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1.
Yield reduction of pea (Pisum sativum) due to various types of infections by Mycosphaerella pinodes on pods was assessed. A range of disease severities was created on pods of pea plants grown in the glasshouse, by painting the pods with different concentrations of spore suspensions, at three different pod development stages: lag phase, the beginning of seed filling (BSF) and mid-filling of the seeds. Seed number at harvest was reduced only if the pods were infected before BSF, as shown previously for whole plant infections. Pod infections led to individual seed weight (ISW) losses from zero (for late infections, at mid-filling) to 20% (for earlier infections and severe disease). Infection during the lag phase affected ISW by reducing seed growth rate, whereas infection at BSF tended to reduce the duration of seed filling. There was a linear relationship between the area under the disease progress curve and the percentage decrease in ISW. This model should be complemented by the effect of leaves and stem infections, in order to predict ISW losses in diseased crop conditions, in which epidemics occur on all aerial parts of the pea plant.  相似文献   

2.
马树庆  王琪  罗新兰 《生态学报》2008,28(5):2131-2131~2139
利用在东北地区中部开展玉米(Zea mays)分期播种试验资料,分析气候变化对玉米出苗速度、生长发育速度、灌浆过程、植株干物质积累和产量的影响,进而分析未来气候变化对东北地区玉米生产的影响及适应性对策.结果表明,气候变化对玉米生长发育和产量的影响十分明显,在水分基本适宜的条件下,东北地区气候变暖导致玉米生长季气温升高、积温增加,使玉米生长发育和灌浆速度加快,生物量增加,从而提高单产.但气候变暖的同时,气候变干会限制热量资源的利用,将缩短玉米灌浆时间,降低灌浆速率,使千粒重下降,从而造成明显减产,而且减产幅度明显大于温度升高的增产幅度.在水分条件基本得到满足的条件下,未来夏半年气候变暖对东北地区玉米生产是有利的,偏晚熟玉米品种比例可以适当扩大,东北玉米带可以向北部和东部扩展,单产和总产都会增加;但如果水分得不到满足,气候的暖干化趋势会使东北地区的中、西部玉米主产区的农业干旱变得更加严重且频繁,造成产量下降和不稳定,给玉米生产带来严重威胁,因而更应加强农业干旱的综合防御工作.  相似文献   

3.
Fallopia japonica, commonly known as Japanese knotweed, is an increasingly serious invasive alien weed in the UK and large parts of mainland Europe, as well as in North America. There is an urgent need to include classical biological control (CBC) into any integrated pest management strategy. The leaf-spot pathogen Mycosphaerella polygoni-cuspidati, a coevolved natural enemy of F. japonica present throughout its native Japanese range, is considered to have high potential as a CBC agent. In this study, the disease development of M. polygoni-cuspidati in the field and the optimum infection parameters under controlled conditions were investigated to elucidate the pathogen’s potential biocontrol efficacy against Japanese knotweed. Field observation in Japan showed that M. polygoni-cuspidati caused severe damage to its host plant. When sentinel knotweed plants from the UK were placed amongst naturally-infected field populations of F. japonica, disease incidence and severity were highest in July when monthly precipitation was also highest. In greenhouse inoculation tests, F. japonica was shown to be most susceptible at the young leaf stage (7–12 days after opening). Disease severity was highest after an initial dew period of 42–48 h, and severe defoliation followed inoculation at a temperature range of 15–25 °C. The optimum post-inoculation temperature after dew treatment for disease severity was 20–25 °C. In field inoculation tests, high disease incidence and severity indicate that the pathogen has the potential to control the plant effectively in the field. Humidity and temperature were shown to be the main factors influencing disease expression and lesion development of M. polygoni-cuspidati in a field situation. These results provide valuable information for any future use of M. polygoni-cuspidati as a CBC agent for management of Japanese knotweed in the UK.  相似文献   

