油茶根腐病发生规律和综合防治研究

油茶根腐病是油茶林的新病害，植株自发病至死亡为２～３年，其病菌为根际土壤习居菌，喜酸性和较低温度，病菌侵入植株的途径主要是伤口，潜育期２０ｄ左右．防治本病的关键是保护幼树根颈部及主根不受伤害，加强管理，增强树势．此外，用熟石灰在根际处与表土层拌匀覆盖和用多菌灵、退菌特等杀菌剂及时进行防治，并辅以营林技术措施治理，可收到良好的防治效果．     

Role of basidiomycete fungi in the grapevine trunk disease esca

Phaeomoniella chlamydospora and wood-rotting basidiomycete fungi, namely Fomitiporia spp., are known esca pathogens. However, the effect of their mixed infections and the sequence of infection on disease development is unclear. To determine the effects of single and co-inoculations on symptoms, potted Vitis vinifera ‘Crimson Seedless’ was inoculated with P. chlamydospora either alone or in combination with one of four basidiomycetes: Coprinellus radians, Fomitiporia langloisii, F. polymorpha and the novel species Tropicoporus texanus. Basidiomycetes were isolated from vines with foliar symptoms of esca in California and Texas. In sequential co-inoculations, the effects of different sequences of infection (P. chlamydospora first, basidiomycete 6 months later; and vice versa) were tested, compared to simultaneous co-inoculations. Plants inoculated with P. chlamydospora either alone or in combination with a basidiomycete (in any sequence) did not differ significantly in the length of black-streaking lesions. In plants inoculated only with a basidiomycete, the appearance of large brown lesions, coupled with the absence of this wood symptom from control plants, suggests that C. radians, F. langloisii and T. texanus are pathogenic. Foliar symptoms resembling those of esca in the field (marginal and/or interveinal scorching, combined with red and/or yellow discoloration) were statistically more frequent among plants inoculated with F. polymorpha or T. texanus, either simultaneously or following P. chlamydospora, compared to single inoculations. Sequential co-inoculations of a basidiomycete before or after P. chlamydospora were associated with similar lesion lengths, suggesting that basidiomycetes may not require infection by P. chlamydospora in order to extensively colonize the wood.     

高通量测序发现河南开封、中牟西瓜病毒病由多种病毒复合侵染导致

 调查发现河南省开封市祥符区和郑州市中牟县西瓜田病毒病严重发生,症状表现为叶片黄化、蕨叶、皱缩、卷曲,枝梢翘起,果实变小和瓜纹不清。为明确其病毒种类,通过小RNA测序及生物信息学分析发现采集的西瓜样本中存在8种病毒。其中包括5种已知病毒:小西葫芦黄花叶病毒(Zucchini yellow mosaic virus, ZYMV)、甜瓜蚜传黄化病毒(Melon aphid-borne yellows virus, MABYV)、西瓜花叶病毒(Watermelon mosaic virus, WMV)、黄瓜绿斑驳花叶病毒(Cucumber green mottle mo-saic virus, CGMMV)和西瓜隐潜病毒(Citrullus lanatus cryptic virus, CiLCV);3种为新检出的RNA病毒:西瓜病毒A(Watermelon virus A, WVA)、西瓜皱叶相关病毒1号(Watermelon crinkle leaf-associated virus 1, WCLaV-1)和西瓜皱叶相关病毒2号(Watermelon crinkle leaf-associated virus 2, WCLaV-2)。RT-PCR检测田间66个西瓜标样发现,WMV、CiLCV和ZYMV是侵染两地西瓜的主要病毒,其阳性检出率分别为61%、56%和52%,两种及以上病毒复合侵染的比率达68%。     

