Wild Oat Research Articles

Evaluating seedbank stimulants for wild oat and volunteer cereal management on the Canadian Prairies

Wild oat is a widespread threat to annual crop production on the Canadian Prairies. Infestations are difficult to manage due to a persistent seedbank, complex dormancy, a long emergence window, herbicide resistance, and seed shatter corresponding to crop harvest timings. The study objective was to evaluate the efficacy of potassium nitrate (KNO3) and pyroligneous acid for promoting germination and emergence of wild oat and volunteer wheat, barley, and oat. A total of 24 repeated experiments were conducted using freshly produced seeds to ensure adequate endodormancy. Wheat and barley demonstrated no endodormancy following seed formation and rapidly emerged with moisture. All species imbibed but did not germinate in Petri dishes within pyroligneous acid solutions of 5%–100%. Dormancy release was observed within 0.1% and 1% pyroligneous acid solutions. KNO3 did not stimulate germination or emergence for any species and was inhibitory at 125 kg N ha−1. Pyroligneous acid increased wild oat emergence with 50% and 100% solutions applied at 200 L ha−1 in the first study and with 10% solutions in the second study. Emergence inhibition was noted for oat, barley, and wheat with pyroligneous acid applications. This research further confirms that pyroligneous acid may stimulate wild oat emergence and confirms activity on freshly matured seed.

Weed control in wheat with pyroxasulfone and its combinations with other herbicides

AbstractField and pot investigations were conducted to determine the effectiveness of pyroxasulfone alone and its combinations with other herbicides against diverse weed flora of wheat (Triticum aestivum L.) including multiple herbicide‐resistant (MHR) littleseed canarygrass (Phalaris minor Retz.). Applications of pyroxasulfone 100–127.5 g/ha as pre‐emergence (PE) or early post‐emergence (EPOE) @ 63.75 g/ha at 21–23 days after sowing (1 day before irrigation) were highly effective for control of grass weeds namely P. minor and wild oat (Avena ludoviciana Dur.). It was poor for control of broad‐leaved weeds (Medicago denticulata Willd. and Rumex dentatus L.). However, pyroxasulfone in tank‐mix combination with metsulfuron 4 g/ha, triasulfuron 20 g/ha, and pyroxsulam 18 g/ha effectively controlled (96.5%–99.8%) the diverse weed flora and improved the wheat grain yield (69.5%–285.9%) over untreated weedy control. Also, the pre‐mix of pyroxasulfone + pendimethalin applied as PE was superior to either of these applied alone for weed control and grain yield. Pyroxasulfone 100–127.5 g/ha had yield gain of 119.6%–125.4% and 10.1%–26% over untreated control and pendimethalin 800–1250 g/ha, respectively. In pot studies, straw burnt ash drastically reduced the pyroxasulfone efficacy against P. minor and A. ludoviciana. Pyroxasulfone was also effective in pot studies for control of MHR P. minor having resistance against acetyl‐coA carboxylase (ACCase), acetolactate synthase (ALS), and photosynthesis at the photosystem‐II site‐A (PS‐II) inhibitor herbicides (clodinafop, sulfosulfuron, and isoproturon, respectively). The studies indicate that pyroxasulfone as PE or EPOE can be an alternative grass weed control herbicide in wheat in particular for the control of MHR P. minor.

Origin of Wild Polyploid Avena Species Inferred from Polymorphism of the ITS1 rDNA in Their Genomes

