Variability in seedling emergence for European and North American populations of Abutilon theophrasti

Abutilon theophrasti is a weed that is spreading worldwide and that has had to adapt to different combinations of environmental conditions. Wide interpopulation variability has been reported regarding dormancy and germination. This variability, controlled by the interaction of genetic diversity and maternal effect, could hinder the adoption of Integrated Weed Management (IWM) tools. A collaborative project was conducted to compare emergence dynamics of 12 European and North American populations under diverse environmental conditions. The main aim was to assess interpopulation variability and explain this according to environmental conditions in the seed collection sites. Seeds were sown at six experimental sites, and seedling emergence was monitored. The AlertInf model was tested to evaluate its ability to predict emergence dynamics of the different populations. A wide interpopulation variability was observed for emergence percentage and dynamics with consistent trends across sites and related to different seed dormancy levels. Populations from Catalonia, Iowa and Minnesota reached higher emergence percentage with earlier and concentrated emergence flushes probably due to low dormancy level, while populations from Croatia, Serbia and Hungary, given their low average emergence percentage, presented high dormancy levels. Good predictive accuracy of AlertInf model was obtained at the different sites, confirming the possibility of adopting it across a wide range of environmental conditions. Achieving a better knowledge of interpopulation variability can allow specific control strategies to be designed, facilitating the replacement of solely herbicide‐based management with true IWM.     

Observed changes in soyabean growth and seed yield from Abutilon theophrasti competition as a function of carbon dioxide concentration

Soyabean (Glycine max) was grown at ambient and projected levels of atmospheric carbon dioxide (+250 μmol mol^?1 above ambient) over two field seasons with and without the presence of a weed, Abutilon theophrasti, to quantify the potential effect of rising atmospheric carbon dioxide concentration on weed–crop interactions and potential yield loss in soyabean. Under weed‐free conditions, elevated CO₂ resulted in stimulations in soyabean seed yield and associated components, including pod number. At an approximate density of 6 plants m^?2, A. theophrasti competition resulted in a significant reduction (?40%) in soyabean seed yield. Although differences in seed yield reduction by A. theophrasti were observed as a function of year, the relative decrease in seed yield with A. theophrasti biomass did not differ in response to CO₂. Although careful weed management will be necessary if CO₂‐induced increases in seed yield for soyabean are to be achieved, these data suggest that soyabean seed yield may be more resilient in competition with A. theophrasti as a function of rising atmospheric levels of carbon dioxide.     

ISSR variation in a worldwide collection of velvetleaf (Abutilon theophrasti) and the genetic background of weedy strains mingled in grains imported into Japan

Velvetleaf seeds have been found in imported grains in Japan. The plants from these seeds show a weedy growth habit, such as that seen in the noxious velvetleaf which has recently emerged in Japan and noted in our previous study. To elucidate the genetic background of the velvetleaf strains found in imported grains we evaluated the genetic variation of six strains and an additional 39 worldwide velvetleaf accessions using the intersimple sequence repeat (ISSR) polymorphism. Cluster analysis based on the ISSR polymorphism emitted two major clusters which corresponded well with classification by growth habit, that is, crop type and weed type. Five of the six strains from the imported grains formed a small cluster. All six strains united into one major cluster containing the weed type accessions, while all of the old Japanese accessions formed another major cluster containing the crop type accessions. The genetic difference between imported weedy velvetleaf and old Japanese accessions suggests that imported velvetleaves are the source of the recent outbreak of the noxious velvetleaf in Japan.     

