Resistance to foliage-feeding insects in conifers: implications for pest management

The ecological implications of insect resistance in conifers are rarely discussed. It is however a fairly straightforward plant-insect interaction and should be treated as such, making use of the increasing amount of information in this field. Work on tree breeding is usually carried out by silviculturalists who, not surprisingly, rarely consider the insect component of the environment in which the treess are growing. In all fairness, it must be stated that many entomologists, fail to consider the plant component of the interaction. Clonal forestry will almost certainly result in the loss of genetic variability. The use of clonal material has already been cited as a possible source for the diminution of the resistance against pests and diseases and if particular resistance mechanisms against forest pests are sought in the future the reduction in genetic material caused by clonal selection could have serious consequences. The ethics of clonal forestry have been questioned as have the ethics of biotechnological advances in the area of recombinant DNA molecules. The potential of both these techniques should be publicized and brought to the attention of the general public and the scientific community at large and evaluated. To improve our forest environment and to protect the environment as a whole, entomologists, geneticists, physiologists and silviculturalists must work together to produce better trees that require little, if any, chemical aid, be it insecticides, herbicides, fungicides or fertilizers. An increasing awareness of the environmental problems generated by large-scale insecticide applications to forest plantations, coupled with an increasingly chemophobic work-force and the difficulty in obtaining pesticide registration for use in forest environments, means that the forest industry world-wide must look to the use of integrated control measures with more diligence than has been shown in the past. Many recent outbreaks of pests and diseases have been linked with particular seed origins of tree crops. Host plant resistance as part of a suite of other proposed integrated control tools is thus an obvious candidate for development. Despite this, scientists concerned with tree improvement continue to select largely for silvicultural traits rather than for resistance to pests and disease. The different avenues open to plant breeders are examined and the potential of breeding trees resistant to insect attack highlighted. Using resistant trees as part of an integrated pest management system has five very important properties. Firstly, there is no additional pest control cost to the grower, secondly, it operates at all levels of insect incidence and not just when the pest is at high population levels, thirdly, it reduces the insect population cumulatively, fourthly it avoids toxic residues and environmental pollution and, finally, it usually interacts well with the other integrated pest management strategies in existence.     

Biological characteristics of maize dwarf mosaic potyvirus from Spain

Two isolates of maize dwarf mosaic virus (MDMV-Sp and MDMV-Spl) obtained from maize in the northeast of Spain were studied. Both isolates induced similar reactions on 6 sorghum cultivars, johnsongrass and oat (cv. Clintland), with the exception of MDMV-Sp which produced a different reaction on one sorghum cultivar. Thirty-three grass species were tested as possible hosts (16 previously untested) and 18 were found to be susceptible. Among those, eight were previously unidentified hosts for MDMV:Aegilops ovata, A. ventricosa, Avena barbata, Bromus alopecurus, B. diandrus, B. fasciculatus, Echinaria capitata andLolium rigidum. Both isolates were transmitted from maize to maize nonpersistently byRhopalosiphum maidis, R. padi, Schizaphis graminum andSitobium avenae. The virus was not seed-transmitted in Mo17 and B73 maize inbred lines. Pinwheels, scrolls and short curved laminated aggregates were observed in the cytoplasm of maize cells infected by MDMV-Sp or MDMV-Sp1. In addition, laminated aggregates were observed in cells infected by MDMV-Sp1.     

应用赤眼蜂蛹人工饲养尼氏钝绥螨的研究初报

本文首次报导应用赤眼蜂蛹作为替代食料人工饲养尼氏钝绥螨。日食蛹量,幼螨为0.18头,产卵前期成螨达1.18头,而产卵期成螨则为0.95头左右。在25℃饲养条件下,每雌产卵达45粒,卵历期48小时,孵化率近92％,幼螨存活率88％,成螨雌性占55％,雌成螨寿命25天。用赤眼蜂蛹连代饲养的尼氏钝绥螨在桔园释放,对柑桔全爪螨具有明显的控制作用。     

Greenhouse and field screening of wild<Emphasis Type="Italic">Lycopersicon</Emphasis> germplasm for resistance to the whitefly<Emphasis Type="Italic">Bemisia argentifolii</Emphasis>

Thirty-two accessions of wild tomato (Lycopersicon spp.) germplasm were evaluated for resistance to the whiteflyBemisia argentifolii Bellows ⇐p; Perring in a greenhouse choice bioassay. Density data were recorded for the adaxial and abaxial leaf surfaces for (i) all life stages ofB. argentifolii and (ii) types I, IV, V and VI trichomes. Individual plant selections (33 from 22 wild tomato accessions) with high resistance were subsequently tested in the field to verify the resistance found in the greenhouse screening. Resistance was defined by the density of all life stages of the whitefly observed on the eight leaflets sampled at nodes 5 and 7. Only type IV trichomes had a consistent (but low) and significant negative correlation between trichome density and whitefly density for various life stages. The highest whitefly resistance was observed inLycopersicon pennellii accessions LA 716, LA 1340 and LA 2560. The most resistantL. hirsutum f.typicum accessions were LA 1777 and LA 1353. http://www.phytoparasitica.org posting Dec. 9, 2002.     