In this article, we analyzed the origin of wild polyploid oats (Avena L., Poaceae) using the region 18S rDNA (partially)–ITS1–5.8S rDNA obtained via NGS. There are six tetraploid (2n = 28) and four hexaploid (2n = 42) wild species differing by specific genome combinations: A. barbata, A. vaviloviana (AB), A. agadiriana (AB or BB), A. magna, A. murphyi, A. insularis (AC or CD), A. ludoviciana, A. sterilis, A. fatua, and A. occidentalis (ACD). We compared the pool of marker sequences of polyploid oats with those of their putative diploid ancestors: A. atlantica (As-genome), A. hirtula (As), A. canariensis (Ac), A. ventricosa (Cv), and A. clauda (paleopolyploid with Cp and A-related rDNA). We found 15 major ribotypes (more than 1000 reads per rDNA pool) in polyploid oats. Comparing them, we found that the AB-tetraploid oats possibly inherited their A-genome ribotypes from A. atlantica (As1-ribotype), whereas their B-genome ribotype is specific and can be a derivative of the A-genome family. Our data do not support the hypothesis of the CD-genome set in A. magna, A. murphyi, and A. insularis: they have an AC-genome ribotype constitution instead. The C-genome-related sequences could have been obtained from A. ventricosa. Hexaploids show a different ribotype pattern than tetraploids; the main ribotypes of A. fatua, A. ludoviciana, and A. sterilis probably belong to the D-group and are also shared with one of the major ribotypes of A. clauda.

The collection of oat genetic resources held by VIr as a source of information on the history of cultivation and taxonomy of the genus, and breeding trends (a review)

Oat is one of the leading cereals cultivated in the world and in Russia; it has an important fodder and nutritional value. To preserve the entire crop agrobiodiversity worldwide, there is a network of genebanks that hold more than 200,000 oat accessions. International and national genebanks are located in all the world’s countries, but one of the largest oat collections is located in Russia.The global collection of the genus Avena L. (Oats) at the N.I. Vavilov All-Russian Institute of Plant Genetic Resources (VIR) is one of the largest worldwide and consists of over 13,000 accessions. The collection preserves and maintains live accessions of all cultivated oat species: A. sativa L., A. byzantina K. Koch, A. strigosa Schreb. and A. abyssinica Hochst., landraces, breeding lines, spring and winter forms, covered and naked genotypes, and all geographic diversity of 22 wild Avena spp. from 50 countries. This review provides historical background of the collection of cultivated and wild oat species, and who were the main donors of these holdings. The taxonomic system of the genus is briefly presented, which is used as a tool for efficient work and guaranteed safe preservation of accessions. Most of the cultivars developed in Russia have in their pedigree accessions obtained from the global collection of VIR. The passport database contains detailed information about all accessions of the collection, which makes it possible to improve the work with the oat collection, including safe preservation of accessions and their effective evaluation and use as source material for breeding in the leading breeding centers of Russia.Thus, the global oat collection at VIR has factual and potential value for the sustainable development of environmentally friendly agriculture, efficient processing of agricultural products, and production of safe and high-quality food products, including functional foods.

Variation of some physical and chemical quality traits of Moroccan domesticated tetraploid oat lines of <i>Avena murphyi</i> Ladiz

A potential in improving nutrition and health is the consumption of high balanced whole grains. A breeding program was launched by the National Institute for Agricultural Research (INRA-Morocco), aiming to develop new domesticated tetraploid oat lines of Avena murphyi Ladiz., with high nutritional benefits. A sequence-based diversity study was conducted on ten tetraploid oat lines of A. murphyi to shed light not only on the importance of domesticating wild oat species for crop improvement but also to highlight the nutritional traits of those oat lines. In this study, we assessed the lines for some grain nutritional traits, such as groat contents of proteins and lipids as well as ash, fiber fractions, carbohydrates, and minerals.The obtained results showed a wide range of chemical contents among lines. The results revealed a high significant difference (P < 0.001) in the groat contents of proteins (11.46–15.12%), fat (4.14–10.14%), carbohydrates (48.68–57.38%), and ash (2.71–5.18%). Analysis of total fiber fractions (NDF, ADF, ADL and CF), showed the presence of significant differences between the assessed lines. The lines A. murphyi 8 and 9, recorded the highest groat protein contents of 15.12% and 13.66%, with an interesting macroelement profile, mainly magnesium and phosphorus, and iron and manganese as minor mineral profile.Due to their biochemical composition, Moroccan domesticated tetraploid oat lines of A. murphyi offer many opportunities to improve oat cultivation in Morocco and serve as an excellent raw material for foodstuffs formulation.

Assessment of ACC and P450 Genes Expression in Wild Oat (Avena ludoviciana) in Different Tissues Under Herbicide Application.