4.
Light leaf spot (Pyrenopeziza brassicae) was assessed as % plants with light leaf spot, % leaves with light leaf spot or % leaf area with light leaf spot in winter oilseed rape field experiments done at different sites (Rothamsted, Hertfordshire; Boxworth, Cambridgeshire; near Aberdeen, Scotland), with different cultivars (e.g. Bristol and Capitol), different fungicide treatments, on plants sampled at different dates. Regression analyses on data from these experiments showed that there were consistently good relationships between % leaves with light leaf spot and % plants with light leaf spot for plants sampled during the autumn and winter, until the % plants with light leaf spot approached 100%. The slopes and positions of regression lines were sometimes affected by cultivar, fungicide treatment or sampling date, but not by site. The relationship between % leaf area with light leaf spot (square root-transformed) and % leaves with light leaf spot was less consistent than that between % leaves with light leaf spot and % plants with light leaf spot and was sometimes affected by cultivar, fungicide treatment or sampling date but not by site. The relationship between % leaf area with light leaf spot (square root-transformed) and % plants with light leaf spot was also inconsistent and was sometimes affected by cultivar, fungicide treatment, sampling date and site.  相似文献   

5.
A program for simulating the patterns of egg-laying by populations of the cabbage root fly was used to model the effects of global warming on future cabbage root fly attacks. An increase of 3°C in mean daily temperature would cause the cabbage root fly to become active about a month earlier in the year than at present. Under such conditions, the emergence of flies from the overwintering population would be less synchronised, as the completion of diapause and post-diapause development would occur at the same time in different individuals within the population. However, there would continue to be only three generations of fly each year, even in the south of England. With temperature increases of 5°C or 10°C, the fly would complete four generations each year and aestivation would seriously disrupt egg-laying. These rises in temperature would have a major impact on cabbage root fly activity and would require new strategies for controlling this pest.  相似文献   

6.
Recently, single nucleotide polymorphisms (SNPs) located in specific loci or genes have been identified associated with susceptibility to colorectal cancer (CRC) in Genome-Wide Association Studies (GWAS). However, in different ethnicities and regions, the genetic variations and the environmental factors can widely vary. Therefore, here we propose a post-GWAS analysis method to investigate the CRC susceptibility SNPs in Taiwan by conducting a replication analysis and bioinformatics analysis. One hundred and forty-four significant SNPs from published GWAS results were collected by a literature survey, and two hundred and eighteen CRC samples and 385 normal samples were collected for post-GWAS analysis. Finally, twenty-six significant SNPs were identified and reported as associated with susceptibility to colorectal cancer, other cancers, obesity, and celiac disease in a previous GWAS study. Functional analysis results of 26 SNPs indicate that most biological processes identified are involved in regulating immune responses and apoptosis. In addition, an efficient prediction model was constructed by applying Jackknife feature selection and ANOVA testing. As compared to another risk prediction model of CRC for European Caucasians population, which performs 0.616 of AUC by using 54 SNPs, the proposed model shows good performance in predicting CRC risk within the Taiwanese population, i.e., 0.724 AUC by using 16 SNPs. We believe that the proposed risk prediction model is highly promising for predicting CRC risk within the Taiwanese population. In addition, the functional analysis results could be helpful to explore the potential associated regulatory mechanisms that may be involved in CRC development.  相似文献   

7.
Northeast China (NEC) accounts for about 30% of the nation's maize production in China. In the past three decades, maize yields in NEC have increased under changes in climate, cultivar selection and crop management. It is important to investigate the contribution of these changing factors to the historical yield increases to improve our understanding of how we can ensure increased yields in the future. In this study, we use phenology observations at six sites from 1981 to 2007 to detect trends in sowing dates and length of maize growing period, and then combine these observations with in situ temperature data to determine the trends of thermal time in the maize growing period, as a measure of changes in maize cultivars. The area in the vicinity of these six sites accounts for 30% of NEC's total maize production. The agricultural production systems simulator, APSIM‐Maize model, was used to separate the impacts of changes in climate, sowing dates and thermal time requirements on maize phenology and yields. In NEC, sowing dates trended earlier in four of six sites and maturity dates trended later by 4–21 days. Therefore, the period from sowing to maturity ranged from 2 to 38 days longer in 2007 than it was in 1981. Our results indicate that climate trends alone would have led to a negative impact on maize. However, results from the adaptation assessments indicate that earlier sowing dates increased yields by up to 4%, and adoption of longer season cultivars caused a substantial increase in yield ranging from 13% to 38% over the past 27 years. Therefore, earlier sowing dates and introduction of cultivars with higher thermal time requirements in NEC have overcome the negative effects of climate change and turned what would have otherwise been a loss into a significant increase in maize yield.  相似文献   

