Analysis of Inter-Individual Bacterial Variation in Gut of Cicada Meimuna mongolica (Hemiptera: Cicadidae)

Intestinal bacterial community plays a crucial role in the nutrition, development, survival, and reproduction of insects. When compared with other insects with piercing-sucking mouthparts, the habitats of cicada nymphs and adults are totally different. However, little is known about the differences in the gut bacterial communities in the nymphs and adults within any cicada species. The diversity of bacteria in the gut of nymphs and adults of both genders of Meimuna mongolica (Distant) was studied using the denaturing gradient gel electrophoresis (DGGE) method. Few inter-individual variations among gut microbiota were observed, suggesting that M. mongolica typically harbors a limited and consistent suite of bacterial species. Bacteria in the genera Pseudomonas and Enterobacter were the predominant components of the gut microflora of M. mongolica at all life stages. Bacteria of Pantoea, Streptococcus, and Uruburuella were also widespread in the cicada samples but at relatively lower concentrations. The relative stability and similarity of the PCR-DGGE patterns indicate that all individuals of this cicada species harbor a characteristic bacterial community which is independent from developmental stages and genders. Related endosymbionts that could be harbored in bacteromes of cicadas were not detected in any gut samples, which could be related to the cicada species and the distribution of these endosymbionts in the cicada cavity, or due to some of the possible limitations of PCR-DGGE community profiling. It is worthwhile to further address if related cicada endosymbiont clades distribute in the alimentary canals and other internal organs through diagnostic PCR using group-specific primer sets.     

鹅副粘病毒的人工感染试验

鹅副粘病毒是最新发现的,能引起各种年龄鹅发病的并致死的一种病毒。我们通过ＳＰＦ鸡胚分离的病毒尿囊液第４代,对鹅进行人工感染试验。结果表明,人工感染后,成年鹅群的发病率达到１００％,死亡率达３０％,１５日龄雏鹅感染后发病率和死亡率均达到１００％,这与自然发病鹅群的发病率和死亡率基本相同,而且人工感染后不管成年鹅还是雏鹅其临床病状和病理变化均与自然发病的鹅的病理变化相同,从而证实了该病理分离株的致病性及病原性。     

Random amplified polymorphic DNA markers reveal low genetic variation and a single dominant genotype in Eichhornia crassipes populations throughout China

Genetic variation within and between 34 populations of Eichhornia crassipes (water hyacinth) in China was surveyed using random amplified polymorphic DNA (RAPD) markers. A total of 1009 individuals were analysed, for which 12 RAPD primers amplified 69 reproducible bands, with 22 (32%) being polymorphic. The percentage of polymorphic loci (p) within a population ranged from 4.4% to 17.4%, and the mean Nei's gene diversity (H_e) was 0.046 ± 0.0145, indicating a low genetic diversity of E. crassipes in China. Each population contained at least four RAPD phenotypes (genotypes), and the same particular genotype was invariably dominant in all the populations sampled. The mean proportion of distinguishable genotypes was 0.29. Analysis of molecular variance revealed a large proportion of genetic variation (83.9%) residing within populations and a slightly larger proportion (88.1%) within localities, indicating a low genetic differentiation of E. crassipes populations, both locally and regionally. Human-mediated dispersal, vigorous clonal growth, and a generally low level of sexual reproduction were thought to be responsible for such a pattern of genetic structure.     

黄土丘陵区多次降雨补充下草灌地土壤水分空间变化规律

利用黄土丘陵区燕沟流域42场模拟降雨下土壤水分观测数据,研究2种坡度的草地、灌木地在不同经营方式(原状地、刈割地、翻耕地)下的土壤水分对模拟降雨的响应。结果表明:(1)在5次降雨补充下,依据土壤水分的标准差和变异系数,0~100 cm土壤水分受土地经营方式影响表现为:原状草灌地土壤水分可划分为活跃层、次活跃层和相对稳定层;刈割地全剖面为相对稳定层,翻耕地可分为活跃层和相对稳定层。(2)单次降雨事件则随降雨量增加,各经营方式下的水分活跃层逐渐变薄或消失,次活跃层变厚,而相对稳定层变薄,整个土壤剖面水分变化趋于一致。(3)对于受高强度降雨补充后的土壤水分变异性分层,建议采用更加灵敏的土壤水分标准差和变异系数判别标准:活跃层,标准差大于1.4%,变异系数大于12%;次活跃层,标准差1.4%~0.9%,变异系数12%~8%;相对稳定层,标准差小于0.9%,变异系数小于8%。(4)坡度越小土壤水分含量越高,坡度对草灌木地、刈割地的影响较翻耕地显著,且对50~100 cm土层水分影响远大于对表层0~50cm的影响。总之,降雨后土壤水分0~100 cm土层不断增加,且剖面土壤水分逐渐一致,土地经营方式、坡度因素对土壤水分变化强度和在不同深度土层中的表现有显著影响。     

