麦田猪殃殃对苯磺隆抗药性的快速检测

以采自山东、河南、安徽、陕西等地麦田及非农田的10个猪殃殃Galium aparine生物型为试材,运用单剂量甄别技术对不同生物型对苯磺隆的抗药性进行了检测,并以温室盆栽法及皿内抗性水平测定法验证其可靠性和可行性。结果表明:在甄别剂量(有效成分)85 mg/L下,猪殃殃不同生物型萌发率存在显著性差异,可以较好区分猪殃殃抗、感生物型;温室盆栽法及皿内抗性水平测定法结果一致,除采自山东泰安和陕西周至的麦田猪殃殃对苯磺隆仍处于敏感状态外,其他3个地区麦田猪殃殃均产生了不同程度的抗药性,且均与皿内单剂量甄别法结果一致,表明皿内单剂量甄别法具有可靠性和可行性。     

Effects of the seed weight and burial depth on the seed behavior of common ragweed (Ambrosia artemisiifolia)

Common ragweed (Ambrosia artemisiifolia L.) is one of the annual plants that were described recently as invasive weeds in Europe. This species is described as an invasive plant that produces seeds that are highly variable. Its production of variably sized seeds is regarded as promoting its spread in different environments. Experiments were carried out to determine the influence of the seed weight and temperature on germination and the influence of the seed weight and burial depth on seedling emergence. The seeds were divided into a number of classes of weight and the seed weight effect on germination was evaluated by Petri dish assays. In another experiment, the seeds were buried at different depths in a clay soil/sand mix to estimate the burial effect on germination and seedling emergence. The germination level of A. artemisiifolia was high overall, between 76.8% and 94.2%. The seed germination was modified by temperature but it was not influenced by the seed weight. The amounts of germination and seedling emergence were greater for the seeds on the soil surface and decreased with an increasing burial depth, from 2 to 8 cm. No germination or emergence was observed for the seeds that were buried at 10 and 12 cm. The lightest seeds were more sensitive to burial. A greater level of seedling emergence for those seeds that were placed near the soil surface could explain the success of this species in open habitats, where the probability of deeper burial is low. After high seed production, the management of A. artemisiifolia in fields could be partly achieved through soil tillage, burying seeds below 10 cm, and not carrying out deep soil tillage the following year.     

The dormancy of wild oat seed (Avena fatua L.) from plants grown under various temperature and soil moisture conditions

Wild oat plants of types fA, fB and fC were grown at a constant 15 or 20°C during the period of seed maturation. Seed of the three types differed little in dormancy when grown at 15°C, but at 20°C a larger proportion of seeds of type fA were dormant compared with fB or fC. Overall, dormancy of seed produced at 15 and 20°C was 97 and 63% respectively. Plants of another collection of type fB were grown from seed at 15 or 20°C with or without water stress applied only from the time of panicle emergence. Water stress and high temperature reduced viable seed production. Seed dormancy was tested immediately after collection by planting the seed in soil, and by Petri dish tests. Further Petri dish tests were made after 6 months storage. Seedling emergence in the first autumn from seeds of plants matured without water stress at 15°C was 10% compared with 30% for seeds grown at 20°C. Seeds grown with water stress at 15°C gave 47%, and at 20°C 78% emergence. The majority of emergence from seeds formed at 15°C without water stress occurred in the second spring after burial. Petri dish tests support these findings and suggest that seeds produced in hot dry summers are less dormant than those produced in cool moist ones.     

A new design for a seed germinator with 100 independently temperature controlled cells

Design and performance of a 100-cell seed germinator capable of simultaneously generating 100 different diurnal temperature cycles with extremes lying between 0 and 45°C is discussed. Each individual cell is equipped with a separate electronic temperature controller employing a thermistor for temperature sensing. The set temperature for each cell is determined by a precision reference resistor in the controller circuit. Six different reference resistors corresponding to six different temperatures are provided for each cell. The reference resistors are mounted on plug-in modules with one module for each cell. Heating or cooling of the individual cells is provided by thermoelectric heat pumps. Temperature cycling, which approximates a sine function, is achieved by switching the six reference resistors, one at a time, into the controller circuits at appropriate times during a 24h period. Each cell is designed to accept a standard 100 mm Petri dish to contain the seeds. The cells have glass covers to allow entry of light essential for germination of some species. The benefit of using this type of germinator to assess the germination response of Alyssum alyssoides L., Artemisia absinthium L., Euphorbia esula L. and Setaria viridis (L.) Beauv., is discussed. Three dimensional germination response surfaces are given for the four species.     

