Avena Sterilis Research Articles

Different Non-Target Site Mechanisms Endow Different Glyphosate Susceptibility in Avena Species from Spain

In recent decades, cereal agriculture across main producing areas in Spain has progressively adopted direct sowing, associated with an increased use of herbicides in pre-sowing. Weedy species from genus Avena have been observed after the application of glyphosate in wheat. Here, Avena fatua (two accessions), Avena byzantina and Avena sterilis subsp. sterilis, one accession each, were taxonomically characterized by a biometric study. Dose-response trials confirmed that one A. fatua accession evolved to resistance, because it was four times more resistant (R) than the others, ascribed as susceptible (S). In addition, based on LD50, A. byzantina and A. sterilis had low susceptibility to glyphosate, with 604 and 458 g ae ha−1. Shikimic acid accumulation was able to discriminate between high susceptible (A. fatua (S)), low susceptible (A. byzantina and A. sterilis), and low resistant (A. fatua (R)) populations. On the other hand, the study revealed that A. fatua (R), A. byzantina and A. sterilis had low foliar uptake and decreased movement of glyphosate. In addition, the metabolism study showed less metabolite accumulation in A. byzantina and A. fatua (S). However, at 96 h after glyphosate application, A. fatua (R) and A. sterilis were able to convert more than 30% of glyphosate to aminomethylphosphonic acid (AMPA) and sarcosine. Enzyme basal activity and I50 values predicted high affinity between the herbicide and the target enzyme for all accessions, thus indicating that a target-site (TS) mechanism is probably not involved in the differences in glyphosate susceptibility. In closing, non-target site (NTS) mechanisms could participate both in A. fatua R to glyphosate, and low susceptibility in A. byzantina and A. sterilis from Spain.

Avena sterilis L.’in Mikrosatellit İşaretleyicileri ile Genetik Çeşitlilik Analizi

Avena sterilis is an important grassy weed that causes a problem in wheat cultivation areas, and intensive herbicides are used to control it. Genetic diversity study is important to have information how on the effect weed species of the environmental factors and herbicides. The high level of genetic diversity within the species is a guarantee for adaptation to changing environmental conditions. This study was conducted based on complaints of the loss of effectiveness during the chemical control. Analyses were carried out on 27 selected populations collected from wheat cultivation areas in Turkey's Middle Black Sea region. Seventy-seven alleles from microsatellite loci were detected, and the average number of alleles per locus was determined as five using 17 microsatellite primers. The average gene diversity (GD) and polymorphism information content (PIC) values were 0.894 and 0.732, respectively. According to the UPGMA dendrogram generated using Average Linkage, the populations were clustered into two main groups. A high degree of diversity was found among the studied steril oat genotypes, and it is seen that there is no geographical isolation. It is understood that this situation primarily provides adaptation to those geographical areas by transporting weed seeds from other provinces in various ways. According to these findings, issues such as crop rotation, cultural control methods, encouraging the use of certified seeds, and the use of herbicides with different mechanisms of action can be listed among the measures that can be taken to control the high genetic diversity, which is an indicator of herbicide resistance.

Freezing Stress Affects Herbicide Efficacy On Sterile Oat and Turnipweed in Wheat

Freezing Stress Affects Herbicide Efficacy On Sterile Oat and Turnipweed in Wheat

Elevated Temperature Affects Avena sterilis ssp. ludoviciana Reproductive Biology

