Utility of defeated resistance genes to powdery mildew,Erysiphe graminis f. sp. hordei,in spring barley variety mixtures

In 1980 and 1981 experiments have been performed to study the utility of defeated resistance genes to powdery mildew in spring barley variety mixtures. For this purpose the epidemic development of powdery mildew in pure stands and mixtures of four spring barley varieties was monitored. In three varieties the resistance was overcome several years ago. One variety is still resistant. Changes in frequencies of corresponding virulence genes were also studied.It was found that the variety mixtures slowed down the mildew epidemic only at the beginning of the season. Some reduction was lost later on since the pure stands reached their saturation level of infection at an earlier date than the more healthy mixtures. The level of reduction of infection depended on the composition of the mixtures and the number of components. Two-way mixtures appeared to be very risky due to the high frequency of corresponding combinations of virulence genes in the pathogen. Furthermore, two-way mixtures appeared to be unable to reduce the infection rate sufficiently when the infection pressure was high.In 1981 the frequencies of combinations of corresponding virulence genes increased very much in the Diva-Mazurka mixture but declined in the pure stands of both varieties.On the basis of these results it is concluded that the utility of defeated resistance genes involved in this study is very limited.The low number and the irregular distribution of the Dutch spring barley varieties over the different resistance groups prohibit the use of variety mixtures in the Netherlands.Samenvatting In 1980 en 1981 is onderzoek verricht over de bruikbaarheid van doorbroken resistentiegenen tegen meeldauw,Erysiphe graminis f. sp.hordei, in zomergerstrassenmengsels. Daartoe werd de epidemieontwikkeling in monocultures en mengsels van vier zomergerstrassen bestudeerd. Van drie rassen is de resistentie reeds verscheidene jaren doorbroken. Eén ras is nog resistent. De frequenties van compatibele meeldauwvirulentiegenen werden eveneens bepaald.Het bleek dat in vergelijking met de monocultures in de rassenmengsels de meeldauwepidemie alleen in het begin van het seizoen werd afgeremd. Later in het seizoen ging weer enige reductie in aantasting van de mengsels verloren doordat in de monocultures de aantasting eerder het verzadigingspunt bereikte dan in de minder aangetaste mengsels. De mate waarin de aantasting gereduceerd werd was afhankelijk van de aard en het aantal componenten in het mengsel. Twee-componentenmengsels bleken vrij riskant te zijn vanwege de aanwezigheid van combinaties van corresponderende virulentiegenen in de meeldauwpopulatie. Verder bleken tweecomponentenmengsels niet in staat de infectiesnelheid afdoende af te remmen wanneer de infectiedruk hoog werd.De frequentie van combinaties van corresponderende virulentiegenen nam sterk toe in het Diva-Mazurka-mengsel doch nam af in de monocultures van deze beide rassen.Gezien de verkregen resultaten lijkt de bruikbaarheid van de in dit onderzoek betrokken doorbroken resistentiegenen erg beperkt. Het geringe aantal zomergerstrassen op de rassenlijst en de ongelijke verdeling over de te onderscheiden resistentiegroepen belemmeren de toepassing van rassenmengsels in de Nederlandse akkerbouw.     

Climatic factors associated with the infection of herds of cattle with bluetongue viruses

The incidence of bluetongue virus infection of 15 cattle herds in Queensland, Australia, was determined by a serum neutralization test. The maximum temperature (°C), minimum temperature (°C) and rainfall (mm) data were obtained from the meteorological recording stations closest to each herd. Using unweighted least-squares regression analysis, the best statistical model explaining the most variability in the herd incidence rate included the ratio between the maximum and minimum temperature recorded at both 1 month and 6 months preceding seroconversion, and rainfall recorded at both 2 months and 6 months preceding seroconversion. More than 90% of the variability in the incidence of bluetongue virus infection in the herds was explained by the model, a considerable improvement on previous models that used prevalence data. The prospective nature of the study also supports a strong causal relationship between climatic factors and the occurrence of infection in cattle herds.Abbreviations SN serum neutralization - R _infa ^sup2 adjusted coefficient of multiple determination - AIC Akaike's information criterion - FPE Akaike's final prediction error - PRESS predicted sum of squares     

Influence of time of transition from night to day temperature regimes on incidence of Didymella bryoniae and influence of the disease on growth and yield of glasshouse cucumbers

