Emerging issues in genomic selection

Genomic selection (GS) is now practiced successfully across many species. However, many questions remain, such as long-term effects, estimations of genomic parameters, robustness of genome-wide association study (GWAS) with small and large datasets, and stability of genomic predictions. This study summarizes presentations from the authors at the 2020 American Society of Animal Science (ASAS) symposium. The focus of many studies until now is on linkage disequilibrium between two loci. Ignoring higher-level equilibrium may lead to phantom dominance and epistasis. The Bulmer effect leads to a reduction of the additive variance; however, the selection for increased recombination rate can release anew genetic variance. With genomic information, estimates of genetic parameters may be biased by genomic preselection, but costs of estimation can increase drastically due to the dense form of the genomic information. To make the computation of estimates feasible, genotypes could be retained only for the most important animals, and methods of estimation should use algorithms that can recognize dense blocks in sparse matrices. GWASs using small genomic datasets frequently find many marker-trait associations, whereas studies using much bigger datasets find only a few. Most of the current tools use very simple models for GWAS, possibly causing artifacts. These models are adequate for large datasets where pseudo-phenotypes such as deregressed proofs indirectly account for important effects for traits of interest. Artifacts arising in GWAS with small datasets can be minimized by using data from all animals (whether genotyped or not), realistic models, and methods that account for population structure. Recent developments permit the computation of P-values from genomic best linear unbiased prediction (GBLUP), where models can be arbitrarily complex but restricted to genotyped animals only, and single-step GBLUP that also uses phenotypes from ungenotyped animals. Stability was an important part of nongenomic evaluations, where genetic predictions were stable in the absence of new data even with low prediction accuracies. Unfortunately, genomic evaluations for such animals change because all animals with genotypes are connected. A top-ranked animal can easily drop in the next evaluation, causing a crisis of confidence in genomic evaluations. While correlations between consecutive genomic evaluations are high, outliers can have differences as high as 1 SD. A solution to fluctuating genomic evaluations is to base selection decisions on groups of animals. Although many issues in GS have been solved, many new issues that require additional research continue to surface.     

双表达去势DNA疫苗的构建及其稳定性研究

试验旨在构建一种更安全有效的新型免疫去势DNA疫苗,通过选取下丘脑-垂体-性腺轴（hypot halamic-pituitary-gonadal axis,HPG）的上游调控基因吻素1（KISS1）和促性腺激素释放激素（GnRH）作为靶标,借助2A肽的自剪切功能,引入平衡致死系统代替抗性基因筛选流程,成功将GnRH和KISS1转入非抗性筛选质粒pVAX-asd中,酶切验证和测序对比验证目的基因的插入方向和序列完全正确。重组质粒转染HeLa细胞,反转录后扩增目的基因结果显示,重组质粒在真核细胞内能够正常转录,保证重组质粒在导入机体后能够正常表达,从而引起特异性免疫反应。将构建成功的质粒转入减毒的猪霍乱沙门氏菌C500中,获得可直接口服免疫的活载体疫苗,酶切和测序结果表明,双表达重组质粒成功导入工程菌中。将活菌疫苗在体外连续传代50次,选取0、2、5、10、20、30、40、50代的菌株进行稳定性研究,生长曲线检测结果表明,工程菌在体外连续传代50次的过程中,其生长特性无明显变化,且与减毒猪霍乱沙门氏菌C500的生长特性一致,未因携带质粒发生明显变化;同时将各代菌液扩增沙门氏菌标志基因（invA）和毒力基因（crp）,结果表明多次传代后工程菌仍然具有沙门氏菌的特性,其减毒特性也无变化。各代菌液质粒酶切验证显示,多次传代并不影响质粒的稳定性,重组双表达质粒能够在沙门氏菌C500中维持正常拷贝功能。综上所述,该重组质粒和工程菌疫苗均具有良好的稳定性,可直接应用于动物免疫去势的研究。     

水头可调薄壁堰式渠道流量智能测控系统优化试验研究

采用巴赞堰流公式计算流量的水头可调薄壁堰式渠道流量智能测控系统通过渠道流量量测与控制试验,验证了其精准的测流功能和智能控制技术的可行性。为进一步提高该测控系统运行的效率和稳定性,减少运行能耗,对矩形薄壁堰堰流公式进行水力试验研究,通过分析堰上水头和流量关系,拟合出矩形薄壁堰流量计算公式。通过向该拟合公式引入修正系数λ=0.848,将测控系统测得的堰上水头数据值代入该拟合公式求得的流量值与电磁流量计测得流量值的差值的平均值为-0.004L/s,标准差为0.119,线性相关系数R2=0.989 1。该拟合公式相对于巴赞堰流公式形式简单、参数较少、运算简便,同时也满足节水灌溉对精准测流的要求,更适用于水头可调薄壁堰式渠道流量智能测控系统,对于在灌区推广和使用该测控系统具有重要的意义。     

一个水稻三倍体×二倍体杂交F2群体的微卫星杂合性丧失

DB102为一田间发现的三倍体水稻,利用它做母本与二倍体水稻中作59杂交,得到一个早世代(F2)稳定群体,通过微卫星分析发现,该群体中有一些微卫星位点发生了杂合性丧失,且至少6条染色体上发生微卫星位点杂合性丧失(loss of heterzygoisity LOH)可能有DNA序列变化。而微卫星位点的杂合性丧失又可能与该杂交组合早世代稳定有关。     

黑豆色素的研究进展

本文综述了近年来黑豆色素的研究进展.提出了综合开发利用的前景.     

土质边坡稳定安全系数影响因素的

土质边坡稳定安全系数的计算值主要与采用的简化计算方法和土工参数有关。采用正交试验法计算分析了不同的计算方法、材料参数、水位及其相关荷载、地震作用等对边坡安全系数计算值的影响，进而对设计中的计算方法和材料参数提出了一些有益的建议，并提出了在工程运行管理中应尽量避免低水位或水位骤降情况的意见，为土石坝类工程的设计与运行管理提供了重要参考。     

Stability Analysis on Excavated High Slope of Mozong River Power Station in Wulong

The subject matter of this paper is to analyze the stability of excavated high slope. On the base of typical engineering case in Wulong, Chongqing, the geological conditions and potential failure pattern of the high slope are discussed. Then, the limit equilibrium method and the stereographic projection method are used to synthetically analyze the stability of excavated high slope. As a result, it indicates that the stability of the high slope in insufficient and some retaining structures ought to be adopted for the high slope as soon as possible.     

Vehicle Lateral Stability Control Based on Sliding Model Control

In view of the vehicle cornering or path changing under ultimate handling maneuver, a 3-DOF nonlinear vehicle dynamics model which takes the vehicle lateral velocity, yaw rate and body roll angle as the State variables is presented. Based on the dynamic analysis, the method which using additional yaw moment produced by different longitudinal braking force among each wheels to improving vehicle handling stability in emergency situations is discussed. Considering the sideslip angle as one of the vehicle state variables is difficult to measuring, the sideslip angle estimation based on vehicle dynamic model and kinematics is designed. And then, based on the theory of siding model control, the combining sliding model control system is founded, which taking the vehicle yaw rate and body side-slip angle errors between the estimated and the real as the input variables, and taking the braking torque and the steering angle as control aims. The simulation results indicate that the control method can effectively improve the vehicle lateral handling stability.