≈2.3‐fold) following recurrent prosulfocarb selection, to levels comparable to those observed in susceptible plants or when trifluralin metabolism was inhibited by treatment with the insecticide phorate. CONCLUSIONS: This study provides evidence that trait(s) enabling efficient trifluralin metabolism in L. rigidum are purged from the population under prosulfocarb recurrent selection. The level of trifluralin metabolism in vitro and its inhibition caused by phorate action on trifluralin‐metabolizing enzyme(s) is equivalent to the effect produced by prosulfocarb selection. The hypothetical link between the two phenomena is that the putative monooxygenase(s) conferring trifluralin metabolic resistance also mediate the activation of prosulfocarb to its toxic sulfoxide. Thus, we speculate that survival to prosulfocarb via a lack of metabolic herbicide activation, and survival to trifluralin conferred by enhanced herbicide metabolism, are mutually exclusive. These findings not only open up a new research direction in terms of the interaction between different herbicide resistance mechanisms in L. rigidum, but also offer strategies for immediate management of the population dynamics of metabolism‐based resistance in the field. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The potential of oilseed rape to suppress weed growth while maintaining optimal yield and quality is not well understood under field conditions in Australia. This study, conducted in Condobolin and Wagga Wagga, New South Wales (NSW), during 2015 and 2016, examined a diverse range of commercial oilseed rape cultivars for their inherent ability to suppress weeds and maintain yields when in competition with natural weed infestations, with and without pre‐emergent herbicide treatment. Cultivar differences were observed in oilseed rape canopy architecture and yield; however, early‐season biomass, light interception, leaf area index and visual vigour ratings exhibited both year and location interactions. Cultivars with the highest biomass, light interception, leaf area indices and visual vigour were typically also the most weed‐suppressive, in particular GT‐50 and Hyola 600RR. Although crop and weed biomass accumulation differed significantly among cultivars for both location and year, weed biomass was inversely related to cultivar biomass in both years and locations. Hybrid Hyola and GT‐50 cultivars exhibited up to 50% less weed biomass while maintaining consistently high levels of dry crop biomass. In addition, pre‐emergent herbicide applications reduced weed infestation and contributed to higher crop yield in both locations and years. Given the consistent aboveground competitive ability of certain oilseed rape cultivars, our study demonstrated that diverse cultivar‐dependent competitive traits such as early growth vigour, biomass production, absorption of photosynthetically active radiation and production and retention of crop residue significantly impacted weed establishment and total weed biomass. Our findings suggest that cultivar selection offers potential as a tool for maintaining suitable grain yield in the presence of weeds while potentially delaying the development of herbicide resistance through efficacious weed suppression. [ABSTRACT FROM AUTHOR]

Conyza bonariensis (L.) Cronq. (syn. of Erigeron bonariensis L.) is a difficult-to-control summer weed species in the cropping belt of south-eastern Australia. Herbicide resistance may be affecting the ability to control C. bonariensis in the agricultural region of north-eastern Victoria; therefore, a survey was conducted to evaluate resistance to herbicides from several mode-of-action groups. Of the populations collected, 40% were resistant to glyphosate at 1080 g ha–1. Chlorsulfuron failed to control any of the populations collected. Further research identified multiple herbicide resistance to glyphosate, chlorsulfuron, metsulfuron-methyl and sulfometuron-methyl in five of nine populations fully characterised. Resistance was not found to 2,4-D, clopyralid or paraquat. There was no correlation between prevailing land use and the frequency of glyphosate-resistant populations, suggesting that resistance had been selected in multiple production systems. The high frequency of resistance could explain the difficulty experienced in controlling C. bonariensis across north-eastern Victoria and demonstrates the importance of integrated weed management to manage this weed. Flax-leaf fleabane is a difficult-to-control summer weed in Australia. This work showed that one reason for this problem is that populations are becoming resistance to glyphosate, the most common herbicide used in summer fallows. Some of these populations have multiple resistance to other important herbicides used in crop production. [ABSTRACT FROM AUTHOR]