Germination behaviour of dormant oilseed rape seeds in relation to temperature

Seeds of oilseed rape ( Brassica napus L., cv. Liglandor) were induced into secondary dormancy by imbibing them for 2-4 weeks in an osmotic solution at -1500 kPa in darkness. Treated seeds were then transferred into pots or Petri dishes, where they were given adequate water for germinatton. These pots and Petri dishes were exposed to various temperature regimes during the course of the following 6–14 months. During that time, seed samples were taken at 2- to 6- weekly intervals to monitor survival of seeds and to study their dormancy. The ntimber of seeds that had not germinated in pots or Petri dishes remained constant in the majority of treatments. but it declined when seeds were exposed to pronounced daily temperature alternations. This decline was due to germination and not to death of seeds from other causes. Germination tests on subsamples of seeds showed that they were light sensitive, more seeds germinating in the light than in the dark. The seeds'germination behaviour differed between samphng dates. This variation in germination behaviour appeared not to display the classical dormancy:non-dormancy cycle. Part of the variation seemed to be due to the changes in temperature that the seeds experienced when taken from pots and set up in the germination tests. Seeds exposed to a constant temperature for 1 year appeared lo become more dormant with time. The relevance of this work in relation to the persistence of volunteer oilseed rape is discussed.     

水稻粒黑穗病侵染的研究

 稻粒黑穗病在川东焉蔓延已久的病害。解放前万孙熊家乡长民曾企图用温汤浸梗法以防治此病,结果无效。     

银胶菊的花对稗草的化感作用及其化感物质分离与鉴定

为明确银胶菊的花组织对稗草的化感作用及其活性物质成分,采用培养皿法和室内盆栽法,研究了其水浸提液的乙酸乙酯相、正丁醇相和剩余水相对稗草生长的影响。结果表明,乙酸乙酯相的化感抑制活性最高,其中,温室盆栽试验中对稗草萌发、株高、鲜重的抑制率分别为11.1%、10.2%和14.6%。采用GC-MS技术,从乙酸乙酯相较高活性组分中分离鉴定了15种主要化合物,分别为烃类及其衍生物、萘类、醇类、苯类、酸类、酮类和酯类。     

Allelopathic potential of wild onion (Asphodelus tenuifolius) on the germination and seedling growth of chickpea (Cicer arietinum)

Water extracts obtained from the roots, shoots, and fruits of mature wild onion ( Asphodelus tenuifolius ) plants and soil taken from an A. tenuifolius field were used to determine their allelopathic effects on the germination and seedling growth of chickpea ( Cicer arietinum ) in the laboratory. The roots, shoots, and fruits of A. tenuifolius were soaked individually in water in a ratio of 1:20 (w/v) for 24 h to prepare the extracts. Distilled water was used as the control. The germinated seeds were taken out from the Petri dishes and counted every day for 12 days. The seeds of chickpea were also sown in sand and in each of the controlled, normal soil and the soil taken from the A. tenuifolius -infested field in Petri dishes to record the length and weight of the roots and shoots 18 days after sowing. The mean germination time reached the maximum amount for the stem and fruit extracts. The fruit extract caused the most reduction in the germination index and the germination percentage of chickpea. The different wild onion organ extracts significantly reduced the root and shoot length and biomass of the chickpea seedlings compared with the distilled water. The fruit extract of wild onion proved to be the most detrimental to the root length, shoot length, and dry weight of the chickpea seedlings. The soil beneath the A. tenuifolius plants significantly reduced the emergence, root length, shoot length, shoot dry weight, and seedling dry weight but increased the root dry weight of the chickpea seedlings. It is suggested that A. tenuifolius releases phytotoxic compound(s).     