Taxonomy,distribution and biology of lettuce powdery mildew (Golovinomyces cichoracearum sensu stricto)

This paper reviews the taxonomy, biology, importance, host–pathogen interactions and control of lettuce powdery mildew. The main causal agent of this disease, Golovinomyces cichoracearum s.s., is an important powdery mildew pathogen of many members of the family Asteraceae. The pathogen is distributed worldwide and occurs on Lactuca sativa as well as wild Lactuca spp. and related taxa (e.g. Cichorium spp.). Powdery mildew of lettuce can be a major problem in production areas with favourable environmental conditions for disease development (dry, hot weather). The fungus grows ectophytically and appears as white, powdery growth on both the upper and lower sides of leaves. There is rather limited information on the geographic distribution of powdery mildew on wild Lactuca spp. Most L. sativa cultivars have been found to be susceptible. Large variability in virulence was confirmed and existence of different races is supposed. Resistance in L. sativa and some related wild Lactuca spp. is characterized by race‐specificity, but the genetic background of resistance is poorly understood. Sources of resistance are known in L. saligna and L. virosa. Lettuce powdery mildew can be effectively controlled by common fungicides (e.g. sulphur, myclobutanil, quinoline, strobilurins, etc.) and protective compounds (e.g. extract of neem oil, Reynoutria sachaliensis extracts). However, fungicide resistance may arise. Non‐fungicidal activators of plant systemic acquired resistance (SAR) had no direct effect on the causal agent. Future issues regarding lettuce powdery mildew research are summarized.     

甘肃河东春季透雨日期与海温的相关分析

利用甘肃河东和宁夏回族自治区中南部1971～2000年67个站的春季第一场透雨日期资料,用EOF和REOF方法对其做了分解,进行了透雨日期的气候分区,分析了春季第一场透雨日期的时空分布特征,并计算了其与北太平洋海温的相关关系。结果表明,北部透雨平均日期与南部透雨平均日期具有相反的趋势,北部最迟在5月下旬,南部最早在4月中旬;20世纪70年代透雨日期偏迟,80年代透雨日期偏早,90年代偏迟。透雨早的年份,春季降水偏多,透雨迟的年份,春季降水偏少;透雨日期与北太平洋海温呈显著的负相关,当北太平洋地区的海温偏高时,甘肃河东春季透雨日期偏早。当北太平洋地区的海温偏低时,甘肃河东春季透雨日期偏迟。     

水稻黑条矮缩病毒S6片段的序列多样性与进化分析

<正>0 引言植物RNA病毒在进化中具有快速变异的能力,有利于病毒扩大寄主范围甚至进化为新病毒[1]。突变和重组是植物RNA病毒变异和遗传多样性的共同进化因素,是群体基因变异的最初来源[2]。由灰飞虱传播的水稻黑条矮缩病毒(Rice black streaked dwarf virus, RBSDV) 属于呼肠孤病毒科(Reoviridae)斐济病毒属(Fijivirus),能引发玉米粗缩病和水稻黑条矮缩病。     

苹果杂交后代果实性状遗传变异分析

以216株"富士"×"粉红女士"杂交F1代实生苗为试材,对果实大小、果实形状、果实色泽、风味、成熟期等性状遗传表现进行了研究。结果表明:苹果果皮表色遗传表现为简单的质量遗传,红色遗传表现为多基因控制的数量遗传。果形表现了明显的趋中变异现象,果实大小、可溶性固形物及含糖量呈退化的负向优势,后代群体有劣变趋势。杂交后代果实分别呈现肉质变粗、质地变硬、果汁减少的趋势。双亲晚熟,杂交后代未分离早熟类型,表现双亲遗传优势。