Glufosinate targets glutamine synthetase (GS), but its fast herbicidal action is triggered by reactive oxygen species (ROS). The relationship between GS inhibition and ROS accumulation was investigated in Amaranthus palmeri. Glufosinate's fast action is light-dependent with no visual symptoms or ROS formation in the dark. Inhibition of GS leads to accumulation of ammonia and metabolites of the photorespiration pathway, such as glycolate and glyoxylate, as well as depletion of other intermediates such as glycine, serine, hydroxypyruvate, and glycerate. Exogenous supply of glycolate to glufosinate-treated plants enhanced herbicidal activity and dramatically increased hydrogen peroxide accumulation (possibly from peroxisomal glycolate oxidase activity). Glufosinate affected the balance between ROS generation and scavenging. The activity of superoxide dismutase, catalase, ascorbate peroxidase, and glutathione reductase increased after glufosinate treatment in an attempt to quench the nascent ROS burst. Low doses of atrazine and dinoseb were used to investigate the sources of ROS by manipulating photosynthetic electron transport and oxygen (O2) evolution. ROS formation depended on electron flow and O2 evolution in photosystem II (PSII). Inhibition of GS disrupted photorespiration, carbon assimilation, and linear electron flow in the light reactions. Consequently, the antioxidant machinery and the water–water cycle are overwhelmed in the presence of light and glufosinate. The O2 generated by the splitting of water in PSII becomes the acceptor of electrons, generating ROS. The cascade of events leads to lipid peroxidation and forms the basis for the fast action of glufosinate. [ABSTRACT FROM AUTHOR]

Background: Resistance to glyphosate has been reported in flaxleaf fleabane populations within a number of grain growing areas in southern Queensland and northern New South Wales and other cropping regions across Australia. Results: To investigate the processes contributing to the evolution and spread of glyphosate-resistant flaxleaf fleabane, the resistant populations tested in dose-response experiments varied in their responses to glyphosate from two to eight times the recommended rate. The different dose responses obtained may indicate different mechanisms of resistance. This can possibly be attributed to an independent evolution of resistance. Conclusion: The results demonstrate that glyphosate resistance is widespread across Australia and has likely evolved multiple times as well as dispersing by seeds. [ABSTRACT FROM AUTHOR]

BACKGROUND: Glyphosate failed to control two populations of Hordeum glaucum (northern barley grass) along a fence line and around stockyards near Arthurton on the Yorke Peninsula, South Australia after more than a decade of regular use of glyphosate. These were investigated to confirm resistance and to determine resistance mechanisms. RESULTS: Dose–response experiments confirmed resistance of these populations to glyphosate with resistance levels of 2.8–6.6‐fold compared with two susceptible populations. Shikimate assays confirmed resistance to glyphosate with less shikimate accumulation in the resistant populations compared with the susceptible populations. Quantitative PCR of genomic DNA showed increased gene copy number in the resistant populations with 9–11‐fold more copies of EPSPS compared with the susceptible populations, suggesting resistance is likely conferred by gene amplification. CONCLUSION: This study identified the first examples of glyphosate resistance in the grass species H. glaucum with resistance associated with EPSPS gene amplification. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

John Martyn's Methodus plantarum circa Cantabrigiam nascentium was printed in 1727 and was given to his friends and students, but not offered for sale. It has hitherto been thought that the 24 printed pages of a proposed second edition, the "abortive edition", are a rare survival of an unpublished work. However, examination of 24 copies of the Methodus reveals that pages of the abortive edition are present in nine, and they must have been made available to students in the same way as the first edition. They are easily overlooked, especially in copies in which these 24 pages replace the first 20 pages of the earlier edition. The 24 pages cover mainly bryophytes, lichens and fungi, and Martyn's failure to complete the new edition has obscured his role in the investigation of these groups. [ABSTRACT FROM AUTHOR]