Hormetic UV-C seed treatments for the control of tomato diseases

Hormesis is a dose response phenomenon in which low, non-damaging doses of a stressor bring about a positive response in the organism undergoing treatment. Evidence is provided here that hormetic UV-C treatments of tomato seed can control disease caused by Botrytis cinerea, Fusarium oxysporum f. sp. lycopersici (FOL) and f. sp. radicis-lycopersici (FORL) on tomato (Solanum lycopersicum). Treating seeds with a 4 kJ m⁻² dose of UV-C significantly reduced both the disease incidence and progression of B. cinerea, with approximately 10% reductions in both on cv. Shirley. Disease severity assays for FOL and FORL on cv. Moneymaker showed dose-dependent responses: UV-C treatments of 4 and 6 kJ m⁻² significantly reduced the disease severity scores of FOL, whilst only the 6 kJ m⁻² showed significant reductions for FORL. To determine the effects of treatment on germination and seedling growth, UV-C doses of 4, 8 and 12 kJ m⁻² were performed on cv. Shirley. No negative impacts on germination or seedling growth were observed for any of the treatments. However, the 8 kJ m⁻² treatment showed significant biostimulation, with increases in seedling, root and hypocotyl dry weight of 11.4%, 23.1% and 12.0%, respectively, when compared to the control. Furthermore, significant increases in the root-mass fraction (10.6%) and root:shoot ratio (13.1%) along with a decrease in shoot-mass fraction (2.0%) indicates that the 8 kJ m⁻² treatment stimulated root growth to the greatest extent. There was no effect on hypocotyl and primary root length or the number of lateral roots, indicating no adverse effects to basic root architecture or seedling growth.     

Differences in flowering phenology and seed production of four morning glory (Ipomoea) species in Japan

The spread of morning glory (Ipomoea spp.) in soybean fields in Japan has severely decreased soybean yield. Yet, current control measures do not control the proliferation of Ipomoea spp. As little is known about the flowering period and seed production among the different invading Ipomoea spp., it is challenging to create targeted control measures based on ecological characteristics. This study aimed to reveal the characteristics of the flowering phenology and seed production of four morning glory species, namely, Ipomoea coccinea L. (red morning glory), Ipomoea lacunosa L. (pitted morning glory), Ipomoea hederacea L. Jacq. var. integriuscula A. Gray (entireleaf morning glory), and Ipomoea triloba L. (three-lobe morning glory). Between 2017 and 2019, the four selected study species were grown under similar conditions of soil quality, irrigation, and environmental influences and their flowering phenology and seed data were recorded. The flowering period ranged from 36 to 40 days, and the initial flowering of I. triloba was approximately 2 weeks later than the others. I. coccinea had the highest flowering number and seed production, followed by I. lacunosa, I. triloba, and I. hederacea var. integriuscula. The fruit setting rate of I. triloba decreased later in the reproductive stage but tended to increase as the daily mean temperature increased on each flowering day. Thus, we report that the flowering phenology and seed production differed greatly among the Ipomoea spp. These findings can provide crucial insights into designing targeted species-specific control measures against the spread of Ipomoea spp. in Japan.     

Factors affecting the seed germination and seedling emergence of redflower ragleaf (Crassocephalum crepidioides)

Redflower ragleaf (Crassocephalum crepidioides) is a weed, as well as a minor vegetable, in tropical and subtropical regions of the world. The influence of environmental factors and seed conditions on the germination and emergence of redflower ragleaf have been evaluated in order to help understand its distribution and to develop effective management strategies. The seeds germinated at a constant temperature in the range of 10–30°C and reached a maximum at 15–20°C. The highest germination rate was recorded at an alternating temperature of 20/15°C (day/night). The seeds germinated over a wide pH range (2–12), with the highest germination rate at between 4 and 10. Germination under saturated and flooded conditions was also high. The germination of seeds from opened (mature) capitula was significantly higher than from partially opened or unopened capitula. The germination of seeds without a pappus was significantly higher than for seeds with a pappus. The germination rate of 1 year old seeds decreased drastically when compared to that of freshly harvested seeds. The seedling emergence rate was ～63% for those seeds placed on the soil surface, but no seedling emerged from a depth of ≥1 cm. These results indicate that redflower ragleaf seeds can germinate in various environmental conditions, but that the percentage that germinates will be different in different environments. Regeneration could be effectively prevented by at least a 1 cm soil covering or by destroying the plant before the capitula open. In contrast, freshly harvested seeds from opened capitula should be sown on the soil surface when redflower ragleaf is to be cultivated as a vegetable.     

