苹果花脸病田间病情发展及ASSVd在组培条件下的传播

为了明确苹果锈果类病毒（apple scar skin viroid,ASSVd）引起的苹果花脸病在田间的病情发展情况以及ASSVd在组培条件下的传播方式,2012—2015年对河北省顺平南神南村3个果园进行持续调查和检测。结果显示,果园A、B、C的显症率分别从3.00%、19.35%和10.00%上升至10.00%、34.41%和22.00%,带毒率分别从11.00%、20.43%和14.00%上升至23.00%、37.63%和30.00%,带毒率和显症率都逐年增加,而且带毒率大于显症率,即有些带毒果树不显症。发病果树田间分布有明显的发病中心。通过高通量测序发现显症果树ASSVd vsiRNA reads数是带毒未显症reads数的4.08倍,同时实时荧光定量PCR检测发现显症树ASSVd病毒积累量显著高于带毒未显症树。以携带ASSVd的组培苗和无毒组培苗为试材,利用RT-PCR检测明确了ASSVd可通过伤口沾染带毒汁液、组培剪污染、含毒培养基、根系接触进行传播,其中根系接触传染率较高。     

Basal internode elongation of rice as affected by light intensity and leaf area

Short basal internodes are important for lodging resistance of rice(Oryza sativa L.).Several canopy indices affect the elongation of basal internodes,but uncertainty as to the key factors determining elongation of basal internodes persists.The objectives of this study were(1)to identify key factors affecting the elongation of basal internodes and(2)to establish a quantitative relationship between basal internode length and canopy indices.An inbred rice cultivar,Yinjingruanzhan,was grown in two split-plot field experiments with three N rates(0,75,and 150 kg N ha−1 in early season and 0,90,and 180 kg N ha−1 in late season)as main plots,three seedling densities(16.7,75.0,and 187.5 seedlings m−2)as subplots,and three replications in the 2015 early and late seasons in Guangzhou,China.Light intensity at base of canopy(Lb),light quality as determined from red/far-red light ratio(R/FR),light transmission ratio(LTR),leaf area index(LAI),leaf N concentration(NLV)and final length of second internode(counted from soil surface upward)(FIL)were recorded.Higher N rate and seedling density resulted in significantly longer FIL.FIL was negatively correlated with Lb,LTR,and R/FR(P<0.01)and positively correlated with LAI(P<0.01),but not correlated with NLV(P>0.05).Stepwise linear regression analysis showed that FIL was strongly associated with Lb and LAI(R2=0.82).Heavy N application to pot-grown rice at the beginning of first internode elongation did not change FIL.We conclude that FIL is determined mainly by Lb and LAI at jointing stage.NLV has no direct effect on the elongation of basal internodes.N application indirectly affects FIL by changing LAI and light conditions in the rice canopy.Reducing LAI and improving canopy light transmission at jointing stage can shorten the basal internodes and increase the lodging resistance of rice.     

汽车变速器齿轮修形仿真分析

汽车变速器的关键部件齿轮因其加工和装配质量的影响,工作时容易引起振动噪声大及承载能力降低等问题,而齿轮修形是解决这些问题的有效方法,且成本较低。针对某款汽车变速器,利用Romax对齿轮进行修形分析。结果表明,修形后减小了齿轮的传动误差和最大接触应力,齿面载荷分布更加合理。有效改善了齿轮的传动性能,增加了齿轮寿命。     

Serologic and molecular survey for major viral pathogens in grazing hybrid wild boars in Northeast China

Hybrid wild boar husbandry is an important component of livestock production in Northeast China. However, the current disease situation of these animals is largely unknown due to a lack of disease surveillance. The present study was conducted to determine the prevalence of several important viral diseases in the hybrid wild boar population of Northeast China. Between September 2015 to December 2016, 169 blood and 61 tissue samples were collected from apparently healthy hybrid wild boars from farms in Jilin, Inner Mongolia and Heilongjiang provinces. ELISA detected serum antibodies against classical swine fever virus(CSFV), porcine reproductive and respiratory syndrome virus(PRRSV), pseudorabies virus(PRV), porcine circovirus type 2(PCV2) and Japanese encephalitis virus(JEV), but not against African swine fever virus(ASFV), with PCV2 having the highest seropositive rate(87.2–100% in different farms). RT-PCR or PCR performed on the processed samples detected only PCV2, with 33.1%(56/169) of blood samples and 32.8%(20/61) of spleen samples being positive, respectively, indicating widespread PCV2 infection in hybrid wild boars. Phylogenetic analysis of 15 PCV2 ORF2 sequences showed that they belong to genotypes PCV2a, PCV2b and PCV2d, with nucleotide and deduced amino acid homologies of 88.5–100% and 88.1–100%, respectively.     