Background: Continual application of herbicides for flaxleaf fleabane control readily results in the evolution of herbicide resistance. Flaxleaf fleabane has evolved resistance to different modes of action herbicides in many countries. Due to the comprehensive geographical distribution of flaxleaf fleabane in Australia, it was classified as a cosmopolitan weed and it therefore has no specific climatic requirement. Results: The high percentage of polymorphisms in the samples of the susceptible population (79.8%, 75%) suggests that susceptible populations of flaxleaf fleabane, even within one site, originated from a number of parents. However, the percentage of polymorphism in the resistant populations (51.5%, 66.8%) suggests that resistant populations of flaxleaf fleabane within one site could have originated from fewer parents. In addition, any site containing resistant and susceptible populations of flaxleaf fleabane may have been populated by a large number of parents, evidenced by the relatively high percentage of polymorphisms detected by amplified fragment length polymorphism (AFLP) analysis (86.5%). Despite the large geographic distances between collection locations, populations from across states clustered in several groups showing a close genetic relationship among these populations over these large distances. These high levels of genetic diversity within and between populations confirmed in the sequencing of enolpyruvylshikimate-3-phosphate above support the results of AFLP studies and gave the author more confidence to report the genetic diversity seen within and between population studies. Conclusion: To prevent further resistance spread, flaxleaf fleabane management in infested areas should focus on decreasing seed movement from resistant sites as well as reducing the selection pressure for resistance to glyphosate by adopting alternative management strategies. [ABSTRACT FROM AUTHOR]

Multiple field experiments and a controlled-environment temperature study were conducted to investigate soil and weather conditions responsible for herbicide phytotoxicity in lentil (Lens culinaris Medik.) from post-emergent application of metribuzin. A linear relationship was observed between plant injury (% necrosis) and metribuzin rate in all 12 environments, but in only 11 environments for anthesis dry weight and nine environments for both plant density and grain yield. Grain-yield reduction from label metribuzin rates of 135 g a.i. ha–1 for sand and 285 g a.i. ha–1 for clay ranged from 0% to 32% and 0% to 67%, respectively, across all environments. Principal component analysis of soil and weather factors around the time of herbicide application suggested that metribuzin-induced plant damage in lentil was due to a combination of multiple soil and weather factors. However, heavy rainfall within 10 days of herbicide application, particularly on light-textured soils or where soil moisture was low, was most strongly linked to plant damage. Experiments targeting the impact of reductions in temperature post-metribuzin application showed no effect, and of light intensities pre- and post-metribuzin application showed low effects on plant-damage measures. Because rainfall in the 10 days after application is a major determinant of metribuzin damage in winter-grown lentil in southern Australia, a higher level of selective tolerance to metribuzin than that present in commercial cultivars is needed for its safe post-emergent use. Early and late measures of plant damage will be required to assess accurately plant tolerance to post-emergent metribuzin application in lentil. Lentil is a pulse crop of expanding importance in Australia, but production is limited by weed competition and a lack of safe and effective herbicides. Metribuzin is a broad-spectrum herbicide used in lentil; however, multiple soil and weather conditions exacerbated plant damage, particularly heavy-rainfall events within 10 days of post-emergent application on light-textured soils low in soil moisture. This research highlights the need for the development of lentil cultivars with a higher level of tolerance to metribuzin under Australian conditions. [ABSTRACT FROM AUTHOR]

BACKGROUND: Faba bean (Vicia faba L.) is an important crop in Australian farming systems, however, weed control is a major constraint due to a lack of in‐crop broadleaf herbicide options. To address this, we developed acetohydroxyacid synthase (AHAS) inhibitor herbicide tolerance in faba bean using mutagenesis techniques. Dose–response experiments, agronomic field evaluation and DNA sequencing of the AHAS gene were used to quantify and validate tolerance traits. RESULTS: Four M2 faba bean single‐plant biotypes (IMI‐1, IMI‐2, IMI‐3 and IMI‐4) at a frequency of 3.63 × 10−6 were successfully recovered. Molecular characterisation of the AHAS gene identified two known target site mutations (resulting in protein substitutions Ala205Val and Ser653Asn) conferring tolerance. Phenotypic characterisation found that both mutations conferred high levels of tolerance to the imidazolinone herbicide imazapyr. However, although the Ala205Val substitution showed improved levels of cross‐tolerance to a range of sulfonylurea chemistries, the Ser653Asn substitution did not. In the field, IMI‐3 showed the highest level of agronomic tolerance across a range of imidazolinone herbicides. CONCLUSIONS: Mutagenesis techniques were successful in the development of tolerance to AHAS inhibitor herbicides in faba bean, and could facilitate the first safe in‐crop broadleaf herbicide control option in Australian faba bean production. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