The influence of transition from night to day temperature 3 h before, 1 h before, 1h after and 3 h after sunrise on the incidence ofDidymella bryoniae was studied both on inoculated and on uninoculated glasshouse-grown cucumber plants. The effect of inoculation on plant growth and fruit production was studied as well.The later the transition to day temperature took place, the longer were the periods with a high relative air humidity and of condensation of water on fruits.The time of transition had no effect on plant growth, yield, disease incidence on growing tips, number of lesions on the main stems of uninoculated plants and external fruit rot. The later the transition to day temperature took place, the more lesions on the main stem of inoculated plants appeared and the higher was the incidence of internal fruit rot.Inoculation of plants increased the number of lesions on the main stem, the disease incidence on growing tips, the production of misshapen fruits and the internal and external fruit rot. The number of secondary side shoots was incrreased but the total number of their internodes was reduced by inoculation.Inoculation caused an 18% reduction in number of internodes over a period of four weeks and a 10% reduction in number of fruits in the corresponding harvest period.The consequences of a more humid glasshouse climate and of a high infection pressure ofD. bryoniae for the grower are briefly discussed.Samenvatting De invloed van het 3 uur vóór, 1 urr vóór, 1 uur na en 3 uur na zonsopgang overgaan van de nacht-naar de dagtemperatuur op het optreden vanDidymella bryoniae werd zowel op geïnoculleerde als op niet-geïnocullerde planten van kaskomkommers onderzocht. De invloed van inoculatie op de groei van de planten en de produktie van vruchten werd eveneens nagegaan.Hoe later naar de dagtemperatuur werd overgegaan, hoe langer de perioden met een hoge relatieve luchtvochtigheid waren en hoe langer de perioden waarin condensatie van water op vruchten optrad.Het tijdstip van overgang had geen effect op de groei van de planten, de opbrengst, de aantasting van groeipunten, het aantal lesies op de hoofdstengel van niet geïnoculeerde planten en uitwendig vruchtrot. Hoe later naar de dagtemperatuur werd overgegaan, hoe meer lesies na vier weken op de hoofdstengel van geïnoculeerde planten en hoe meer vruchten met inwendig rot voorkwamen.Door inoculatie van de planten nam het aantal lesies op de hoofdstengel, de aantasting van groeipunten, de produktie van stekvruchten en het aantal vruchten met inen uitwendig rot toe. Het aantal zijscheuten van de tweede orde nam toe, maar het totaal aantal internodiën ervan nam door inoculatie af. Inoculatie reduceerde het aantal internodiën met 18% over een periode van vier weken en die van het aantal vruchten met 10% in de overeenkomstige oogstperiode. De praktische consequenties van eenSeconded to the Glashouse Crops Research and Experiment Station, Zuidweg 38, 2671 MN Naaldwijk, the Netherlands     

Intercalibrating SCOR, NORPAC and bongo nets and the consequences for interpreting decadal-scale variation in zooplankton biomass in the Gulf of Alaska

The Canadian weathership time series of zooplankton wet weight biomass, collected at Ocean Station Papa in the Gulf of Alaska from 1956 to 1981, is one of the most comprehensive of its kind in marine science. In 1966, the sampling gear changed from a white North Pacific (NORPAC) net to a black Scientific Committee on Oceanic Research (SCOR) net and it was recently discovered that insufficient intercalibration samples were collected to understand how their sampling properties differed. A Canada‐GLOBEC project to redo the intercalibration of these net types and to understand how they relate to current sampling gear (bongo net) started in 1997. Seventy replicates of the three net types were collected in deep water in the Gulf of Alaska. The major finding is that all nets have similar sampling characteristics, whereas earlier reports indicated that NORPAC biomass values should be multiplied by a factor of 1.538 to be equivalent to the SCOR net. It now appears that this factor arose because flowmeters were not used in the original 1956–81 sampling (volume filtered was estimated from tow length × mouth area). A positive bias was introduced into the SCOR values because relatively more water passed through the SCOR net (undetected without a flow meter) than through the NORPAC net. This means that the unmetered NORPAC samples from 1956 to 1966 should not be adjusted and the unmetered SCOR values should be reduced by a factor that is related to wire angle. The general effect on the entire series is to lower the average biomass estimates, but more so for the early portion of the series than the later years.     