Target-site resistance (TSR) and non-target-site resistance (NTSR) to herbicides in arable weeds are increasing rapidly all over the world and threatening universal food safety. Resistance to herbicides that inhibit ACCase activity has been identified in wild oat. In this study, expression of ACC1, ACC2, CYP71R4 and CYP81B1 genes under herbicide stress conditions were studied in two TSR (resistant in the residue Ile1781-Leu and Ile2041-Asn of ACCase) biotypes, two NTSR biotypes and one susceptible biotype of A. ludoviciana for the first time. Treated and untreated biotypes with ACCase-inhibitor clodinafop propargyl herbicide were sampled from the stem and leaf tissues at 24h after treatment. Our results showed an increase in gene expression levels in different tissues of both types of resistance biotypes that occurred under herbicide treatment compared with non-herbicide treatment. In all samples, the expression levels of leaf tissue in all studied genes were higher than in stem tissue. The results of ACC gene expression showed that the expression level of ACC1 was significantly higher than that of ACC2. Also, expression levels of TSR biotypes were higher than NTSR biotypes for the ACC1 gene. For both CYP71R4 and CYP81B1 genes, the expression ratio increased significantly in TSR and NTSR biotypes in different tissues after herbicide treatment. In contrast, the expression levels of CYP genes in NTSR biotypes were higher than in TSR biotypes. Our results support the hypothesis that the reaction of plants to herbicide is carried out through a different regulation of genes, which can be the result of the interaction of resistance type in the target or non-target-site.

Biological Control of some Weeds with Aqueous Extract of Wheat (Triticum aestivum L.)

Allelopathic effects of wheat aqueous extract were studied on seeds germination and seedling growth of four weeds Canary grass (Phalaris minor L.), Mallow (Malva rotundifolia L.), Sweet clover (Mililotus indica Mill), and Wild oats (Avena fatua), that shown seeds germination and seedlings growth of all weed species were inhibited with in all treatment of Wheat (Triticum aestivum L.) residues at concentration 5, 10, 15% on germination and early seedling growth of weeds, results showed the inhibitory effect of aqueous extract of wheat was hat higher 5% of EWC (%). from results that Mallow was more sensitive for treatments, While the less sensitive was Canary.

ОБОСНОВАНИЕ ПАРАМЕТРОВ ЛЕНТОЧНОГО ПИТАТЕЛЯ ДЛЯ ПОДАЧИ ПРИМЕСИ В ЭКСПЕРИМЕНТАЛЬНЫЙ ТРИЕР

The requirements and technical possibilities for ensuring the reproducibility of experimental conditions in the study of screener technologies for cleaning grain mixtures in terms of the stability of their component composition over time, by means of separate feeding of components into the screener, are substantiated. A belt feeder that makes it possible to ensure the reproducibility of experiments with the initial clogging of the grain mixture in the range Zi = 1 - 3% and the productivity of the trier WT = 1.2 - 4.35 t / h is proposed for impurity components with high particle cohesion (oats, wild oats). The distribution of the impurity component along the length of the tape is carried out by means of a box without a bottom. The parameters of the box section were adopted based on the analysis of the contradiction, which consists in the fact that an increase in the horizontal section of the box (Sk) leads to an increase in the relative error in the distribution of the impurity component during its laying, and a decrease in Sk increases the dynamics of the formation of an impurity layer on the tape, reducing the efficiency of using its width. The box parameters turned out to be preferable for the experimental conditions at Zi = 1 - 3% and Wt = 1.2 - 4.35 t/h: width - 60 mm; height - 70 mm. A significant influence of the dynamics of the formation of an impurity layer on the tape was experimentally established: the angle of repose decreases by a factor of 2.5 (30° to 12°); the layer width increases by 1.6 times (from 170 mm to 270 mm). Reducing the dynamic impact on the impurity component by reducing the height of the box leads to a decrease in the efficiency of using the width of the tape - the cross section of the impurity layer becomes trapezoidal. Prevention of impurity losses in the feeder operation is ensured by flexible collars fixed on the edges of the belt. The qualitative distribution of impurities along the length of the box in experiments with partial loading of the trier is carried out by a special leveler - a vertical gate placed in a slider with the possibility of adjusting the position and fixing it with a clamp. To control the distribution of impurities in the box, it is advisable to make at least one of its side walls from a transparent material.

