The Recent Advances in Plant Protection Researches of China

There are eight examples briefly given in this paper, namely, (1) Polymyxa graminis and the cereal viruses it transmits; (2) the geographical types and facultative migration of cotton bollworm as well as the safety of Bt transgenic cotton; (3) development of crop near-isogenic lines with resistance to diseases; (4) molecular-biological researches induced resistance of rice by infection of blast fungus;(5) to use cytological and molecular-biological techniques for breeding wheat varieties resistant to barley yellow dwarf virus; (6) mass rearing and field releasing of Microplitis mediator for cotton bollworm control; (7) identification and recombination of insecticidal crystal genes of Bacillus thuringiensis; and (8) interplanting of diverse resistance rice varieties for sustainable control of blast disease; which reflect the general situation of recent advances in plant protection researches of China.     

木霉菌制剂对禾谷全蚀病的防治作用

木霉菌是对多种植物病原真菌有作用的拮抗体,包括Gaeumannomyces graminis var.tritici(Ggt),Pythium spp.,Rhizoctonia solani以及Fusarium spp．木霉菌能产生抑制植物病原真菌生长与活力的抗菌物质,是理想的植物病害生物防治菌。有效的生物防治方法可为农民提供低风险而又灵活的病害防治措施,特别是在需要减缓病原菌对化学杀菌剂产生抗药性的情况下。本文综合介绍了在南澳大利亚田间进行的利用康宁木霉菌(T.koningii)防治禾谷类根部病害的结果,并重点介绍澳大利亚在商品化开发方面的工作进展。在病害发生严重的情况下,康宁木霉菌可降低小麦全蚀病和丝核菌根腐病发病程度分别达2,4％和48％。小麦产量增加7％,也能降低大麦丝核菌根腐病发病程度达59％。康宁木霉菌也能够防治由Ceratocystis paradoxa引起的甘蔗凤梨病。     

大麦、油菜的抗耐病性与过氧化物酶同工酶的关系

利用过氧化物酶同工酶分析比较了上海地区大麦抗、感黄花叶病的品种和油菜耐、感菌核病的品种间的酶谱差异。结果表明,两类作物的抗耐病性在酶谱上呈现相同趋势。感病品种的酶带数量和强度要高于抗耐病品种。试验显示,过氧化物酶同工酶分析可作为大麦、油菜抗病育种中的一个鉴定手段予以利用。     

斑点免疫结合法检测3种植物病毒

研究了改进的斑点免疫结合法在检测芜菁花叶病毒、烟草花叶病毒和小西葫芦黄化花叶病毒中的应用.无论是使用全抗血清还是纯化的免疫球蛋白,检测感染组织粗汁液中的病毒或纯化的病毒,均获得了满意的结果.同时进行的斑点免疫结合试验、酶联免疫吸附试验和免疫吸附电子显微术等的比较结果表明:无论是检测纯化病毒还是感染组织粗汁液中的病毒,斑点免疫结合法的检测敏感性均优于后2种方法,病毒的可测感度芜菁花叶病毒为0.65ng,烟草花叶病毒为0.39 ng,小西葫芦黄化花叶病毒为0.45 ng;应用碱性磷酸酶标记抗体及羟基吲哚磷酸盐和氮兰四唑为底物较为合适,这种底物可在室温下长期保存,并且反应产物为不褪色的紫色,易于观察和保存.     

Genetic recombination between RNA components of a multipartite plant virus

Genetic recombination of DNA is one of the fundamental mechanisms underlying the evolution of DNA-based organisms and results in their diversity and adaptability. The importance of the role of recombination is far less evident for the RNA-based genomes that occur in most plant viruses and in many animal viruses. RNA recombination has been shown to promote the evolutionary variation of picornaviruses, it is involved in the creation of defective interfering (DI) RNAs of positive- and negative-strand viruses and is implicated in the synthesis of the messenger RNAs of influenza virus and coronavirus. However, RNA recombination has not been found to date in viruses that infect plants. In fact, the lack of DI RNAs and the inability to demonstrate recombination in mixedly infected plants has been regarded as evidence that plants do not support recombination of viral RNAs. Here we provide the first molecular evidence for recombination of plant viral RNA. For brome mosaic virus (BMV), a plus-stranded, tripartite-genome virus of monocots, we show that a deletion in the 3' end region of a single BMV RNA genomic component can be repaired during the development of infection by recombination with the homologous region of either of the two remaining wild-type BMV RNA components. This result clearly shows that plant viruses have available powerful recombinatory mechanisms that previously were thought to exist only in animal hosts, thus they are able to adapt and diversify in a manner comparable to animal viruses. Moreover, our observation suggests an increased versatility of viruses for use as vectors in introducing new genes into plants.     

