水稻旱作覆膜节水增产试验研究

通过水稻旱作全程覆膜与半程覆膜、旱作不覆膜及水栽对比试验，研究其耗水规律，计算其节水量与增产量，并进行经济效益分析，提出了适合本地区的栽培模式。     

苦荞麦脱壳工艺及主要参数的优化

为了提高苦荞产品脱壳的成品率,采用砂盘式、蒸汽润湿-砂盘式和蒸汽润湿-橡胶盘式脱壳方法,就影响脱壳的因素进行了试验对比。试验结果表明,在室温条件下,润湿时间为40s,磨盘间隙为2.4mm,转速为1311r/min,工作面宽度为5cm,对苦荞进行脱壳,整半仁率可达到37.6%。     

亚硝酸盐氮对克氏原螯虾仔虾的急性毒性效应

研究了亚硝酸盐氮对克氏原螯虾(Procambarus Clarkii)仔虾的急性毒性效应,结果表明:克氏原螯虾仔虾对亚硝酸盐氮的耐受性随接触时间的增加而明显降低;亚硝酸盐氮对克氏原螯虾仔虾24 h、48 h、72 h、96 h半致死浓度分别为28.69 mg/L、22.69 mg/L、18.92 mg/L、15.19 mg/L,安全浓度为1.52 mg/L.     

可见半面树冠法预测油松种子产量的研究

以可见半面树冠法估测的油松球果成熟前数量来预测油松当年种子产量 ,结果得出 :油松球果数目和种子产量有着密切的直线相关关系 ,可以用油松球果数进行种子产量的预测 ;这是一种方便而且精度高的方法。二者呈直线相关 ,相关系数 r =0 .86 0 3,预测精度为 86 .99%。     

Marker‐assisted parentage analysis reveals high individual selfing rates in tetraploid red clover genotypes selected for seed yield

Seed yield is a major breeding target in tetraploid red clover. We investigated if marker‐assisted parentage analysis can identify progeny plants with two high seed‐yielding parents in tetraploid red clover and if this technique is more advantageous than traditional half‐sib selection. Parentage analysis was successfully performed on the progeny from the 10% highest seed‐yielding genotypes from a second‐cycle family selection trial: 16.0% of progeny were identified with a high seed‐yielding father. However, progeny plants with two high seed‐yielding parents did not produce more seeds than traditionally selected progeny (27.3 g vs. 30.7 g/plant, respectively). The 10% highest seed‐yielding genotypes displayed on average 2% self‐fertilization. Four genotypes were self‐fertile with individual selfing rates up to 20%. Our results discourage the use of marker‐assisted parentage analysis to improve seed yield in tetraploid red clover when the material has been preselected for seed yield. Breeders should be aware that intensive selection for seed yield in tetraploid red clover may inadvertently lead to selection for increased self‐fertility, which may increase inbreeding in the long term.     

西双版纳地区引种的澳洲坚果抗寒性

以3年生无性繁殖澳洲坚果10个品种的幼苗为材料.采用电导法和全株冰冻测试法测定西双版纳引种的10个澳洲坚果品种叶片的抗寒力变化.结果表明:10个澳洲坚果品种抗寒力(半致死温度)介于-0.72～2.36℃之间,H2和HY属于低温敏感性相对较弱的L类型,抗寒力较强;HAES900、A16和Special抗寒力较弱,属于低温敏感性较强的H类型;D4、OC、HAES816、A4和D等品种属于抗寒力中等的M类型.     

异育银鲫“中科三号”对盐度和碳酸盐碱度的耐受性

研究了盐度和碳酸盐碱度对不同规格异育银鲫(Carassius auratus gibelio)"中科三号"鱼种的急性和慢性毒性。结果表明,异育银鲫"中科三号"大规格鱼种[L=(8.81±0.62)cm]48、72 h和96 h的盐度半致死浓度分别为15.433、14.352、13.855,盐度安全浓度为4.63;碳酸盐碱度在24、48、72、96 h的半致死浓度分别为73.105、71.861、71.198、70.368 mmol·L-1,碳酸盐碱度的安全浓度为20.33 mmol·L-1。小规格鱼种[L=(1.78±0.12)cm]24、48、72 h和96 h盐度的半致死浓度分别为11.339、11.026、10.653、10.080,盐度安全浓度为2.98;碳酸盐碱度的半致死浓度分别为52.656、51.889、50.378、49.664 mmol·L-1,碳酸盐碱度的安全浓度为13.20 mmol·L-1。大规格"中科三号"鱼种对盐度和碳酸盐碱度的耐受性均比小规格鱼种强;慢性毒性实验中异育银鲫"中科三号"鱼种[L=(3.73±0.12)cm]的特定生长率和相对增重率均随着盐碱浓度的增大而降低。60 d实验后盐度3、5和7组的特定生长率分别为1.14、0.67和0.23,相对增重率分别为98.64、49.24和14.80;碳酸盐碱度7、12和17 mmol·L-1组的特定生长率分别为1.12、0.66和0.29,相对增重率分别为96.06、48.40和19.23。盐度和碳酸盐碱度浓度越强,对异育银鲫"中科三号"鱼种生长的影响越大。     

