Modelling land use strategies to optimise crop production and protection of ecologically important weed species

There is a need to develop farming systems that enable both a satisfactory level of crop production and suitable environmental conditions for natural species. Wildlife‐friendly cropping techniques, such as a reduced amount of applied herbicide or a lower crop density, might be adopted in order to maintain populations of weed species of biological interest. An alternative might be to adopt an intensive cropping system in a part of the field and spare the other part as set‐aside or field margins, available for the natural development of plant species. The objective of this study was to present a method to compare two strategies for maintaining a desirable level of abundance of a given species of interest in agricultural areas, specifically (i) a strategy based on a wildlife‐friendly cropping system in a large cultivated area and (ii) a strategy based on a more intensive cropping system in a reduced area of cultivation, i.e. with land‐sparing. The principle is to calculate the ratio of crop production obtained with strategy (i) to the production obtained with strategy (ii) for a given target density of natural species. We show that the value of this ratio, and thus the relative performance of the two strategies, depends on the density of the weed species that can be maintained in an uncultivated ecological area. The method is applied in case studies of two plant species with contrasting ecology and conservation goals. The numerical results show that the strategy based on a wildlife‐friendly cropping system is more profitable in most situations.     

1960-2009年毛乌素沙地腹地气候变化的多重时间尺度分析——以乌审旗为例

采用一维Morlet复值小波变换对毛乌素沙地腹地1960-2009年气候变化的时间尺度特征进行了分析,结果表明:50年来,毛乌素沙地腹地年平均气温上升的气候变化倾向率为0.25℃/10a,年降水量下降的倾向率大小为11.383mm/10a;年平均气温存在着28a、13a和6a,年降水存在9a、28a、7a、5a和14a的多重时间尺度上的复杂嵌套结构,气温变化以28a尺度的周期振荡最强,降水变化以9a尺度的周期振荡最强。     

The role of primary germ tubes in the life cycle of Blumeria graminis: The primary germ tube is responsible for the suppression of resistance induction of a host plant cell

When the conidia of Blumeria graminis f. sp. hordei (Bgh) are inoculated on barley coleoptile cells they produce short germ tubes called primary germ tubes (PGTs) about 2 h after inoculation. We evaluated the positive role of a PGT in inducing accessibility of the host cell under the germ tube. When an appressorium (APP) penetrated the same cell on which a PGT was present, the ratio of haustorium formation (penetration efficiency) was significantly higher than when an APP penetrated the cell adjacent to the one on which a PGT was present. When an APP penetrated the cell laterally adjacent to the one on which a PGT was present we killed the cell under the PGT by puncturing it with a microneedle and then investigated the penetration efficiency of the cell adjacent to the dead cell. As a control we killed the cell longitudinally adjacent to the one on which a PGT was present and investigated the penetration efficiency of the laterally adjacent cell. The results showed that the penetration efficiency of the former was significantly lower than that of the latter. This suggests that some accessibility factor might transfer from a cell on which a PGT is present to a laterally adjacent cell. The existence of a conidium body but not a PGT was not effective for induced accessibility of the host cell. Moreover, when a Bgh germling was removed 6 h after inoculation and another germling was transferred to the same cell, the penetration efficiency was significantly higher than that of control. As a control, a Bgh germling was transferred to a cell on which no germling was present. These results suggest that the existence of PGT is effective for induced accessibility of a host cell when penetrated by Bgh. However, it is unclear whether or not a PGT secretes some substance(s) which suppresses the resistance induction of a host cell.     

The role of primary germ tubes in the life cycle of Blumeria graminis: The primary germ tube is responsible for the suppression of resistance induction of a host plant cell