中国、澳大利亚小麦、蔬菜以及棉花根部土传病害生物防治研究进展

土传病害是作物产量的经常性限制因素。在禾谷类生产中,某些病害在少耕制度下异常严重。因此,有利于保护土壤侵蚀的管理措施(例如减少耕作、保留农作物残体等)能导致病害发生更为严重,从而造成作物减产,这要求研究新的病害防治措施,而不能依靠农业耕作措施或轮作进行防治。生物防治是病害防治措施的一种,在中国和澳大利亚都已进行了研究。蔬菜和棉花的苗期病害一般是利用化学杀菌剂进行防治,或者病害严重发生导致毁种后重新播种。在这些病害防治方面,人们探索了生物防治措施,旨在发展安全、无残留的防治方法,本文介绍的合作研究,主要是在田间和盆栽条件下筛选、评价一系列澳大利亚和中国的土壤细菌和真菌在中国和澳大利亚东南部对土传病害的防治作用,从而建立有效可靠的作物病害生物防治方法。在两国进行的实验研究中,对象作物为小麦、蔬菜(番茄、黄瓜和辣椒)以及棉花。另外,还对枯草芽孢杆菌的作用机理以及重要植物病原菌如腐霉菌的生态学进行了研究。     

利用PCR扩增的核糖体DNAs鉴定禾顶囊壳菌和瓶梗霉

小麦全蚀病是由禾顶囊壳菌引起的小麦根部病害,在全世界范围内普遍发生.用传统的方法鉴别和区分病原菌与非致病菌花费时间长而且有时不准确.本研究利用PCR技术,扩增了15个禾顶囊壳菌和瓶梗霉分离株的核糖体DNAs,并用限制性内切酶Dde I酶切后电泳,结果表明,该法可有效鉴别禾顶囊壳菌和瓶梗霉这2个不同的种.     

Synthesis of brome mosaic virus subgenomic RNA in vitro by internal initiation on (-)-sense genomic RNA

The genomes of many (+)-stranded RNA viruses, including plant viruses and alphaviruses, consist of polycistronic RNAs whose internal genes are expressed via subgenomic messenger RNAs. The mechanism(s) by which these subgenomic mRNAs arise are poorly understood. Based on indirect evidence, three models have been proposed: (1) internal initiation by the replicase on the (-)-strand of genomic RNA, (2) premature termination during (-)-strand synthesis, followed by independent replication of the subgenomic RNA and (3) processing by nuclease cleavage of genome-length RNA. Using an RNA-dependent RNA polymerase (replicase) preparation from barley leaves infected with brome mosaic virus (BMV) to synthesize the viral subgenomic RNA in vitro, we now provide evidence that subgenomic RNA arises by internal initiation on the (-)-strand of genomic RNA. We believe that this also represents the first in vitro demonstration of a replicase from a eukaryotic (+)-stranded RNA virus capable of initiating synthesis of (+)-sense RNA.     

加工番茄CMV与ToMV的ELISA检测及其相关性分析

用针对CMV和ToMV的单克隆抗体对田间表现病毒病症状的137个加工番茄自然病株进行了间接ELISA检测,检测结果表明,CMV和ToMV在加工番茄上的侵染率分别为83．2％和61．3％,并且2种病毒常复合侵染,复合侵染率达58．4％。用Eviews3．0软件借助加权最小二乘法（WLS）分析CMV和ToMV在病株上的带毒量,结果表明,2种病毒在病株上的积累是相互影响的,互为正相关关系。     

Generation of transgenic wheat resistant to wheat yellow mosaic virus and identification of gene silence induced by virus infection

The plasmid containing the promoter Act1, the coat protein (cp) gene of wheat yellow mosaic virus (WYMV) and the selectable bar gene, was delivered via particle bombardment, directly into immature embryos of a wheat cultivars. PCR and PCR-RFLP were employed to screen the existence of the cp gene in T0 and T1 generations. Seeds from the positive T1 plants were sowed in fields heavily contaminated with WYMV to detect their resistance. In field trial of virus infection, one of the transgenic wheat lines, P8-T2, exhibited highly disease-resistance. Western blot and RT-PCR analysis showed that the expression level of cp gene in the resistant transgenic line was reduced greatly compared to those susceptible to WYMV infection. This provided evidence to presume that the resistance obtained by the transgenic wheat line was stimulated by the mechanism of the virus induced gene silencing.     

SNARE-protein-mediated disease resistance at the plant cell wall

Failure of pathogenic fungi to breach the plant cell wall constitutes a major component of immunity of non-host plant species--species outside the pathogen host range--and accounts for a proportion of aborted infection attempts on 'susceptible' host plants (basal resistance). Neither form of penetration resistance is understood at the molecular level. We developed a screen for penetration (pen) mutants of Arabidopsis, which are disabled in non-host penetration resistance against barley powdery mildew, Blumeria graminis f. sp. hordei, and we isolated the PEN1 gene. We also isolated barley ROR2 (ref. 2), which is required for basal penetration resistance against B. g. hordei. The genes encode functionally homologous syntaxins, demonstrating a mechanistic link between non-host resistance and basal penetration resistance in monocotyledons and dicotyledons. We show that resistance in barley requires a SNAP-25 (synaptosome-associated protein, molecular mass 25 kDa) homologue capable of forming a binary SNAP receptor (SNARE) complex with ROR2. Genetic control of vesicle behaviour at penetration sites, and plasma membrane location of PEN1/ROR2, is consistent with a proposed involvement of SNARE-complex-mediated exocytosis and/or homotypic vesicle fusion events in resistance. Functions associated with SNARE-dependent penetration resistance are dispensable for immunity mediated by race-specific resistance (R) genes, highlighting fundamental differences between these two resistance forms.     