BACKGROUND Weed competition is a major limitation to worldwide lentil (Lens culinaris Medik.) production in part due to limited effective safe herbicide options. Metribuzin is a photosystem II inhibiting herbicide that provides broad spectrum weed control, however it causes excessive injury in lentil. Dose response analysis of photosystem II inhibiting herbicides and DNA sequencing of the psbA chloroplast gene occurred to quantify the spectrum and mechanism of herbicide resistance in two ethyl‐methanesulfonate (EMS) induced mutant lentils. RESULTS: Compared to susceptible parent PBA Flash, the level of metribuzin resistance was 33‐fold for mutant M043 and 10‐fold for M009. No improvement in resistance occurred in either mutant to bromoxynil, diuron, bromacil and atrazine herbicides. Nucleotide sequencing of the psbA gene of both mutants identified a substitution at position 751 compared to PBA Flash. The resulting deduced amino acid sequence indicated an Ala251Thr substitution as being most likely responsible for the high level of metribuzin resistance. CONCLUSIONS: The Ala251Thr substitution discovered in this study is unique in mutagenized higher plants and the first report of an induced psbA target site mutation in higher plants. This target site metribuzin resistance is likely to have a significant impact on lentil production in Australia and worldwide. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Main conclusion: Glufosinate is primarily toxic to plants due to a massive light-dependent generation of reactive oxygen species rather than ammonia accumulation or carbon assimilation inhibition. Glutamine synthetase (GS) plays a key role in plant nitrogen metabolism and photorespiration. Glufosinate (C5H12NO4P) targets GS and causes catastrophic consequences leading to rapid plant cell death, and the causes for phytoxicity have been attributed to ammonia accumulation and carbon assimilation restriction. This study aimed to examine the biochemical and physiological consequences of GS inhibition to identify the actual cause for rapid phytotoxicity. Monocotyledonous and dicotyledonous species with different forms of carbon assimilation (C3 versus C4) were selected as model plants. Glufosinate sensitivity was proportional to the uptake of herbicide between species. Herbicide uptake also correlated with the level of GS inhibition and ammonia accumulation in planta even with all species having the same levels of enzyme sensitivity in vitro. Depletion of both glutamine and glutamate occurred in glufosinate-treated leaves; however, amino acid starvation would be expected to cause a slow plant response. Ammonia accumulation in response to GS inhibition, often reported as the driver of glufosinate phytotoxicity, occurred in all species, but did not correlate with either reductions in carbon assimilation or cell death. This is supported by the fact that plants can accumulate high levels of ammonia but show low inhibition of carbon assimilation and absence of phytotoxicity. Glufosinate-treated plants showed a massive light-dependent generation of reactive oxygen species, followed by malondialdehyde accumulation. Consequently, we propose that glufosinate is toxic to plants not because of ammonia accumulation nor carbon assimilation inhibition, but the production of reactive oxygen species driving the catastrophic lipid peroxidation of the cell membranes and rapid cell death. [ABSTRACT FROM AUTHOR]

BACKGROUND: An oriental mustard population (P40) was identified as resistant to diflufenican by screening at the field rate. As diflufenican and picolinafen both target phytoene desaturase (PDS), cross‐resistance to picolinafen was suspected. The mechanism of resistance and its inheritance to diflufenican and picolinafen were investigated. RESULTS: At the lethal dose (LD50) level, population P40 was 237‐fold more resistant to diflufenican and seven‐fold more resistant to picolinafen compared to two susceptible populations. Population P40 also had a significantly higher resistance to diflufenican (237‐fold) than a previously described P3 population (143‐fold). In addition to the Leu‐498‐Val mutation in PDS identified in all individuals of the P3 and P40 populations, a Glu‐425‐Asp mutation was also found in P40. Neither mutation was detected in any individuals of the susceptible population. As the segregation of phenotype and genotype of the F2 individuals fitted the model for a single dominant allele, resistance to both diflufenican and picolinafen is likely encoded on the nuclear genome and is dominant. CONCLUSION: Resistance to diflufenican and picolinafen in the P40 population is likely conferred by Leu‐498‐Val and Glu‐425‐Asp mutations in the PDS gene. Inheritance of resistance to these herbicides is managed by a single dominant gene. © 2018 Society of Chemical Industry The evolution of herbicide resistance in oriental mustard has significantly increased in Australian cropping systems. This article presents the mechanism and inheritance of cross‐resistance to diflufenican and picolinafen in this weed species. [ABSTRACT FROM AUTHOR]

