Forest fragmentation and duration of forest tent caterpillar (Malacosoma disstria Hübner) outbreaks in northern hardwood forests

In northern forests dominated by aspen (Populus spp.), the duration of outbreaks of forest tent caterpillar (Malacosoma disstria Hübner) has been reported to increase with forest fragmentation. This relationship has not been tested in other forest types affected by this widespread native defoliator. From 2002 to 2007, a large-scale outbreak of this insect in the northeastern United States defoliated millions of hectares, with sugar maple (Acer saccharum Marsh.) the primary host. We used digital defoliation maps generated from aerial surveys and national land cover data to assess the effect of fragmentation on outbreak duration in areas of NY, MA, VT, and NH. We found that outbreak duration increased with forest cover and decreased with the forest edge, in opposition to the pattern previously reported for aspen-dominated forests in Canada. This pattern was significant from plot sizes ranging from 100 m to 1000 m in radius. The relationship between FTC and its natural enemies, which was postulated to underlie the effect of fragmentation on outbreaks in aspen forests, may be affected differently in northern hardwood forests, or other factors may be more important in determining outbreak duration in this forest type.     

取食不同寄主植物椰心叶甲后代对杀虫剂的敏感性差异

测定了不同寄主植物饲养的椰心叶甲种群对3种杀虫剂的敏感性变化情况。结果表明,取食不同食料的椰心叶甲后代对啶虫脒敏感性顺序为:鱼尾葵>酒瓶椰子>大王棕>椰子叶,对高效氯氰菊酯敏感性顺序为:鱼尾葵>酒瓶椰子>椰子叶>大王棕,对阿维菌素敏感性顺序为:酒瓶椰子>椰子叶>大王棕>鱼尾葵;其中对阿维菌素的敏感性差异幅度最大,为14.18倍,对高效氯氰菊酯和啶虫脒的敏感性差异幅度较小,分别为3.47倍和2.54倍。表明取食不同的寄主植物可引起椰心叶甲对杀虫剂的敏感性变化。     

Antimicrobial Resistance Profiles and Clonal Relatedness of Canine and Feline Escherichia coli Pathogens Expressing Multidrug Resistance in the United States

Background: Antimicrobial resistance is increasing among Escherichia coli isolates associated with spontaneous infection in dogs and cats. Objectives: To describe E. coli resistance phenotypes and clonal relatedness and their regional prevalence. Animals: Isolates of E. coli (n = 376) collected from dogs and cats in the United States between May and September 2005. Methods: Isolates submitted from the South, West, Northeast, and Midwest regions of the United States were prospectively studied. Phenotype was based on E‐test susceptibility to 7 antimicrobials. Isolates were classified as no (NDR), single (SDR), or multidrug resistance (MDR). Clonal relatedness was determined by pulsed‐field gel electrophoresis (PFGE). Results: One hundred and ninety‐three (51%) isolates expressed resistance to at least 1 drug, yielding 42 phenotypes. SDR isolates (n = 84; 44%, 8 phenotypes), expressed resistance most commonly to amoxicillin (30%, n = 25) and least commonly to cefpodoxime (1%, n = 1). MDR isolates (n = 109; 56%, 31 phenotypes) were resistant to amoxicillin (96%, n = 105), amoxicillin‐clavulanate (85%, n = 93), and enrofloxacin (64%, n = 70); 18% (n = 20) were resistant to all drugs tested. The frequency of MDR did not differ regionally (P= .066). MDR minimum inhibitory concentrations (MICs) were 6‐fold higher than SDR MICs (P < .0001). Dendrograms of 91 isolates representing 25 phenotypes revealed 62 different PFGE profiles. Conclusions and Clinical Importance: E. coli strains spontaneously infecting dogs and cats are genetically and phenotypically diverse. Given the current prevalence of MDR among clinical isolates of E. coli in United States, implementation of a robust surveillance program is warranted.     

岩土介质强度参数相关性的敏感度分析

 岩土介质的强度参数特别是C,Φ互相关性分析一直是岩土工程界研究的热点。本文在分析C,Φ互相关性和分布检验方法后,通过随机空间正交变换将具有互相关性的C,Φ变换得到独立随机变量,基于Mohr-Coulumb准则,详尽分析了C,Φ互相关性对准则可靠度的敏感度。并得出一些对工程可靠度设计有重要意义的结论。     

基于原位LAMP技术的牡蛎疱疹病毒(OsHV-1)易感宿主调查

牡蛎疱疹病毒(Ostreid herpesvirus 1, OsHV-1)给世界双壳贝类养殖业造成了严重的经济损失。10余种双壳贝类陆续被认定为易感宿主,仍有其他几种贝类仅有PCR核酸阳性数据,因确诊证据不足导致其易感性未得到充分评估。原位环介导等温核酸扩增(LAMP)检测技术相对传统原位杂交技术具有灵敏度高、方便快捷、可作为病原微生物感染证据的优点。为了在OsHV-1流行病学调查过程中实现病毒感染的快速检测和确诊,根据已报道的OsHV-1特异性LAMP检测引物,设计内引物,优化反应条件,建立了OsHV-1的原位LAMP检测方法。基于该方法对2019年以来采集的长牡蛎(Crassostrea gigas)、福建牡蛎(Crassostrea angulata)、栉孔扇贝(Chlamys farreri)、虾夷扇贝(Mizuhopecten yessoensis)、毛蚶(Scapharca subcrenata)和菲律宾蛤仔(Ruditapes philippinarum)样本进行检测。结果显示,毛蚶样本的OsHV-1原位LAMP检测结果呈阳性;其他几种贝类部分样本的实时定量PCR (qPCR)检测呈阳性,但原位LAMP检测呈阴性。对毛蚶样本的原位LAMP检测结果分析发现,病毒杂交信号主要分布在外套膜和肝胰腺等器官的结缔组织,推测感染的细胞为成纤维细胞和血淋巴细胞;在闭壳肌和斧足肌肉组织的肌细胞细胞核中也发现较多杂交信号。鳃丝内和周边偶现阳性信号,推测来自渗出的血淋巴细胞。基于原位LAMP技术的OsHV-1检测结果显示,毛蚶是OsHV-1的一种易感宿主,毛蚶结缔组织、肌肉组织和血淋巴细胞对该病毒有强亲嗜性。     