Frequency of herbicide resistance in wild oats (Avena spp.), brome grass (Bromus spp.) and barley grass (Hordeum spp.) as determined by random surveys across south-eastern Australia

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.

Weed Control Using Allelopathic Properties of Rapeseed Residues and Crop Management

Planting date, density and allelopathic properties are important tools of crop management in controlling weeds in crops. Allelopathy refers to any direct or indirect inhibitory or stimulating effect of one plant on another through the production and release of secondary metabolites in the environment. Two experiments performed separately, in order to investigate the effect of allelopathic properties of rapeseed residues and crop management on the control of rapeseed weeds and its yield. The first experiment was conducted during two agricultural years (2018-2019 and 2019-2020) in a factorial form of a randomized complete block design with 3 replications at the Qarakhil agricultural research station (QaemShahr). The treatments were included: planting date in 3 treatment levels (October 17, November 6 and November 26), seed rate in 3 treatment levels (3, 5 and 7 kg per hectare) and weed management in 2 treatment levels presence of weed (no control) and the absence of weed (control). The second experiment was conducted as a factorial in the form of a completely random design in three repetitions in the research laboratory of the Islamic Azad University, QaemShahr branch in 2020. The experimental treatments included weeds [wild oat (Avena fatua), darnel regrass (Lolium temulentum), phalaris (Phalaris minor)] and charlock mustard (Sinapis arvensis)) different concentrations of rapeseed root and stalk extracts (0, 25, 50, 75 and 100%). The results of the first experiment showed that, in general, the rapeseed seed yield was affected by the planting date and density, so that the rapeseed seed yield on the delayed planting date (November 26) decreased compared to the first planting date (October 17) by 49 and 59 percent, respectively in the first and second year of the experiment, and this decrease was more intense in the second year. Also, the results showed that the highest dry weight of weeds was obtained in both years at a density of three kilograms per hectare and in the cultivation of November 26 (except for the highest dry weight of wild oats that was observed in the cultivation of October 17). While the highest weight of seed yield was obtained in both crop years at a density of 7 kg per hectare. The results of the second experiment showed that the extract obtained from the root and stem of the rape plant had a negative and significant effect on the speed, percentage and inhibition of germination in all weeds. However, no significant difference was observed between the concentration of root and stem extracts at the 5% level. A significant negative linear regression relationship was observed between the concentration of the extract (root and stem) with the percentage and speed of germination. Also, a significant positive linear regression relationship was observed between inhibition percentage and extract concentration (root and stem). Therefore, the germination and seedling growth of the seeds of all three weed species had a negative reaction to the concentration of rapeseed extract, but the highest sensitivity was observed in wild oat seeds. Therefore, according to the results, rapeseed extract can be used in the biological control of weeds. In general, the results of two experiments showed that the planting date, density and rapeseed residues can be used effectively in controlling weeds in rapeseed fields.

Case Report of Avena sterilis subsp. sterilis ACCase Herbicide Resistance in Southern Spain

Wild oats are worldwide grassy weeds that cause substantial yield losses, particularly in winter cereal crops. In addition, wild oat herbicide resistant cases have increased; indeed, up to 52 cases have been registered. Despite this, no wild oat herbicide resistant cases have been described in Spain, where farmers and technicians have reported poor herbicide efficacy in sterile oats (Avena sterilis subsp. sterilis L.). A dose-response experiment was conducted comparing the behavior of two populations of A. sterilis from southern Spain to a susceptible population. These populations were collected from two commercial farms where a low efficacy of chemical control had been described. Clodinafop-propargyl and Pinoxaden were tested as active ingredients in the dose-response experiment. Additionally, an alternative herbicide, which consisted of a mixture of Mesosulfuron-methyl and Propoxycarbazone-Na, was also tested at a field dose. The two populations of A. sterilis studied provided a resistant factor higher than 10 for Clodinafop-propargyl and higher than 4 for Pinoxaden. A total control was achieved for plants treated with Mesosulfuron-methyl and Propoxycarbazone-Na.

