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881.
为了筛选拌种防治二点委夜蛾的有效药剂,并明确其对玉米种子萌发的安全性。本文通过培养皿法和室内盆栽试验比较了9种不同类型杀虫剂拌种对玉米种子萌发的影响以及保苗效果。结果表明,60%溴氰虫酰胺SC和20%氯虫苯甲酰胺SC拌种处理效果较好,保苗效果分别达到90.02%和70.07%,可将死苗率控制在10%以内,被害指数控制在20%以内,且对玉米出苗安全。因此,60%溴氰虫酰胺SC和20%氯虫苯甲酰胺SC可作为拌种防止玉米二点委夜蛾为害的有效药剂。 相似文献
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883.
树流感即栎树猝死病(SOD)自从在美国发现以来,已经造成了美国加利福尼亚州树木大量死亡,并且扩散到了俄勒冈州。对树流感未来暴发风险区域的研究能够为树流感防控提供科学依据,同时为中国防治类似森林病虫害提供借鉴。联合国气候变化政府间专门委员会(IPCC)在第5次评估报告中指出,根据温室气体排放模式的不同未来气候变化有4种可能趋势。该研究基于现在的全球植被覆盖数据、过去的气候数据和未来4种不同排放模式下的气候数据,运用Maxent模型预测了北美西海岸地区在2000年、2050年、2070年树流感暴发风险区域。对预测结果的时空对比分析发现,北美西海岸地区未来树流感暴发高风险区域将会往北和西海岸地区扩张,在各种气候模式下扩张的情况不一样,其中相对于2000年,在RCP85排放模式下2070年北美西海岸地区的高风险区域将会增加174%。 相似文献
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885.
On sunny summer days, the top 10 cm of soil in southern Australia are heated to temperatures between 50 and 80 °C for a few hours a day, often for several successive days. These extreme temperature events are likely to have profound effects on the microbiota in these soils, but we do not know how this recurrent heat exposure influences microbial dynamics and associated nutrient cycling. In this study, an air-dry soil from southern Australia was exposed to one or two diurnal heating events with maximum temperature of 50 or 70 °C. The control was left at ambient temperature (Amb). All soils were rapidly rewet. Soil respiration was measured for 7 days after rewetting; microbial biomass C, available N and P were determined before rewetting and 1 and 7 days after rewetting. After heating and before rewetting compared to Amb, microbial biomass C (MBC) was 50–80% lower, but available P was 25% higher in heated soils. Available N differed little between Amb and heated soils. Rewetting resulted in a flush of respiration in Amb and soils heated once, but there was no respiration flush in soils heated twice. Cumulative respiration compared to Amb was about 10% higher in soils heated once and about 25% lower in soils heated twice. In Amb, MBC 1 day after rewetting was similar as before rewetting. But in heated soils, MBC increased from before rewetting to 1 day after rewetting about fourfold. Compared to Amb, available N 1 day after rewetting was 20–30% higher in soils heated to 70 °C. Seven days after rewetting, available N was 10% higher than Amb only in soils heated twice to 70 °C. It can be concluded that diurnal heating kills a large proportion of the microbial biomass and influences soil respiration and nutrient availability after rewetting of soils. The effect of heating depends on both maximum temperature and number of events. 相似文献
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BACKGROUND: Resistance gene analogues (RGAs) have been isolated from many crops and offer potential in breeding for disease resistance through marker-assisted selection, either as closely linked or as perfect markers. Many R-gene sequences contain kinase domains, and indeed kinase genes have been reported as being proximal to R-genes, making kinase analogues an additionally promising target. The first step towards utilizing RGAs as markers for disease resistance is isolation and characterization of the sequences. RESULTS: Sugarcane clone US01-1158 was identified as resistant to yellow leaf caused by the sugarcane yellow leaf virus (SCYLV) and moderately resistant to rust caused by Puccinia melanocephala Sydow & Sydow. Degenerate primers that had previously proved useful for isolating RGAs and kinase analogues in wheat and soybean were used to amplify DNA from sugarcane (Saccharum spp.) clone US-01-1158. Sequences generated from 1512 positive clones were assembled into 134 contigs of between two and 105 sequences. Comparison of the contig consensuses with the NCBI sequence database using BLASTx showed that 20 had sequence homology to nuclear binding site and leucine rich repeat (NBS-LRR) RGAs, and eight to kinase genes. Alignment of the deduced amino acid sequences with similar sequences from the NCBI database allowed the identification of several conserved domains. The alignment and resulting phenetic tree showed that many of the sequences had greater similarity to sequences from other species than to one another. CONCLUSION: The use of degenerate primers is a useful method for isolating novel sugarcane RGA and kinase gene analogues. Further studies are needed to evaluate the role of these genes in disease resistance. 相似文献
888.
重点从微观角度研究半干旱草原区植被建设生态需水相关问题。介绍植被恢复过程现状生态需水量计算方法,以充实和完善生态需水理论的研究,并为半干旱草原区生态建设提供一定科学依据。 相似文献
889.
艾晶丽 《吉林粮食高等专科学校学报》2002,17(3):19-21
论述粮食带式输送机胶带运行偏斜的几种解决办法 ,调偏后能保证带式输送机的正常工作 ,提高运输效率 相似文献
890.
Joshi A Naqvi SM Bag S Dang AK Sharma RC Rawat PS Mittal JP 《Tropical animal health and production》2003,35(3):249-257
The Garole is a prolific but less well known and rare breed of small sheep found in the hot and humid Sunderban region of West Bengal. An ability to breed throughout the year and to graze in knee-deep water, resistance to foot rot and a strong mothering instinct are some of the special features of this breed. Garole rams could provide germplasm to incorporate prolificacy traits by artificial insemination of the nonprolific sheep breeds found in abundance in the semi-arid and arid tropical climates of India. The aim of the present study was to evaluate the semen production by Garole rams maintained in a semi-arid climate for three years and to objectively assess their semen quality by a computer-assisted sperm analysis technique. The donor rams were randomly selected each year from the original flock procured from their natural habitat or from the offspring born at the Institute farm. Semen was collected weekly for three weeks each autumn for three consecutive years from 8 rams each year. The overall means (SD) of the traits that did not differ significantly with age or year were volume, concentration, curvilinear velocity, average path velocity, amplitude of lateral head displacement, beat frequency, motility and the percentages of rapid motile sperms and of slow motile sperms. The age of the rams had a significant effect (p<0.05) on the straight-line velocity but this was not significantly affected by the length of exposure to the semi-arid climate. However, the age and year had significant effects (p<0.05) on linearity, straightness and the percentage of medium motile sperms. It was concluded that Garole rams are capable of producing good-quality semen even after a prolonged period of exposure to a semi-arid tropical climate. 相似文献