The weed Avena sterilis ssp. ludoviciana has a high economic impact in the winter cereal crop production systems of Australia’s northern grains region (NGR). In the NGR, the frequency of high-temperature periods at the end of winter is increasing. This shift in climate may modify this weed’s maturity time and reproductive biology, and thereby impact on crop production. This study examined the reproductive biology of four A. ludoviciana biotypes in relation to elevated temperature when applied at different times during their seed development. Plants of all four A. ludoviciana biotypes were grown in an ambient temperature glasshouse (23/14 °C day/night). At panicle initiation, a portion of the plants were transferred to an elevated temperature glasshouse (29/23 °C day/night) and remained there until maturity. This process of plant movement was repeated on three further occasions with separate batches of plants, each 10 days apart. The remaining plants were kept under ambient conditions for their whole lifespan. Plants exposed to elevated temperature from panicle initiation to maturity, matured 18 days earlier than plants kept under ambient conditions, had 30% fewer filled seeds, 37% lower seed mass, and 40% less seed dormancy. Depending on the time and duration of plants exposed to elevated temperature, predicted seed longevity was ranged from 1 to 4 years in the soil seedbank. All reproductive traits were less affected when plants were exposed to elevated temperature at a later stage of development. If the frequency of high-temperature periods continues to increase, then it may lead to the development of less dormant populations of this weed that would be ready to germinate and re-infest the next winter crops under no-tillage conservation agriculture (that does not bury seeds deep in the soil profile). However, the seasonal climatic variability of the NGR in addition to the weed’s natural genetic variability may contribute to a seedbank of both dormant and less dormant seeds—making this species an even more difficult-to-control weed.

Interference of sterile oat (Avena ludoviciana) and Mexican pricklepoppy (Argemone mexicana) in chickpea

Context Knowledge gaps exist for the interference of Avena ludoviciana and Argemone mexicana in chickpea grown in eastern Australia. Aims This research aimed to examine the effect of different interference levels of A. ludoviciana and A. mexicana for their potential to cause yield loss in chickpea. Methods Experiments were conducted in a randomised complete block design with five weed infestation levels of both weeds (none, low, medium, high, and very high) in three replications. Key results Infestations of A. ludoviciana and A. mexicana at 15 and 17 plants m−2 caused an 83 and 48% reduction in chickpea yield, respectively, compared with weed-free situations. Based on the regression model, a 50% yield reduction of chickpea occurred at 10 and 17 plants m−2 of A. ludoviciana and A. mexicana, respectively. Based on the modified hyperbolic model, maximum seed production of A. ludoviciana and A. mexicana in chickpea at an infestation level of 1 plant m−2 was estimated at 366 and 7800 seeds m−2, respectively. At crop harvest, seed retention of A. ludoviciana and A. mexicana was greater than 50 and 90%, respectively. Conclusions A. ludoviciana and A. mexicana infestation in chickpea caused a substantial reduction in crop yield. High seed retention in A. mexicana and A. ludoviciana in chickpea suggests the possibility to manage these two weeds through harvest weed seed control. Implications The information generated from this study could help in strengthening integrated weed management in chickpea.

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.

Chromosomal Location of Pm12-A Novel Powdery Mildew Resistance Gene from Avena sterilis.

Identification of new, effective disease resistance genes is a very important aspect of plant breeding. Also important is the precise location of individual loci and tagging them with DNA markers for marker assisted selection. The aim of the present study was identification of the molecular markers linked with Pm12, a new effective resistance gene to powdery mildew, and their location in the oat genome. The analysis was performed on 167 F2 individuals from a hybrid of Fuchs × CN67383, with the status of the locus in each individual verified by progeny test in F3. Segregation ratios confirmed the monogenic nature of resistance. Making use of the sequence data of DNA markers and the oat OT3098 v2 genome reference assembly, Pm12 is located on chromosome 7C. A comparison was also made with the reference consensus map, to which there are more reports of mapped genes to date. The mapping results suggest that Pm12 is located in the interval 103.8-111.7 cM on this map. No powdery mildew resistance locus has been identified in this region so far, suggesting that Avena sterilis CN67383 carries a novel locus offering effective resistance in oat breeding. The information included in the oat genome annotation allowed for the identification of candidate genes in the close region of the marker cluster for Pm12. This information may provide an interesting source of further analysis of the pathways of various genes in response to the stress of powdery mildew infection.

