Capsid protein sequence gene analysis of <Emphasis Type="Italic">Apple mosaic virus</Emphasis> infecting pears

Apple mosaic virus (ApMV, genus Ilarvirus) was detected in pears, a previously non-reported virus host. No symptoms were visible on the hosts leaves. Seventeen out of 22 randomly selected pear trees in Italy (Lombardy) and in three regions in the Czech Republic were ApMV-infected. All nine newly sequenced ApMV isolates from pears had a 15-nucleotide insertion in the capsid protein gene in identical position of that of apple isolates compared with isolates from hop and prunes. The insertion is the most prominent (but not essential) modification of the capsid protein gene, which results in a phylogenetic separation of ApMV isolates into three clusters. Sequence analysis data of an additional 15 isolates revealed a sequence correlation with kernelled fruit trees (apple and pear).     

The status of host fish populations and fish species richness in European freshwater pearl mussel (Margaritifera margaritifera) streams

• 1. The status of host fish populations and fish species richness was investigated at 36 sites of 20 extant freshwater pearl mussel populations, including the drainages of the Elbe, Danube, Rhine, Weser, Aulne, Kemijoki and Tuuloma in Germany, the Czech Republic, France and Finland, by carrying out comparative electrofishings.
• 2. Brown trout (Salmo trutta f. fario) were found to be the available host fish for pearl mussels in all except one of the streams investigated with mean densities of 2861 ha^?1 (range 0–8710 ha^?1) and a mean biomass of 119 kg ha^?1 (range 0–478 kg ha^?1). Streams that had been frequently stocked with brown trout had higher trout biomass and densities of host fish than natural populations, but trout stocking had no positive effect in two of the streams investigated.
• 3. Fish species richness ranged from 2 to 16 species per stream and showed a negative correlation with host fish biomass and host fish densities. Undisturbed oligotrophic pearl mussel headwater streams usually only yielded a low number of fish species. Habitat degradation can reduce competitiveness of specialized trout and result in an increased abundance of ubiquitous or atypical species.
• 4. A link between the lack of juvenile pearl mussels and a lack of suitable host fish was only rarely observed. Functional pearl mussel populations with relatively high numbers of juveniles had significantly lower densities and biomass of host fish than pearl mussel populations without recent recruitment.
• 5. This study suggests that 0+ host fish are not necessarily required to sustain functional pearl mussel populations. Low densities of host fish can be compensated by the higher glochidia carrying capacity of older host fish with limited previous contact with pearl mussel glochidia, by the long reproductive period of mussels, and by low mortality rates of juvenile mussels during their post‐parasitic phase.

Copyright © 2005 John Wiley & Sons, Ltd.     

Typology in Mediterranean transitional waters: new challenges and perspectives

• 1. Transitional waters are ecotones between terrestrial, freshwater and marine ecosystems, being characterized by high spatial heterogeneity and temporal variability.
• 2. The EU Water Framework Directive (WFD) posed to the scientific community the challenge to classify these ecosystems into a small number of types, while retaining a functional classification of ecosystem types.
• 3. A niche theory approach is proposed to identify the limiting forcing factors organizing biological quality elements, i.e. the limiting niche dimensions.
• 4. The analysis of a macro‐invertebrate dataset from published papers on 36 Italian lagoons suggested a two‐level typological classification of Mediterranean lagoons.
• 5. Basic ecological theories, such as niche and island biogeography theories, have fundamental implications for the process of developing a typological classification for all aquatic ecosystems, as required by the WFD.

Copyright © 2006 John Wiley & Sons, Ltd.     