When the conidia of Blumeria graminis f. sp. hordei (Bgh) are inoculated on barley coleoptile cells they produce short germ tubes called primary germ tubes (PGTs) about 2 h after inoculation. We evaluated the positive role of a PGT in inducing accessibility of the host cell under the germ tube. When an appressorium (APP) penetrated the same cell on which a PGT was present, the ratio of haustorium formation (penetration efficiency) was significantly higher than when an APP penetrated the cell adjacent to the one on which a PGT was present. When an APP penetrated the cell laterally adjacent to the one on which a PGT was present we killed the cell under the PGT by puncturing it with a microneedle and then investigated the penetration efficiency of the cell adjacent to the dead cell. As a control we killed the cell longitudinally adjacent to the one on which a PGT was present and investigated the penetration efficiency of the laterally adjacent cell. The results showed that the penetration efficiency of the former was significantly lower than that of the latter. This suggests that some accessibility factor might transfer from a cell on which a PGT is present to a laterally adjacent cell. The existence of a conidium body but not a PGT was not effective for induced accessibility of the host cell. Moreover, when a Bgh germling was removed 6 h after inoculation and another germling was transferred to the same cell, the penetration efficiency was significantly higher than that of control. As a control, a Bgh germling was transferred to a cell on which no germling was present. These results suggest that the existence of PGT is effective for induced accessibility of a host cell when penetrated by Bgh. However, it is unclear whether or not a PGT secretes some substance(s) which suppresses the resistance induction of a host cell.     

长武塬区苹果园和农田相互转换的深层土壤水环境效应

研究长武塬区苹果园和农田相互转换后0~1 000 cm土壤含水量特征，分析了苹果园土壤干燥化和苹果园转换为农田后土壤水分的恢复效应。结果表明：2、7、17、23、29 a苹果园200~1 000 cm的平均土壤含水量分别为22.8%、21.4%、16.8%、15.4%、14.9%。500~1 000 cm土层中，29 a苹果园平均土壤含水量（14.5%）高于23 a的果园（13.3%）；17~29 a的苹果园均表现为轻度干燥化；基于苹果园和农田转换后土壤水分变化情况估算，苹果园最大种植年限为21 a。苹果园转换为农田1、5、10 a后，农田200~1 000 cm土层土壤含水量分别为：15.3%、15.7%和16.2%，恢复到土壤稳定湿度以上的土层厚度分别为140 cm（1 a）、220 cm（5 a）和400 cm（10 a）。     

Ultrastructure of a new type of sensory ending in Echinostoma revolutum cercaria (Trematoda: Echinostomatidae)

Two pairs of hitherto unknown multiciliate sensory endings have been demonstrated in free-swimming cercariae of Echinostoma revolutum using transmission and scanning electron microscopy. This type of receptor consists of a bundle of 36--40 short, conically projecting cilia ensheathed by a collar formed by a circular evagination of tegument in shape of a cup. The cilia projecting from the centre of a widened nerve fibre, filled with electron-lucid vesicles, possess a well developed basal body and do not contain a ciliary rootlet. The function of this receptor is discussed.     

Studies on very-low volume (VLV) water-based sprays for the control of cotton pests

We evaluated, water-based very-low volume (VLV) sprays of various pyrethroids at different dosage levels, comparing these with ultra-low volume (ULV) sprays for the control of cotton pests in the Nampula province of Mozambique. The results showed that karate (lambda-cyhalothrin) 2.5% SG at a dosage level of 15 g a.i./ha applied as VLV gave a significantly higher yield than karate 0.8% ULV (28 g a.i./ha). Also, karate 3.75% WG (12 and 15 g a.i./ha) gave a similar yield to that of karate 0.8% ULV (28 g a.i./ha). Karate 5% EC (15 and 20 g a.i./ha) gave a yield similar to Karate 0.8% ULV (28 g a.i./ha). Baythroid (cyfluthrin) 5% EC at 15, 22.5 and 30 g a.i./ha gave a yield similar to baythroid 1.2% ULV (36 g a.i./ha). Bulldock (beta-cyfluthrin) 12.5% SC at dosage levels of 6, 9 and 12 g a.i./ha gave a similar yield to that using baythroid 1.2% ULV (36 g a.i./ha). In all four trials, water-based VLV sprays gave a yield of cotton and degree of pest-control similar to those obtained with the ULV formulations at comparatively lower dosage levels. Integrated with other pest management practices, these could play an important role in the cost effective management of insect pests of cotton on small-scale farms in many countries.     