气候要素对给排水工程的影响

论述了在给排水工程设计中 ,当地气候要素对给排水工程的影响是重大的 ,它往往是决定工程规模、造价和总体布局等的重要因素     

泉州市森林植物检疫对象及危险性病虫(疫情)调查和疫区划定的技术研究

本文对泉州市森林植物检疫对象及危险性病虫(疫情)的种类、分布、危害程度进行了全面调查;并划定了疫区和保护区,提出了疫区、保护区的管理办法。调查成果直接应用于生产,挽回直接经济损失170多万元,取得了较为显著的经济、生态和社会效益。     

基于DNDC模型的高寒草甸土壤有机碳含量动态研究

研究发现以气温升高为主导的气候变化严重影响高寒草甸土壤有机碳含量的动态变化,然而,关于气候变化和放牧对土壤有机碳的耦合效应知之甚少。本研究采用增温-放牧试验结合DNDC(denitrification-decomposition)模型,检测气候变化和放牧对青藏高原高寒草甸土壤有机碳含量的影响,并评估气候变化和放牧对土壤有机碳含量变化的贡献率。结果表明:气候变化对土壤有机碳产生负面影响;放牧强度通过增加践踏、落叶和粪便返还影响土壤有机碳含量。温度、降水结合放牧强度,解释了高寒草甸土壤有机碳含量变化的63.4%。气候变化是导致土壤有机碳波动的主要因素,该因素解释了土壤有机碳变化的61.9%。相比之下,放牧强度解释了其变化的1.6%。持续的气候变化和放牧会影响土壤有机碳的动态变化,进而影响草地生态系统的服务功能。草地生态系统管理应考虑到潜在的气候变化,以实现该系统的可持续发展。     

2013—2018年国内毛皮动物细小病毒性肠炎流行情况分析

2013—2018年,齐鲁动物保健品有限公司研究所临床检测中心接诊毛皮动物病例3 601例,经过剖检、实验室PCR检测,确诊细小病毒性肠炎案例98例,对这些病例进行了汇总分析,结果表明:毛皮动物细小病毒性肠炎一年四季均可发生,当年幼兽最易发,7月份是该病发病高峰期;通过对近6年国内细小病毒性肠炎发病率统计分析,发现毛皮动物细小病毒性肠炎发病率呈上升趋势,2018年发病率9%左右,发病兽主要是当年仔兽及青年兽,水貂、狐发病率在低位徘徊,貉发病率呈明显上升趋势。     

PEDV、TGEV、PDCoV、PRoV多重TaqMan荧光定量RT-PCR检测方法的建立及应用

为建立鉴别检测猪流行性腹泻病毒(PEDV)、猪传染性胃肠炎病毒(TGEV)、猪德尔塔冠状病毒(PDCoV)和猪轮状病毒(PRoV)的方法,本研究分别针对PEDVN基因、TGEVM基因、PDCoVM基因和PRoVVP6基因设计特异性引物和TaqMan探针,经过优化反应条件,建立了同时检测4种病毒的多重TaqMan荧光定量RT-PCR方法。结果显示,该方法仅特异性扩增PEDV、TGEV、PDCoV和PRoV,与猪其它主要病毒无交叉反应,特异性较强;对PEDV、TGEV、PDCoV和PRoV的质粒标准品的最低检出限分别为2.06×10^2拷贝/μL、2.06×10^2拷贝/μL、2.06×10^1拷贝/μL、2.06×10^3拷贝/μL,具有较高敏感性;组内与组间变异系数均小于1.1%,具有良好的重复性。应用该方法和普通多重RT-PCR检测临床采集的243份腹泻病料样品,两者的符合率为96.71%。本研究建立的方法为临床PEDV、TGEV、PDCoV、PRoV的鉴别检测及流行病学调查提供了一种快速、特异、敏感、高效的技术手段。     

猪流行性腹泻病毒RT-LAMP可视化检测方法的建立

为建立一种适用于现场快速检测的猪流行性腹泻病毒(PEDV)LAMP技术,基于羟基萘酚蓝(HNB)的可视化显色特点,根据PEDV M基因编码区序列,设计合成1套引物,通过反应物浓度和反应条件优化,建立了可闭管检测的PEDV RT-LAMP检测方法。特异性和灵敏度试验结果显示,建立的RT-LAMP检测技术快速、灵敏、特异,可于1 h内检出0.2 mL 0.1 TCID₅₀/mL的病毒RNA,与实时荧光RT-PCR检测方法灵敏度一致,与猪瘟病毒、猪伪狂犬病病毒、猪繁殖与呼吸综合征病毒、猪圆环病毒2型以及猪链球菌2型核酸不发生交叉反应。利用该方法对187份送检的粪拭子及病死猪组织样品进行应用检测,检出阳性样品9份,与荧光定量RT-PCR方法检测结果一致。试验结果表明,所建立的方法快速、特异,重复性满足要求,适用于送检样品的PEDV快速检测。