枣镰翅小卷蛾成虫的寄主趋向和产卵选择

采用固相微萃取(SPME)和GC-MS分析研究木枣和酸枣挥发物成分,并测试枣镰翅小卷蛾触角电位(EAG)反应、寄主趋向和产卵选择,以探明枣镰翅小卷蛾的寄主选择机制。结果显示,在萌芽期,木枣和酸枣嫩叶的挥发成分均为罗勒烯、2-甲基-2-菠烯、α-法呢烯和邻苯二甲酸二丁酯4种,但相对含量稍有不同。枣镰翅小卷蛾成虫对木枣和酸枣2种寄主都有强烈的EAG反应,且同一寄主上雌蛾的EAG反应值极显著地高于雄蛾,其EAG值是雄蛾的3.3倍。枣镰翅小卷蛾对木枣表现强烈的趋向反应,而对酸枣的趋向不明显,且雌虫的趋向反应显著高于雄虫。木枣上的产卵量显著高于酸枣,且木枣枣吊上的单雌产卵量为307.9粒,极显著地高于酸枣枣吊上的产卵量(182.9粒)。研究表明,枣镰翅小卷蛾雌蛾在寄主选择中起主导作用,木枣是其嗜好寄主。     

塔克拉玛干沙漠荒漠过渡带空气动力学粗糙度分析

根据塔克拉玛干沙漠北缘荒漠过渡带哈德、肖塘2个试验点的风、温梯度观测数据,利用风速比法计算了中性大气层结、无风沙运动条件的空气动力学粗糙度[WTBX](z0),并分析探讨z0[WTBZ]与下垫面状况、大气稳定度及风速的相互关系。结果表明：哈德、肖塘中性条件下z₀的取值范围分别为 1.81×10^-11～1.20×10^-3m,1.00×10^-11～1.65×10^-3m,平均值为2.70×10^-5m 和6.05×10^-5m,与平坦沙面的值较为接近;z₀随下垫面性质变化明显;空气动力学粗糙度总体上随着理查逊数(R_i)增大而变大,但又呈现出一定的离散程度;空气动力学粗糙度与2 m高度风速呈显著的负指数关系;大气稳定度对空气动力学粗糙度的影响作用有待于进一步确定。      

一种引起茄科作物病害的病原:Candidatus Liberibacter solanacearum

Candidatus Liberibacter solanacearum是Liefting等人于2009年鉴定并命名的一种能够引起茄科作物病害的新病原,该病菌可引起茄科作物植株矮化、畸形并造成巨大的经济损失。目前该病菌在我国尚无分布。本文从病原鉴定、寄主范围、地理分布、传播途径、危害情况及防控措施等几方面对该病菌进行了简要介绍,以期引起重视,并为防范其入侵提供参考。     

亚洲型舞毒蛾幼虫寄主选择与龄期关系初探

舞毒蛾是一种世界性的害虫,常被分为欧洲型和亚洲型2种类型,欧洲型舞毒蛾在传入美国之后造成了巨大危害。之前报道指出亚洲型舞毒蛾的寄主范围比欧洲型舞毒蛾的广,故造成的危害和损失更大,北美植物保护组织据此对中国的高风险港口实施了船舶特别检疫措施,对我国的进出口贸易产生了巨大影响。鉴于此,本实验以16种北美和中国常见的行道树种和绿化树种作为供试树种,分析了不同寄主植物对亚洲型舞毒蛾生长发育指标的影响规律。结果表明:饲喂白桦、加杨和糖槭的幼虫可以完成生活周期。饲喂杜松、女贞、大叶黄杨、红皮云杉、合欢、杂交鹅掌楸、马尾松、黑松和白皮松的幼虫在2龄以前全部死亡。虽然2龄以前幼虫饲喂北美乔松、油松和柿树后死亡率较高,但用人工饲料将幼虫饲养至4龄以后再替换饲喂以上3种植物,幼虫的死亡率则显著下降。分析表明,亚洲型舞毒蛾低龄幼虫(1、2龄)的寄主选择范围要窄于高龄幼虫(4龄以后的幼虫)。     

温度和贮存时间对花绒寄甲替代寄主生活力的影响

在实验室恒温(10,5,2℃)条件下,分别将花绒寄甲的替代寄主贮存3,5,7,9,11,13,15d,观察、记录花绒寄甲的幼虫数和结茧数。结果表明:替代寄主在10℃的温度下储存7d,花绒寄甲的幼虫数和结茧数最多,均为2.9头;5℃时,储存11d幼虫数和结茧数最多,分别为2.7头和2.8头;在2℃条件下,储存3d幼虫数和结茧数最多,分别为3.0头和2.8头,说明贮存时间对替代寄主的生活力有显著影响。同时,研究也表明贮存温度对替代寄主的生活力无显著影响。