Identification and extraction of herbicidal compounds from metabolites of Trichoderma polysporum HZ-31

AbstractTrichoderma polysporum (Link) Rifai HZ-31 fermentation broth was separated and purified by extraction, column chromatography, and high-performance liquid chromatography. Four monomer compounds with strong herbicidal activity were obtained: p-hydroxyphenyl-2,3-dihydroxypropyl ether, o-hydroxy-3-carbonyl-1-phenylpropanol, 1,8-propanediol o-xylene, and 2-3-dihydroxypropyl propionate. The biological activity verification test indicated that the four monomer compounds could inhibit the germination of wild oat (Avena fatua L.) and canola (Brassica napus L.) seeds. Of the four, compound 3 (1,8-propanediol o-xylene) had obvious inhibitory effects on the germination of A. fatua and B. napus seeds, with inhibition rates of 83.33% and 86.67%, respectively. Therefore, the identification of this monomer compound lays a foundation for the further development of a novel microbial herbicide by directly utilizing it and developing new derivatives with herbicidal functions as lead compounds.

Seed Meals from Allelopathic Crops as a Potential Bio-Based Herbicide on Herbicide-Susceptible and -Resistant Biotypes of Wild Oat (Avena fatua L.)

Wild oat is a nuisance monocot weed mainly in cereal canopies. The increasing problem of herbicide resistance and the implementation of integrated pest management includes the use of seed meals from species with allelopathic potential. This study aimed to assess the efficacy of seed meals as an environmentally friendly alternative for the control of herbicide-susceptible (S) and -resistant (R) wild oat biotypes. A pot experiment was carried out under greenhouse conditions at the Swojczyce Research and Training Station in Wrocław (Poland) to determine the impact of seed meals from Fagopyrum esculentum, Lupinus luteus, Ornithopus sativus, Phacelia tanacetifolia, Raphanus sativus var. oleiformis and Sinapis alba at two concentrations—1 and 3%. The lowest percentage of seedling emergence was recorded after the application of S. alba seed meal. Seed meals from S. alba reduced the emergence of both S and R biotypes by approximately 82 and 61 percentage points, respectively, and limited the initial growth of both biotypes. F. esculentum, O. sativus and R. sativus seed meals generally did not decrease the number of seedlings. Almost all the seed meals inhibited the growth of the aboveground parts of the susceptible biotype of wild oat to a greater extent than the herbicide treatment.

Are populations less genetically diverse and more differentiated at the species range edges? Analysis of the quantitative trait and molecular variation in wild oat Avena sterilis

Abstract Although understanding factors determining the genetic makeup of natural populations has long been an important goal of evolutionary biology, the effect of population position within the species range (i.e., interior vs. edge) on species genetic variation is still unclear. According to the ‘abundant center’ hypothesis, the range edge populations are expected to exhibit lower genetic variation and higher differentiation than core populations because of their greater spatial isolation and smaller size. We tested these predictions by comparing the extent and structure of neutral (SSR) and quantitative trait genetic variation in 20 populations of an annual grass Avena sterilis hierarchically sampled at the species range core and two opposite edges. Within-population genetic diversity was reduced at the desert range edge compared to the range core as assessed by six SSR markers but not by eight quantitative traits; no reduction was detected at the mountain edge. Genetic differentiation among populations was higher at the desert range edge than the range core in both molecular markers and quantitative traits, but not at the mountain edge. Our results imply that the pattern of population genetic variation at the species range edges largely depends on the steepness of the environmental cline that has a major effect on species fitness. The more gradual the environmental cline from the species interior towards the edge, the higher the probability of detecting reduced genetic diversity and increased differentiation of peripheral populations as predicted by the ‘abundant center’ hypothesis.