基于GIS的甘肃省土地利用程度高程模型构建

土地利用垂直分异规律是土地利用空间分异规律研究的重要内容之一,其定量研究可为模拟和预测土地利用程度变化提供理论基础和途径。以甘肃省土地利用程度垂直分异为研究对象,运用GIS空间分析技术对土地利用数据和数字高程模型(DEM)数据进行处理,结合数理统计分析方法构建了甘肃省土地利用程度高程模型。研究表明:甘肃省土地利用程度随高程变化呈现出4个趋势:1)海拔高度600～1120m之间,土地利用程度随海拔增高表现为线性递减趋势;2)在1130～3600m高度带内,土地利用程度呈先增后减趋势,且在2600m附近达到最大值;3)在3610～5530m高度带内,土地利用程度呈先减后增趋势,即土地利用程度与海拔高度呈"U"型关系,且在4550m附近达到最小值;4)在海拔高度5530m以上,土地利用类型单一且均为水域,因此土地利用程度保持不变。最后,结合各区域自然条件和经济发展水平对土地利用垂直分异规律成因进行了探讨,分析发现数量众多的未利用和难利用土地是导致土地利用程度整体较低和呈现不同垂直分异特征的主要原因。     

Seasonal patterns of dispersal of ascospores of Cryphonectria parasitica (chestnut blight)

Infected barks of chestnut blight cankers, caused by Cryphonectria parasitica , were collected from a naturally infected orchard and incubated at different temperatures. Cankers started to discharge ascospores about a week after incubation at 15–25°C; most ascospores were collected at 20 and 25°C. When incubated at 5, 10 or 30°C, only a few cankers released a small number of ascospores and only during the later stages of incubation. However, the rate of formation of perithecia was not affected by the incubation temperature. The number of airborne ascospores was monitored using a volumetric spore trap in a chestnut orchard during 1996 and 1997. In both years, the number of ascospores trapped daily varied greatly, but in general it increased sharply from March onwards, reached a peak in May, and then declined steeply. There was a significant correlation between daily counts of ascospores and air temperature. Time-series transfer function (TF) analysis showed a positive association of the daily number of ascospores with increasing temperature, rain events and wet/humid conditions. In general, values predicted by the TF model agreed well with the observed pattern. However, a multiple regression equation based on TF analysis failed to provide a satisfactory prediction of the daily number of ascospores.     

Resistance management in Europe: a preliminary proposal for the determination of a minimum number of active substances necessary to manage resistance

The evolution of resistance to plant protection products (PPPs) is an increasing management challenge that relates to both an increasing number of species and a limited number of active substances. The number of available active substances (a.s.) has decreased considerably over the past two decades, increasing the gravity of the resistance problem. Managing the threat of resistance is based on a reasoned choice of a.s., their sequence and combination. No quantitative information is available on how many different PPPs are needed for a sustainable control system of a given pest. This paper provides a first expert judgement‐based attempt at estimating the number of different a.s. necessary for sustainable control of a pest in which the evolution of resistance is prevented.     

Synopsis on the taxonomy of the genus xanthomonas

ABSTRACT The genus Xanthomonas exhibits a high phytopathogenic diversity in contrast to a phenotypic uniformity, which has hampered the genesis of a stable classification for a long time. In past decades, a large number of Xanthomonas strains have been characterized by a variety of phenotypic and genotypic methods in a multitude of studies. Extensive DNA hybridization studies and repetitive sequence-based polymerase chain reaction and amplified fragment length polymorphism genomic fingerprinting have clearly revealed the genomic diversity and relationships within the genus. A review of the current classification of the genus Xanthomonas based on the synopsis of these studies is given here.     

Pseudodelphis limnicola sp. n. (Dracunculoidea: Guyanemidae) from the heart of Percichthys trucha (Perciformes: Percichthyidae) in Patagonian Andean Lakes (Argentina)

During a survey of parasites of Percichthys trucha (Cuvier et Valenciennes) (Perciformes: Percichthyidae) in northwestern Patagonian lakes, a new dracunculoid of the family Guyanemidae was found parasitizing as adults the heart of the fish. This species belongs to the genus Pseudodelphis Adamson et Roth, 1990 by having deirids, glandular multinucleate oesophagus and anterior branch of the uterus, and by lacking caudal alae and a gubernaculum. Pseudodelphis limnicola sp. n. differs from Pseudodelphis oligocotti Adamson et Roth, 1990 by the number and distribution of the cephalic papillae, a muscular oesophagus submerged into the glandular portion and by lacking a peribuccal ring. This is the first record of a guyanemid inhabiting the heart of a Neotropical perciform fish.     