Abstract: There have been previous calls for, and efforts focused on, realizing the power and potential of weed genomics for better understanding of weeds. Sustained advances in genome sequencing and assembly technologies now make it possible for individual research groups to generate reference genomes for multiple weed species at reasonable costs. Here, we present the outcomes from several meetings, discussions, and workshops focused on establishing an International Weed Genomics Consortium (IWGC) for a coordinated international effort in weed genomics. We review the ‘state of the art’ in genomics and weed genomics, including technologies, applications, and on‐going weed genome projects. We also report the outcomes from a workshop and a global survey of the weed science community to identify priority species, key biological questions, and weed management applications that can be addressed through greater availability of, and access to, genomic resources. Major focus areas include the evolution of herbicide resistance and weedy traits, the development of molecular diagnostics, and the identification of novel targets and approaches for weed management. There is increasing interest in, and need for, weed genomics, and the establishment of the IWGC will provide the necessary global platform for communication and coordination of weed genomics research. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Abstract: BACKGROUND: An oriental mustard population (P3) collected near Quambatook, Victoria was identified as being resistant to diflufenican by screening with the field rate (200 g a.i. ha‐1) of the herbicide. The mechanism(s) of diflufenican resistance and its inheritance in this population were therefore investigated. RESULTS: Dose‐response experiments confirmed that population P3 was 140‐fold more resistant to diflufenican than susceptible populations, as determined by the comparison of 50% lethal (LD50) values. The phytoene desaturase (PDS) gene from five individuals each of the S1 [susceptible (S)] and P3 [resistant (R)] populations was sequenced, and a substitution of valine for leucine at position 526 (Leu‐526‐Val) was detected in all five individuals of P3, but not in the S1 population. Inheritance studies showed that diflufenican resistance is encoded in the nuclear genome and is dominant, as the response to diflufenican at 200 g a.i. ha‐1 of F1 families was equivalent to that of the resistant biotype. The segregation of F2 phenotypes fitted a 3:1 inheritance model. Segregation of 42 F2 individuals by genotype sequencing fitted a 1:2:1 (ss:Rs:RR) ratio. CONCLUSION: Resistance to diflufenican in oriental mustard is conferred by the Leu‐526‐Val mutation in the PDS gene. Inheritance of resistance is managed by a single gene with high levels of dominance. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Abstract: BACKGROUND: Two oriental mustard populations (P2 and P13) collected from Port Broughton, South Australia were identified as resistant to 2,4‐D. The level of resistance, mechanism and the mode of inheritance for 2,4‐D resistance in these populations were investigated. RESULTS: Populations P2 and P13 were confirmed to be resistant to 2,4‐D at the field rate (600 g a.e. ha−1). P2 and P13 were 81‐ and 67‐fold more resistant than the susceptible populations (S1 and S2) at the dose required for 50% mortality (LD50), respectively. No predicted amino acid modification was detected in sequences of potential target‐site genes (ABP, TIR1 and AFB5). Resistant populations had reduced 2,4‐D translocation compared with the susceptible populations, with 77% of [14C]2,4‐D retained in the treated leaf versus 32% at 72 h after treatment. Resistance to 2,4‐D is encoded on the nuclear genome and is dominant, as the response to 2,4‐D of all F2 individuals were similar to the resistant biotypes. The segregation of F2 phenotypes fitted a 3: 1 (R: S) inheritance model. CONCLUSION: Resistance to 2,4‐D in oriental mustard is likely due to reduced translocation of 2,4‐D out of the treated leaf. Inheritance of 2,4‐D resistance is conferred by a single gene with a high level of dominance. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Abstract: BACKGROUND: Five glyphosate‐resistant populations of Chloris truncata originally collected from New South Wales were compared with one susceptible (S) population from South Australia to confirm glyphosate resistance and elucidate possible mechanisms of resistance. RESULTS: Based on the amounts of glyphosate required to kill 50% of treated plants (LD50), glyphosate resistance (GR) was confirmed in five populations of C. truncata (A536, A528, T27, A534 and A535.1). GR plants were 2.4–8.7‐fold more resistant and accumulated less shikimate after glyphosate treatment than S plants. There was no difference in glyphosate absorption and translocation between GR and S plants. The EPSPS gene did not contain any point mutation that had previously been associated with resistance to glyphosate. The resistant plants (A528 and A536) contained up to 32–48 more copies of the EPSPS gene than the susceptible plants. CONCLUSION: This study has identified EPSPS gene amplification contributing to glyphosate resistance in C. truncata. In addition, a Glu‐91‐Ala mutation within EPSPS was identified that may contribute to glyphosate resistance in this species. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Abstract: BACKGROUND: Chloris virgata is a warm‐season, C4, annual grass weed affecting field crops in northern Australia that has become an emerging weed in southern Australia. Four populations with suspected resistance to glyphosate were collected in South Australia, Queensland and New South Wales, Australia, and compared with one susceptible (S) population to confirm glyphosate resistance and elucidate possible mechanisms of resistance. RESULTS: Based on the rate of glyphosate required to kill 50% of treated plants (LD50), glyphosate resistance (GR) was confirmed in four populations of C. virgata (V12, V14.2, V14.16 and V15). GR plants were 2–9.7‐fold more resistant and accumulated less shikimate after glyphosate treatment than S plants. GR and S plants did not differ in glyphosate absorption and translocation. Target‐site EPSPS mutations corresponding to Pro‐106‐Leu (V14.2) and Pro‐106‐Ser (V15, V14.16 and V12) substitutions were found in GR populations. The population with Pro‐106‐Leu substitution was 2.9–4.9‐fold more resistant than the three other populations with Pro‐106‐Ser substitution. CONCLUSION: This report confirms glyphosate resistance in C. virgata and shows that target‐site EPSPS mutations confer resistance to glyphosate in this species. The evolution of glyphosate resistance in C. virgata highlights the need to identify alternative control tactics. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