Breaking Dormancy and Enhancing Germination of Avena sterilis L. and Amaranthus retroflexus L. Weeds by Gibberellic Acid and Potassium Nitrate to Keep Soil and Crops Healthy

Soils infested with weed seeds are considered hostile lands for crop production. In this context, great wild oat (Avena sp.) in winter seasons and redroot pigweed (Amaranthus sp.) in summer seasons represent problematic weeds in cropland fields. In a series of laboratory trials, we estimated the effects of gibberellic acid (GA3) and potassium nitrate (KNO3) on germination and seedling growth of Avena sterilis L. and Amaranthus retroflexus L. Different concentrations of GA3 and KNO3 were evaluated in randomized complete block design with four replicates. Findings revealed that GA3 at a rate of 200 mg L−1 along each of 150 and 250 mg L−1 treatment showed the maximum increases in germination percentage, radicle length, plumule length and seedling dry weight of A. sterilis L. All applied concentrations of KNO3 were similar (p ≥ 0.05) in enhancing seed germination of A. sterilis L. exceeding the control treatment. Application of GA3 at rates of 250, 500 and 750 mg L−1 surpassed the treatments of 0 and 1000 mg L−1 GA3 for activating A. retroflexus L. seeds germination. Addition of 250 and 500 mg L−1 KNO3 were the potent treatments for stimulating the radicle length of A. retroflexus L. It could be concluded that for breaking dormancy efficiently, addition of gibberellic acid or potassium nitrate with Avena sterilis L. as well as gibberellic acid with Amaranthus retroflexus L. is recommended. Such chemicals could be involved in weed management programs, since distinctive promotion of seed germination for the target weeds was achieved. This undoubtedly will keep the soil and crops healthy.

Annual Ryegrass (Lolium rigidum), Wild Oats (Avena spp.) and Sowthistle (Sonchus oleraceus) Are the Most Commonly Occurring Weeds in New South Wales Cropping Fields

Weeds are a major impediment to crop and pasture production and profitability in Australian farming systems, and knowledge of their occurrence is vital in devising weed management solutions. This study examined the relationships between weed and crop species from observations made during surveys of randomly selected fields in grain and/or pasture production. Between 2013 and 2017, 996 fields across New South Wales (NSW) were surveyed to record the occurrence and density of weed species. Annual ryegrass (Lolium rigidum) (69% of fields), wild oats (Avena spp.) (60%), and sowthistle (Sonchus oleraceus) (34%) were the most common species identified, with a total of 65 weed species recorded to be occurring in NSW cropping fields. Densities of occurring weeds were low, at one plant per square metre or less. Multiple species of wild oats were recorded, with their occurrence varying between survey regions; for example, Avena sterilis subsp. ludoviciana was more prevalent in the north and Avena fatua in the south. Differences in weed species occurrence were noted between this survey and those previously conducted in NSW, with marked increases in annual ryegrass and sowthistle, and this is attributed to the change in crop production practices between survey periods. The study of variable distribution patterns of weed species across cropping systems allows for informed decision-making regarding weed management research and development planning.

Study of phylogenetic relationships between wild and cultivated oat species (Avena L.)

We performed next generation sequencing (NGS) of wild and cultivated oat species (Avena L.) ITS1 sequence and the beginning of the gene 5.8S rRNA on the Illumina platform. For the first time, the NGS method was used to carry out a phylogenetic analysis of the domestication pathways of three cultivated oat species: tetraploid A. abyssinica (AB), hexaploid A. sativa and A. byzantina (ACD). We found that the A. abyssinica genome with the most massive number of reads is the A-genome, while in A. sativa, it is the D-genome. Also, we studied the putative ways of obtaining polyploid genomes from diploid species. According to NGS sequencing data, it was revealed that the most widespread A. sativa ribotype is inherited from A. ludoviciana, A. byzantina has two unique families of ribotypes, and A. abyssinica probably comes from the wild A. vaviloviana (A-genome was obtained by this species from the diploid A. atlantica (As-genome)). Putative ancestor of A. abyssinica, tetraploid A. agadiriana, forms unique families of ribotypes, to which the most widespread ribotype belongs. It most likely was not a direct ancestor of A. abyssinica. C-genome species A. clauda turned out to be related to the D-genome of A. sativa; it could also be involved in the formation of the hexaploid A. ludoviciana.