Germination requirements for 29 terrestrial and wetland wild plant species appropriate for phytotoxicity testing

BACKGROUND: Species selected for phytotoxicity testing have been limited to a few standard crop species owing to restrictive recommendations at the regulatory level. However, guidelines by the Organisation for Economic Development and Cooperation (OECD) were recently amended in 2006 to include a list of herbaceous non‐crop plant species suitable for testing. The objective of this study was to outline the optimum germination requirements for a selection of wild species for which seeds were readily available from commercial suppliers. RESULTS: Of the 29 herbaceous terrestrial and wetland species included in this study, all achieved 50% germination and 23 reached > 70% germination to meet the criterion outlined in the OECD guidelines. Most species attained their maximum germination within 14 days or less. Cold stratification of imbibed seeds improved germination for 14 species. Increasing sowing soil depth did not improve seed germination. The variance attained in this experiment between replicates was low, especially for species with > 70% germination (standard error ～5%). CONCLUSION: The present study showed that 23 of the 29 species tested required minimal pretreatments and produced consistent, reliable and uniform germination reaching at least 70%. The inclusion of wild plant species in regulatory testing should be given real consideration. Copyright © 2008 Crown in the right of Canada. Published by John Wiley & Sons, Ltd     

Stimulation of dormant weed seed germination by 2-chloroethylphosphonic acid

Mainly dormant seeds of nine weed species were incubated with 2-chloroethylphosphonic acid in Petri dishes. Four species showed markedly increased germination percentages with doses up to 100 ppm. Interactions of 2-chloroethylphosphonic acid with light in Matricaria recutita L. and with crop root exudates in Striga hermontheca Benth. were found.     

Glyphosate-resistant Lolium multiflorum in Chilean orchards

Summary Lolium multiflorum (Italian ryegrass) seeds suspected of being resistant to glyphosate were collected from fruit orchards at two locations, San Bernardo (SB) and Olivar (OL), Chile, that had been treated an average of three times per year with the isopropylamine salt of glyphosate during the previous 8–10 years. Laboratory experiments were conducted for each orchard population and a susceptible population, a commercial cultivar called Tama (TM), using Petri dishes containing filter paper saturated with 5 mL of glyphosate solution (0–160 mg a.e. L⁻¹) . Pot dose–response experiments were also conducted in the greenhouse. The three L. multiflorum populations were treated with glyphosate (0.00–4.32 kg a.e. ha⁻¹). The dose needed to reduce shoot length (Petri dish experiment) and fresh weight (pot dose–response experiment) by 50% was determined for each population. Compared with the TM population, the Petri dish experiment found that the SB and OL populations were five- and sixfold, respectively, more resistant to glyphosate, whereas the pot dose–response experiment found that the SB and OL populations were two- and fourfold, respectively, more resistant to glyphosate. These results confirm a new case of glyphosate resistance in a novel species, L. multiflorum , and correspond to the first case of glyphosate resistance reported from South America.     

How much of seed dormancy in weeds can be related to seed traits?

Seed dormancy contributes to species persistence in unpredictable environments and is a key process to be taken into account in weed dynamics models. As the level of seed dormancy, photosensitivity and the dates of dormancy induction and release are difficult to measure, our objective was to relate weed seed dormancy with morphological, chemical or physiological seed traits and with expert knowledge. Dormancy of four species was studied experimentally during a 2‐year seed burial experiment. Experiments were supplemented with data from the literature to increase the number of species analysed, resulting in a data set of 29 species. Proportions of non–dormant seeds were higher for elongated than spherical seeds, even when accounting for phylogenetic relatedness between species. Elongated seeds, which tend to remain on the soil surface in undisturbed habitats, may have been selected for lack of dormancy and immediate germination to limit mortality due to predation. Dormancy increased with seed coat thickness, which can act as a chemical and physical barrier to germination, while no relation was found with seed lipid or protein content. No correlation was found between photosensitivity parameters and any of the species traits analysed. Variations in dormancy dates (induction and release) were highly correlated with average field emergence season estimated from expert knowledge. The observed correlations suggest that the level of dormancy results both from direct and from indirect effects of traits being involved in trade‐offs together with seed mortality.     

Comparing after-ripening response and germination requirements of Conyza canadensis and C. bonariensis (Asteraceae) through logistic functions

Germination requirements and after‐ripening effects during one year of dry storage at 15/5 and 25/15°C (day/night) were compared for Conyza bonariensis and C. canadensis (Asteraceae). A logistic function was fitted to the results from tests over time in various incubation conditions, using three populations of each species as replicates. Time required for response to dry storage was measured by using a new method, the third derivative of the logistic function. Therefore, a point when major germination was achieved could be detected, without having to rely on maximum germination (which is uncertain), individual data points or any subjectively chosen limit. Fresh seeds of both species were dependent on light for germination and after‐ripening was mainly manifested by increasing germination in darkness. Low dormancy status and light requirement might indicate that soil cultivations should rapidly reduce the seedbanks of these species, although fecundity and wind dispersal will affect population levels. The species differed in their germination response, with C. bonariensis germinating at lower temperatures than C. canadensis. This seemingly counter‐intuitive result may explain the prevention of fatal germination of C. canadensis in cold conditions and its behaviour as a summer annual in northern climates, while C. bonariensis is restricted to warmer parts of the world.     