种子处理对西瓜苗期3种病害的防治效果

为了筛选防治西瓜苗期立枯病、猝倒病和枯萎病的有效种子处理剂,在人工控制的条件下,选择了6.25%精甲·咯菌腈悬浮种衣剂、2.5%咯菌腈悬浮种衣剂、3.5%精甲·咯菌腈悬浮种衣剂、72%霜霉威盐酸盐水剂和50%多菌灵可湿性粉剂5种杀菌剂对西瓜种子进行处理。分析了处理种子的活力和幼苗的生长特性;以及在人工接种3种病原菌的胁迫下不同处理种子在基质中的出苗率和发病情况。结果表明:5种杀菌剂对种子的活力和幼苗的生长特性没有明显的影响,但3.5%精甲·咯菌腈悬浮种衣剂包衣降低了每株幼苗的鲜重,50%多菌灵可湿性粉剂浸种则提高了幼苗的整齐度。接种西瓜立枯病菌和猝倒病菌的种子出苗率降低,接种西瓜枯萎病菌的种子出苗率没有明显变化;6.25%精甲·咯菌腈悬浮种衣剂和2.5%咯菌腈悬浮种衣剂包衣种子对西瓜立枯病的防效最佳,72%霜霉威盐酸盐水剂浸种对西瓜猝倒病有一定的防效,对西瓜枯萎病的防治没有特别有效的药剂。     

50%噻虫嗪悬浮种衣剂的研制及其对棉花蚜虫的防治效果

为研制高含量的噻虫嗪悬浮种衣剂,提高其对棉花蚜虫的防治效果,分别采用流点法及因素轮选法等对润湿剂、分散剂、成膜剂和增稠剂等助剂进行筛选及优化,最终采用湿法砂磨超微粉碎法研制了50%噻虫嗪悬浮种衣剂,对其性能指标进行了测试,并测定了其对棉花种子发芽势和发芽率的影响以及对棉花蚜虫的田间防治效果。结果表明:以质量分数为50%的噻虫嗪为有效成分、3%的FD及1%的BC-10为润湿剂、2.5%的SP-2836及2.5%的SK-24为分散剂、1%的硅酸铝镁及0.05%的黄原胶为增稠剂和2.5%的BF308为成膜剂而研制的50%噻虫嗪悬浮种衣剂性状良好,悬浮率高,热贮稳定性好,对棉花种子的发芽势及发芽率的影响较清水对照差异显著。田间试验结果显示,在有效剂量为187.5 g/hm2时50%噻虫嗪悬浮种衣剂对棉花4、5叶期蚜虫的防效分别达83.94%和53.94%,适合田间应用。     

4种药剂拌种对白背飞虱的防治效果

白背飞虱是水稻上的重要害虫,而且是近年来发生严重的南方水稻黑条矮缩病毒的唯一传播介体。为有效降低白背飞虱自身的危害及其传播的南方水稻黑条矮缩病的发生,在云南德宏开展了4种拌种剂防治白背飞虱的田间药效试验。在25%吡蚜酮WP、60%吡虫啉FSC、35%丁硫克百威DS及70%噻虫嗪WS中,35%丁硫克百威DS在拌种后31d对白背飞虱种群的防效仍高达93.6%,其他3种拌种剂的防效分别为75.0%、55.0%及49.3%。因此35%丁硫克百威DS是适合于当地防治白背飞虱的水稻拌种剂。     

两系稻制种穗期病害发生较重的原因及防治措施

调查分析稻粒黑粉病、穗颈稻瘟等两系杂交稻制种穗期主要病害的发生原因,提出了清除菌源、轮换制种、健身栽培、对口药剂防治等防治措施。     

Field emergence and the long‐term efficacy of control of Heracleum sosnowskyi plants of different ages in southern Poland

