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41.
Between 2006 and 2009, seven strains of infectious bronchitis (IB) virus (IBV) were isolated from vaccinated chicken flocks on different chicken farms in China. The pathogenic characters of seven IBV strains were assessed. Each of the seven strains was infective to the test chickens and could induce an immune response. The results from chicken embryo cross-neutralization assays showed that these strains were antigenically distinct from classic IBV strains of H120, M41, Conn, and Gray. Compared to H120 vaccine strain, point mutation, short insertion, and deletion occurred at many positions in the S1 protein of the seven strains. Five of the seven strains had the motif (HRRRR), which was identical to that of the epidemic IBV strains in China. Two new motifs (HRLRR and RRIRR) emerged in the isolated strains. The homology of the nucleotide and amino acid sequences of the S1 gene among the seven isolates was 81.7%-99.7% and 79.0%-99.4%, respectively. These seven strains were also genetically different from the vaccine strains and non-China IBV strains but closely related to large numbers of Chinese strains. The seven isolates and 36 reference IBV strains were clustered into six distinct groups (I-VI). The seven strains were categorized into groups I, II, and III, forming a big phylogenetic branch, which is closely related to Chinese IBVs, whereas the vaccine strains belonging to group VI are genetically distant from groups I, II, and III. The results from this study indicate that different IBV strains cocirculate in the chicken population in China. 相似文献
42.
意蜂采用2,3日龄工蜂幼虫产浆的研究 总被引:1,自引:0,他引:1
对意蜂采用2和3日龄工蜂幼虫产浆的王台接受率和不同时间取浆浆量进行了研究。研究结果显示:①2日龄工蜂幼虫的王台接受率(82.42%)与采用3日龄幼虫的(81.21%)无显著差异;②2和3日龄幼虫产浆的台平均产浆量最高峰分别在各自移虫后第60小时和第48小时,浆量较高时段分别在移虫后上时和第42-54小时;③2日龄幼虫产浆最高时段台平产浆量(0.3754g)极显著高于3日龄的(0.3157g)但采用 相似文献
43.
为研究进水管的设置距离和角度对双管进水式圆形循环水养殖池水动力特性的影响,该研究通过模型试验的方法,利用粒子图像测速技术(Particle Image Velocimetry,PIV)测量了不同进水管设置方式下养殖池内的流场。试验设计了3组进水管距池壁距离(进水管与池壁的最近距离,即进水管设置距离d),每组距离工况下设计了8组进水角度(出水方向与养殖池切线形成的锐角,即进水管设置角度α)。利用PIV技术测量了不同工况下距离池底1 cm水层的流场,从水动力特征量(平均流速vavg和速度均匀系数U)分析进水管设置方式对养殖池水动力特性的影响。试验结果表明进水管设置方式明显影响养殖池的水动力特性:d=0时,随着α的增加,平均流速整体呈现先增大后下降的规律,在α=45°时取得最大值,但流场均匀系数随角度的增加而逐渐增加;d=1/4 r(r为养殖池半径)时,随着α的增加,平均流速和流场均匀系数都先缓慢增加然后再下降,分别在α=40°和30°时取得最大值;d=1/2 r时,随着α的增加,平均流速和流场均匀系数整体都呈现逐渐下降的趋势。综合比较24个试验工况的平均流速vavg和速度均匀系数U,建议将进水管设置为d=1/4 r,α=30°~40°,以期使养殖池内水动力特征有利于固体颗粒物的运动汇集,提升养殖池的集排污能力。该文研究成果可以为工厂化循环水圆形养殖池进水管设置方式提供参考。 相似文献
44.
45.
采用生物素标记的(GGAT)4寡核苷酸探针对C57BL/6J、BALB/c和DBA/2三种近交系小鼠进行了DNA指纹图分析.结果表明:(GGAT)4寡核苷酸探针对上述3种近交系小鼠产生的DNA指纹图的图带数均为10-12条,具有良好的多态性,品系内平均DNA指纹图的相似系数在0.92~1.00的范围内,具有相同指纹图的概率均在0.40以上,极显著地高于品系间的相似系数(0.21~0.39)和相同指纹图的概率(P<3.10×10-7),说明(GGAT)4寡核苷酸探针可用于制作近交系小鼠的DNA指纹图,以对其进行遗传检测. 相似文献
46.
Influence of Ammoniacal Copper Quaternary treatments on mechanical properties of blue-stained Lodgepole Pine wood 总被引:1,自引:0,他引:1
Three concentrations (2.8%, 2.0%, 1.2%) of Ammoniacal Copper Quaternary (ACQ) was selected to treat Lodgepole pine wood for evaluating ACQ treatment on mechanical properties of blue-stained wood. The bending modules of elasticity (MOE), modules of rupture (MOR), toughness and shearing strength parallel to grain on tangential surface, are tested according to the criteria GB1927-1943-91. Non-treated sample were also tested according to the same procedure. The results showed that the three groups specimen impregnated by different concentrations of ACQ solution met the AWPA standard 2003 of America (UC4A 6.4g/cm^3). There were significant difference of toughness between treated wood and non-treated wood (p=0.01), but there were no statistically significant differences among three concentrations in terms of toughness, and toughness of treated wood was approximately 20% lower than non-treated. MOR, MOE as well as sheafing strength parallel to grain were found to be not significantly different between treated wood and non-treated one, and there were no statistically significant difference among three concentrations of ACQ too. Toughness, MOR, MOE and sheafing strength parallel to grain increased with decrease of concentration of ACQ, but they were hardly affected by ACQ preservatives. 相似文献
47.
