烟粉虱成虫在日光温室内的分布和日活动规律

采用中色粘虫板(黄板)和植株调查方法在河北省固安县日光温室内研究了烟粉虱成虫在黄瓜结瓜盛期(4月下旬~5月上旬)的分布和日活动规律。结果表明,温室北边平均诱集量((668·8±663·9)头/(板·d))是南边((357·5±349·4)头/(板·d))的1·87倍;除8∶00~10∶00以外,其他时段内北边诱集量均显著高于南边;同时,北边植株上烟粉虱成虫数量也显著高于南边。温室东边逐日和各时段诱集量均高于西边,但差异不显著。在垂直方向,烟粉虱成虫在黄瓜所有叶片上均有分布。烟粉虱成虫从6∶00~18∶00各时段均很活跃,但不同时段活动水平存在差异。8∶00~10∶00平均诱集比例最高(25·7%±9·7%),12∶00~14∶00最低(13·2%±5·2%);8∶00~10∶00的诱集量显著高于其他时段。另外,黄板南面诱集量((352·5±186·1)头/(板·d))显著高于北面诱集量((160·7±90·4)头/(板·d))。对日光温室黄瓜上烟粉虱的监测、成虫诱杀和综合治理的意义进行了讨论。     

Augmentative biological control of whiteflies using transplants

Field studies showed that transplants can be used to move parasitoids into fields of commercially grown cantaloupe, Cucumis melo (Cucurbitaceae), and augment parasitism of sweet potato whitefly, Bemisia tabaci biotype B (= Bemisia argentifolii) (Homoptera: Aleyrodidae). Methods were developed to inoculate cantaloupe seedlings with newly imported Eretmocerus spp. (Hymenoptera: Aphelinidae), then transfer plants into both organic and conventional fields of cantaloupe in the desert growing region of southeastern California. Several obstacles to inoculating banker plants with an adequate number of parasitized whiteflies were overcome and numbers of parasitoids per transplant increased. In 1999 the use of banker plants was compared to a standard hand-release method and a no-release control in a replicated study at an organic farm. Augmentation through releases of parasitoids increased parasitism over that in the no-release controls (p <0.05). Banker plants increased the proportion of parasitized whiteflies more than the hand-release method (0.21 vs. 0.08). During a region-wide demonstration spring 2000, plots receiving banker plants significantly increased parasitism over paired control plots at seven commercial farms of cantaloupe. Parasitism in banker plant treated plots in 2000 was higher in organic fields (seasonal average =0.30) than conventional ones (seasonal average =0.06). Differences may be due to the use of imidacloprid, a systemic insecticide, in conventional fields for whitefly control. Over the 2-year study, however, releases of parasitoids did not consistently reduce densities of B. tabaci. Only in late season at some sites in 2000 were whitefly densities lower in release plots than paired controls. Most of the parasitoids recovered and identified from plots receiving parasitoids were the same as those released, Eretmocerus spp. (ex. Ethiopia M96076), and E. hayati(M95012, ex. Pakistan).     

Spatial correlograms of soil cover as an indicator of landscape heterogeneity

Soil cover, which is one of the most informative and integrative landscape factors, can be used for the analysis of landscape patterns. We studied the spatial autocorrelation (Moran's I) of raster format soil maps (1:10,000; 10 m pixel size) in 35 study areas representing all landscape regions in Estonia. The carbonate concentration of soils, volumetric soil moisture (%) and the depth of the groundwater table were taken into consideration in compiling a scale of contrast of 17 soil groups. We introduce a simple characteristic based on spatial correlograms: a half-value distance lag, h_I = 0.5—a distance where Moran's I drops below 0.5. Spatial autocorrelation decreased very rapidly in the case of heights with a very heterogeneous landscape composition, showing low values of h_I = 0.5 (<100 m in all 6 study areas). In uplands and depressions, the spatial autocorrelation also decreased relatively rapidly (h_I = 0.5 < 200 m). In most of the plains, coastal lowlands, sea islands and inland paludified lowlands, the values of Moran's I did decrease slowly with increasing lag, being >200 m in all forest and bog areas with complex topographical conditions due to the variety of glacial landforms and peatlands. All of the eight FRAGSTATS landscape metrics studied demonstrated significant correlations with h_I = 0.5, whereas five of them – Contrast Weighted Edge Density (CWED); Percentage of Like Adjacencies (PLADJ), Edge Density (ED), Patch Density (PD) and Mean Patch Area Distribution (AREA_MN) – had Spearman Rank Order Correlation values higher than 0.8. Landscapes with high ED, PD, and CWED values have a low autocorrelation: PD, ED, and CWED correlated negatively with h_I = 0.5. PD, ED, and CWED decreased and PLADJ increased with the power-law relationship with increasing h_I = 0.5. Spatial autocorrelation is lower in landscapes with complex structure and high contrast. The positive relationship with PLADJ indicates the same. Thus, spatial correlograms of potential landscape structure based on soil cover analysis can be used for the characterization of human-influenced landscape (land use) structure.     