8.
Ascospores of Pyrenopeziza brassicae were produced in apothecia (cup‐shaped ascomata) on oilseed rape debris. The conidia, which were morphologically identical to the ascospores, were produced in acervular conidiomata was greater than for lesions caused by ascospores. In June 2000, on the ground under a crop with light on the surface of living oilseed rape tissues. Ascospores were more infective than conidia on oilseed rape leaves. The proportion of lesions caused by conidia located on leaf veins leaf spot, numbers of petioles with apothecia decreased with increasing distance into the crop from the edge of pathways. Air‐borne ascospores of P. brassicae were first collected above debris of oilseed rape affected with light leaf spot on 5 October 1998 and 18 September 1999,12 or 23 days, respectively, after the debris had been exposed outdoors. P. brassicae conidia were first observed on leaves of winter oilseed rape on 6 January 1999 and 15 February 2000, respectively, after plots had been inoculated with debris in November 1998 and October 1999. In 1991/92, numbers of ascospores above a naturally infected crop were small from January to April and increased in June and July. P. brassicae conidia were first observed in February and the percentage plants with leaves, stems or pods with light leaf spot increased greatly in May and June. In 1992/93, in a crop inoculated with debris, numbers of airborne ascospores were small from October to January and increased from April to June. P. brassicae conidia were first observed on leaves in late November and light leaf spot was seen on stems and pods in March and June 1993, respectively.  相似文献   

9.
Intense fishing pressure and climate change are major threats to the fish population and coastal fisheries. Larimichthys crocea (large yellow croaker) is a long‐lived fish, which performs seasonal migrations from its spawning and nursery grounds along the coast of the East China Sea (ECS) to overwintering grounds offshore. This study used length‐based analysis and habitat suitability index (HSI) model to evaluate the current life‐history parameters and overwintering habitat suitability of L. crocea, respectively. We compared recent (2019) and historical (1971–1982) life‐history parameters and overwintering HSI to analyze the fishing pressure and climate change effects on the overall population and overwintering phase of L. crocea. The length‐based analysis indicated serious overfishing of L. crocea, characterized by reduced catch, size truncation, constrained distribution, and advanced maturation causing a recruitment bottleneck. The overwintering HSI modeling results indicated that climate change has led to decreased sea surface temperature during L. crocea overwintering phase over the last half‐century, which in turn led to area decrease and an offshore‐oriented shifting of optimal overwintering habitat of L. crocea. The fishing‐caused size truncation may have constrained the migratory ability, and distribution of L. crocea subsequently led to the mismatch of the optimal overwintering habitat against climate change background, namely habitat bottleneck. Hence, while heavy fishing was the major cause of L. crocea collapse, climate‐induced overwintering habitat suitability may have intensified the fishery collapse of L. crocea population. It is important for management to consider both overfishing and climate change issues when developing stock enhancement activities and policy regulations, particularly for migratory long‐lived fish that share a similar life history to L. crocea. Combined with China''s current restocking and stock enhancement initiatives, we propose recommendations for the future restocking of L. crocea in China.  相似文献   

10.

Background and Aims

Environmental change is increasingly impacting ecosystems worldwide. However, our knowledge about the interacting effects of various drivers of global change on sexual reproduction of plants, one of their key mechanisms to cope with change, is limited. This study examines populations of poorly regenerating and threatened common juniper (Juniperus communis) to determine the influence of four drivers of global change (rising temperatures, nitrogen deposition, potentially acidifying deposition and altering precipitation patterns) on two key developmental phases during sexual reproduction, gametogenesis and fertilization (seed phase two, SP2) and embryo development (seed phase three, SP3), and on the ripening time of seeds.

Methods

In 42 populations throughout the distribution range of common juniper in Europe, 11 943 seeds of two developmental phases were sampled. Seed viability was determined using seed dissection and related to accumulated temperature (expressed as growing degree-days), nitrogen and potentially acidifying deposition (nitrogen plus sulfur), and precipitation data.

