Comparison of susceptibility of various fish species to experimental infection with channel catfish virus

Channel catfish virus (CCV) disease is an acute haemorrhagic disease in juvenile channel catfish ( Ictalurus punctatus ). To date channel catfish is the only species affected by natural outbreaks of the CCV but juvenile large mouth bass ( Micropterus salmoides ) and silurus ( Silurus meriaionalis ) have suffered high mortalities in recent years in China. Histopathological phenomenon of sick fish is similar to CCV disease, and the identified virus was CCV. In this report, the pathogenicity of infectious CCV was examined by infection trials on the first known host species, the channel catfish and other teleosts. Our results indicated that there were higher detection rates of CCV from large mouth bass and silurus fish. Channel catfish virus did not induce mortality in other cypriniformes, but histopathological studies revealed that carp might be infected by both bathing and intraperitoneal infection. No deaths, clinical or histopathological signs, were found in the six other species exposed by immersion or injection. Experimental infection studies confirm that CCV infect not only channel catfish but also other species (large mouth bass, silutus and carp). The outbreaks of CCV disease only occurred when the cultured temperature was above 25 °C.     

Effects of all‐male,mixed‐sex and all‐female freshwater prawn in polyculture with major carps and molas in the fallow rice fields

This study was conducted to evaluate the effects of all‐male, mixed‐sex and all‐female freshwater prawn (Macrobrachium rosenbergii) in a polyculture with major carps (Catla catla and Labeo rohita) and self‐recruiting small fish molas (Amblypharyngodon mola) in the fallow rice fields of Bangladesh. There were three treatments with three replicates. All ponds were stocked with carps and molas plus either all‐male prawns (treatment MP), mixed‐sex prawns (MFP) or all‐female prawns (FP). Prawn, mola, catla and rohu were stocked 20 000, 20 000, 1750 and 750 ha^?1, respectively, in all treatments. The prawns were fed twice daily, starting at 8% body weight and gradually reduced to 3% body weight. The fish were fed in the morning with mustard oil cake and rice bran (1:2 ratios) at 3% body weight. Significantly higher production of prawns (697 kg ha^?1) was obtained in treatment MP, which yielded 34.7% and 56.2% more production than MFP and FP respectively. Significantly higher total production of 1620 kg ha^?1 and a higher benefit–cost ratio of 2.10:1 were also obtained in treatment MP. It can be concluded that an all‐male prawn culture is economically more viable than all‐female and mixed‐sex prawn cultures, along with other fish like major carps and the nutrient‐dense molas in the polyculture.     

马尾松毛虫质型多角体病毒替代寄主——棉铃虫人工饲养技术

介绍了生产马尾松毛虫质型多角体病毒的替代寄主棉铃虫的人工饲养技术。     

不同酯酶型球孢白僵菌株系及相同酯酶型株系经寄主转移后毒力变化的研究

对12个酯酶型的16株白僵菌进行了毒力生物测定.结果表明,不同酯酶型株系对松毛虫的毒力差异显著,LT50可相差数倍;同一酯酶型株系经不同寄主转移后,其毒力也发生了较明显的变化.如从松灰象甲上分离出的不同酯酶型的2株白僵菌[MGS980404-21(酯酶型05),MGS980510-06(酯酶型06)]和人工释放的酯酶型02菌株Bb13毒力都很高,而从松灰象甲分离出的与释放菌株属同一酯酶型的另一个菌株MGS980507-34,毒力虽然很低,但却是林间最常见的流行菌株.上述结果理解为白僵菌在林间的宿存,尤其是它在松毛虫低虫口状态下能在林间长期宿存不绝的原因,以及对于从林间采集筛选高毒菌株提供了可能.     

银海枣褐斑病的病原鉴定与化学防治

对广东省新近发现的一种银海枣叶部病害进行了病原鉴定，该病病原为链格孢Alternaria alternata（Fr.）Keissl．以生长速率法和孢子萌发法对该病害进行化学防治试验的结果表明：在参试的11种杀菌剂中，叶斑净和世高的防治效果最好，对病斑扩展的抑制率分别达52．82％和33．62％．     

饲用益生素与抗生素的比较研究

对饲用益生素与抗生素的研究进行了比较分析，主要对其研究的历史和现况，作用机理，合理使用的条件与可行性进行了综述。     

小麦品种抗性多样化中寄主群体抗性量化的研究

 在一个地区范围内利用病原群体毒性及寄主群体抗性的观点,可把多个具不同抗锈性小麦品种在不同布局条件下,将其整体抗性加以综合量化,其结果在预测预报小麦锈病流行强度的研究中,有助于品种抗性因子对锈病流行强度所产生干扰作用的大小能够量化进入预测式.     

中国小麦秆锈菌鉴别寄主品种Rulofen抗秆锈病基因的单体分析

普通小麦品种Rulofen是我国小麦杆锈菌的鉴別寄主。用中国春单体系列和对Rulofen无毒性的小麦秆锈菌的三个生理小种21C3、34、34C2对Rulofen进行了抗秆锈病基因的单体分析,并将Rulofen所含的抗秆锈病基因与国际上已命名的Sr基因进行了异同比较。结果表明;Rulofen在2D染色体上含有兼抗三个供试生理小种的抗病基因Sr6.其抗性效应为;-;1~ 或1X~=-x~- ,因环境条件的影响,Sr6的抗性反应型不稳定;在5D染色体上含有兼抗21C3、34和34C2三个生理小种的抗病基因Sr30,其抗性效应为2=、抗秆锈病基因Sr6和Sr30对我国的小麦秆锈菌小种34类群都具有进一步的区分作用。     

小麦叶锈菌生理小种研究

根据全国统一的８个寄主鉴定结果，仍以叶１（２６），叶２（３６０）和洛１０小种群为主要优势小种（群）。在洛１０小种中仍以３６１，２６１，３６３和３７７出现频率较高。近年来，叶１，叶２出现频率在逐年增长，叶３在下降。用新鉴别寄主鉴定的小种，以Ｖ１，９－１２，１５－１６；Ｖ１，９－１２，１５－１６；Ｖ１，９－１６；Ｖ１，９－１２，１４－１６；Ｖ１，９－１３；１５－１６出现频率较高。用毒力频率分析，ＩＲＮ６６—３３１，Ｒｅｄｍａｎ６０６８，百农３２１７和丰抗１３抗性较好，而东方红３号，丰产３号等品种高度感病，能侵染洛１０品种小种在逐年上升，毒力频率均达８３．３３％。这为抗锈育种寻找抗源提出了新的要求。     

取食不同寄主植物的小菜娥对溴氰菊酯和氯氰菊酯敏感性的变化

取食不同寄主植物的小菜蛾３龄幼虫对溴氰菊酯和氯氰菊酯的敏感性发生了变化。其中，以取食萝卜的小菜蛾３龄幼虫最为敏感，其次是甘蓝、菜心、白菜和西洋菜，取食花椰菜的最不敏感。但用不同寄主植物饲养小莱蛾１个完整的世代，再用菜心统一饲养至３龄，用上述药剂生测的结果是，其敏感性差异不明显。本文还对因不同寄主植物诱导的小菜蛾药剂敏感性变化的实质进行了讨论。