番茄黄化曲叶病毒安徽分离物的基因组结构特征及变异分析

利用滚环扩增（RCA）技术从安徽淮北番茄温室表现曲叶症状的番茄上获得番茄黄化曲叶病毒（tomato yellow leaf curl virus, TYLCV）的2个分离物全基因组。 2个TYLCV DNA-A核苷酸序列全长均为2 781 nts,共编码6个ORF。序列比对结果表明,2个TYLCV安徽分离物DNA-A核苷酸序列同源性为99.7%,与已报道的国内外其他24个TYLCV各分离物同源性高达97.8% ~ 99.9%。系统进化分析显示,TYLCV安徽分离物与来自吉林、沈阳、天津、邯郸和山东的5个TYLCV分离物亲缘关系最近。     

比格犬的繁殖技术Ⅰ.采精及精液冷冻

采用手握法采取比格犬精液,成功率为71.4％,平均射精量2.67mL;精液呈弱酸性,每次射出的精液分三段,精子主要在第二段,精子平均密度为2.105×10~8/mL;新鲜精液的活力为0.8～0.9;精液用两种稀释液稀释后在液氮中保存14～60d,解冻后,其孵活率分别为0.425和0.427.     

Effects of dietary protein to carbohydrate ratios on growth and body composition of juvenile yellow catfish, Pelteobagrus fulvidraco (Siluriformes, Bagridae, Pelteobagrus)

The present experiment was conducted to investigate the effects of dietary protein to carbohydrate ratios on growth and body composition of juvenile yellow catfish, Pelteobagrus fulvidraco . Nine diets were formulated to contain three protein levels (30%, 36% and 42%), each with three carbohydrate levels (24%, 30% and 36%). Each diet was randomly assigned to triplicate groups of 20 fish (initial mean body weight: 8.24±0.20 g) in indoor flow – through fibreglass tanks. The experiment continued for 8 weeks. Weight gain and specific growth rate were similar for the fish fed the 36% and 42% protein diets but higher than that fed the 30% protein diet. At the 36% protein level, carbohydrate contents varying from 24% to 36% ( P / E ratio of 24.0–28.2 mg protein kJ⁻¹) had no significant effects on growth performance and feed utilization ( P >0.05). Protein efficiency ratio tended to increase with dietary carbohydrate level at the same protein level. Dietary treatments significantly influenced body composition ( P <0.05), but not the condition factor, viscerosomatic index, hepatosomatic index and intraperitoneal fat ratio ( P >0.05). Based on these observations, 36% protein and 24–36% carbohydrate with the P / E ratio of 24.0–28.2 mg protein kJ⁻¹ seemed suitable for optimal growth and feed utilization, and carbohydrate could cause protein-sparing effect in diets for juvenile yellow catfish.     

黔中地区旱地黄壤抗干旱能力研究

对地处贵州中部的旱地黄壤水分特征曲线测定的基础上,通过2年的定位观测,旱地黄壤无效水分含量高、有效水分贮量少,作物利用难度大,抗干旱能力低,黄壤季节性干旱主要受制于降水;土壤水分耗竭随季节性气候特点和作物种类而异,旱地灌溉应结合季节性气候特点和作物种类等因素进行综合考虑,因地制宜地发展集雨工程,确定灌溉合理的灌水量是解决黄壤旱地季节性干旱的主要措施。     

In vitro and in vivo selection of probiotic purple nonsulphur bacteria with an ability to inhibit shrimp pathogens: acute hepatopancreatic necrosis disease‐causing Vibrio parahaemolyticus and other vibrios

Shrimp cultivation has been faced with huge losses in productivity caused by infectious shrimp pathogenic vibrios, especially Vibrio parahaemolyticus that causes acute hepatopancreatic necrosis disease (AHPND). Hence, purple nonsulphur bacteria (PNSB) were isolated from shrimp ponds for investigating their abilities to control shrimp pathogenic Vibrio spp. and their use as probiotics for sustainable shrimp cultivation. Based on their probiotic properties, strains S3W10 and SS15 were selected because of their strong abilities to produce amylase, gelatinase and vitamin B12. However, only three PNSB strains (SS15, TKW17 and STW181) strongly inhibited V. harveyi_KSAAHRC and V. vulnificus_KSAAHRC including V. parahaemolyticusAHPND strains by secreting antivibrio compounds. Four selected PNSB also grew in the presence of pancreatic enzymes, and they were identified as Rhodobacter sphaeroides for strains S3W10, SS15 and TKW17 and Afifella marina for strain STW181. The effects of a mixed culture were also investigated as follows: T1 (S3W10 + SS15), T2 (S3W10 + TKW17) and T3 (S3W10 + STW181) on postlarval white shrimp (Litopenaeus vannamei) for 60 days by comparison with a control. All three probiotic PNSB sets significantly improved the digestive enzyme activities and shrimp growth with their proliferation in shrimp gastrointestinal tract although the shrimp survival was not significantly different. They also significantly reduced the cumulative mortality of shrimp exposed to a virulent AHPND strain (V. parahaemolyticusSR2). This is the first to conclude that selected probiotic PNSB strains have great potential to be used for shrimp cultivation to control vibrios including AHPND strains.     