Design and use of a simulation model to evaluate germplasm for antibiotic resistance to the greenhouse whitefly (Trialeurodes vaporariorum) and the sweetpotato whitefly (Bemisia tabaci)

SARAH (Software for theAssessment of antibioticResistance toAleyrodidae inHost plants) is a deterministic simulation model of whitefly population growth based on whitefly life-history components determined on individual plants. The life-history components recorded were oviposition rate, adult survival, pre-adult survival, developmental period, and sex ratio. The simulation model serves as a tool to combine these components and to obtain a single criterion for (antibiotic) resistance. The criterion used was the decrease in simulated intrinsic population growth rate, r _s , relative the r _s value determined on a susceptible control genotype. This model-based evaluation method was tested using the greenhouse whitefly,Trialeurodes vaporariorum Westwood, on tomato and the sweetpotato whitefly,Bemisia tabaci Gennadius, on tomato, eggplant, collard, and pepper. To study its consistency over time, the evaluation method was repeated six times forT. vaporariorum on a susceptible and a resistant tomato cultivar. Simulated intrinsic population growth rate was more consistent in indicating resistance than any of the individual life-history components. Of tenL. hirsutum accessions tested for resistance toT. vaporariorum, three exhibited r _s values that were significantly lower than those for the susceptible control. In addition, on these tenL. hirsutum accessions, a significant positive correlation was observed between r _s and sex ratio (# females/# males). Four host plant species (tomato, collard, eggplant, and pepper) were evaluated for resistance toB. tabaci. All life-history components and r _s values varied among host species, while a negative r _s value was observed forB. tabaci on pepper. A high correlation was found between results from a sensitivity analysis of SARAH and results from a sensitivity analysis of a validated whitefly population simulation model by Yanoet al. (1989a). Significant correlations were found for the relationships between oviposition rate, adult survival, or pre-adult survival and r _s , indicating that none of these life-history components can be omitted from the test procedure. This model-based evaluation method offers a standardized way to quantify levels of antibiotic resistance to whiteflies and will enhance efficiency in breeding programs.     

A two-step procedure for coupling development and usage of a pair of human neck models

Both finite element models and multi-body models of human head-neck complex had been widely used in neck injuries analysis, as the former could be used to generate detailed stress strain information and the later could generate dynamic responses with high efficiency. Sometimes, detailed stress and strain information were hoped to be obtained more efficiently, but current methods were not effective enough when they were used to analyze responses of human head neck complex to long duration undulate accelerations. In this paper, a two-step procedure for ‘parallel’ development and ‘sequential’ usage of a pair of human head neck models was discussed. The pair of models contained a finite element model and a multi-body model, which were developed based on the coupling ‘parallel’ procedure using the same bio-realistic geometry. After being validated using available data, the pair of human neck models were applied to analyze biomechanical responses of pilot’s neck during arrested landing operation according to the ‘sequential’ procedure, because typical sustained undulate accelerations usually appeared during such processes. The results, including both kinematic and detailed biomechanical responses of human head-neck complex, were obtained with preferable efficiency. This research provided an effective way for biomechanical analysis of human head neck responses to sustained undulate accelerations.     

Determination and diagnostic value of CA9 mRNA in peripheral blood of patients with oral leukoplakia

Background: Oral leukoplakia is one of the most common oral premalignant disorder. The classical evaluation through tissue biopsy is not always valid to evaluate the risk of malignization.

Material and methods: RT-qPCR was performed on 47 blood samples (21 patients with leukoplakia, 2 with oral squamous cell carcinoma (OSCC), and 24 healthy patients) and on 11 tissue samples (3 leukoplakia, 4 OSCC, and 4 samples of healthy tissue).

Results: There are significant differences in expression between the different groups (F?=?4.057, p?=?.006). The Duncan post hoc test shows that the only group that differentiates is the tumour tissue. Using Wilcoxon test, different covariables of patients with leukoplakia were analysed with respect to the group of healthy patients and no significant differences were observed.

Conclusions: The diagnostic route through liquid biopsy has not been conclusive in this study, but there are significant differences in the levels analysed in the different tissue samples.     