Research and Design of Hydro-mechanical Continuously Variable Transmission for Tractors

The working condition of tractors is bad, and the outside load fluctuation is frequent. All that require engine or transmission to change revolution speed and torque timely to accommodate the variation of load and motion resistance, and ensure the dynamic…     

水稻籽粒直链淀粉含量非破坏性活体测定方法研究

对533份杂交稻和常规稻材料的糙米和精米直链淀粉含量进行化学分析,并结合近红外透射光谱数据,采用改进偏最小二乘法（MPLS）分别建立糙米、精米的直链淀粉含量（AC）预测定标模型,并对其进行内部和外部验证.结果表明,杂交稻糙米及精米模型的定标相关系数（RSQ）分别为0.873和0.922,常规稻糙米及精米模型的RSQ则分别为0.924和0.939,定标标准偏差（SEC）分别为1.100,0.956,1.537,1.547;内部交叉验证预测值和真实值之间的RSQ分别为0.866,0.901,0.892和0.921,外部验证的RSQ分别为0.9506,0.9352,0.9116,0.9180,所建模型的相关性较高,预测值与真实值之间的误差小.常规稻模型可应用于大量育种材料快速、无损的早代筛选,杂交稻模型可用于新组合直链淀粉含量的快速鉴定,促进稻米品质改良,提高育种效率.     

丁型流感病毒在中国的流行状况及研究进展

丁型流感病毒是继甲型、乙型和丙型流感病毒之后的一种新型正粘病毒,2011年首次由美国从表现出流感样症状的猪只中分离出来,并于2016年被国际病毒分类委员会正式命名为丁型流感病毒。目前丁型流感病毒已广泛分布于美洲、亚洲、欧洲和非洲的数十个国家。丁型流感病毒利用牛作为其自然宿主和扩增宿主,并定期扩散到其他哺乳动物物种,包括猪、马、羊和骆驼等。因此,丁型流感病毒具有广泛的地域分布和宽泛的宿主范围。丁型流感病毒感染可导致牛患轻度至中度呼吸道疾病,被认为是牛呼吸系统疾病综合征的重要关联因子。血清学证据表明,丁型流感病毒具有感染人的潜在风险。我国研究人员于2014年首次在山东省的牛群中检测到丁型流感病毒,随后,来自不同团队的研究人员分别于2017、2021和2022年报道了丁型流感病毒核酸阳性病例。为更好地了解丁型流感病毒对我国畜牧养殖业的影响,系统综述了丁型流感病毒在我国的分布情况和研究进展,并分析了丁型流感病毒在我国的流行趋势及对我国畜牧养殖业的潜在威胁。     

基于链合模型的中国禽蛋供应链价格传导机制研究

以我国禽蛋供应链价格系统为研究对象,采用2000-01—2012-02的蛋鸡配合饲料价格、商品代蛋雏鸡价格、鸡蛋批发价格和鸡蛋零售价格月度数据应用链合模型研究整个系统内部的价格传导机制。结果表明:我国禽蛋供应链价格系统内部存在显著的长期协整关系;系统内部各个价格序列的调整系数均小于0.2,调整速度缓慢;蛋鸡配合饲料价格和鸡蛋批发价格分别是下游鸡蛋零售价格的Granger原因,而是鸡蛋零售价格仅是上游商品代蛋雏鸡价格的Granger原因;蛋鸡配合饲料价格对鸡蛋零售价格的动态影响最大,在整个禽蛋供应链中占有重要地位。政府部门应加大对整个供应链价格的监测和预警,特别是对上游蛋鸡配合饲料价格的干预和适时调控。     

应用可见/近红外光谱技术快速鉴别山西陈醋品种

为了实现对山西老陈醋品种的快速鉴别,应用可见/近红外光谱透射技术,结合化学计量学方法,进行了山西老陈醋品种的判别分类试验研究。对4个不同品种共240个山西老陈醋样品采集其光谱数据,结合主成分分析和神经网络技术分别对山西陈醋原始光谱、一阶微分光谱、二阶微分光谱进行了判别分析。结果表明:可见/近红外原始光谱结合主成分分析神经网络判别分析法的分析结果最优,校正集正确分类的百分比达92.1%,预测集达85.0%;二阶微分光谱分析结果最差。