Response of selected okra cultivars to Meloidogyne incognita

Root–knot nematodes (Meloidogyne spp.) are major pests of vegetables especially in the tropics and subtropics. All commercial okra varieties are susceptible to root knot nematodes and cause substantial losses. The objective of this study is to find out resistant germplasm in order to facilitate our breeders for gene manipulation. A greenhouse study was conducted to evaluate 28 okra cultivars against Meloidogyne incognita inoculated with 5000 eggs. Five cultivars (Bamya Yalova, 19,232, 19,236, 1,922,121, and Green Wonder) had significantly fewer root galls and eggs and less reduction in plant growth (shoot weight and root length), than most of the other entries. A positive relationship was demonstrated between root galls and reduction in plant growth parameters measured. These cultivars may improve okra production in fields infested with M. incognita. During our study, none of the cultivars tested were observed to be immune or resistant to nematode infection according to a scale where: good host [susceptible] when Pf/Pi (Pf = Final population of nematodes after harvest and Pi = Initial population of nematodes which was used as inoculum during experiment) > 5.0, fair, better [moderately resistant] if 5.0 ≥ Pf/Pi > 1, poor if 1 > Pf/Pi > 0, and non-host [resistant] when Pf/Pi = 0. The cultivars, including 19,224, 19,235, Pusa Sawami, Ikra-1, Ikra-2 and Sabzperi China Red, were found to be susceptible with Pf/Pi > 5.0, and they were declared as good hosts of M. incognita. While all the other cultivars were moderately resistant, with 0 ≥ Pf/Pi > 1 but still a significant penetration of nematodes was found. The regression studies showed positive and significant relationships between the number of galls and the reduction in shoot weight (r² = 0.95), number of galls and reduction in shoot length (r² = 0.81), and number of galls and decrease in root length (r² = 0.89).     

Drought Tolerance Screening Under Controlled Conditions Predicts Ranking of Water‐Limited Yield of Field‐Grown Soybean Genotypes

Drought is a major limitation to crop yields worldwide. Screening for soybean yield under water deficit is often a bottleneck in breeding programmes. We assessed the validity of a standardized drought tolerance screening method to predict water‐limited field performance of soybean in NW Argentina. First, to determine the phenological period when yield of glasshouse‐grown plants was more sensitive to water deficit, we applied treatments during 21 days in V₇, R₃ or R₅ stages, being the period from R₅ to R₆ the most critical for yield. Afterwards, two glasshouse experiments were carried out to quantify the tolerance of either eight or four genotypes, respectively, by applying a controlled water deficit of constant intensity during the critical period. Finally, yield data obtained in field trials in Argentina across several locations and seasons classified according to rainfall were analysed. Drought Susceptibility Index was calculated for each experiment and for field data, and rankings of tolerance were similar in all cases. This standardized method, which can be automated for high‐throughput phenotyping, could represent a useful tool in breeding programmes for identifying soybean cultivars with improved performance under drought conditions.     

Nematodes and weevil of bananas and plantains in Cameroon: Occurrence,importance and host susceptibility

The resistance of ashgourd to the melon-cottonaphid, Aphis gossypii (Glover), and the incidence of aphid-transmitted viral diseases was investigated following recording of aphid numbers and trichome (plant hair) numbers per cm² of leaf on four parts of the cucurbit, ashgourd, representing four genotypes (Local Sylhet, Local Round, High Female and CQ-10-90). The Local Sylhet genotype was found to have the highest trichome density compared with those of Local Round, High Female, and CQ-10-90 ashgourd genotypes, and was least infested by Aphis gossypii. The percentage of virus-infected plants was also found to be lowest on the Local Sylhet genotype. Aphid numbers were lowest on the terminal and young leaves of ashgourd compared with mature and senescent leaves, due to the higher trichome density in the former leaf categories. Trichome density was found to have a significant negative influence on the number of aphids. Trichomes in ashgourd play a major role by providing a first line defence in reducing aphid infestation, with a subsequent beneficial effect of reducing the incidence of virus.     

生物农药对小十三星瓢虫的敏感性测定

在室内条件下采用喷雾法.以10%吡虫啉做对照,分别测定2种生物农药1.8%阿维菌素乳油、1%苦参碱可溶性液剂对小十三星瓢虫的敏感性试验.结果表明:供试药剂毒性大小依次为阿维菌素＞苦参碱＞吡虫啉(对照药剂).阿维菌素的毒力最高为LG50 3.71807 mg/L是对照药剂的3.96倍,其次苦参碱LG50 4.18463 mg/L是对照药剂的3.52倍,说明生物农药对小十三星瓢虫比较敏感,生物农药毒力高于对照药剂吡虫啉(新烟碱类)的毒力.