RAPD Characterization of Single Females of the Root-knot Nematodes, Meloidogyne Spp.

Random amplified polymorphic DNA fingerprinting was performed on single females of root-knot nematodes, Meloidogyne spp., using a new procedure for DNA isolation. One-fourth of the total DNA amount isolated from a single female proved to be sufficient as a template in a polymerase chain reaction. Electrophoretic patterns of the amplified fragments were reproducible between replicates from a single female or sister females from the same progeny, and identical to those obtained with genomic DNA purified from a large number of nematodes. Moreover, a comparative analysis over three successive generations showed stability of the amplification patterns, thus demonstrating the utility of this procedure for epidemiological and ecological studies on root-knot nematodes.     

以树木年轮宽度资料重建湟水河过去248年来6-7月份河流径流量

基于树轮宽度指标,精确重建了黄河上游一级支流湟水河过去248年来6-7月份河流径流量,发现湟水河6-7月份径流量有明显的枯水期和丰水期的变化。重建结果与历史记载的相对旱涝时期比较吻合,证明了重建结果的可靠性。其中枯水期为:1753-1766年、1785-1802年、1815-1832年、1861-1887年、1918-1941年、1963-1978年、1993-1998年;丰水期为:1767-1784年、1803-1814年、1834-1860年、1891-1916年、1944-1961年、1979-1992年。周期分析表明,湟水河过去近250年6-7月份径流量有明显的2.00a、2.29a、2.31a、2.33a、2.35a、34.29a、40.00a和48.00a的变化周期。     

The Assessment of Economic Losses due to Late Blight of Potato1

The development of a method which reliably estimates the loss for any given level of disease is a prerequisite to the development of a rational disease control program. Such a method was developed between 1953-1970 using results from field experiments; it led to a multiple regression equation in which the yield loss is the dependent variable. The decrease in marketable tubers because of their reduced size was also considered. The method of estimating yield loss due to late blight is currently being used in conjunction with a disease simulator.     

AnthracnoseTracer: A Spatiotemporal Model for Simulating the Spread of Anthracnose in a Lupin Field

ABSTRACT A spatiotemporal model has been developed to simulate the spread of anthracnose, initiated by infected seed, in a lupin field. The model quantifies the loss of healthy growing points of lupin in all 1-m(2) subunits of a field throughout a growing season. The development of growing points is modeled as a function of temperature using a 1-day time step, and disease-induced compensatory growth is accounted for. Dispersal of spores is simulated explicitly using Monte Carlo techniques. Spread of spores occurs during rainfall events on a 1-h time step. The distance traveled by spores is partially dependent on wind speed and is generated by adding the values selected from half-Cauchy distributions. The direction of travel of the spores is influenced by wind direction. The model has been employed to produce a theoretical assessment of damage from disease in two environments at five levels of seed infection. It was calculated that in a susceptible lupin cultivar with a 0.01% initial seed infection, anthracnose would cause approximately 15% loss of healthy growing points in a high rainfall environment in Western Australia. In a low rainfall environment, similar damage would be unlikely even with a much higher (1%) level of seed infection.     

忍冬科的系统发育核糖体DNA ITS区序列证据

以败酱草科Valerianaceae的Centranthu rubber为外类群,使用Phylip 3.65软件对忍冬科Caprifoliaceae 12个属12个代表种的ITS区序列进行了系统发育分析.采用最大简约法分析获得了5个最简约树,步长为580,一致性指数(CI)和维持性指数(RI)值分别为0.783 2和0.741 5.利用5个最简约树获取严格一致树.结果表明:①荚蒾属Viburnum与接骨木属Sambucus是姐妹群,自展支持率100%;并与忍冬科内七子花属Heptacodium、锦带花属Weigela构成姐妹群,虽然自展支持率为60%,从遗传距离上可看出荚蒾属与忍冬科内其他属之间仍有较近的亲缘关系,所以支持荚蒾属和接骨木属置于忍冬科内.②忍冬属Lonicera与鬼吹萧属Leycesteria聚成一小支,并构成姐妹群,自展支持率为100%;并与毛核木属Symphoricarpos、莛子镳属Triosteum构成姐妹群,自展支持率为100%,故不支持将毛核木属置于北极花族内Linnaceae;北极花属Linnaea、六道木属Abelia、猬实属Kolkwitzia、双盾木属Dipelta聚成姐妹群,自展支持率为100%,说明四者亲缘关系较近,仍置于北极花族内.     

