Acoustic evaluation of the vertical distribution of dwarf ayu Plecoglossus altivelis altivelis in Lake Biwa

SUMMARY: The vertical distribution of dwarf ayu Plecoglossus altivelis altivelis in the pelagic waters of Lake Biwa was evaluated from June to September in 1995–97 from eight acoustic surveys using a quantitative echosounder. In each survey, echoes from a depth range of 3 m to the sea bottom were collected at a station every 2.7 s for 24 h together with measurements of vertical profiles of water temperature and chlorophyll-a. The ayu's echoes were identified using an underwater video camera. The ayu were observed near the maximum chlorophyll-a depth and above the thermocline. Their density was highest at depths of 4–11 m with 2–4 individuals/m ³ and was almost zero below 20 m. Echo signs were recorded as having a frequent duration of more than 1 h at night, whereas were of a shorter duration in the day. The fish stay in the epilimnion during the day without any clear vertical migration, but are distributed more uniformly at night. The advantages of remaining in the epilimnion are discussed in terms of food availability and predator avoidance.     

Horizontal transmission and host-virulence attenuation of totivirus in violet root rot fungus Helicobasidium mompa

Monokaryotic strains of Helicobasidium mompa were used as vectors of a mycovirus between various H. mompa isolates to examine the transmissibility of one of the mycoviruses, totivirus (HmTV1–17 virus) in the hypovirulent isolate V17 of H. mompa. The isolates that acquired HmTV1–17 virus were also examined for any alteration in the virulence. Twelve dikaryotic isolates of H. mompa, belonging to 11 mycelial compatibility groups (MCGs) and being mycelially incompatible with isolate V17, were used as recipients of HmTV1–17 virus. Two monokaryotic isolates that were mycelially incompatible with isolate V17 and all of the recipients were also used as vectors of HmTV1-17 virus between isolate V17 and the recipients. When isolate V17 and recipients were directly paired on plate media, HmTV1-17 virus was transmitted from isolate V17 into 2 of the 12 recipients (i.e., 2 of the 11 MCGs). Two monokaryotic strains were paired with isolate V17, and the monokaryotic strains that acquired HmTV1-17 virus were then used as new virus donors. When the monokaryotic strains containing HmTV1-17 virus were paired with the 12 recipients, HmTV1-17 virus was transmitted into 7 of the 12 recipients from the monokaryotic strains (i.e., 7 of 11 MCGs). Based on these results, we concluded that monokaryotic strains could act as vectors to transmit HmTV1-17 virus into H. mompa isolates. When four of the H. mompa isolates that acquired HmTV1-17 virus were used to inoculate apple rootstock Malus prunifolia, the virulence of all of the isolates was attenuated from that of their parental isolates. Moreover, because the DNA fingerprints of the fungal isolates that acquired HmTV1-17 virus were the same as those of their parental isolates, the infection with HmTV1-17 virus is considered the cause of virulence attenuation of H. mompa.     

手动比例复合阀在中高压液压绞纲机中的应用

中高压液压技术在海洋捕捞机械—绞纲机中的使用推动了我国渔业机械的发展,手动比例复合阀在中高压液压技术上的应用则大大加快了液压绞纲机在国内渔业生产中的普及。目前,我国浙江、江苏、福建、广东和山东等省沿海渔民使用的绞纲机普遍采用带手动比例复合阀的液压系统。为此,对手动比例复合阀换向、溢流、调速集成等功能进行了分析。     

基于单片机的脉码传输仪设计

以单片机为核心,采用软件、硬件相结合的方法,充分利用单片机的硬件中断资源,实时响应地面的声波逻辑脉冲,分离其接收和发射逻辑。同时该仪器以地面声波逻辑为工作时序,分时采集模拟道数据、脉冲道数据及向地面传输PCM数据。该脉码传输仪既能完成PCM3506的全部功能,又能监测仪器工作环境的温度及测井套管接箍的压力。     

Importance of Cell Wall Degrading Enzymes Produced by Fusarium graminearum during Infection of Wheat Heads

Cytological studies were carried out to elucidate the importance of cell wall degrading enzymes (CWDE) during infection of wheat spikes by Fusarium graminearum. Scanning electron micrographs revealed that at 6–24 hours after inoculation (hai) of single spikelets with macroconidia of F. graminearum, the fungus germinated by forming several germ tubes and developed a dense hyphal network in the cavity of the spikelet. At 24–36hai, the fungus formed infection hyphae which invaded the ovary and inner surface of the lemma and palea. Transmission electron microscopical studies revealed that the fungus extended inter- and intracellularly in the ovary, lemma and rachis and caused considerable damage and alterations to the host cell walls. In different tissues of healthy and F. graminearum-infected wheat spikes the cell wall components cellulose, xylan and pectin were localized by means of enzyme-gold and immuno-gold labelling techniques. Localization of cellulose, xylan and pectin showed that host cell walls which were in direct contact with the pathogen surface had reduced gold labelling compared to considerable higher labelling densities of walls distant from the pathogen–host interface or in non-colonized tissues. The reduced gold labelling densities in the infected host cell walls indicate that these polysaccharide degrading enzymes might be important pathogenicity factors of F. graminearum during infection of wheat spikes. The results revealed that, infection and colonization of wheat spikes by F. graminearum and reactions of infected host tissue were similar to those reported for F. culmorum.     