Integrated Management of Wild Oat (Avena fatua) and Feather Fingergrass (Chloris virgata) Using Simulated Grazing and Herbicides

Wild oat (Avena fatua L.) and feather fingergrass (Chloris virgata Sw.) are among the most problematic weed species in Australian winter and summer cropping systems, respectively. Pot trials were conducted in respective seasons to evaluate the integrated effect of simulated grazing and foliar-applied herbicides on the control of these weed species. Different herbicides were applied 1, 5, and 12 d after grazing on A. fatua plants and 1, 3, 7, 10, and 14 d after grazing on C. virgata. In general, the efficacy of herbicides was better on A. fatua when applied 5 or 12 d after grazing (i.e., 7–20 cm tall plants) and 7 to 14 d (i.e., 10–22 cm tall plants) after grazing on C. virgata. Clethodim 90 g a.i.·ha−1, and haloxyfop 52 and 78 g a.i.·ha−1 resulted in 100% mortality of A. fatua seedlings, irrespective of their application timings. Delayed application (5 or 12 d after grazing) of clethodim 60 g a.i.·ha−1 and pinoxaden 20 and 30 g a.i.·ha−1 resulted in 100% mortality of A. fatua. Glyphosate at the field rate (370 g a.e. ha−1) was the least effective herbicide to control A. fatua plants after grazing. Glufosinate application after grazing resulted in the greatest mortality (69 to 81%) of C. virgata. Depending on application timing, only glufosinate was able to provide complete control of C. virgata seed production. Butroxydim, clethodim, and haloxyfop were found to be promising herbicides to manage C. virgata after grazing but their applications had to be delayed by 7 to 14 d after grazing. This study identified several successful herbicide treatments that could be applied after grazing or mowing for integrated control of A. fatua and C. virgata. However, to achieve complete control of C. virgata, the application of these herbicides needs to be followed by other tools, including additional herbicide applications.

Retraction: The impact of seed burial depths and post-emergence herbicides on seedling emergence and biomass production of wild oat (Avena fatua L.): Implications for management.

Retraction: The impact of seed burial depths and post-emergence herbicides on seedling emergence and biomass production of wild oat (Avena fatua L.): Implications for management.

Freezing stress affects the efficacy of clodinafop-propargyl and 2,4-D plus MCPA on wild oat (Avena ludoviciana Durieu) and turnipweed [Rapistrum rugosum (L.) All.] in wheat (Triticum aestivum L.).

The occurrence of freezing stress around herbicides application is one of the most important factors influencing their performance. This experiment was performed to evaluate the efficacy of clodinafop-propargyl and 2,4-D plus MCPA (2,4-Dichlorophenoxyacetic acid plus 2-methyl-4-chlorophenoxyacetic acid), the most important herbicides used in wheat fields in Iran, under the influence of a freezing treatment (-4°C). Wheat and its two common weeds, winter wild oat (Avena ludoviciana Durieu) and turnipweed [Rapistrum rugosum (L.) All.], were exposed to the freezing treatment for three nights from 7:00 P.M. to 5:00 A.M. before and after herbicide application, and their response was compared with plants that did not grow under freezing stress. Under no freezing (NF) and freezing after spray (FAS) conditions, winter wild oat was completely controlled with the recommended dose of clodinafop-propargyl (64 g ai ha-1; hereafter g ha-1). However, the survival percentage of winter wild oat in the freezing before spray (FBS) of clodinafop-propargyl 64 g ha-1 was 7%, and it was completely controlled with twice the recommended dose (128 g ha-1). Under NF conditions and FAS treatment, turnipweed was completely controlled with twice the recommended dose of 2,4-D plus MCPA (2025 g ae ha-1; hereafter g ha-1), while there was no complete control under recommended rate. However, in the FBS treatment, the survival of turnipweed was 7% under double dose. The LD50 (dose required to control 50% of individuals in the population) and GR50 (dose causing 50% growth reduction of plants) rankings were NF<FBS<FAS for clodinafop-propargyl and NF<FAS<FBS for 2,4-D plus MCPA. Selectivity index for clodinafop-propargyl in NF conditions, FBS, and FAS treatments was 2.4, 0.91, and 0.78, respectively, and, for 2,4-D plus MCPA, it was 2.6, 0.12, and 0.88, respectively. According to the results of LD50, it can be stated that the freezing stress after the spraying of clodinafop-propargyl and before the spraying of 2,4-D plus MCPA would further reduce the efficacy of these herbicides.