In the rapidly expanding literature on the ethics of climate engineering, a lot has been made of the fact that stratospheric aerosol injection would for the first time create a world whose climate had been intentionally shaped by deliberate human decisions. Intention has always mattered in ethics. Due to the importance of intention in assigning culpability for harms, one might expect that the moral responsibility for any harms created during an attempt to reconstruct the global climate using stratospheric aerosols would be considerable. This article investigates such an expectation by making a comparison between the culpability for any unintended harms resulting from stratospheric aerosol injection and culpability for the unintended harms already taking place due to carbon emissions. To make this comparison, both types of unintended harms are viewed through the lens of the doctrine of double effect. The conclusion reached goes against what many might expect. The article closes by suggesting that a good way to read this surprising conclusion is that it points toward the continuing moral importance of prioritizing emission reductions. [ABSTRACT FROM AUTHOR]

In southern Australia, oriental mustard ( Sisymbrium orientale) has been controlled successfully by triazine herbicides for several decades. The screening of 40 populations that were collected from the southern grain belt of Australia during 2010 and 2013 for resistance to six different herbicides (glyphosate, diflufenican, imazamox, chlorsulfuron, atrazine and 2,4-dichlorophenoxyacetic acid) identified two oriental mustard populations as highly resistant to atrazine. Compared to the known oriental mustard-susceptible populations (S1 and S2), these two resistant populations (P17 and P18) from near Horsham, Victoria, Australia, were 311- and 315-fold resistant to atrazine, as determined by a comparison of the LD50 values. However, there was no resistance to diuron detected in these populations. Sequencing of the chloroplast psbA gene identified a missense mutation of serine 264 to glycine in both herbicide-resistant oriental mustard populations, which is known to confer high-level atrazine resistance in other species. [ABSTRACT FROM AUTHOR]

