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991.
从广东省揭西县坪下牛蛙养殖场收集患黄杆菌病的病蛙,其症状是歪头、狂游、双眼白内障、肝脏肿大充血,腹水严重。从病蛙脑髓、眼底等处分离到62菌株。经急性毒性试验证明分离菌株对健康牛蛙有较强的致病性。选用其中有代表性的981229—1等菌株进行系统的生理生化试验结果显示,981229—3等菌株革兰氏染色阴性、短直杆菌、无动力、无芽孢、好氧型、不利用葡萄糖。内毒素试验阳性。经VITEK-AMS-60自动化检测系统鉴定为脑膜炎脓毒性黄杆菌(Flavobacterium meninosepticum)。选取47种抗菌药物,通过K—B纸片扩散法对分离菌进行耐药性试验结果显示,病原菌对40种试验药物耐药(85.11%)、中等敏感药物2种(4.26%)、敏感药物5种(10.64%)。以试管稀释法、测定分离菌株对5种敏感药物的平均 MIC分别是:利福平 0.24、环丙沙星 0.70、氧氟沙星 0.70、氟啶酸 1.20和麦迪霉素7.80μg/ml。 相似文献
992.
Effects of dietary vitamin E level on growth and tissue lipid peroxidation of soft-shelled turtle, Pelodiscus sinensis (Wiegmann) 总被引:1,自引:0,他引:1
A feeding trial was conducted to determine the effect of dietary vitamin E supplementation on growth, liver lipid peroxidation and liver and muscle vitamin E level of soft‐shelled turtle, Pelodiscus sinensis. Eight experimental diets analysed to contain 0–457 IU vitamin E kg?1 were fed to juvenile soft‐shelled turtle of 4.8 g initial body weight for 12 weeks. Weight gain (WG) of the turtles fed the diet containing no vitamin E was significantly lower than those fed diets containing 83–457 IU vitamin E kg?1 (P<0.05). Feed conversion ratio and protein efficiency ratio showed similar trends to that of WG. No significant difference (P>0.05) was found in whole‐body composition among turtles fed the different diets. Dietary vitamin E requirement using WG as the response and estimated using the broken‐line regression model is approximately 88 IU kg?1. Liver and muscle vitamin E content increased when dietary vitamin E level increased. Ascorbate‐induced lipid peroxidation in liver tissue of turtles fed diets containing 0 and 17 IU vitamin E kg?1 was significantly (P<0.05) greater than those fed diets containing high vitamin E (≥35 IU kg?1). 相似文献
993.
The brown planthopper (Nilaparvata lugens Stål) is one of the most destructive pests of rice crops in Asian countries including China, Vietnam, Thailand, etc. Evolution of resistance in this pest insect to isoprocarb, buprofezin, pymetrozine, imidacloprid and other neonicotinoid insecticides has been reported. In order to investigate the current status of resistance to commonly used insecticides, nine field populations of N. lugens were collected from Central China, East China and South China, and resistance to insecticides was monitored from 2009 to 2012. All the 9 field populations collected in 2012 had developed extremely high resistance to imidacloprid, with resistance ratios (RR) ranging from 209.3 to 616.6. Resistance to imidacloprid was much higher in 2012 than in 2009. The RR of thiamethoxam varied from 17.4 to 47.1, and the RR of nitenpyram varied from 1.4 to 3.7 in 2012. Of the 9 field populations, six populations showed higher resistance to nitenpyram in 2012 than in 2011. RR for buprofezin varied from 110.1 to 221.6 in 2012 whereas resistance was at a medium level (RR 20.4 ∼ 39.4-fold) in 2009. RR for pymetrozine ranged from 34.9 to 46.8 in 2012. As for isoprocarb, RR ranged from 21.7 to 38.1 in 2012. The obvious increase in resistance to widely applied insecticides indicates that insecticide resistance management strategies are urgently needed to prevent or delay further increase of insecticide resistance in N. lugens. 相似文献
994.
The sugarcane borer, Diatraea saccharalis (F.), is a key pest of sugarcane and other grasses, which is a current focus of research aiming to develop transgenically resistant genotypes. However, the current susceptibility of Brazilian populations of the sugarcane borer to Bt toxins is unknown. Laboratory assays were carried out to characterize the susceptibility of sugarcane borer to the Bt toxin Cry1Ab and to select a resistant strain for additional studies on Cry1Ab resistance. Susceptibility was characterized by exposing neonates of different Brazilian colonies of sugarcane borer to different concentrations in meridic diet using surface application of Cry1Ab toxin. Selection for Cry1Ab resistance was carried out by exposing neonates to Cry1Ab-expressing maize (MON 810). The resistance of the borer populations to Cry1Ab was variable with LC50 and EC50 values reaching about 30-fold. The larvae responded positively to Cry1Ab selection exhibiting a 55-fold increase in resistance after four generations. This suggests the suitability of using leaves containing Bt-expressing genes for selection and the existence of variability of Bt-resistance in populations of the sugarcane borer. 相似文献
995.
996.
997.
Processing contaminants may be defined as substances that are produced in a food when it is cooked or processed, are not present or are present at much lower concentrations in the raw, unprocessed food, and are undesirable either because they have an adverse effect on product quality or because they are potentially harmful. The presence of very low levels of processing contaminants in common foods is becoming an increasingly important issue for the food industry, as developments in analytical techniques and equipment bring foods under closer and closer scrutiny. This review considers the formation of lipid oxidation products, hydrogenation of polyunsaturated fatty acids to prevent lipid oxidation and the associated risk of trans fatty acid formation. The formation of acrylamide in the Maillard reaction is described, as well as the genetic and agronomic approaches being taken to reduce the acrylamide-forming potential of cereal grain. The multiple routes for the formation of furan and associated chemicals, including hydroxymethylfurfuryl, are also described. The evolving regulatory and public perception situations for these processing contaminants and their implications for the cereal supply chain are discussed, emphasising the need for cereal breeders to engage with the contaminants issue. 相似文献
998.
香蕉枯萎病己成为香蕉的毁灭性病害。该病属于土传性病害,扩散蔓延速度快,难于进行生物控制、药物防治及轮作、浸田等常用防治方法的防治。因此,防治香蕉枯萎病的最佳方法是进行香蕉遗传改良,培育抗病品种。选用从INIBAP[(International Network for the Improvement of Bnana and Plantain,国际香(大)蕉改良网络)]引进的42份香蕉种质资源,采用伤根侵染法,用含2×106个孢子/L的香蕉枯萎病1号和4号小种菌液分别对42份香蕉幼苗进行处理,筛选抗香蕉枯萎病种质。结果表明:在侵染1号小种时,7份材料表现高感,13份感病,22份中抗,无高抗;在侵染4号小种时,25份材料表现高感,12份感病,5份中抗,无高抗。综合分析显示,M11和M25对枯萎病1号和4号小种均表现中抗。 相似文献
999.
1000.