烟草Hsc70-2的克隆及对马铃薯Y病毒侵染烟草的促进作用

【目的】马铃薯Y病毒（Potato virus Y,PVY）是危害烟草、马铃薯、番茄、辣椒等主要农作物的重要病毒,给农业生产带来巨大损失。论文旨在克隆Hsc70-2蛋白在本氏烟（Nicotiana benthamiana）中的基因序列并分析其生物学信息,研究NbHsc70-2蛋白对PVY侵染烟草的影响,为进一步解析PVY的侵染机制提供理论依据。【方法】以本氏烟为材料,克隆NbHsc70-2蛋白的基因编码序列（coding sequence,CDS）,利用MEGA 6.0 进行多序列比对并构建系统进化树;利用实时荧光定量PCR（qRT-PCR）分析NbHsc70-2在本氏烟各组织中的表达水平;采用在线软件BaCeILo和SignalP 4.0对NbHsc70-2进行生物信息学分析;构建NbHsc70-2-RFP融合蛋白确定该蛋白的亚细胞定位;研究PVY处理对本氏烟叶片中NbHsc70-2的影响;利用激光共聚焦观察PVY-GFP处理对NbHsc70-2-RFP定位的影响;构建NbHsc70-2 VIGS沉默体系及瞬时表达载体,采用qRT-PCR比较NbHsc70-2在沉默/过表达后对PVY表达的影响。【结果】NbHsc70-2编码649个氨基酸,系统进化树分析表明,NbHsc70-2与普通烟NaHsc70-2序列相似性最高,亲缘关系最近,属于热激蛋白家族,C端具有热激蛋白家族的高度保守基序结构;qRT-PCR分析表明,NbHsc70-2在叶中表达量最高,在根和茎中的表达量较低;BaCeILo预测及激光共聚焦显微镜观察均显示NbHsc70-2定位在细胞质中,并且PVY-GFP侵染本氏烟后NbHsc70-2-RFP部分转移至细胞核,与PVY-GFP共定位在细胞质及细胞核中;将NbHsc70-2基因沉默载体pTRV::NbHsc70-2导入本氏烟中7 d后相比于对照组,沉默组出现心叶皱缩及矮化现象;接种PVY-GFP 7 d后通过手持紫外灯观察到沉默组中无明显绿色荧光出现,而对照组中PVY-GFP系统侵染使得非接种叶片呈现荧光现象,沉默组荧光点数约为对照组28%;接种PVY后,利用qRT-PCR检测沉默NbHsc70-2后1、3、5 d的PVY CP基因积累量,结果表明沉默NbHsc70-2后PVY CP基因积累量下降,其中3 d和5 d与对照相比差异显著,基因表达水平分别为对照的14%和0.004%;将NbHsc70-2过表达载体pEarleyGate100::GWC::NbHsc70-2与PVY同时导入本氏烟后,结果表明相比于对照组,过表达组48 h和72 h 其PVY CP基因积累量显著上升,基因表达水平分别为对照组的2.31、2.56倍。【结论】PVY侵染会引起NbHsc70-2表达量上升;NbHsc70-2是PVY侵染本氏烟重要的组成成分,沉默该基因显著抑制PVY的表达,过表达NbHsc70-2则显著提高PVY的表达,即NbHsc70-2的表达水平与PVY复制呈正相关,NbHsc70-2蛋白促进PVY对烟草的侵染。     

Identification and pathogenicity study of emerging fish pathogens Acinetobacter junii and Acinetobacter pittii recovered from a disease outbreak in Labeo catla (Hamilton, 1822) and Hypophthalmichthys molitrix (Valenciennes, 1844) of freshwater wetland in West Bengal,India

The disease outbreaks in aquaculture system of wetlands are the major cause of fish mortality. Among various bacterial septicaemic diseases, fish mortality caused by Acinetobacter spp. is recently reported in different fish species. Fish disease outbreak was investigated in a wetland of West Bengal, India to identify the aetiological factors involved. The moribund fish were examined and subjected to bacterial isolation. Two bacterial causative agents were identified as Acinetobacter junii and Acinetobacter pittii by biochemical characterization and 16S rRNA gene amplification. Both the isolates were oxidase‐negative, nitrate‐negative, catalase‐positive and indole‐negative. The molecular identification using 16S rRNA gene sequencing and phylogenetic tree analysis further confirmed the two Acinetobacter spp. with 97%–99% similarity. The antibiotic resistance patterns of these two bacteria revealed that both of them were resistant to β‐lactam, cefalexin, cephalothin, amoxyclav, cefuroxime, cefadroxil, clindamycin, vancomycin and penicillin. In addition, A. pittii was also resistant to other antibiotics of cephams group such as ceftazidime and cefotaxime. In the challenge experiment, both A. junii and A. pittii were found to be pathogenic with LD₅₀ of 1.24 × 10⁵ and 1.88 × 10⁷ cfu/fish respectively. Histopathological examination of gill, liver and kidney revealed prominent changes supporting bacterial septicaemia. The investigation reports for the first time on concurrent infection by A. junii and multidrug‐resistant (MDR)‐A. pittii as emerging fish pathogens to cause severe mortality in Labeo catla and Hypophthalmichthys molitrix in a freshwater wetland.     