Accounting for uncertainty in pedotransfer functions in vulnerability assessments of pesticide leaching to groundwater

A simulation tool for site-specific vulnerability assessments of pesticide leaching to groundwater was developed, based on the pesticide fate and transport model MACRO, parameterized using pedotransfer functions and reasonable worst-case parameter values. The effects of uncertainty in the pedotransfer functions on simulation results were examined for 48 combinations of soils, pesticides and application timings, by sampling pedotransfer function regression errors and propagating them through the simulation model in a Monte Carlo analysis. An uncertainty factor, f(u), was derived, defined as the ratio between the concentration simulated with no errors, c(sim), and the 80th percentile concentration for the scenario. The pedotransfer function errors caused a large variation in simulation results, with f(u) ranging from 1.14 to 1440, with a median of 2.8. A non-linear relationship was found between f(u) and c(sim), which can be used to account for parameter uncertainty by correcting the simulated concentration, c(sim), to an estimated 80th percentile value. For fine-textured soils, the predictions were most sensitive to errors in the pedotransfer functions for two parameters regulating macropore flow (the saturated matrix hydraulic conductivity, K(b), and the effective diffusion pathlength, d) and two water retention function parameters (van Genuchten's N and alpha parameters). For coarse-textured soils, the model was also sensitive to errors in the exponent in the degradation water response function and the dispersivity, in addition to K(b), but showed little sensitivity to d. To reduce uncertainty in model predictions, improved pedotransfer functions for K(b), d, N and alpha would therefore be most useful.     

土壤传递函数模型的研究进展

研究评述了线性回归、非线性回归、神经网络等方法构建土壤传递函数模型的优缺点,介绍了传递函数模型及其应用不确定性分析中常用的Bootstrap analysis、改进的Monte Carlo、最小二乘法等方法,探讨了输入数据、模型结构和参数对传递函数及其应用不确定性的影响,并指出今后可借鉴分析法里的格林函数法和耦合去耦等方法开展土壤传递函数及其预测不确定性的研究,明确传递函数模型不确定性的主要来源,提高模型的应用效率。     

Factors affecting the seed germination and seedling emergence of muskweed (Myagrum perfoliatum)

Myagrum perfoliatum is a noxious broad‐leaved weed in western Iranian farming systems. A better understanding of the timing of seedling emergence would facilitate the development of better control strategies for this weed. Therefore, the objective of this study was to examine the effects of different factors on muskweed seed germination. Only 2.8% of the seeds of this species, which are encapsulated in siliques, germinated by, while the seeds that had been removed from the siliques had a 50% germination rate. The immersion of muskweed fruits in concentrated sulfuric acid for 110 min was the best treatment for promoting germination. Gibberellic acid stimulated the germination of the naked seeds by 29.1%, potassium nitrate (40 mmol L^‐1) increased the germination rate to 71%, while higher concentrations of potassium nitrate inhibited germination. The optimum germination temperature for the naked seeds was 20/10°C (day/night) and light was not required for germination. No seedling emerged when the seeds were buried 6 cm deep. The seeds were sensitive to both osmotic and salinity stress, but they germinated to 46–49% over a pH range of 4–10. The results of this study revealed that the seeds of M . perfoliatum have physiological dormancy and that it is slowly broken via after‐ripening. However, the fruit wall can prevent germination after physiological dormancy is broken. Thus, this species has the potential to form a persistent seed bank because of the presence of the fruit wall.     

Seed germination behavior of glyphosate‐resistant and susceptible Italian ryegrass (Lolium multiflorum Lam.)