新家蚕品种“雄晓”的选育技术及性状介绍

苏州大学蚕桑研究所发明现行蚕品种转育成荧光茧色判性蚕品种的方法,新育成的蚕品种“雄晓”雄茧为黄荧光,雌茧为紫荧光,判性率100%。茧质成绩：全茧量1．499g,茧层量0．366g,茧层率24．42%,具生产实用性。     

<Emphasis Type="Italic">Amaranthus leaf mottle virus</Emphasis>: 3′-end RNA sequence proves classification as distinct virus and reveals affinities within the genus <Emphasis Type="Italic">Potyvirus</Emphasis>

Amaranthus leaf mottle virus (AmLMV) was classified as a member of the genus Potyvirus on the basis of its particle morphology, serology, and biological properties (Casetta et al., 1986). Based on these properties, an Amaranthus viridis-infecting virus isolated in Spain, causing mottle and leaf blistering as well as reduced growth has been identified as AmLMV. The 3′ terminal genomic region of this and a reference isolate from Italy has been sequenced and reveals a 95% nucleotide identity between the two isolates. The sequenced part comprises the coat protein with 281 amino acids and 315 nucleotides of the 3′ untranslated region (UTR) preceding a polyadenylated tail. Pairwise comparisons and phylogenetic analysis of the nucleotide and deduced amino acid sequences of the CP and 3′ UTR of the cloned cDNAs with those of other potyviruses shows that AmLMV is a distinct potyvirus closely related to Potato virus Y.     

植物挥发性次生物质对植食性昆虫的影响

植物挥发性次生物质对植食性昆虫的寄主选择、取食、交配、产卵等行为有着重要的影响作用。本文就植物挥发性次生物质对植食性昆虫影响的研究状况及其进展进行综述报道,以便为进一步深入开展这方面的研究提供借鉴。     

卷叶螟绒茧蜂寄生棉大卷叶螟的行为及其与寄主密度的关系

卷叶螟绒茧蜂Apanteles derogatae Watanabe是棉大卷叶螟Sylepta derogata Fabricius幼虫期的一种重要内寄生蜂,对棉大卷叶螟种群有较好的控制作用。在实验室条件下,运用人工接虫观察法研究卷叶螟绒茧蜂对棉大卷叶螟幼虫的寄生行为。结果表明,该蜂搜寻寄主的时间平均为2．38 min,处理寄主的时间仅需0．86 min;寄生寄主的最适龄期为寄主2龄幼虫;对1龄幼虫的致死率达32%,但其寄生率仅为16%,其余16%的个体为穿刺致死。饲喂蜂蜜水能显著增加该蜂的产卵量,延长其产卵历期和增强其穿刺能力。寄生蜂的寄生能力与寄主密度的关系呈抛物线型:在寄生蜂均为16头/m~3雌蜂条件下,当寄主密度从80头/m~3增加到320头/m~3时,寄主的被寄生个体数随之增加,但当寄主密度超过320头/m~3后,寄主的被寄生个体数反而随寄主密度的上升呈下降趋势。     

不同食料植物对安婀珍蝶幼虫生长发育影响

恒温条件下用薇甘菊、香泽兰、野茼蒿、菜苔和青菜为食料饲养安婀珍蝶,测定各龄幼虫的体长、体重和头壳宽度,研究不同食料植物饲养对安婀珍蝶幼虫生长发育的影响。结果表明:安婀珍蝶取食野茼蒿、菜苔和青菜虽然程度有不同,但生长发育受到影响,高龄幼虫体长、体重和头壳宽度明显低于薇甘菊饲养的试虫,不能完成生活世代。     

加拿大蓟天敌─欧洲方喙象的寄主专一性测定

在温度为25～28 ℃的养虫室内选择具有代表性的菊科植物及豆科、禾本科牧草共10科30种植物对欧洲方喙象进行寄主专一性测定试验，结果表明其食性专一，只取食加拿大蓟，个别成虫或幼虫在饥饿状态下仅少量取食菊科其他植物，但随后即拒绝取食。非选择性试验（饥饿试验）表明欧洲方喙象耐饥饿能力强，不同龄期平均达28 d。欧洲方喙象最适宜的生长温度是25 ℃，高于30 ℃或低于10 ℃，生长发育则受到抑制。