Erythromycin and florfenicol treatment of rainbow trout Oncorhynchus mykiss (Walbaum) experimentally infected with Flavobacterium psychrophilum

Flavobacterium psychrophilum is responsible for significant economic losses in rainbow trout aquaculture. Antimicrobial treatment remains the primary means of control; however, there are limited choices available for use. The objectives of the study were therefore to determine the minimum inhibitory concentrations for erythromycin and florfenicol in selected F. psychrophilum isolates and to evaluate their clinical treatment efficacy in experimentally infected rainbow trout. All isolates tested had moderate susceptibility to florfenicol and erythromycin except one isolate, which had low susceptibility to erythromycin. Two isolates (one with moderate and one with low susceptibility to erythromycin) were used in an experimental infection trial. Rainbow trout juveniles were injected intraperitoneally with 10⁸ cfu/fish and after mortality had begun, fish were given erythromycin‐ and florfenicol‐medicated feed at a rate of 75 mg kg^?1 day^?1 and 10 mg kg^?1 day^?1 fish body weight, respectively, for 10 consecutive days. The splenic F. psychrophilum load was determined using an rpoC quantitative PCR throughout the 30‐day trial. Relative to antibiotic‐free controls, erythromycin treatment significantly (p < 0.05) reduced mortality of rainbow trout juveniles infected with FPG101, even when treatment was initiated after clinical signs developed.     

我国玉米茎腐病研究进展

玉米茎腐病是一种世界性土传真菌病害，该病害在我国玉米产区均有发生。近年来，受耕作制度（如保护性耕作、秸秆还田等）的改变和气候变化的影响，生产中使用的高抗茎腐病的玉米品种不多等因素，致使田间病原菌数量增加，我国玉米茎腐病有逐渐加重的趋势。针对玉米茎腐病危害逐年加重的现状，本文系统综述了玉米茎腐病致病菌、发病症状表现、病情分级标准、病害侵染规律、抗性鉴定评价方法等方面的研究进展情况，并提出了玉米茎腐病的防治策略。     

皖南黄肉种鸡种蛋中禽白血病病毒的感染状态检测

本研究首次通过检测种蛋中禽白血病病毒(ALV)评价了皖南黄父母代肉种鸡的ALV感染状态.收集该鸡群的120枚鸡蛋,取40枚鸡蛋孵化至9～11 d后分别制备CEF,培养10 d,取细胞上清用ELISA试剂盒检测ALV p27抗原.另取80枚鸡蛋卵白直接检测p27抗原,同时分别将80枚鸡蛋卵白接种CEF(DF1),培养10 d后取细胞上清检测p27抗原.比较p27阳性检出率的结果表明,受精蛋孵化9～11 d后制备CEF,再培养10 d的细胞上清检出率(10/36)高于直接检测卵白(17/80)与卵白接种CEF(DF1)的细胞上清(7/80).将经DF1培养后p27抗原阳性样品,用针对ALV-J的单抗JE9做IFA,ALV-J的阳性率为6/7.检测该80枚鸡蛋的卵黄抗体,ALV-J、ALV-AB的抗体阳性率分别为18/80、1/80.结果表明,该皖南黄父母代肉种鸡群存在的外源性ALV感染主要为ALV-J.该研究为ALV的净化提供了可行性检测方法.     

栽培蓝莓菌根侵染特性研究

摘要：为了解贵州省麻江县蓝莓基地菌根侵染情况，采用酸性品红染色法对麻江县3个蓝莓基地的兔眼蓝莓和龙崩基地不同品种的蓝莓进行菌根侵染情况调查，并对其根际土壤进行分析，结果表明：蓝莓菌根比较简单，主要有四种类型：丛枝菌根、杜鹃花类菌根、具柱状囊泡类型的菌根和外生菌根。各样地蓝莓菌根侵染情况不高；不同基地蓝莓菌根侵染率差异不明显（P＞0.05）；不同品种蓝莓菌根侵染率存在显著差异（P＜0.05）；15a生蓝莓菌根侵染率显著高于3～5a生蓝莓（P＜0.05）。蓝莓根系菌根侵染率与土壤P、SOC呈显著正相关（r＞0.9，P＜0.01）、与全K、pH值呈显著负相关（r＜-0.89，P＜0.01）。