Deforestation and degradation of productive lands are serious threats to the sustainability of forestry/agricultural practices
in Kenya. In the last two decades farm forestry (FF) has been promoted through pilot projects among local communities as an
example of sustainable land use. However adoption of FF is limited outside the project locations because FF improvement measures
focused mainly on biological (e.g. succession, biodiversity and traditional industrial timber production) and technical concerns
(e.g. material input delivery such as providing free tree seedlings for field planting) rather than local values, and interests
and the constraints facing farmers. This study examined the local farm priorities and constraints and the prospects for the
wider implementation of farm-level tree planting in four communities in Rachuonyo District. Using interviews with 597 randomly
selected household heads, the study assessed farmer’s production assets and activities, land tenure, priority tree species
and the constraints to growing trees on farms. Results show that farm labour is represented by a young population, 56.3% under
the age of forty. They are mainly engaged in small-scale mixed cropping integrated with multipurpose trees and some livestock.
Tree products contribute about 32% to household cash income, more than any other source (agricultural products, labour sales,
etc). Females were more often household heads and had considerable influence over productive activities, making them an important
target group in FF development. Farmers preferred exotic tree species due to their ability to provide short-term cash income,
fuel and shade. Farmers’ concerns included population pressure on limited farmlands and the problem of credit for agricultural
inputs. Given the feeling of secured tenure arrangement and influence of tree products on the household economy, farmers are
likely to invest more in efficient land uses such as FF if consideration is given to local priorities. 相似文献
48.
Syed Jawad Ahmad Shah Shaukat Hussain Musharaf Ahmad Farhatullah Iftikhar Ali Muhammad Ibrahim 《Journal of General Plant Pathology》2011,77(3):174-177
Fifty wheat varieties along with Jupateco-73 and Morocco were studied for the expression of leaf tip necrosis (LTN), a trait
linked with the durable rust resistance gene pair Lr34/Yr18. LTN was frequent (i.e., ≥6) in nine replications of a field experiment over 3 years in 17 genotypes, and the varieties were
considered positive for LTN. In molecular analyses of these varieties, having relative severity values up to 78 for yellow
rust and 45 for leaf rust, the 150-bp Lr34/Yr18-linked allele was consistently amplified. Expression of LTN in six of nine replications is an appropriate threshold for predicting
the presence of Lr34/Yr18 gene pair, and genotypes can be selected using this trait. 相似文献
49.
50.
Fang Xiao Wei Han Yongxiu Li Yixuan Qiu Qing Sun 《The Journal of Horticultural Science and Biotechnology》2018,93(3):306-315
To study the effects of day and night temperature difference (DIF) on tomato growth, a controlled experiment using Solanum lycopersicum L., cv. Jinguan 5 was conducted. The daily mean temperature (Tm) was maintained at 18°C and 25°C, and the DIF was set at 0°C, 6°C, and 12°C. The results indicated that chlorophyll a (Chl a) and chlorophyll b (Chl b) gradually increased as DIF rose. At 18°C Tm, the carotenoid content reached a maximum at 12°C DIF. The Chl a/Chl b, net photosynthetic rate (PN), photosynthetic rate at irradiation saturation (Pmax), stomatal conductance (gs), intercellular CO2 concentration (Ci), stomatal limitation value, the maximum assimilation rate (Amax), apparent quantum efficiency (Aq), carboxylation efficiency (Ce), superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), gibberellin A3 (GA3), and indole-3-acetic acid (IAA) were highest, while malondialdehyde (MDA) was lowest at 6°C DIF. At 25°C Tm, PN, Pmax, Amax, Aq, Ce, gs, Ci, CAT, POD, GA3, IAA, and zeatin reached the maximum under 6°C DIF, while SOD and MDA reached the maximum under 12°C DIF. Furthermore, the morphological index peaked at 6°C DIF under 18°C and 25°C Tm. The results suggested that 6°C DIF improved the growth and development of tomato during the flowering stage. ABBREVIATIONS: Aq – apparent quantum efficiency; Amax – the maximum assimilation rate; CAT – Catalase; Chl a(b) – chlorophyll a(b); Ca – ambient CO2 concentration; Ce – carboxylation efficiency; Ci – intercellular CO2 concentration; DIF – difference between day temperature (TD) and night temperature(TN); FM – fresh mass; gs – stomatal conductance; GA3 – gibberellin A3; IAA – indole-3-acetic acid; Ls – stomatal limitation value; MDA – malondialdehyde; Pmax – photosynthetic rate at irradiation saturation; PN – net photosynthetic rate; POD – peroxidase; ROS – reactive oxygen species; SOD – superoxidedismutase; Tm – daily mean temperature; ZT – zeatin. 相似文献