Heracleum sosnowskyi is one of the three so‐called tall or giant hogweeds currently invading Asia, Europe and North America. These plants are dangerous invasive weeds, causing severe skin injuries in humans and animals. In the present study, based on four field experiments, we assessed seedling emergence in the field and evaluated methods for the long‐term mechanical and chemical control of H. sosnowskyi of various ages (1–5 years old). The field experiments were set up in the mountainous regions of southern Poland, on soil not previously infested with H. sosnowskyi seeds. The results showed that the successful eradication of this species from an invaded area is possible. The results revealed that when no new flush of seeds is delivered to the soil seedbank, the longevity of H. sosnowskyi seeds is approximately five years, with the majority of seedlings emerging in the spring of the first year following sowing. Long‐term shoot cutting, particularly the intensity of this technique, is ineffective for the control of H. sosnowskyi. Cutting three times a year for five years resulted in an H. sosnowskyi control outcome of 42–97%. Total control of this weed is obtained either by cutting the roots of plants up to 5 years old at a depth of 15 cm or by continuous (5 years long) herbicide spraying three times during the vegetative season, using a tank mixture of glyphosate and flazasulfuron (1260 g a.i. glyphosate ha^?1 + 50 g a.i. flazasulfuron ha^?1).     

Effects of selective cutting and timing of herbicide application on growth and development of Cirsium arvense in spring barley

Recently, a new implement for controlling weeds in cereals (CombCut) has been developed. It cuts weeds in growing cereals without damaging them by using the physical differences (in height, stem thickness, straw stiffness and branching pattern) between crops and weeds. To evaluate and compare the effects of selective cutting with different timings of herbicide application on Cirsium arvense in spring barley, a randomised block experiment was conducted in Sweden in 2015–2017, in a field with a naturally occurring C. arvense population. Treatments consisted of control (C), herbicide application at 4–5‐leaf stage of C. arvense (H1), herbicide application at 8–10‐leaf stage (H2) and selective cutting at 10‐leaf stage (S). The treatments were performed in 2015 and repeated in 2016 in the same plots, and a final evaluation was performed in 2017. Compared to the control, S, H1 and H2 were equally efficient in reducing above‐ground biomass production of C. arvense and increasing spring barley grain yield per unit area. The number of C. arvense shoots per area was, however, higher in S compared to H1 and H2. No differences in control effects on shoot number were observed between H1 and H2. Our study indicates that (i) selective cutting (S) reduces C. arvense equally efficient as herbicide application and (ii) early herbicide spraying is as efficient as spraying later in the season.     

Seed retention of ten common weed species at oat harvest reveals the potential for harvest weed seed control

We assessed the seed production and shedding pattern of 10 common weed species in two oat fields in Denmark. The aim was to evaluate the possibility of harvesting retained seeds on weeds at crop harvest by a combine harvester based on estimation of weed seed retention. Before flowering, ten plants of each weed species were selected and surrounded by a seed trap comprising of a porous net. When the plants started shedding seeds, the seeds were collected from the traps and counted weekly until oat harvest. Just before oat harvest, the retained seeds on the plants were counted and the ratio of harvestable seeds and shed seeds during the growing season was determined. The seed production and shedding patterns varied between the 2 years. Across both years, Anagallis arvensis L., Capsella bursa-pastoris L. Medik, Chenopodium album L., Geranium molle L., Persicaria maculosa Gray, Polygonum aviculare L., Silene noctiflora L., Sonchus arvensis L., Veronica persica Poir. and Viola arvensis Murray retained on average 61.6%, 52.7%, 67.2%, 58.4%, 32.05%, 59.5%, 95.7%, 23.5%, 51.7% and 33.9%, respectively, of their produced seeds at crop harvest. Silene noctiflora was classified as a good target for harvest weed seed control; C. bursa-pastoris, C. album, G. molle, P. maculosa, S. arvensis and V. arvensis were classified as intermediate targets; and A. arvensis, P. aviculare and V. persica were classified as poor targets.     

Breeding systems and seed production for six weedy taxa of Bidens

Successful reproduction is considered to be the major determining factor for a weedy population to establish, colonize and infest. The breeding systems and seed production of six weedy taxa of Bidens were studied at an experimental garden in Jiangsu province in China. The results from four treatments (open pollination, bagged capitulum, decapitated capitulum, and pollen supplement) indicated that, with the exception of Bidens pilosa var. radiata, all the other five Bidens taxa; namely, B. pilosa var. pilosa, B. pilosa var. minor, B. frondosa, B.bipinnata, and B. biternata, were self‐fertile with a high seed‐set in bagged capitula, and a high autofertility index. Including the trait of vegetative propagation in self‐incompatible B. pilosa var. radiata, all the six weedy taxa of Bidens had the capacity of uniparental reproduction. The pollen limitation values for all six Bidens taxa were low in the present study. However, the seed production of B. pilosa var. radiata is likely to decrease in the absence of sufficient pollinators, related to its high pollen contribution and potential pollen limitation indices. The seed production per plant and per capitulum of the three varieties of B. pilosa was the highest among the six taxa and might contribute to their serious weediness. The breeding system type and seed number per capitulum could be used as a classification reference for Bidens taxa.     