苏云金素在水中和植株上的衰减与残留

用ＨＰＬＣ检测了苏云金素在鱼塘水和清水中的衰减速率。清水中该物质的半衰期长达４３３小时；在鱼塘水中苏云素的衰减呈双指数消除模型，开始消除半衰期为２．４３－１０．６８小时，终末消除半衰期为１２８．５７－１４２．０１小时。     

Sequences of the 3′ Halves of the Genomes of Barley Yellow Dwarf Virus-PAV cpA Isolates that Vary in Symptom Severity

Barley yellow dwarf virus (BYDV)-PAV isolates from USA have been separated into two distinct clusters (Chay et al. (1996) Virology 219: 57–65; Chay et al. (1996) Phytopathology 86: 370–377). Following this finding we have shown that BYDV-PAV is divided into two groups cpA and cpB based on their coat protein gene sequence, and distinct host preferences (Mastari et al. (1998) Phytopathology 88: 818–821). We have sequenced the complete 3 half of the genomes of two lethal and two mild cpA isolates and compared them with those of several known PAV cpA isolates to assess variability and locate potential determinants of severity. Open reading frames (ORFs) 3, 4, 5, 6 and the 3 untranslated regions had different percent homologies between isolates: ORF5 (92–97%), ORF3 (88–98%) 3-translational enhancer (87–100%) ORF4 (85–99%), 3 untranslated region (72–97%) and ORF6 (61–99%). In contrast to the mild isolates, the field-lethal isolates (FHv1 and FHv2) fell into the same cluster, regardless of the genomic region analysed. The isolates FHv1 and FHv2 differed from mild isolates by eight amino acid substitutions in ORFs 3 and 4, and insertions in ORF5. Four amino acid substitutions in the 17-kDa protein encoded by ORF4 caused a change in local net charge in the field-lethal isolates. Two insertions of four amino acids were identified in the C-terminal half of ORF5 of the field-lethal isolates, but were not present systematically in all lethal isolates analysed. The potential relationships of these differences in predicted amino acid sequences to disease severity are discussed.     

Turnover of Se in adequately fed chickens using Se‐75 as a tracer

Inorganic selenium (Se) in the form of selenite is applied to livestock to avoid Se deficiency. Selenite is, however, an artificial Se source in diets of unsupplemented chickens. It is therefore hypothesized that organic Se sources, such as Se‐enriched yeast and wheat, could be a more suitable Se supply in animal nutrition, although information on the transition of Se from organic Se sources in fast‐growing chickens is scarce. In this work, chickens were fed a low Se diet (0.27 ± 0.01 mg Se/kg, Se‐enriched yeast) until 20 days of age, after which the Se concentration was increased to maximum concentration allowed by the poultry industry in Europe (0.5 p.p.m. Se). At the same time, a daily contribution of carrier‐free ⁷⁵Se tracer from labelled wheat was administered from day 20 to 27. The chickens showed S and Se homeostasis, as the concentration of S and Se in liver, blood or kidney remained about constant, and steady state of S and Se in the other organs was reached 1 day after the diet shift. The uptake of ⁷⁵Se was readily seen in all organs. After 1 week, the depuration of the ⁷⁵Se tracer was followed, and biological half‐lives and retention in individual organs were determined. The shortest biological half‐lives were observed in major metabolic organs, the liver, kidney and pancreas with half‐lives close to 4 days. There was a significant (p < 0.05) uptake in lung, brain and muscle that reached steady state when the administration of ⁷⁵Se was terminated. The half‐life of ⁷⁵Se in heart was 9 days and 7 days in blood. The longest half‐lives were observed in muscle (12 days), brain and lungs (13 days). All half‐lives were shorter than in Se deplete animals.