The insecticidal and acaricidal actions of compounds fromAzadirachta indica (A. Juss.) and their use in tropical pest management

The pest control potential demonstrated by various extracts and compounds isolated from the kernels and leaves of the neem plant (Azadirachta indica) A. Juss. (Meliaceae) seem to be of tremendous importance for agriculture in developing countries. Laboratory and field trial data have revealed that neem extracts are toxic to over 400 species of insect pests some of which have developed resistance to conventional pesticides, e.g. sweet potato whitefly (Bemisia tabaci Genn. Diptera: Aleyrodidae), the diamond back moth (Plutella xylostella L. Lepidoptera: Plutellidae) and cattle ticks (Amblyomma cajennense F. Acarina: Ixodidae andBoophilus microplus Canestrini. Acarina: Ixodidae). The compounds isolated from the neem plant manifest their effects on the test organisms in many ways, e.g. as antifeedants, growth regulators, repellents, toxicants and chemosterilants. This review strives to assess critically the pest control potential of neem extracts and compounds for their use in the tropics. This assessment is based on the information available on the wide range of pests against which neem extracts and compounds have proven to be toxic, toxicity to non-target organisms, e.g. parasitoids, pollinators, mammals and fish, formulations, stability and phytotoxicity.     

干旱区土地退化生态系统的评价方法

本文简要介绍了我国干旱区的二种分类方法、分布面积和自然特点。干旱区土地生态系统退化的主要类型有草场退化，而养耕地退化和灌溉地退化，国内外各种退化类型的分布面积。提出退化土地生态系统评价原则，主要退化土地的评价指标体系，评价因子权重的确定方法，综合评价方法及地理信息系统的应用。     

新疆昌吉州波斑鸨分布与数量考察初报

本文报道了波斑鸨（Ｏｔｉｓｕｎｄｕｌａｔａ＝Ｕｎｄｕｌａｔａｕｎｄｕｌａｔａ）在新疆昌吉州境内的分布和种群数量。昌吉州为我国波斑鸨的主要繁殖地，繁殖区由三片不连续的地区组成，总面积约１３４００ｋｍ２，界于Ｅ８８°３０’－９１°１５’，Ｎ４３°５７’－４５°之间。据１２条样带统计结果，平均栖息密度为０．０３２±０．００８２只／ｋｍ２，种群数量为４２８．８±１００．８８只，即３１９—５３９只。     

温度对截形叶螨生长发育和繁殖的影响

在室内15—35℃恒温条件下,截形叶螨的发育历期与温度呈负相关,在15、25和35℃下雌螨一代平均历期分别为32.13、9.02和5.64天;雌、雄螨一代发育起点温度分别为10.90和11.33℃,有效积温分别为135.42和110.47日度;不同温度对世代存活率及子代雌雄性比的影响无显著差异,但雌成螨的寿命及产卵期均随着温度的升高而缩短;30℃下内禀增长率(0.3298)、周限增长率(1.3907)、净增殖率(130.993)、日产卵量(10.98)及总产卵量(181.90)都最高,30℃是种群繁殖增长的最适温度。     

马铃薯纺锤块茎类病毒的检测和防治

马铃薯纺锤块茎类病毒病(potato spindle tuber viroid,PSTVd)是一种严重为害马铃薯生产的病害,降低产量20%—30%。防治的主要措施是应用无类病毒的种薯。由于目前还没有脱掉类病毒的有效措施,只能从未被饱和侵染的群体中鉴定筛选出未被侵染的个体,再脱掉其它病毒,作为核心繁殖材料。1987年以来,利用自制的电泳设备,以往复聚丙烯酰胺凝胶电泳法(return-polyacrylamide gel electrophoresis,R-PAGE)检测类病毒,筛选出未感病的个体,再用茎尖组织培养法脱掉其它病毒。经用马铃薯卷叶病毒等8种病毒酶标抗体鉴定筛选,获得既无类病毒也无主要马铃薯病毒的克新1、2、3和4号等主栽马铃薯品种的核心种。并已提供给省内外的良种场繁殖推广。1989和1990年抽样检测克山良种场繁殖的原种、一级和二级良种,未检测到类病毒。     

Specificity of polycllonal and monoclonal antibodies for the identification of Xanthomonas campestris pv. campestris

