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。     

Ice core evidence for Antarctic sea ice decline since the 1950s

The instrumental record of Antarctic sea ice in recent decades does not reveal a clear signature of warming despite observational evidence from coastal Antarctica. Here we report a significant correlation (P < 0.002) between methanesulphonic acid (MSA) concentrations from a Law Dome ice core and 22 years of satellite-derived sea ice extent (SIE) for the 80 degrees E to 140 degrees E sector. Applying this instrumental calibration to longer term MSA data (1841 to 1995 A.D.) suggests that there has been a 20% decline in SIE since about 1950. The decline is not uniform, showing large cyclical variations, with periods of about 11 years, that confuse trend detection over the relatively short satellite era.     

Purification and serological analysis of tomato spotted wilt virus

A modified procedure for the purification of TSWV is described which consists of differential centrifugation, treatment with antiserum against sap from healthyN. rustica and density-gradient centrifugation in sucrose gradients. Centrifugation in the zonal-rotor proved efficient for processing large amounts of infected leaves.Antisera to purified TSWV were produced in rabbits. These sera reacted with healthyN. rustica sap. This reaction could be abolished by absorption with either healthyN. rustica sap or polysaccharides purified fromN. rustica. Unabsorbed sera reacted with the major TSWV structural proteins following their electrophoretic separation in polyacrylamide-gels. The positions of the precipitin lines corresponded with those of the structural proteins visualized by staining. The intensity of these lines was greatly diminished after absorption of the antisera with either healthyN. rustica sap or polysaccharides. It was concluded that the reaction of TSWV antiserum with the structural proteins is partly due to host-derived polysaccharides covalently bound to the virus proteins.Samenvatting Het bronsvlekkenvirus van de tomaat (TSWV) werd gezuiverd met een procedure die bestond uit een cyclus van differentiële centrifugering, behandeling van de virus-suspensie met antiserum tegen bestanddelen van gezonde planten (N. rustica) en dichtheidsgradiëntcentrifugering (Fig. 1 en Fig. 3). De zone rotor kon worden gebruikt wanneer grote hoeveelheden bladmateriaal werden gebruikt (Fig. 2).Twee antisera, die elk een verschillende activiteit tegen TSWV (Tabel 1, Fig. 4) hadden, werden bereid. Deze sera reageerden ook met sap en polysacchariden uitN. rustica (Fig. 6). Door verzadiging met polysacchariden werd de reactie tegen TSWV aanmerkelijk verzwakt. Analyse van de eiwitbandjes die na polyacrylamidegel-elektroforese waren gevormd, toonde aan dat de activiteit van de sera tegen de eiwitcomponenten van TSWV was gericht (Fig. 5) en dat deze activiteit na verzadiging met polysacchariden zwakker was. Uit deze reacties kan geconcludeerd worden dat polysacchariden van de waardplant aan de structurele eiwitten van TSWV zijn gebonden. Niet geabsorbeerd antiserum geeft met TSWV drie precipitatielijnen (Fig. 4), maar na absorptie met compleet virus trad nog slechts één precipitatielijntje op (Fig. 7). Mogelijk wordt dit lijntje gevormd door het nucleocapside-eiwit dat door de dissociatie van het virus vrij komt. Sera die tegen normale bestanddelen vanN. rustica zijn bereid, vormen geen zichtbare reactie met compleet virus; wel wordt er een lijntje gevormd indien het virus met guanidine-HCl wordt gedissociëerd (Fig. 8). Deze waarneming kan verklaren dat deze antisera kunnen worden gebruikt bij de zuivering van TSWV ondanks het feit dat dit virus polysacchariden uit de waardplant draagt.     

The Effect of Kefir as a Dietary Supplement on Nonspecific Immune Response and Disease Resistance in Juvenile Rainbow Trout,Oncorhynchus mykiss (Walbaum 1792)

In this study, juvenile rainbow trout fed with commercial pellets containing kefir provided increased nonspecific immune response and improved disease resistance against lactococcosis and yersiniosis. Kefir was used as a feed supplement at 2, 5, and 10% inclusion rates and several nonspecific immune parameters were observed at day(s) 1, 7, 14, 21, 28, and 35 following the treatment. A total of four experimental groups, including control, was established. The various parameters including hematocrits, nitroblue tetrazolium positive neutrophils, total leukocytes, serum lysozyme activity, total serum protein, and immunoglobulin M (IgM) levels were examined. As a result of this study, kefir‐fed fish had an increase in measured nonspecific immune parameters, especially in the group received the 10% kefir treatment. The challenged fish fed with kefir‐supplemented diet showed a better survival rate against Lactococcus garvieae than Yersinia ruckeri. Kefir supplementation reduced fish mortality significantly against L. garvieae.     

