黄瓜根腐病致病病原的鉴定

在天津市及周边地区采集病株进行组织分离，同时分离到两类病原菌，经初步的生物学特性鉴定表明，引起黄瓜根腐病的主要病原菌为甜瓜疫霉、尖孢镰刀菌和茄病镰刀菌。经接种试验，认为甜瓜疫霉为主要致病菌。     

褐藻糖胶脱蛋白及脱色方法研究

采用Sevag法、三氯乙酸(TCA)法和Sevag法与三氯乙酸法相结合的方法对褐藻糖胶进行脱蛋白研究,并研究脱蛋白与未脱蛋白对褐藻糖胶脱色的影响.结果表明,Sevag法与三氯乙酸法相结合脱蛋白效果最佳,当Sevag法操作2次,TCA溶液添加量为1.3 mL/10mL多糖溶液时,蛋白脱除率为78.68%,多糖损失率为28...     

Accuracy of an anaemia scoring chart applied on goats in sub-humid Kenya and its potential for control of Haemonchus contortus infections

We tested the practical application of an anaemia scoring chart (the FAMACHA chart) as a method for controlling Haemonchus contortus in goats kept under smallholder conditions in a sub-humid area of Central Kenya. The objectives were: (1) to test the accuracy of the FAMACHA chart in identifying anaemic goats (PCV< or =18); (2) to quantify the proportion of goats left untreated at farm level when using the chart. On each of two farms, Small East African goats of various ages were allocated to two treatment groups; a FAMACHA group (F1 (n=34) and F2 (n=31) on farms 1 and 2, respectively) and a control group (C1 (n=34) and C2 (n=30)). In F1 and F2 goats with a FAMACHA score of 3, 4 or 5 were treated with anthelmintic after scoring. In C1 and C2 goats were treated every 4 weeks from 15 February to 20 July. Every 2 weeks all goats were scored with the FAMACHA chart and weighed. Furthermore, faecal samples were collected for faecal egg counts (FEC) and blood samples were collected for packed cell volume (PCV) determination. H. contortus was found to be the predominant nematode on both farms. The mean FECs were higher on farm 1 compared to farm 2, while in contrast the mean PCV levels were lowest on farm 2. The latter was most likely due to the presence of Fasciola spp., flea and tick infections on farm 2. The accuracy of the chart was evaluated by using PCV as the gold standard for anaemia (PCV< or =18%). The mean percentage of false-negative scorings per sampling was 0.7% on farm 1 and 1.6% on farm 2, while the mean percentage of false-positive scorings was 9.7% and 21.4%, respectively. It is most likely that the accuracy of the chart was negatively affected by the concurrent parasite infections on farm 2. The mean proportion of untreated goats per sampling was 89% and 77% on farm 1 and farm 2. It was concluded that the FAMACHA chart can be a valuable tool for decision-making in control of H. contortus in goats kept under smallholder conditions, without morbidity or mortality unacceptable to the farmer. The application may further reduce the risk of development of anthelmintic resistance by increasing refugia. However, caution should be taken under conditions where other anaemia-causing parasites are present (e.g. Fasciola spp. and ecto-parasites), since this possibly decreases the accuracy of the FAMACHA chart.     

Assessment and up-scaling of CO2 exchange by patches of the herbaceous vegetation mosaic in a Portuguese cork oak woodland

Long-term eddy covariance measurements over a montado oak woodland in southern Portugal have documented a vulnerability to predicted decreases in springtime rainfall, since water availability during spring limits annual CO₂ gain, the growth of fodder for animals, and the production of cork by Quercus suber. The current study examined CO₂ exchange of three different herbaceous vegetation components distributed over montado landscapes and within the footprint of long-term landscape eddy covariance monitoring studies. Simultaneous measurements with eddy covariance at two sites and with manually operated chambers at multiple locations revealed that slow drainage of shallow basins, the onset of drying at higher sites and a high release of CO₂ below tree canopies significantly influenced the overall course of montado ecosystem gas exchange during the spring.Hyperbolic light response models were employed to up-scale and compare herbaceous gas exchange with landscape net ecosystem CO₂ flux. The up-scaling demonstrates the importance of the herbaceous understory in determining annual carbon balance of the montado and suggests a relatively small additional CO₂ uptake by the tree canopies and boles, i.e., by the aboveground tree compartment, during springtime. Annual flux totals obtained during the extremely dry year 2005 and a normal precipitation year 2006 for the oak woodland and a nearby grassland were essentially the same, indicating that both ecosystems similarly exploit available resources. Based on comparisons with additional temperate grasslands, we can visualize the montado herbaceous cover as a typical European grassland canopy, but where temperature fluctuations in winter control uptake, and where total production depends on springtime rainfall as it controls phenological events and eventually dieback of the vegetation. On the other hand, tree canopies remain active longer during late spring and early summer, modifying the montado response from that of grassland. Uncertainties in flux estimates via both chamber and eddy covariance methodologies currently prevent a full understanding of vegetation/atmosphere coupling, of the recycling of CO₂ between the understory communities and trees, and of relationships between exchange rates of individual components of the vegetation mosaic and overall carbon and water balances in montado landscapes.