Evaluation of permethrin for the protection of cattle against mosquitoes (diptera: Culicidae), applied as electrostatic and low pressure sprays

Permethrin was tested for the protection of cattle against field populations of mosquitoes. Permethrin (500 ml of a permethrin 4·0 g liter^?1 aqueous emulsion) applied with a ‘Dual-Cloud’ electrostatic sprayer was effective in providing coverage of the cattle body surface of a group of four animals; 100 ml of a permethrin 5·0 g liter^?1 aqueous emulsion applied with a ‘Dual-Cloud'’ electrostatic sprayer as a total body spray to a yearling heifer provided 70% or better protection from field populations of mosquitoes for at least 72 h; 500 ml of a permethrin 1·0 g liter^?1 aqueous emulsion applied as a low-pressure spray to the body of a yearling heifer provided 70% or better protection from mosquitoes for at least 140 h. Permethrin applied as a total body-spray thus provides adequate protection to cattle from field populations of mosquitoes.     

Relation between Soil Health, Wave-like Fluctuations in Microbial Populations, and Soil-borne Plant Disease Management

A healthy soil is often defined as a stable soil system with high levels of biological diversity and activity, internal nutrient cycling, and resilience to disturbance. This implies that microbial fluctuations after a disturbance would dampen more quickly in a healthy than in a chronically damaged and biologically impoverished soil. Soil could be disturbed by various processes, for example addition of a nutrient source, tillage, or drying-rewetting. As a result of any disturbance, the numbers of heterotrophic bacteria and of individual species start to oscillate, both in time and space. The oscillations appear as moving waves along the path of a moving nutrient source such as a root tip. The phase and period for different trophic groups and species of bacteria may be shifted indicating that succession occurs. DGGE, Biolog and FAME analysis of subsequent populations in oscillation have confirmed that there is a cyclic succession in microbial communities. Microbial diversity oscillates in opposite direction from oscillations in microbial populations. In a healthy soil, the amplitudes of these oscillations will be small, but the background levels of microbial diversity and activity are high, so that soil-borne diseases will face more competitors and antagonists. However, soil-borne pathogens and antagonists alike will fluctuate in time and space as a result of growing plant roots and other disturbances, and the periods and phases of the oscillations may vary. As a consequence, biological control by members of a single trophic group or species may never be complete, as pathogens will encounter varying populations of the biocontrol agent on the root surface. A mixture of different trophic groups may provide more complete biological control because peaks of different trophic groups occur at subsequent locations along a root. Alternatively, regular addition of soil organic matter may increase background levels of microbial activity, increase nutrient cycling, lower the concentrations of easily available nutrient sources, increase microbial diversity, and enhance natural disease suppression.     

A rapid quantitative bioassay for the determination of biologically available bromacil in soils

A simple rapid bioassay is described for the determination of biologically available bromacil residues in soils. A clear aqueous extract was made from a soil fortified with a known amount of the herbicide, and similar extracts were made from samples of soil taken from plots that had been sprayed with a bromacil formulation at a rate of 4 kg ha⁻¹. Samples of these extracts were added to a suspension of the unicellular green alga Selenastrum capricornutum. The net photosynthetic oxygen production by the alga was then measured using an oxygen electrode. The results were expressed as a percentage of the oxygen production by a control suspension. The concentration of biologically available bromacil was determined by reference to a previously established dose-response curve of the percentage reduction in oxygen production against bromacil concentration. The accuracy of this bioassay was determined by comparing the results with those obtained using capillary gas-liquid chromatography. The results obtained by the two different methods showed good agreement.