Key Results

Precipitation had no influence on the viability of the seeds or on the ripening time. Increasing temperatures had a negative impact on the viability of SP2 and SP3 seeds and decreased the ripening time. Potentially acidifying depositions negatively influenced SP3 seed viability, while enhanced nitrogen deposition led to lower ripening times.

Conclusions

Higher temperatures and atmospheric deposition affected SP3 seeds more than SP2 seeds. However, this is possibly a delayed effect as juniper seeds develop practically independently, due to the absence of vascular communication with the parent plant from shortly after fertilization. It is proposed that the failure of natural regeneration in many European juniper populations might be attributed to climate warming as well as enhanced atmospheric deposition of nitrogen and sulfur.  相似文献   

11.
Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae), known as common cutworm, is a worldwide pest that causes severe damage to various crops and vegetables in South Korea. In this study, we predicted the potential distribution of S. litura in South Korea in a climate change scenario by applying species distribution modeling. We used the CLIMEX software as a main tool and determined optimal parameter values to simulate the current distribution of S. litura in Asia. We then used these parameter values to predict the species' future distribution in South Korea. As a result, we prepared maps indicating areas with suitable climate for S. litura and showed that these areas gradually increased as a result of climate change. Approximately 98% of the areas in South Korea were predicted to have a favorable climate for S. litura in 2100; 63.2% of the area in South Korea is currently favorable. To the best of our knowledge, this is the first study to predict the potential distribution of S. litura in South Korea, and it provides the basic data necessary to establish an optimal control strategy of this species.  相似文献   

12.

Background and Aims

Seed yield and dormancy status are key components of species fitness that are influenced by the maternal environment, in particular temperature. Responses to environmental conditions can differ between ecotypes of the same species. Therefore, to investigate the effect of maternal environment on seed production, this study compared two contrasting Arabidopsis thaliana ecotypes, Cape Verdi Isle (Cvi) and Burren (Bur). Cvi is adapted to a hot dry climate and Bur to a cool damp climate, and they exhibit winter and summer annual phenotypes, respectively.

Methods

Bur and Cvi plants were grown in reciprocal controlled environments that simulated their native environments. Reproductive development, seed production and subsequent germination behaviour were investigated. Measurements included: pollen viability, the development of floral structure, and germination at 10 and 25 °C in the light to determine dormancy status. Floral development was further investigated by applying gibberellins (GAs) to alter the pistil:stamen ratio.

Key Results

Temperature during seed development determined seed dormancy status. In addition, seed yield was greatly reduced by higher temperature, especially in Bur (>90 %) compared with Cvi (approx. 50 %). The reproductive organs (i.e. stamens) of Bur plants were very sensitive to high temperature during early flowering. Viability of pollen was unaffected, but limited filament extension relative to that of the pistils resulted in failure to pollinate. Thus GA applied to flowers to enhance filament extension largely overcame the effect of high temperature on yield.

Conclusions

High temperature in the maternal environment reduced dormancy and negatively affected the final seed yield of both ecotypes; however, the extent of these responses differed, demonstrating natural variation. Reduced seed yield in Bur resulted from altered floral development not reduced pollen viability. Future higher temperatures will impact on seed performance, but the consequences may differ significantly between ecotypes of the same species.  相似文献   

13.
To predict the response of aquatic ecosystems to future global climate change, data on the ecology and distribution of keystone groups in freshwater ecosystems are needed. In contrast to mid‐ and high‐latitude zones, such data are scarce across tropical South America (Neotropics). We present the distribution and diversity of chironomid species using surface sediments of 59 lakes from the Andes to the Amazon (0.1–17°S and 64–78°W) within the Neotropics. We assess the spatial variation in community assemblages and identify the key variables influencing the distributional patterns. The relationships between environmental variables (pH, conductivity, depth, and sediment organic content), climatic data, and chironomid assemblages were assessed using multivariate statistics (detrended correspondence analysis and canonical correspondence analysis). Climatic parameters (temperature and precipitation) were most significant in describing the variance in chironomid assemblages. Temperature and precipitation are both predicted to change under future climate change scenarios in the tropical Andes. Our findings suggest taxa of Orthocladiinae, which show a preference to cold high‐elevation oligotrophic lakes, will likely see range contraction under future anthropogenic‐induced climate change. Taxa abundant in areas of high precipitation, such as Micropsectra and Phaenopsectra, will likely become restricted to the inner tropical Andes, as the outer tropical Andes become drier. The sensitivity of chironomids to climate parameters makes them important bio‐indicators of regional climate change in the Neotropics. Furthermore, the distribution of chironomid taxa presented here is a vital first step toward providing urgently needed autecological data for interpreting fossil chironomid records of past ecological and climate change from the tropical Andes.  相似文献   