Occurrence and activity of <Emphasis Type=Italic>Bemisia tabaci</Emphasis> parasitoids on cassava in different agro-ecologies in Uganda

Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) is the vector of cassava mosaic geminiviruses that cause cassava mosaic disease (CMD), which in turn causes devastating yield losses. Surveys were conducted from October 2000 to November 2001 in four agro-ecologies in Uganda to enhance the understanding of parasitoid fauna and parasitism of B. tabaci in cassava fields. Such an understanding is an essential prerequisite for the development of biological control methods of B. tabaci to complement current CMD control practices. Parasitoid abundance and parasitism efficiency varied between locations and sampling dates within the locations; highest parasitoid densities were observed at Namulonge in the Lake Victoria crescent while the lowest was at Kalangala. In all locations, parasitism was mainly due to Encarsia sophia Dodd and Girault and Eretmocerus mundus Mercet (all Hymenoptera: Aphelinidae). Two occasionally observed species included Encarsia mineoi Viggiani (Hymenoptera: Aphelinidae), only observed at Namulonge, and blackhead Encarsia (Hymenoptera: Aphelinidae) observed at Bulisa, Namulonge and Lyantonde. Parasitism efficiency was highest at Bulisa (57.9%), but ranged from 40.2 to 46.9% at the other three sites. This paper discusses the possible causes of variations in parasitoid abundance and parasitism efficiency, and proposes further studies that might be carried out to assess the potential for augmentation of parasitoids to control B. tabacipopulations and CMD.     

Classical Biological Control of the Citrus Blackfly <Emphasis Type="Italic">Aleurocanthus Woglumi</Emphasis> by <Emphasis Type="Italic">Amitus Hesperidum</Emphasis> in Trinidad

The citrus blackfly Aleurocanthus woglumi Ashby (Homoptera: Aleyrodidae), a native of South East Asia, was first reported in Trinidad in 1998. As part of a classical biological control programme against the pest, releases of Amitus hesperidum Silvestri (Hymenoptera: Platygasteridae) were made in Trinidad from June to August 2000. Field studies were conducted on three commercial citrus farms, two large estates ( >500 ha) and one small orchard (<50 ha) where releases were initially made. Adult blackfly and Amitus populations were monitored weekly with yellow sticky traps. Immature blackfly and parasitism rates were monitored monthly by field sampling. During the study period, citrus blackfly populations declined by more than 98% at all sites while parasitism increased to 60–90%. There were, however, differences between locations, with control at Cumuto being reached within 4 months, at Todd’s Road between 6 and 7 months and at La Gloria about 13 months. This was consistent with the parasitism rates recorded. Although Encarsia perplexa Huang and Polaszek (Hymenoptera: Aphelinidae) was also introduced, it would seem that A. hesperidum was capable of bringing down and maintaining citrus blackfly populations at acceptable levels by itself.     

Sweetpotato whitefly resistance to insecticides in Hawaii: Intra-island variation is related to insecticide use

Susceptibility to acephate, methomyl, and permethrin was determined with laboratory bioassays of field-collected adults from 15 populations of the B biotype of sweetpotato whitefly,Bemisia tabaci (Gennadius) (Homoptera:Aleyrodidae), from Hawaii. Comparisons at the LC₅₀ showed up to 24-fold resistance to acephate, 18-fold resistance to methomyl, and 4-fold resistance to permethrin. Analysis of variance showed significant intra-island variation in susceptibility to each insecticide, but no significant variation among islands. Insecticide use varied from 4 to 103 insecticide sprays per site per season. Acephate and methomyl were used more often than permethrin. The frequency of application and LC₅₀ for each insecticide were positively correlated across sites. These results suggest that local variation in insecticide use was a primary cause of variation in susceptibility. If local insecticide use is a key determinant of resistance, as our results suggest, growers can retard resistance development locally by reducing their own insecticide use.     

The mechanism of action of T7 DNA polymerase

The recent crystal structure determination of T7 DNA polymerase complexed to a deoxynucleoside triphosphate and primer—template DNA has provided the first glimpse of a replicative DNA polymerase in a catalytic complex. The structure complements many functional and structural studies of this and other DNA polymerases, allowing a detailed evaluation of proposals for the mechanism of nucleotidyl transfer and the exploration of the basis for the high fidelity of template-directed DNA synthesis.     

Photoprocesses

The development of supramolecular chemistry has allowed the construction of structurally organized and functionally integrated chemical systems capable of elaborating the energy and information input of photons to perform complex functions. Model systems capable of mimicking the two fundamental steps of photosynthesis, namely light harvesting and photoinduced charge separation, have recently been developed.