Herbicide options for sterile oats (Avena ludoviciana) control in winter-planted sorghum

AbstractAustralian grain growers are showing interest in winter-planted sorghum to avoid heat and water stress during the grain-filling stage. Winter-planted sorghum may face competition from winter weeds, including sterile oats, and no herbicides are registered for controlling winter weeds in winter-planted sorghum. The objectives of this study were to (1) identify alternate herbicide options for sterile oats control in winter-sown imidazolinone (IMI)-resistant sorghum and (2) assess the crop injury levels due to herbicides. Sterile oats control with pendimethalin at 0.59 kg ai ha−1, trifluralin at 0.38 kg ai ha−1, and prosulfocarb + S-metolachlor at 2.3 kg ai ha−1 was poor (<30%). Atrazine at 2.7 kg ai ha−1, imazamox + imazapyr at 0.048 kg ai ha−1, and atrazine at 2.7 kg ai ha−1 followed by imazamox + imazapyr at 0.048 kg ai ha−1 reduced the sterile oats biomass by 93%, 96%, and 100% and increased yields by 116%, 136%, and 140%, respectively, compared with nontreated control. Pendimethalin at 0.59 kg ai ha−1 and trifluralin at 0.38 kg ai ha−1 caused phytotoxicity to the crop and gave similar yields to nontreated control. Triallate at 0.8 kg ai ha−1, pyroxasulfone at 0.1 kg ai ha−1, and terbuthylazine at 1.0 kg ai ha−1 provided moderate weed control (44% to 65%) and increased yields by 68%, 108%, and 80%, respectively, compared with nontreated control. This research identified herbicide treatments for the effective control of sterile oats in winter-sown IMI-resistant sorghum that could be used in rotations to reduce the reliance on single herbicide treatments.

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.

Feeding ecology of the vulnerable aoudad (Ammotragus lervia) in north‐western Sahara

AbstractThe feeding ecology of the aoudad (Ammotragus lervia) was investigated for the first time in north‐western Sahara, Djebel Antar (Bechar province, Algeria), from autumn 2015 to summer 2016. Microhistological analyses of faeces revealed an annual diet composed of 23 identified taxa belonging to 16 plant families. The highest species diversity was recorded in spring and summer (23 species), despite a marked consumption of two species: Vachellia tortilis (17.7%) and Avena sterilis (14.0%); diet diversity was lower in autumn and winter (16 species), including mainly Teucrium polium (14.7%, 21.0%) and Gymnocarpos decander (19.7%, 10.0%). The main plant parts consumed during these seasons were stems (77.7%, 65.3%), while leaves and inflorescences were mostly consumed during spring and summer (54.7%, 52.3%). Forbs dominated the aoudad's diet, with 46.3% average relative abundance, including mainly T. polium, Limoniastrum feei, and Chrysanthemum macrocarpum. Woody plants including mainly V. tortilis and G. decander accounted for 33.3% (50.0% in autumn), and grasses including A. sterilis and H. murinum for 20.4% (32.0% in summer). Based on this diet, A. lervia can be classified as a “generalist mixed‐feeder.”

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.

First Report of Take-All Root Rot Caused by Gaeumannomyces graminis on Hybrid Bermudagrass in China.