14.
1. The long‐term suitability of Bassenthwaite Lake as a habitat for vendace (Coregonus albula) was assessed using two models. The first was the phytoplankton model (PROTECH) that provided temperature and phytoplankton biomass outputs that were used to drive a second model of lake oxygen (LOX). 2. Both temperature and oxygen concentrations were used to define the available habitat for the adult vendace, using 18 °C as an upper and 2 mg L?1 as a lower threshold, respectively. The outputs of both models were compared with 4 years of observed data for the purposes of validation and produced good simulations of water temperature, total chlorophyll a and oxygen concentrations in the epilimnion, hypolimnion and at the lake bottom. 3. Using the outputs of a regional climate model (RCM) simulating 20 years of both present and future climate conditions for this part of the United Kingdom, both models were re‐run. These data suggest the future climate will cause a mean increase of >2 °C in water temperature, little change in overall phytoplankton biomass and a 10% decline in oxygen concentration. 4. Using the thresholds defined above, the habitat volume will decline greatly under the future climate scenarios, with all of the 20 years simulated having periods of zero habitat volume for >7 consecutive days, primarily caused by high temperature. These results suggest that the long‐term viability of the lake as a habitat for this rare fish is extremely low.  相似文献   

15.
基于单类别支持向量机方法的物种分布模型, 利用政府间气候变化专门委员会(IPCC)气候情景模式和联合国粮食与农业组织(FAO)的全球土壤数据, 模拟1981-2099年我国毛竹(Phyllostachys edulis)的潜在空间分布及变化趋势, 比较考虑土壤因子前后模拟结果的差异, 旨在探究土壤因子对毛竹潜在空间分布模拟结果的影响。结果表明, 仅以气候因子为模拟变量和同时考虑气候与土壤因子为模拟变量的毛竹潜在空间分布模拟均具有较高精度, 毛竹潜在分布区表现为面积增加并向北扩张。模拟因子重要性分析表明表征温暖程度的气候因子在毛竹潜在分布模拟中起主导作用, 而表征土壤质地和酸碱性的土壤因子以限制性作用为主。同时考虑气候与土壤因子的模拟结果具有较高的模拟效率, 且在未来气候变化情景模式下毛竹潜在分布区面积增幅与向北迁移幅度均小于仅使用气候因子的模拟, 表明土壤要素对毛竹潜在分布具有明显的限制作用, 该结果对现在的毛竹潜在分布模拟研究具有重要的补充作用。  相似文献   

16.
1. Warming trends are evident in many parts of the globe but are especially marked at higher latitudes, with complex effects on the biota that include direct effects on growth potential and indirect effects through food webs. 2. Air temperatures have been increasing over the past 50 years in southwestern Alaska, affecting the growth and population dynamics of many organisms, including a variety of aquatic species such as the freshwater mussel Anodonta beringiana. 3. We collected freshwater mussels from Iliamna Lake, in the Bristol Bay region of Alaska, and measured their shells to examine climatic effects on growth patterns. 4. Linear mixed effects models and ordinary least square linear regressions revealed strong positive correlations between local air temperatures (especially in May, October and the summer months) and inter‐annual variation in mussel growth. Slower mussel growth was also significantly correlated with later date of ice break‐up, which was linked to air temperatures in late spring.  相似文献   

17.
Sex-biased mortality in response to environmental adversity during early development occurs in a number of bird species. The three most prominent theories proposed to explain sex-biased mortality in response to early-life adversity are that (1) the heterogametic sex (e.g. females in birds), (2) the larger sex (could be male or female depending on species) or (3) the sex with the more costly and complex endocrine system (e.g. males producing higher levels of testosterone) will suffer higher mortality compared with the other sex when exposed to challenging conditions (e.g. suboptimal weather during early development). We tested for sex-specific differences in the effects of very hot weather on nestling body mass and tarsus length, and survival of fledglings to nutritional independence in the Southern Pied Babbler Turdoides bicolor. The effect of exposure to high air temperatures did not differ by sex but had a consistently negative impact on nestling body mass, nestling tarsus length and fledgling survival, raising concerns about population replacement and the persistence of this species under rapidly advancing climate change.  相似文献   