6种杀菌剂对马铃薯黑痣病菌的毒力和拌种防效

为了探索马铃薯黑痣病高效防控技术,本研究选择240 g/L噻呋酰胺SC、20％嘧菌酯WG、10％苯醚甲环唑ME、0.3％四霉素AS、100万孢子/g寡雄腐霉WP、1％申嗪霉素SC等6种杀菌剂进行室内毒力测定和田间拌种防效试验.结果显示,6种杀菌剂对马铃薯黑痣病菌均有抑菌作用,其中1％申嗪霉素SC、20％嘧菌酯WG、0....     

Effects of temperature and light on seed germination of ephemeral plants in the Gurbantunggut Desert,China: implications for vegetation restoration

Seed germination is a key transitional stage in plant life cycle and is strongly regulated by temperature and light. Therefore, research on the effects of temperature and light on seed germination is extremely meaningful for vegetation restoration, especially in desert ecosystems. Seeds of 28 ephemeral plants collected from the Gurbantunggut Desert of China were incubated at different temperatures (5°C/1°C, 15°C/5°C, 20°C/5°C, 25°C/10°C and 30°C/15°C) in 12-h light/12-h darkness or continuous darkness regimes, and the responses of seed germination to temperature and light and the germination speed were studied in 2016. Results showed that seed germination percentage of the 28 ephemeral plants significantly differed to temperature and light. We classified the studied plants as the following groups based on their responses to temperature: 1 low temperature responsed plants, 12 moderate temperature responsed plants, 7 high temperature responsed plants, 4 non-responsed plants and 5 plants of no germination. It should be noted that Corispermum lehmannianum Bunge is sensitive to both moderate and high temperatures. There were 4 groups of plant in response to light, i.e., 7 light responsed plants, 10 dark responsed plants, 6 light non-responsed plants and 5 plants of no germination. Based on seed germination speed of the 28 ephemeral plants, we divided them into 4 patterns of germination, i.e., very rapid, moderately rapid, moderate and slow. Combining variations of temperature, precipitation and sand dune types in the study area, we suggested that very rapid and moderately rapid germinated plants could be used to moving sand dunes in early spring during vegetation restoration, moderate germinated plants could be used to semi-fixed sand dunes in late autumn, and slow germinated plants could be used to sand plain in summer. Thus, seedling establishment and vegetation restoration would be improved by considering seed germination characteristics of these ephemeral plants in the Gurbantunggut Desert, China.     

Analysis of the seed dispersal patterns of wild soybean as a reference for vegetation management around genetically modified soybean fields

There are concerns that genetically modified soybean might threaten the genetic diversity of the wild soybean populations that are distributed in East Asia because genetically modified soybean has no crossing barrier with wild soybean. A simple and effective method to prevent hybridization via pollen flow is spatial separation between the two species because their hybridization occurs only when they grow in close proximity. Therefore, the invasiveness of wild soybean needs to be known in order to secure the appropriate distances. As wild soybean seeds are dispersed mechanically by pod dehiscence, an experiment was conducted in which white sheets were placed on the ground, concentric circles were drawn around the parent plants, and the number of dispersed seeds within each 0.5 m‐wide zone were counted. About 40% of the produced seeds were dispersed and the number of dispersed seeds gradually declined as the distance from the parent plants increased. The model that explained the relationship between the number and distance of the dispersed seeds was produced by using a generalized linear model procedure. More than 95, 99, and 99.9% of the produced seeds stayed within 3.5, 5.0, and 6.5 m after natural pod dehiscence. Knowing these values is useful for evaluating the level of invasive risk by mechanical seed dispersal. The goal of the work is to efficiently and deliberately prevent hybridization by isolating genetically modified soybean fields and wild soybean populations by vegetation management, including weeding and setting up specific‐width buffer zones.     