Take-all root rot caused by Gaeumannomyces graminis (Sacc.) Arx & Olivier is a destructive disease of hybrid bermudagrass (Cynodon dactylon × C. transvaalensis Burtt-Davy) (Elliott 1991; Stephens et al. 2020). In April 2018, multiple circular to irregular patches (10 to 200 cm in diameter) were evident on 'Tifway419' bermudagrass fairway of Wohu golf course (Huangshan city, Anhui province). Patches were found at five of the 18 fairways and showed a decrease in stand density. Individual plants in patches exhibited off-color to white foliage, dark and necrotic lesions were frequently observed on roots and associated stolons. Ectotrophic runner hyphae and lobed hyphopodia are ubiquitous on the surface of necrotic roots. Two diseased samples were collected from each patch by a soil corer (10 cm in diameter), and a total of ten patches were sampled across the five symptomatic fairways. Symptomatic roots or stolons were cut into 2 to 3 cm length and surface disinfested for 3 min in 0.6% sodium hypochlorite solution. The sterilized tissues were rinsed, air dried on sterile filter paper for 5 min and placed on potato dextrose agar (PDA) amended with 50 mg L-1 each of ampicillin, streptomycin sulfate and tetracycline. Plates were incubated in the dark at 20°C for 5 days, and similar colonies were consistently recovered from 85% of the symptomatic tissues. After hyphae purification, a total of 20 fungal isolates were obtained with morphology similar to G. graminis (Hernández-Restrepo et al. 2016). DNA was extracted and amplified with primers ITS5/ITS4 (White et al. 1990). PCR products were sequenced (deposited as MZ889119 and MZ889120 in GenBank), and showed 99.43 to 99.81% homology when compared with a known G. graminis isolate (accession no. KX306505). To complete Koch's postulates, healthy Tifway419 hybrid bermudagrass was grown in 5 × 20 cm Cone-Tainers containing a sand and Pindstrup substrate (Pindstrup Mosebrug, Pindstrup, Denmark) mixture (1:1, V/V) nine weeks after transplanting from the experimental field of the Institute of Botany, Jiangsu Province and Chinese Academy of Sciences. Five sterile oat seeds infested with G. graminis were inserted 5 cm below the soil surface in the root zone of Tifway419. Cone-Tainers inoculated with five noninfested sterile oat seeds served as controls, and each treatment was replicate 3 times. All Cone-Tainers were transferred into a growth chamber with a 12-h day/night cycle at 25/20°C and 95% relative humidity. They were covered with plastic bags for the first week, and watered once daily to encourage disease development. Hybrid bermudagrass inoculated with G. graminis decreased in plant density and turfgrass quality, black and necrotic roots covered with lobed hyphopodia were observed eight weeks after inoculation, no symptoms were present on the roots and above-ground of noninfested control plants. G. graminis was consistently reisolated from symptomatic roots and stolons, and confirmed by sequencing the ITS region as mentioned above. To our knowledge, this is the first report of G. graminis causing take-all root rot of hybrid bermudagrass in China, which may influence the management of this important root disease.

Identification of sentinel plant species for evaluating phytotoxicity of veterinary antibiotics in Mediterranean Europe

BackgroundAntibiotics used to treat livestock species enter agricultural fields when they are excreted by grazing animals or are present in manure that is added to fields as fertiliser. In the European Union, the potential effects of such antibiotics on terrestrial plants must be evaluated following the standardised OECD 208 method, which specifies the crop and wild species that should serve as “sentinels” for assessing antibiotic exposure. The present study aimed to compare this approved list of sentinel species against crop and wild plant species actually present in agricultural and pasture lands in Mediterranean Europe in order to identify the most appropriate sentinel plants for the region. The study focused on Spain as a region representative of Mediterranean Europe. Georeferenced layers for wild plant species and cultivated areas (crops), livestock density and land cover were combined, and then selection criteria were applied, leading to the identification of sentinel crop and wild species for crop land and pasture scenarios.ResultsIn the crop land scenario, the sentinel crop species were barley (Hordeum vulgare L.), wheat (Triticum spp.), corn (Zea mays L), sunflower (Helianthus annuus L.), dried pea (Pisum sativum L.), alfalfa (Medicago sativa L.), vetch (Vicia sativa L.), oilseed rape (Brassica napus L.) and sugar beet (Saccharum officinarum L.), all of them listed in the OECD 208 method with the exception of alfalfa; the sentinel wild species were Papaver rhoeas L., Galium aparine L. and Chenopodium album L. In the pasture scenario, sentinel wild species were Bromus tectorum L., Agrostis capillaris L., Trifolium pratense L., Lotus corniculatus L. and Galium aparine L. The following common weed species in field boundaries or in pasture lands also emerged as potential sentinel species for risk assessment, even though they are not listed in the OECD 208 method: Sonchus oleraceus L., Avena sterilis L., Dactylis glomerata L., Hordeum murinum L. and Lolium rigidum Gaudin.ConclusionsThe sentinel species identified in this study may be useful in risk assessment procedures covering the Mediterranean Europe. The method developed for this study could be applied to identify sentinel species for other representative agroclimatic regions in Europe (such as Atlantic and Continental).