中越水稻迁飞性害虫稻飞虱、稻纵卷叶螟发生关系分析

中越两国同属东亚季风区,水稻病虫害在发生危害上为一个整体。每年水稻稻飞虱、稻纵卷叶螟(以下简称"两迁"害虫)随着季节和气温变化,在两国间往返迁飞,发生为害,相互影响。研究两国水稻迁飞性害虫发生的关系和影响规律,对于提高监测预警的早期预见性和防控工作的主动性,有效控制其危害具有重要意义。2010年以来,中越两国实施了中越水稻迁飞性害虫监测与防治合作项目,通过连续多年开展交流合作,初步明确了越南"两迁"害虫发生规律。本文简要分析了影响越南"两迁"害虫发生的主要因素,探讨了中越两国水稻"两迁"害虫发生规律的相关性,对提高中国"两迁"害虫中、长期预报能力和综合治理水平发挥了积极作用。     

Impact of grazing intensity on herbage intake, composition, and digestibility and on live weight gain of sheep on the Inner Mongolian steppe

High grazing pressure during the last decades caused severe ecological problems in the steppe of Inner Mongolia, China. The objective of the present study was to determine the effects of grazing intensity of sheep on herbage mass (HM) and intake, chemical composition and digestibility of herbage, and on live weight gain (LWG). A grazing experiment with six different grazing intensities (1.5, 3.0, 4.5, 6.0, 7.5, and 9.0 sheep/ha) was conducted in the growing season of 2005 in the Xilin River Basin. HM decreased from 1.5 t DM/ha at the lowest grazing intensity to 0.6 t DM/ha at the highest grazing intensity. NDF content of the herbage was high (> 700 g/kg DM) and relatively constant, whereas acid detergent lignin (ADL) content increased with grazing intensity and with proceeding grazing season. Digestibility of organic matter ingested (DOM) tended to decrease with grazing intensity as well as intake of organic matter (OMI) and of digestible organic matter (DOMI) per sheep (P = 0.090 and P = 0.065, respectively), whereas LWG per sheep decreased with increasing grazing intensity (P = 0.018). DOM and OMI were negatively related to ADL content. However, herbage intake and LWG per ha increased with grazing intensity (P < 0.001) and reached their maximum at 9 and 7.5 sheep per ha, respectively. This observation confirms the current farmers' practise of high grazing pressure ignoring long term grassland productivity and ecological problems. Therefore, the studies are continued to provide further information on long term effects. This study could show pronounced effects of grazing intensity on animal and grassland productivity and the suitability of the methods applied to measure intake and digestibility of herbage in a large scale grazing experiment with sheep.     

Rotational and continuous grazing of sheep in the Inner Mongolian steppe of China

The aim of this study was to compare the effects of rotational and continuous grazing on herbage mass (HM), organic matter digestibility (dOM) and intake (OMI) and live weight gain (LWG) of sheep grazing on the inner Mongolian steppe, China at a stocking rate of 4.5 sheep/ha during the growing season. In the years 2005 and 2006, four 2-ha plots were used of which two were divided into four 0.5 ha paddocks each for rotational grazing, where sheep were moved each 10 days to the next paddock. The dOM was estimated from faecal crude protein concentration and OMI by oral administration of titanium dioxide. Herbage mass was similar in both grazing systems and dOM and OMI were higher (p < 0.05) at continuous grazing than at rotational grazing, but LWG did not differ probably because of extra energy expenditure for grazing and walking in a larger area. The dOM and OMI decreased (p < 0.05) with progress of the growing season and differed between years. Since precipitation during the growing season in both years was lower than the 30 years average which was probably the reason that positive effects of non-grazing periods on herbage regrowth and quality at rotational grazing could not occur, further studies are required in years with average precipitations before a final evaluation of these grazing systems can be made. Moreover, it seems necessary to quantify energy expenditure for physical activity of animals in grazing studies.     

鹿源细小病毒的分离与鉴定

选用PK-15传代细胞系从吉林农业大学鹿场采集的梅花鹿粪样病料中分离出一株病毒,经血凝试验、血凝抑制试验及电镜观察对该病毒进行鉴定。结果表明:该病毒为鹿源细小病毒。