Effects of crop management practices on Echinochloa crus-galli and Chenopodium album seed production in a maize/soyabean rotation

Seed production of residual weed populations needs to be taken into account when estimating the long-term impact of low-input agronomic practices. The objective of this study was to measure the effects and interactions of crop, weed control, tillage practice and nutrient source on the seed production of the dominant residual weed species in a maize/soyabean rotation at two sites: Echinochloa crus-galli (L.) Beauv. on a Sainte-Rosalie clay and Chenopodium album L. on a Duravin clay loam. Seed production per unit area was estimated in each experimental unit. Weed seed production was greater under mechanical weed control compared with chemical weed control. In 1997, E. crus-galli seed production reached over 326 000 seeds m^–2 in mechanical weed control treatments, but averaged less than 500 seeds m^–2 in the chemical weed control treatments. Chenopodium album produced in the range of 766 000 and 73 000 seeds m^–2 in mechanical and chemical weed control treatments respectively. Very few or no weed seeds were produced in soyabean under chemical control. Tillage intensity and nutrient source did not affect seed production of either weed species, with the exception that E. crus-galli produced more seeds in chisel than in mouldboard plough tillage in soyabean. Weed control method had more impact on seed production than tillage intensity and nutrient source in a maize/soyabean rotation.     

Comparison of growth,survivorship, seed production and shedding of eight weed species in a wheat crop in Western Australia

Development of integrated weed management strategies is dependent on a thorough knowledge of the demography of individual species. The current research established eight winter or summer weed species in a winter annual wheat cropping system at Wongan Hills, Western Australia, and investigated emergence of the first cohort of each species, survivorship, plant size, seed production and seed shedding over three years (2016–2019). The winter weeds Bromus diandrus and Lolium rigidum emerged at the same time as the wheat crop, and the initial cohort of marked plants had 100% survival to seed production in each year. By comparison, other winter weed species like Hordeum leporinum, Rumex hypogaeus, Sonchus oleraceus and Polygonum aviculare frequently emerged later than the crop and had a lower percentage of plants surviving to seed production. However, individual S. oleraceus and P. aviculare plants had the greatest seed production compared to other species. All winter weeds had variable patterns of seed shedding between years, with the exception of L. rigidum. Summer weed species emerged at the same time, but plants in the initial cohort of each species did not always survive to produce seed. The early emergence and high survivorship of B. diandrus indicates high competitive ability, but shedding commenced at a similar time to L. rigidum and harvest weed seed control may be a viable control method for this species.     

圆盘破茬刀切割玉米根茬运动特性测绘装置设计与试验

免耕播种机是保护性耕作的关键机具之一,其播种质量的好坏在很大程度上影响着保护性耕作的效果。为了优化免耕播种机的关键部件破茬刀,研制了一种圆盘破茬刀切割玉米根茬运动特性测绘装置,该装置能够实现实时地测绘出圆盘破茬刀待测点的运动轨迹。通过对三种圆盘破茬刀的运动轨迹的测绘与试验,得出光面圆盘破茬刀上待测点的运动轨迹为光滑的摆线,半圆型缺口盘和阿基米德螺线盘上待测点的运动轨迹为由不同长度的圆弧组成的云曲线。在此基础上对三种圆盘破茬刀冲击情况、入土滑切角和滑切速度变化进行了分析比较,建立了阿基米德螺线型圆盘破茬刀切割根茬运动的运动学模型。描绘出阿基米德螺线型圆盘破茬刀刃口上点的运动轨迹是由不同长度的圆弧组成的云曲线,建立了阿基米德螺线型圆盘破茬刀刃口上点的运动方程。发现阿基米德螺线型圆盘破茬刀刃口上点的轨迹具备了光面圆盘破茬刀的摆线规律,也具备了半圆型缺口圆盘破茬刀的冲击性,并且滑切角较大,滑切性能更好。通过圆盘破茬刀切割玉米根茬运动特性测绘装置的两因素三水平正交试验分析,得出阿基米德螺线型圆盘破茬刀、机具配重为100 kg时破茬效果达90%以上,破茬率较高。