ASSESSMENT OF MORPHOLOGICAL CHANGES AMONG WHEAT AND ASSOCIATEDWEEDS UNDER HIGH CARBON DI-OXIDE ENVIRONMENT

Climate change and rising CO2 levels as well as weed control is disrupted in both natural and traditional biological ways. The effectiveness of bio-control agents will be compromised as a result of this CO2 -induced morphological, phenological, and physiological alterations. The present study was conducted for the assessment of the effects of elevated CO2 on morphology of wheat crop as well as two commonly associated weeds Phalaris minor and Avena ludoviciana. The plant height of wheat was found to be increased in wheat under elevated CO2 conditions in comparison to ambient environment at 30 DAS and 60 DAS. However, both of the weed species had opposite effect of elevated environment in terms of plant height trait. While taking observation on mean numbers of tillers in wheat crop, it was found to be reduced under elevated environment in comparison to ambient environment. However, both weeds had increment in mean numbers of tillers under elevated CO2 conditions at both 30 DAS and 60 DAS. Results of the present study confirm the effects of elevated CO2 on morphology of crop as well as weed species and indicate the need of research in this field because of alarming situations in the future due to expected increase in CO2 level in the environment.

Herbicide resistance in Avena sterilis subsp ludoviciana populations from the wheat fields of Turkey

Avena sterilis L. subsp ludoviciana (Durieu) Gillet and Magne (AVELU) is among the most common and economically important grass weed species, especially in wheat fields of Turkey; therefore, the herbicides with the same mode of action (ACCase and ALS/AHAS inhibitors) are used to control have been successively applied without incessant by farmers. A study was conducted to find out the extent of wild oat problems throughout Turkey including herbicide resistance. This paper includes results of determining the herbicide resistance status of AVELU populations to ACCase and ALS inhibitors that are fenoxaprop (Fen), pinoxaden (Pin), tralkoxydim (Tra), mesosulfuron+iodosulfuron (MeI), and proxycarbazone+mesosulfuron (PrM). AVELU seeds were collected from 213 wheat fields throughout Turkey in 2014?2015 and the response to selected five herbicides was tested under screen-house. Dose-response tests showed that only 42 populations were controlled by all five herbicides. The number of populations that were not controlled varied by herbicides, which were 150, 48, 25, 100, and 100 populations for Fen, Pin, Tra, MeI, and PrM, respectively. Nine populations were resistant to all herbicides and 72 to four of herbicides out of 155 multiple resistance populations. The high number of multiple resistances and higher resistance indexes show the seriousness of the problem. Although resistance to MeI and Tra herbicides are still developing, Fen resistance seems completed and reached moderate and high resistance levels. Integrated weed management is an inevitable challenge to sustain wheat production, a staple crop for Turkey.

Using air thermal time to predict the time course of seedling emergence of &lt;i&gt;Avena sterilis&lt;/i&gt; subsp. &lt;i&gt;sterilis&lt;/i&gt; (sterile oat) under Mediterranean climate

&lt;abstract&gt; &lt;p&gt;&lt;italic&gt;Avena sterilis&lt;/italic&gt; subsp. &lt;italic&gt;sterilis&lt;/italic&gt; (sterile oat) is a troublesome grass weed of winter cereals both in its native range encompassing the Mediterranean up to South Asia, and in regions of America, Northern Europe and Australia where it is introduced. A better understanding of seedling emergence patterns of this weed in cereal fields can help control at early growth stages benefiting efficacy under a changing climate. With this aim, the objective of this research was to develop and validate a field emergence model for this weed based on cumulative air thermal time (CTT, ℃ day). Experiments for model setting and evaluation were carried out in experimental and commercial fields in southern Spain. Two alternative models, Gompertz and Weibull, were compared for their ability to represent emergence time course. The Weibull model provided the best fit to the data. Evaluation through independent experiments showed good model performance in predicting seedling emergence. According to the developed model, the onset of emergence takes place at 130 CTT, and 50% and 90% emergence is achieved at 448 and 632 CTT, respectively. Results indicate that this model could be useful for growers as a tool for decision-making in &lt;italic&gt;A. sterilis&lt;/italic&gt; control.&lt;/p&gt; &lt;/abstract&gt;