Biological and molecular characterization of Tomato spotted wilt Virus in Israel

Received April 24, 1997; received in final form June 29, 1997. Symptoms resembling tomato spotted wilt virus (TSWV) infections were documented among ornamental and vegetable crops in commercial greenhouses and open fields in Israel. Plants exhibiting these symptoms were collected from January 1992 to December 1996. Among cultivated plants analyzed for TSWV by enzyme-linked immunosorbent assay (ELISA), 19 species representing five families were found to be infected; natural infection was also recorded in six plant species of weeds. Virus identity was characterized by host range, serology and electron microscopy. Serological reaction with the isolates, found in Israel, using antisera from different sources as well as the sequence analysis of the nucleocapsid gene, demonstrated that the Israeli isolates of TSWV are a member of tospovirus serogroup I, type I (BR-01 strain). No virus transmission was found in seeds collected from virus-infected vegetable and ornamental crops. A non-radioactive molecular probe derived from the cloned nucleocapsid isolate enables specific detection of the virus in crude sap from infected plants. The detection of TSWV in Israel constitutes a severe potential threat to the ornamental and vegetable industry.     

苹果花脸病田间病情发展及ASSVd在组培条件下的传播

为了明确苹果锈果类病毒(apple scar skin viroid,ASSVd)引起的苹果花脸病在田间的病情发展情况以及ASSVd在组培条件下的传播方式,2012—2015年对河北省顺平南神南村3个果园进行持续调查和检测。结果显示,果园A、B、C的显症率分别从3.00%、19.35%和10.00%上升至10.00%、34.41%和22.00%,带毒率分别从11.00%、20.43%和14.00%上升至23.00%、37.63%和30.00%,带毒率和显症率都逐年增加,而且带毒率大于显症率,即有些带毒果树不显症。发病果树田间分布有明显的发病中心。通过高通量测序发现显症果树ASSVd vsiRNA reads数是带毒未显症reads数的4.08倍,同时实时荧光定量PCR检测发现显症树ASSVd病毒积累量显著高于带毒未显症树。以携带ASSVd的组培苗和无毒组培苗为试材,利用RT-PCR检测明确了ASSVd可通过伤口沾染带毒汁液、组培剪污染、含毒培养基、根系接触进行传播,其中根系接触传染率较高。     

番茄斑驳花叶病毒在我国茄科作物上的发生及生物学特性

【目的】鉴定烟草花叶病毒属(Tobamovirus)新种番茄斑驳花叶病毒(Tomato mottle mosaic virus,ToMMV)当前在我国茄科作物上的发生危害情况、主要分布地区和自然寄主,明确其主要寄主范围、传播途径和致病性等生物学特性。【方法】利用RT-PCR方法对2013—2017年采自我国云南、贵州、四川、海南、湖南、河南、陕西、山东、湖北、浙江、辽宁、西藏和内蒙古13个省(自治区),表现为花叶、皱缩、畸形、黄化、坏死等疑似病毒病症状的茄科作物辣椒、番茄、茄子、马铃薯和烟草等样品进行ToMMV的检测。分别将ToMMV进行摩擦接种和注射接种,对感染ToMMV的珊西烟获得的种子及由种子萌发的幼苗进行ToMMV检测,对由健康种子萌发且在含有ToMMV毒源土壤中生长的6—8叶龄辣椒和番茄幼苗进行ToMMV检测,以此开展ToMMV传播方式的测试。在茄科、葫芦科、豆科和十字花科等6科30种植株上开展ToMMV的寄主范围鉴定和不同辣椒、番茄材料对ToMMV的抗性鉴定。【结果】我国13个省(区)共采集茄科作物疑似病毒病样品1 622份,ToMMV的平均检出率为2.59%,目前ToMM...     

小西葫芦绿斑驳花叶病毒生物学特性及传播方式

小西葫芦绿斑驳花叶病毒(Zucchini green mottle mosaic virus,ZGMMV)是我国新报道的侵染葫芦科作物的烟草花叶病毒属病毒.从感染病毒的葫芦叶片中分离出ZGMMV,摩擦接种西瓜(Citrullus lanatus)、葫芦(Lagenaria siceraria)、西葫芦(Cucurbit...     

Identification of divergent variants of Grapevine virus A

Eight isolates of Grapevine virus A (GVA), which induced different symptoms in leaves of Nicotiana benthamiana, were recovered from various grapevines. The dsRNA patterns of two isolates, which consistently induced mild vein clearing (referred here as mild isolates of GVA) were similar, but different from those of other isolates of GVA. Analysis based on overall nucleotide (nt) sequence identity in the 3 terminal part of the GVA genome, comprising part of ORF3 (putative movement protein, MP), entire ORF4 (capsid protein, CP), entire ORF5 and part of 3 UTR, revealed that GVA isolates separate into three groups (I, II, III), sharing 91.0–99.8% nt sequence identity within groups and 78.0–89.3% nt sequence identity between groups. Mild isolates of the virus were group III and shared only 78.0–79.6% nt sequence identity with the other isolates. The comparison of predicted amino acid sequences for MP and CP revealed many amino acid alterations, revealing distinct local net charges of these proteins for mild isolates of the virus. Based on both conserved and divergent nt regions in the CP and ORF5, oligonucleotide primers were designed for the simultaneous RT-PCR detection of all GVA isolates and for the specific detection of the most divergent virus variants represented here by mild isolates of the virus.