Polyclonal and monoclonal antibodies (PCAs and MCAs), produced to whole cells and flagellar extracts ofXanthomonas campestris pv.campestris (Xcc), respectively, were tested for specificity. In immunofluorescence microscopy (IF) the three PCAs tested, reacted at low dilutions with all Xcc strains, some other xanthomonads and non-xanthomonads. At higher dilutions most cross-reactivity with non-xanthomonad strains disappeared. However, the cross-reactivity with strains ofX. c. pv.vesicatoria (Xcv),X. c. pv.amoraciae (Xca) andX. c. pv.phaseoli var. fuscans (Xcpf) remained.Six MCA-producing cell clones viz. 20H6, 2F4, 18G12, 10C5, 17C12 and 16B5 were selected for specificity tests with an enzyme immunoassay (EIA), IF and a dot-blot immunoassay (DBI). None of the MCAs reacted with all Xcc strains in IF and EIA. In DBI, only MCAs 17C12 and 16B5 reacted with all Xcc strains. All six MCAs tested, cross-reacted in one of either tests with other pathovars ofX. campestris, such as Xcv or Xca. The MCAs were also tested in immunoblotting experiments using total bacterial extracts, cell envelope and flagellar extracts. MCAs 20H6, 2F4, 18G12 and 10C5 reacted with the lipopolysaccharide (LPS) of Xcc. MCAs 16B5 and 17C12 reacted with a 39 kilodalton and a 29 kilodalton protein, respectively.It is concluded that the PCAs and MCAs discussed in this study may be used for routine identification and differentiation of (a group of) Xcc strains. The significance of the cross-reactions with other pathovars ofX. campestris needs to be determined by testing seed lots.     

用免疫分离法检测稻种上的白叶枯病菌

 免疫分离法是一种新型的、高度灵敏和准确的种菌带菌检验法,它结合了利用专化性抗血清的选择法吸附作用和活细菌可形成菌落的两方面的优点,从种苗材料中分离到目标细菌,用纯菌测试它的回收率为50~70%,最低检出率为50~100个菌/ml,人工喷接种和病田收获的病种带菌率达87%,平均每粒自然病种上的细菌数在100个左右。免疫分离所得菌落经致病性测定,大多数为白叶枯菌。     

氟乐灵处理后棉苗对枯萎病菌的抗侵入及抗扩展特性

 以1μg/g土的氟乐灵播前土壤处理,棉花出苗后移栽到无氟乐灵的土壤中并接种棉花枯萎病菌(Fusarium axysporum f.sp.vasinfectum)。结果表明氟乐灵处理明显降低了棉苗枯萎病的株发病率和病情指数,提高了棉苗对枯萎病的抗病性。氟乐灵处理组棉苗根部和茎部枯萎病菌侵染率均低于对照组,特别是上部茎片段中处理组侵染率降低更为明显。氟乐灵处理组棉苗根部和茎部的菌量明显降低,而且处理组茎部菌量的增长明显滞后于对照。以上结果表明,病菌对氟乐灵处理棉苗根部的侵入和病菌在棉苗体内的纵向扩展及增殖受到了阻抑,因而氟乐灵处理后棉苗对枯萎病菌的抗性表现了抗侵入和抗扩展的特性。试验还证明,氟乐灵处理并接种病菌的棉苗茎部组织中类萜烯醛的含量明显提高;并产生一种能抑制病菌大型分生孢子萌发的真菌毒性物质。这些抑菌物质的产生和积累可能与抗扩展特性有关。     

The induction of 1,3-β-glucanases and other enzymes in groundnut leaves infected with Cercospora arachidicola

Infection of groundnut leaves with the early leaf spot pathogen Cercospora arachidicola leads to a marked increase in extracellular 1,3-β-glucanase activity, limited to the infected tissue. Three isoforms of low molecular weight and extreme pI values, typical of pathogenesis-related proteins, were induced. These β-glucanases, when acting together, were capable of degrading the pathogen cell wall in vitro. Glucanases from homogenates of infected leaf tissue were partially purified by ion-exchange chromatography to give enzymes with molecular weights of 35, 32 and 20 kDa and pI values of 3·8, 3·6 and > 9, respectively. They were electrophoretically identical to the β-glucanases found in the intercellular washing fluid. Treatment of groundnut plants with 200 μM mercuric chloride induced the accumulation of identical extracellular β-glucanases. During the course of the infection an increase in peroxidase activity was also observed, but chitinase activity remained more or less constant.     

水稻细菌性条斑病发生及流行因子分析

人工接种及病区调查研究结果表明，在种植感病品种情况下，气温决定了水稻细菌性条斑病的发生与否和潜育期的和短衣病斑长度；病害发生的最低温为１２℃，发病最适温度为２５－３０℃以上，而湿度决定此病发病率及严重度。结合主成分分析，该病在田间的流行取决于温度／湿度及降雨量。台风暴雨造成的伤口有利于病害的流行。