Ryegrass (Lolium multiflorum Lam.) is one of the most difficult annual weeds to control in cultivation systems worldwide, especially in temperate regions. The widespread use of herbicides in the past two decades has selected resistant biotypes of ryegrass in crops in Southern Brazil. Ryegrass seeds are dormant when disseminated and germination can be staggered over time (crop‐growing season). Knowledge of the germination behavior of seeds from herbicide‐resistant plants has been little studied, but it would be very useful in integrated weed management. Thus, this study aimed to characterize the dynamics of the soil seed bank of two biotypes of L. multiflorum, one glyphosate‐resistant and the other glyphosate‐susceptible, under a no‐tillage system. The treatments were arranged in a bifactorial scheme, using seeds from biotypes (glyphosate‐resistant and glyphosate‐susceptible) with monthly periods of removal from field (one to 12 months). Seeds of each biotype were placed on the soil surface and covered with soil and straw to simulate no‐till conditions. The percentage of germinated, dormant, and dead seeds was evaluated every 30 days. The ryegrass seed bank of glyphosate‐susceptible and glyphosate‐resistant biotypes was reduced to 11 and 15% of dormant seeds, respectively, at the end of 12 months. However, there was no variation in germination, dormancy, and seed mortality between susceptible and glyphosate‐resistant ryegrass. Seeds of glyphosate‐resistant biotype and susceptible showed germination behavior with similar dynamics in the soil over a period of 12 months.     

Seed germination ecology of creeping mannagrass (Glyceria acutiflora) and response to POST herbicides

Creeping mannagrass is a perennial grass weed widely distributed in China and is becoming increasingly problematic in nurseries and landscapes in some regions. Understanding the germination ecology and response to commonly available POST herbicides of this weed is critical to determining its adaptive capabilities and potential for infestation, and assist in the development of effective control strategies. In the light/dark regime, creeping mannagrass germinated over a wide range of temperatures (15/5 to 30/20°C), with maximum germination at 20/10°C (95%). No seed germinated at 35/25 or 10/0°C. The time required for 50% of maximum germination increased as temperature decreased. Compared with the light/dark conditions, germination was slightly stimulated when seeds were placed in the dark. Creeping mannagrass is moderately tolerant to osmotic and salt stress, which had 53 and 50% germination rates at ?0.6 mPa osmotic potential and 200 mM NaCl concentration, respectively. Seedling emergence of the seeds buried at a depth of 0.5 cm (86%) was higher than those sowing on the soil surface (17%), but declined with burial depth increasing. There were no differences in the emergence rates from a burial depth 0.5–2 cm. Few seeds (4%) could emerge when seeds were sowed at a depth of 8 cm. POST application of haloxyfop‐R‐methyl, quizalofop‐p‐ethyl, sethoxydim, and pinoxaden provides 100% control of creeping mannagrass at the three‐leaf to five‐leaf stages. To achieve 80% control with clodinafop‐propargyl, mesosulfuron‐methyl, and fenoxaprop‐p‐ethyl, herbicides had to be applied at the three‐leaf stage.     

Teleutospores as origin of systemic infection of Cirsium arvense by Puccinia punctiformis

Teleutospores ofPuccinia punctiformis were used for germination and inoculation experiments. The percentage of germination increased with increasing root extract concentration separately from the spore-suspension present in the same Petri dish.Volatile substances in root extracts of the thistle plant markedly promoted the germination of the teleutospores.Inoculation experiments showed that underground parts of plants ofC. arvense can be infected. The percentage of diseased shoots emerging from inoculated root segments was higher than of those emerging from seeds. Three types of systemically infected shoots could be distinguished.The development of spermogonia on the diseased shoots indicates that at first the hyphae are haploid, but later on become dikaryotic as shown by the formation of uredosori. Teleutospores are thus responsible for the systemic infection of the plants.Samenvatting Teleutosporen vanPuccinia punctiformis zijn gebruikt voor kiemings- en incubatieproeven.Vluchtige substanties, aanwezig in wortelextracten van de akkerdistel, hebben een grote invloed op de kieming van teleutosporen. Het percentage kiemende teleutosporen nam toe bij toenemende concentraties van het wortelextract, aanwezig in dezelfde petrischaal als de sporensuspensie.Inoculatieproeven toonden aan dat ondergrondse plantedelen vanC. arvense kunnen worden geïnfecteerd. Het percentage aangetaste scheuten opkomend uit wortelsegmenten was groter dan dat van scheuten verkregen uit zaden. Behalve systemisch geïnfecteerde scheuten werden ook enkele lokaal geïnfecteerde scheuten aangetroffen. De systemisch geïnfecteerde planten konden worden onderscheiden in drie verschillende types.De ontwikkeling van spermogonia op de systemisch aangetaste scheuten wijst er op dat het aanwezige mycelium haploid is, zoals ook te verwachten is bij infecties met basidiosporen. Pas later worden de hyphen dikaryotisch, zoals blijkt uit de vorming van uredosori.