Ethicists and social scientists alike have advocated for the inclusion of vulnerable populations in research and decision-making on climate engineering. Unfortunately, there have been few efforts to do so. The research presented in this paper was designed to build knowledge about how vulnerable populations think about climate engineering. The goal of this manuscript is to bring the ethics literature on climate engineering into dialogue with emerging social science data documenting the perspectives of vulnerable populations. The results indicate some concerns among vulnerable populations may resemble those outlined by ethicists. However, the perspectives expressed by interviewees also extend previous ethical treatments by indicating ways in which climate engineering could compound existing injustices. [ABSTRACT FROM AUTHOR]

Smooth barley [Hordeum glaucum (Steud.) Tzvelev] has recently evolved resistance to acetyl coenzyme-A carboxylase (ACCase) inhibitors in crop fields of South Australia. Experiments were conducted to determine the inheritance of quizalofop (quizalofop-p-ethyl) resistance in a population of smooth barley. Resistant plants (pollen donor) were crossed with susceptible plants (pollen acceptor) to generate an F1 generation, and the F1 hybrid was selfed to produce an F2 generation. It was observed that the resistant population was >60-fold more resistant to quizalofop as compared with the susceptible population and contained an amino acid change from isoleucine-to-leucine at 1781 in the carboxyl-transferase domain of the ACCase gene. The F1 individual was confirmed to be heterozygous by sequencing the carboxyl-transferase domain of ACCase, indicating that the inheritance of resistance is nuclear encoded. The F2 dose-response indicated that quizalofop resistance in smooth barley is conferred by a single partially dominant gene. The F2 plants segregated in a 3:1 ratio when treated with 6.2 g quizalofop ha-1, and sequencing of the ACCase gene also revealed that resistance alleles segregated in a 1:2:1 ratio, as expected for single-gene inheritance. This study confirms that quizalofop resistance in smooth barley from Australia is inherited by a single, partially dominant nuclear allele encoding a mutation in ACCase that confers resistance at the field rate. [ABSTRACT FROM AUTHOR]

In Australia, over-reliance on clethodim has resulted in the evolution of clethodim resistance in rigid ryegrass (Lolium rigidum Gaudin) populations. Many of these resistant populations contain amino acid modifications in acetyl co-enzyme A carboxylase (ACCase), the target-site for this herbicide. This study was conducted to determine whether a fitness penalty exists for three known mutations (Leu-1781, Asn-2041, and Gly-2078) in clethodim-resistant populations in the absence of herbicide selection pressure and presence of crop competition. In 2014, F2 seedlings of three clethodim-resistant rigid ryegrass populations were planted in wheat (Triticum aestivum L.) crop under two densities (100 and 200 plants m-2). Sequencing of all individuals of each rigid ryegrass population was done to establish the initial frequency of each allele (no mutation, Leu-1781, Asn-2041, and Gly-2078). The F2 plants were allowed to set seed and seeds were collected at the end of the season. In 2015, seedlings established from seed collected in 2014 were grown, and the sequence of ACCase gene examined to determine the change in frequency of each resistant allele. The results showed that there was no significant change in the frequency of Leu-1781, and Asn-2041 alleles in rigid ryegrass populations over one generation in the absence of clethodim use. However, Gly-2078 increase was identified in three populations, even under different competition levels. The absence of fitness penalties associated with these resistant alleles suggests that their frequency will not decrease over time in the absence of clethodim use. [ABSTRACT FROM AUTHOR]