18.
A variety of targets for therapeutic intervention are based upon advances in understanding of the immunopathogenesis of Crohn's disease. Crohn's disease is initiated by an innate immune response, which eventuates in a T-cell driven process, characterized by a T-helper cell 1 type cytokine profile. Several new treatments now focus on suppressing T-cell differentiation or T-cell inflammation. Since inflammatory bowel disease (IBD) represents a state of dysregulated inflammation, drugs that augment the anti-inflammatory response have the potential to downregulate inflammation and thereby hopefully modify the disease. Tumour necrosis factor (TNF) is a major target of research and clinical investigation. TNF has proinflammatory effects in the intestinal mucosa and is a pivotal cytokine in the inflammatory cascade. Certolizumab pegol (CDP870) is a PEGylated, Fab' fragment of a humanized anti-TNF-alpha monoclonal antibody. PEGylation increases the half-life, reduces the requirement for frequent dosing, and possibly reduces antigenicity as well. Certolizumab has been shown in Phase III trials to achieve and maintain clinical response and remission in Crohn's disease patients. It improves the quality of life. Certolizumab pegol will be indicated for moderately to severely active Crohn's disease, but it is not yet licensed in Europe or the US. It is not possible to construct an algorithm for treatment, but when compared with infliximab the two principal advantages are likely to be lower immunogenicity (as shown by anti-drug antibodies, absence of infusion reactions, and low rate of antinuclear antibodies), and a subcutaneous route of administration. These two factors may be sufficient to promote it up the pecking order of anti-TNF agents.  相似文献   

19.
清香木(Pistacia weinmannifolia)是中国西南干旱河谷植被的特征种。本文利用野外调查的165个清香木分布点信息以及22个环境变量数据, 基于最大熵(Maxent)算法构建清香木分布的适宜生境预测模型, 并据此模拟清香木在我国西南地区的适宜分布区, 以及历史和未来不同气候情景下的分布格局变化。结果表明: 清香木生境预测的Maxent模型准确性非常高(AUC = 0.974), 温度季节性变化、极端低温和降水量是限制其分布的主要气候因子。清香木当前的潜在分布区集中在我国西南干旱河谷区, 其适宜生境的气候特征是降水少、温度季节性变化小且无极端低温。对清香木在末次间冰期和末次冰盛期分布的模拟结果表明, 其分布区范围均以诸大江河的河谷为中心, 随气候变化在我国西南地区主要呈现先向东扩张, 然后向西退缩的趋势, 并印证了“冰期走出横断山(glacial out-of-Hengduan Mts.)”的观点。在未来(2061-2080年) 3种典型浓度路径(representative concentration pathway, RCP)的气候情景下, 清香木在我国西南地区的分布都向东扩张, 主要分布在云贵高原与四川盆地结合地带的河谷, 以及云贵高原与广西西部交界地带的河谷中, 这也反映了这些地区河谷地段干旱化的可能, 而当前的潜在分布区趋于消失; 清香木的潜在适宜分布面积在中低浓度路径情景下均将减少约33%, 而在高浓度路径情景下有所增加。  相似文献   

20.
DNA sequences of the mitochondrial control region were analysed from 298 individual sharp-shinned hawks (Accipiter striatus velox) sampled at 12 different migration study sites across North America. The control region proved to be an appropriate genetic marker for identification of continental-scale population genetic structure and for determining the historical demography of population units. These data suggest that sharp-shinned hawks sampled at migration sites in North America are divided into distinct eastern and western groups. The eastern group appears to have recently expanded in response to the retreat of glacial ice at the end of the last glacial maximum. The western group appears to have been strongly effected by the Holocene Hypsithermal dry period, with molecular evidence indicating the most recent expansion following this mid-Holocene climatic event 7000-5000 years before present.  相似文献   

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