Detection of Aphanomyces invadans and epizootic ulcerative syndrome in the Murray‐Darling drainage

Epizootic ulcerative syndrome was diagnosed, and the presence of Aphanomyces invadans confirmed, from an outbreak of clinical disease in wild‐caught bony bream (Nematalosa erebi) from the Darling River near Bourke, in New South Wales, Australia, during 2008. This confirms a significant extension of the agent beyond its historical range.     

坡度和雨强对重庆市黄壤旱坡地产流产沙特征的影响

黄壤作为重庆市山地主要的土壤类型之一,对重庆市农业生产有重要影响。通过人工模拟降雨试验,研究不同坡度和降雨强度条件对黄壤旱坡地产流产沙特征影响及响应过程,结果表明：（1）输沙率随降雨强度的增大而增大,对于短历时强降雨来说,输沙率保持在一个相对平均的水平,比长历时中强度降雨的输沙率大。在坡度0°～25°以内,黄壤旱坡地产流量与坡度之间的关系可以用多相式进行拟合,得到产流临界坡度为22.83°;（2）土壤侵蚀量与坡度符合二次抛物线关系,随坡度的增加出现临界坡度,重庆市黄壤旱坡地土壤侵蚀的临界值坡度为24.7°。在降雨特征参数中,平均降雨强度是反映黄壤旱坡地泥沙量、径流系数和径流泥沙含量的最好特征参数,时段最大降雨强度I10最能反映黄壤旱坡地径流量的变化特征;（3）在10°,15°,20°3个不同坡度下,径流量和产沙量与雨强均表现为幂函数关系,相关系数均在大于0.05置信区间呈显著相关性。     

基于模拟降雨的土壤表土结皮特征及坡面侵蚀响应

土壤表土结皮对坡面侵蚀过程具有重要影响,利用模拟降雨条件下土壤贯入和产流产沙试验,对不同降雨场次紫色土和黄壤表土结皮特征及坡面侵蚀响应进行研究。结果表明：（1）PT型贯入仪测定的贯入数值（P）与含水率（θ）成标准指数函数关系。（2）不同降雨场次表土结皮存在＂无结皮→弱结皮→强结皮→弱结皮→新结皮＂的动态发育过程,相同降雨条件下黄壤表土结皮强度大于紫色土的。（3）持续降雨过程不同降雨场次土壤表土结皮对溅蚀影响不明显,而与产流存在显著的动态响应关系,结皮强度越大产流量也越大,结皮对产流的影响随着降雨进行而有增大趋势,黄壤表土结皮的径流增加量大于紫色土的,而紫色土坡面结皮对产流量变化敏感程度大于黄壤。不同场次降雨过程土壤表土结皮对坡面侵蚀产沙影响存在差异,前4场降雨表土结皮强度与坡面侵蚀产沙有相同的变化趋势,4次降雨后土壤表土结皮表现为对坡面侵蚀有抑制作用。     

三化螟预测模型的通径分析

利用1972-1988年三化螟发生的历史资料和气象资料,对影响因子进行相关分析,应用逐步判别分析的方法组建2代三化螟种群预测的判别模型。文中对判别模型进行通径分析的结果说明,2代三化螟种群预测系统的决定系数 R~2=0.9953,表明预报量的99.53％是由预测模型的全部7个预测因子所决定,尚有0.47％的预报量由未知因素所致,剩余通径系数 P_c=0.0684。经对历史资料的回报检验,该预测模型的判别率达到100％。经过1989和1990年实报。预报等级与实际发生量所代表的等级相符合。证实了2代三化螟种群预测模型预测因子的组成和结构符合预报的要求。     

近50年来黄河源区水文要素周期性分析及模拟

寒区水文过程是寒区生态系统中的重要环节之一,水热状况将直接决定高寒地区的生态环境状况.用滑动趋势法和墨西哥帽状小波变化分别获取了研究区域近50年来气候变化的年际年代变化及其周期分析,基于青藏高原太阳辐射平衡已有成果,结合联合国粮农组织推荐的彭曼-蒙蒂斯模型,对于达日县可能蒸散发进行了数值模拟.得出以下主要结论:近50年来达日县降水年增加率为0.557 mm/a,而该县最大可能蒸散发量的年增加率为0.132 mm/a,气候总体趋势是由干旱向湿润方向发生转变;达日县年气温序列主要呈现20 a、15 a、7 a和5 a的周期振荡,年降水序列表现为15～20 a和7～8 a的周期振荡;近20年来可能蒸散发呈递减的趋势,汛期序列递减率为0.046 7 mm/a,冬春序列递减率为0.108 4 mm/a.