Long-term tillage and weed management effects on weed shifts, phytosociology and crops productivity

The understanding of the diverse weed flora composition and weed shift in conservation agriculture production system is important to identify weed management component to increase agro-ecosystem sustainability. Hence, in this study, different tillage and weed management practices were assessed to evaluate their impact on diverse weed flora composition and shift in maize-wheat cropping system in North Western Himalaya from 2018-20 in an ongoing longterm experiment being conducted since 2013. Fifteen treatment combinations comprising of five tillage treatments, viz. conventional tillage (CT) in maize-CT in wheat; CT-zero tillage (ZT); ZT-ZT; ZT-zero tillage in combination with residue retention (ZTR) and ZTR-ZTR and three weed management treatments, viz. recommended herbicide (H) in maize-recommended herbicide (H) in wheat; integrated weed management (IWM)-IWM and hand weeding (HW)-HW were evaluated in a strip plot design. In CT, annual weed species were dominant, whereas, perennial weeds dominated in zero tillage (ZT). A shift in weed species with greater dominance of monocots and a marginal decrease in dicots was observed. Parthenium hysterophorus, an obnoxious weed, was observed in the experimental field in maize only during 2018. The monocot weed (Echinochloa colona) had higher relative density (RD), relative abundance (RA), relative frequency (RF) and important value index (IVI) compared to the dicot weeds in maize crop. In Rabi (winter) season, Avena ludoviciana (monocot grass) had higher RD, RF and IVI values, while, Daucus carota (perennial weed) had higher RA when compared to the other annual and biennial weeds. The grain yield of main and intercrop and system productivity were higher in conservation agriculture-based production systems in combination with recommended herbicide (ZTR+H-ZTR+H) in maize-wheat based cropping systems.

Germination behaviour of

Context Avena sterilis subsp. ludoviciana (wild oats) is one of the major winter weeds of the Northern Grains Region of Australia. The abundance of this weed increased dramatically after the adoption of no-tillage conservation agriculture (NTCA). However, information is lacking on the germination characteristics of the two types of seed (i.e. primary and secondary) that it produces. Aims We aimed to determine the light and temperature requirements for germination and the time to germination of primary and secondary seeds of A. ludoviciana, in order to find ways to manage this weed effectively under NTCA systems. Methods Primary and secondary seeds and caryopses from two southern and two northern biotypes were exposed to a range of temperature and light regimes in the glasshouse, and germination was assessed. Key results All biotypes had ∼25% higher germination from primary than secondary seeds. Removing the hull increased caryopsis germination by ∼70%. The use of a light/dark photoperiod stimulated germination of both types of seed and caryopses compared with continuous darkness. Based on data for caryopses, 7°C and 9°C were found to be optimal germination temperatures for southern and northern biotypes, respectively. At optimum germination temperature, primary caryopses germinated 7–20 days earlier than secondary caryopses. In addition, a light/dark environment resulted in germination 2–6 days earlier than continuous darkness. Conclusions In the Northern Grains Region, seeds retained on or close to the soil surface (i.e. in NTCA systems) can undergo maximum germination during May–June (late autumn–winter), when long-term average temperatures match optimum germination temperatures. This coincides with winter crop plantings. Implications The seasonal timing of germination and the difference in germination timing between primary and secondary seeds, which help to stagger emergence of this weed, are major issues that need to be addressed in NTCA systems.