体外产气法评价宁夏地区四种非常规粗饲料的营养价值

本研究通过体外产气法研究了甘草茎叶、野草、柠条叶和柠条四种非常规饲料体外发酵24 h的产气量、产气参数,并应用Menke和Steingass(1988)模型估测了四种饲料的有机物消化率和代谢能,其中有机物消化率最高的是甘草茎叶(69.28%)(P<0.05),野草次之(55.73%),柠条最低(22.31%)(P<0.05);四种饲料的代谢能比较,甘草茎叶最高,为10.45 MJ/kg DM(DM,干物质)(P<0.05),野草次之(6.66 MJ/kg DM),柠条最低(4.23 MJ/kg DM)(P<0.05)。通过与中国农业科学院(1984)测定的国产饲料代谢能值比较,并结合四种饲料的有机物消化率值,甘草茎叶、野草和柠条叶对于反刍动物均具有一定的饲喂价值,而柠条营养价值极低,不适宜作为反刍动物的粗饲料。     

枣疯植原体的分布特点及周年消长规律

枣疯病是一种典型的致死性植原体病害,是枣树生产中发生最普遍、危害最严重的毁灭性传染病害,被视为枣树的癌症.     

我国无公害经济林产品(干果)产地环境研究

通过对全国干果主产区果品污染物含量以及产地大气、土壤和灌溉水质量的分析,初步认定我国干果产地环境质量优良,有利于实施无公害果品生产,经济林产品(干果)的安全性有较可靠的保障.与发达国家土壤污染状况相比,我国干果产地污染较轻,具有十分明显的优势.但就我国不同地区果园而言,在环境质量上亦存在一些差异,在未来规划建园和老果园改造时应该引起充分注意.尽管我国干果产地生态环境比较优越,但欲生产安全合格的产品,还必须注意在生产全过程中及采后有效地控制来自各方面的污染.     

棉花早熟品种吸收养分特点及氮肥施用时期研究

本文研究了棉花早熟品种的吸收养分特点,提出了一生吸收积累养分动态方程;应用导数,成功地得到了棉花一生吸收养分的变速率、变加速率动态变化规律;根据棉花早熟品种一生变加速率的动态变化,提出氮素化肥如果需要追施,应在现蕾后进行。田间氮肥适宜施用时期试验证明,早熟品种施用适量氮素化肥,在有一定保肥能力的土壤上,可全做基肥或者基施、蕾追各半为最宜。与其吸收养分特点研究结果相一致。     

凡纳滨对虾弧菌病及其防治方法研究进展

近年来,凡纳滨对虾(Litopenaeus vannamei)养殖生产中弧菌病的发病率越来越高,严重阻碍了我国海水养殖业的发展.文章介绍了凡纳滨对虾养殖过程中容易发生的几种弧菌病及其防治方法的相关研究,并对常见的哈维氏弧菌、溶藻弧菌、霍乱弧菌和副溶血弧菌这4种弧菌的研究进展进行了综述,以期为海水养殖中弧菌病的防治和控制...     

Genome-wide genetic dissection of germplasm resources and implications for breeding by design in soybean

“Breeding by Design” as a concept described by Peleman and van der Voort aims to bring together superior alleles for all genes of agronomic importance from potential genetic resources. This might be achievable through high-resolution allele detection based on precise QTL (quantitative trait locus/loci) mapping of potential parental resources. The present paper reviews the works at the Chinese National Center for Soybean Improvement (NCSI) on exploration of QTL and their superior alleles of agronomic traits for genetic dissection of germplasm resources in soybeans towards practicing “Breeding by Design”. Among the major germplasm resources, i.e. released commercial cultivar (RC), farmers’ landrace (LR) and annual wild soybean accession (WS), the RC was recognized as the primary potential adapted parental sources, with a great number of new alleles (45.9%) having emerged and accumulated during the 90 years’ scientific breeding processes. A mapping strategy, i.e. a full model procedure (including additive (A), epistasis (AA), A × environment (E) and AA × E effects), scanning with QTLNetwork2.0 and followed by verification with other procedures, was suggested and used for the experimental data when the underlying genetic model was usually unknown. In total, 110 data sets of 81 agronomically important traits were analyzed for their QTL, with 14.5% of the data sets showing major QTL (contribution rate more than 10.0% for each QTL), 55.5% showing a few major QTL but more small QTL, and 30.0% having only small QTL. In addition to the detected QTL, the collective unmapped minor QTL sometimes accounted for more than 50% of the genetic variation in a number of traits. Integrated with linkage mapping, association mappings were conducted on germplasm populations and validated to be able to provide complete information on multiple QTL and their multiple alleles. Accordingly, the QTL and their alleles of agronomic traits for large samples of RC, LR and WS were identified and then the QTL-allele matrices were established. Based on which the parental materials can be chosen for complementary recombination among loci and alleles to make the crossing plans genetically optimized. This approach has provided a way towards breeding by design, but the accuracy will depend on the precision of the loci and allele matrices.     

生物统计教学中用SAS程序讲解抽样分布

抽样分布是统计推断理论的基础。介绍了利用SAS程序从有限总体和无限总体中模拟抽样的方法,使学生能直观形象地理解样本平均数的抽样分布,掌握总体参数和抽样分布特征数的关系,提高了学生的学习兴趣和理解能力。     

变速切削过程电机电流的变化特征

机床电机以时变转速方式运行时，瞬时电流确有一定程度的波动，但不影响电机的正常使用；在时变转速参数中，影响电机瞬时电流波动较为显著的因素依次是变速波形、变速频率和变速幅度。电机温升试验结果证明，机床电机对变速切削方式的承受能力是令人满意的。     

山东省金乡县大蒜产业存在问题及发展对策

金乡县2007年大蒜出口创汇达2亿美元，成为全国县级单一农产品出口创汇的第一大县。如何实现产业的可持续发展？杨以兵等提出建立“两园两中心”等措施。     

枣、酸枣授粉生物学基础研究

采用离体培养技术对27个枣品种和酸枣的枣吊花蕾量、单花花粉量、花药开裂时间、花粉发芽率以及枣和酸枣单花不同开放阶段的花粉生活力和花粉贮藏特性进行了系统研究。结果表明:(1)不同枣品种和酸枣的枣吊花蕾量、单花花粉量、花粉发芽率存在极大差异,利用数量性状的概率分级体系可将它们分别分为3级;(2)枣和酸枣的花药开裂时间在蕾黄或蕾裂期;(3)从蕾裂到瓣平期的花粉发芽率极显著的高于蕾黄期、雄蕊展平期和雄蕊下垂期;(4)花粉贮藏后发芽率表现为下降—上升—下降的大体趋势。对杂交育种中父母本的选择、花粉采集和去雄的适宜时期也进行了讨论。