The hepatitis delta (delta) virus possesses a circular RNA

Hepatitis delta (delta) virus (HDV), a satellite virus of the hepatitis B virus (HBV), causes a severe form of viral hepatitis in humans. Here we present evidence based on electron microscopy and electrophoretic behaviour that HDV contains a single stranded circular RNA molecule. This is the first animal virus identified with a circular RNA genome. Circular RNAs have only been found in plant viruses. We have obtained a partial complementary DNA clone representing approximately 25% of the total genome of HDV. Analysis of this cDNA revealed similarity to two plant viruses that may explain the origin of the virus.     

农作物病毒病害绿色防控技术创新

作物病毒病害是限制我国农作物优质稳产的主要因素之一,其主要由媒介生物传播,作物普遍缺乏抗病毒病的种质资源,病毒病害防治难度大,主要依赖化学农药通过防控媒介昆虫进行控制。近年来,随着纳米生物学、分子生物学和组学研究的飞速发展,以及微观生物学技术和理念对宏观生物学的快速渗透与交叉,基因组编辑技术的快速发展,病毒—昆虫—植物三者互作机制等各方面研究取得了诸多重要进展,在寻找病毒病害流行爆发的宏观生态学现象背后的分子生物学与生物化学机制上取得了长足进步,从而促进新型病毒病害的持久防控技术的发展,提供了科学依据和潜在新方案。文章简要回顾了近年来这些新技术的主要机理,并抛砖引玉提出了对未来发展的建议和思考。建议国家和社会组织研究力量,大力加强1)探索利用微纳米递送化学药物或者核酸干扰等防治病毒病害的新方法研究;2)病害发生的多元生物体系互作机制及科学防控科技支撑能力建设;3)基因组编辑创建病毒病害绿色防控的技术等方向的探索与突破,力求在病毒病害绿色生态防控方面为农业提供强有力的科技创新和支撑能力。     

小麦和青稞幼穗脱分化期间过氧化物酶和酯酶同工酶组成的变化

离体培养前的小麦和青稞的幼穗均含有极少量的过氧化物酶和酯酶同工酶。离体培养8h后,外植体中部分同工酶被一些新合成的同工酶替代,同工酶的数量显著增加。随着外植体的发育,新的同工酶分子不断出现。在愈伤组织形成的后期,部分同工酶逐渐消失,同工酶的数量也明显下降,过氧化物酶和酯酶同工酶的变化在小麦和青稞之间无显著的差别,在小麦或青稞中,过氧化物酶同工酶的变化也同酶酶同工酶的变化基本相同。文章讨论了这两种酶的变化与脱分化过程的关系及其与其它非禾各类植物中的酶的差异。     

Cloning and expression of the Chinese wheat mosaic virus RNA2 coat protein readthrough and 19 ku cysteinerich domains and localization of these proteins

The 5′-terminal (RTn) and 3′-terminal (RTc) halves of the coat protein readthrough domain and the 19 ku cysteine-rich protein of Chinese wheat mosaic virus (CWMV) were amplified by RT-PCR, cloned and expressed in E. coli. Antisera and monoclonal antibodies against these proteins were prepared by immunising these purified proteins to mice. Detection of RTn, RTc and 19 ku proteins in CWMV infected wheat sap and leaf tissue indicated that the RTn and RTc proteins were distributed on the surface of virus particles whereas the 19 ku protein was in the cytoplasm of the infected wheat cells.     

High diversity of unknown picorna-like viruses in the sea

Picorna-like viruses are a loosely defined group of positive-sense single-stranded RNA viruses that are major pathogens of animals, plants and insects. They include viruses that are of enormous economic and public-health concern and are responsible for animal diseases (such as poliomyelitis), plant diseases (such as sharka) and insect diseases (such as sacbrood). Viruses from the six divergent families (the Picornaviridae, Caliciviridae, Comoviridae, Sequiviridae, Dicistroviridae and Potyviridae) that comprise the picorna-like virus superfamily have the following features in common: a genome with a protein attached to the 5' end and no overlapping open reading frames, all the RNAs are translated into a polyprotein before processing, and a conserved RNA-dependent RNA polymerase (RdRp) protein. Analyses of RdRp sequences from these viruses produce phylogenies that are congruent with established picorna-like virus family assignments; hence, this gene is an excellent molecular marker for examining the diversity of picorna-like viruses in nature. Here we report, on the basis of analysis of RdRp sequences amplified from marine virus communities, that a diverse array of picorna-like viruses exists in the ocean. All of the sequences amplified were divergent from known picorna-like viruses, and fell within four monophyletic groups that probably belong to at least two new families. Moreover, we show that an isolate belonging to one of these groups is a lytic pathogen of Heterosigma akashiwo, a toxic-bloom-forming alga responsible for severe economic losses to the finfish aquaculture industry, suggesting that picorna-like viruses are important pathogens of marine phytoplankton.