BACKGROUND In Australia, the extensive use of clethodim for the control of Lolium rigidum has resulted in the evolution of many clethodim-resistant L. rigidum populations. Five clethodim-resistant populations of L. rigidum were analysed for the inheritance of clethodim resistance. RESULTS Reciprocal crosses were made between resistant (R) and susceptible (S) populations. Within crosses, dose-responses of reciprocal F1 families of all populations except A61 were similar to each other, indicating that clethodim resistance in these populations is encoded on the nuclear genome. The level of dominance observed in the dose-response experiments ranged from partial to complete within the herbicide rate used. In the A61 population, within each cross, the response of F1 from the maternal and paternal parent was different, indicating that resistance is inherited through the female parent. All backcross populations segregated in a different manner. Only one population, FP, fitted a single-gene model (1:1). Two populations fitted two-gene models: a 3:1 inheritance model for F4 and a 1:3 inheritance model for A91. For population E2, no clear pattern of inheritance was determined, suggesting more complex inheritance. CONCLUSION The results of this study indicate that different patterns of clethodim resistance in L. rigidum exist. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

BACKGROUND Acetyl coenzyme-A carboxylase (ACCase) and/or acetolactate synthase (ALS) inhibitor resistance has been identified by herbicide resistance screening in eight populations obtained from cropping regions of South Australia. This study aimed to quantify the level of resistance and characterise the molecular basis of resistance to ACCase and ALS inhibitors in these H. glaucum populations. RESULTS H. glaucum populations from the Upper-North region were highly resistant (resistance index RI > 12) to the aryloxyphenoxypropionate (APP) herbicides quizalofop and haloxyfop and less resistant (RI = 2-12) to cyclohexanedione (CHD) herbicide clethodim, and some Mid-North populations had a low level of resistance (RI = 2-6) to the sulfonylurea (SU) herbicide mesosulfuron. Gene sequencing confirmed the presence of Ile-1781-Leu, Ile-2041-Asn and Gly-2096-Ala mutations in the ACCase gene, with no mutation found in the ALS gene. The use of the known metabolic inhibitor malathion in combination with mesosulfuron enhanced the activity of this herbicide. These populations were also susceptible to SU herbicide sulfometuron. CONCLUSION This study has documented APP-to-CHD herbicide cross-resistance, the first case of ACCase inhibitor resistance due to Ile-2041-Asn mutation, and characterised the resistance to ALS inhibitors in H. glaucum. Resistance to ACCase inhibitors is due to a target-site mutation. The reversal of SU resistance by malathion and susceptibility to sulfometuron suggests that non-target-site mechanisms confer resistance to ALS inhibitors. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Glyphosate-tolerant (GT) cotton offers a multitude of benefits such as broad-spectrum and cost-effective weed control, simple weed management, and reduced impact on the environment. However, high adoption rates ofGTcotton have led to overreliance on glyphosate in weed management and have decreased the use of other herbicide options and nonchemical weed-management strategies, possibly leading to the emergence of many resistant weeds. Previous surveys in 2006 and 2011 in the cotton-growing regions of New South Wales (NSW) and Queensland, Australia, indicated changes in weed populations over the period and increased prevalence of several weeds. These two surveys indicated increased dominance of Conyza bonariensis, Echinochloa colona, and Chloris virgata in these regions. Periodic weed surveys are necessary to assess weed population dynamics and shifts due to overreliance on glyphosate for weed management. A survey was carried out in the cotton-growing regions of NSW and Queensland in 2014-15, covering 135 fields. Survey results indicated the emergence of volunteer GT cotton as the most common weed present across all of the cotton-growing regions, occurring in 85% of fields, followed by E. colona (67% of fields surveyed), and C. bonariensis and Sonchus oleraceus, which were present in 51% of fields. The most prevalent grass weed after E. colona was C. virgata (37%). Broadleaf weeds Ipomoea lonchophylla and Amaranthus mitchellii were present in 40% and 37% of fields, respectively. Regional-level analysis indicated greater prevalence of Sesbania cannabina and Parthenium hysterophorus in Emerald region of Queensland. Lolium rigidum was present in the Griffith and Warren area of NSW during summer, even though it is a winter weed. The results of this study indicate integration of diversified weed-management options and inclusion of both non-chemical and chemical options because many major weeds observed in this study are tolerant to glyphosate and have already evolved resistance to glyphosate. [ABSTRACT FROM AUTHOR]