玉米粗缩病及自交系抗病性观察与分析

在玉米粗缩病大发生年，观察品种、自交系及育种材料的发病率表明，品种间抗病性差异显著。对185份自交系抗病鉴定表明不同种质材料的选系抗病性差异悬殊。对6个亲本自交系双列杂交的9个杂交种抗病性分析结果，亲本对后代有一定遗传力，各亲本自交系的一般配合力效应差异显著。     

我国玉米上一个水稻黑条矮缩病毒重排体的ORF序列

由水稻黑条矮缩病毒(Rice black-streaked dwarf virus,RBSDV)引起的粗缩病是我国玉米生产中的一种毁灭性病害.本文报道从山东枣庄玉米上得到的RBSDV分离物SDZZ10所有可读框(ORF)的序列.与全基因组序列已知的2个RBS-DV分离物Hbm和Zjr比较,SDZZ10的大多数ORF与Hbm相应ORF的核苷酸序列一致率更高,其蛋白与Hbm相应蛋白的氨基酸一致率也更高,但SDZZ10的ORF3,ORF4,ORF9-2和ORF10与jr相应ORF的核苷酸一致率更高,P4,P9-1和P9-2与Zjr相应蛋白的氨基酸一致率更高.根据ORF8和ORF10构建的系统进化树中,SDZZ10分别属于不同的组,说明SDZZ10是一个自然发生的重排体.     

In vitro but not in planta encapsidation of Rice gall dwarf virus core particles by the outer capsid P8 protein of Rice dwarf virus expressed in transgenic rice plants

Transencapsidation of the Rice gall dwarf virus (RGDV) inner core by the Rice dwarf virus (RDV) outer capsid P8 protein was examined in vitro and in planta. When RGDV core particles were incubated with an extract from RDV P8-transgenic rice leaf tissue, RDV P8 encapsidated the RGDV core particles to form double-shelled virus-like particles in vitro. In contrast, when RDV P8-transgenic rice plants were inoculated with RGDV, progeny RGDV particles contained RGDV P8 but RDV P8 was not detectable in the virions. No significant differences were found in acquisition by the vector insects and subsequent transmission rates between RGDV infecting nontransgenic rice plants and those infecting RDV P8-transgenic rice plants. These results indicate that mechanisms of and/or requirements for interactions between P8 and the inner core particles of phytoreoviruses differ between in vitro and in planta.     

Southern bean Mosaic Virus the Causal Agent of a New Disease of Phaseolus vulgaris beans in Spain

Southern bean mosaic virus (SBMV) has been identified as the cause of a new disease in greenhouse-cultivated common bean (Phaseolus vulgaris), in the south-east of Spain. The identification was based on host range comparisons, morphological and serological characteristics of the virus, the size of its dsRNA species and the nucleotide sequence of an 810-bp fragment from ORF2. The virus could be clearly discriminated from the related sobemovirus Southern cowpea mosaic virus. This is the first report of SBMV in Spain.     

Sequence comparison and transmission of <Emphasis Type="Italic">Blackcurrant reversion virus</Emphasis> isolates in black,red and white currants with black currant reversion disease and full blossom disease symptoms

We collected samples from black, red and white currants showing symptoms of blackcurrant reversion disease (BRD) and full blossom disease (FBD), cultivated in the Czech Republic. Blackcurrant reversion virus (BRV) was detected in all symptomatic plants. After amplification, a substantial part of the 3′ non-translated region (3′-NTR) of RNA2 of 15 new isolates of BRV was sequenced and compared with sequences available in the literature and GenBank. We did not find significant sequence diversity among isolates associated with either FBD or BRD. BRV was graft-transmitted from FBD infected red currant to black currant where symptoms of BRD were observed. Further sequence analysis of BRV isolates resulted in a phylogenetic tree with four branches, each consisting of six to nine isolates. No correlation with geographic origin was visible on the tree as isolates from various countries occurred in all four branches. We also found no correlation between the host and the topology of the tree: most of black currant isolates occurred in branches 3 and 4, but also occurred in branches 1 and 2. Only one white currant and one red currant isolate occurred in branches 3 and 4, respectively. The sequence identity of the Czech isolates in this region ranged from 91.9 to 99.8%. The 17 plant species growing within and in the close vicinity of the BRD-infested plantation were tested negative for BRV by RT-PCR as natural hosts of BRV. BRV was successfully transmitted by mechanical inoculation from black currant to Nicotiana occidentalis and N. tabacum cv. Xanthi, the latter being a new host for BRV. The infection was confirmed by PCR and sequencing.     

水稻苗期感染SRBSDV后赤霉素相关基因表达量及赤霉素含量的变化

为明确水稻在苗期被南方水稻黑条矮缩病毒(Southern rice black-streaked dwarf virus,SRBSDV)浸染后植株体内赤霉素合成相关基因表达量和赤霉素含量的变化情况,利用q RT-PCR技术检测水稻在3叶期感染SRBSDV后的5个时期Os01g0883800、Os03g0856700、Os07g0169700三个赤霉素的生物合成基因表达量;采用高效液相色谱法检测GH998和Y11植株感染SRBSDV后的赤霉素含量;观察GH998病株施用外源赤霉素后病症的缓解效果。结果表明,感染SRBSDV后在GH998叶片中,以在第0天为对照组,Os01g0883800和Os07g0169700相对表达量最大分别下调25.6倍和21.1倍,Os03g0856700在第3天相对表达量下调20.5倍,在第6天上调2.3倍;在茎中,Os01g0883800、Os07g0169700、Os03g0856700的相对表达量在第3天分别下调8.5倍、6.4倍和1.4倍。在Y11叶片中Os01g0883800、Os03g0856700和Os07g0169700相对表达量最大下调分别为6.6倍,42.7倍和16.9倍;在茎中,Os01g0883800、Os07g0169700相对表达量最大下调分别为5.3倍和10.5倍;Os03g0856700在第3天时表达量上调1.5倍,在第12天下调2.8倍。GH998感染SRBSDV后植株体内赤霉素含量显著降低;施用外源赤霉素能缓解SRBSDV部分病症,表现为株高、剑叶长、剑叶宽和根长等均增加。     

Control of Stagonospora nodorum and Septoria tritici in Wheat by Pre-treatment with Drechslera teres, a Non-host Pathogen

A field study is described which explored the possibility of controlling Stagonospora nodorum and Septoria tritici on wheat using a barley pathogen, Drechslera teres. Pre-treatment of wheat cv. Hussar flag leaves with D. teres resulted in a significant reduction in disease caused by S. nodorum and S. tritici, resulting in a significant increase in grain yield. When cv. Brigadier leaves were treated with D. teres prior to inoculation with S. nodorum there was an initial increase in disease expression whilst D. teres had no effect on symptoms produced by S. tritici on cv. Brigadier. There was significantly less disease on leaves of cvs. Hussar and Brigadier pre-treated with D. teres prior to inoculation with an equal mixture of S. nodorum and S. tritici compared to plants pre-treated with water. It is concluded that D. teres and other non-host pathogens show potential as biological control agents for S. nodorum and S. tritici.     

Relationships between Weather Variables, Airborne Spore Concentrations and Severity of Leaf Blight of Garlic Caused by Stemphylium vesicarium in Spain

Ascospores and conidia released into the air were recorded around plots on which garlic debris infected by Stemphylium vesicarium were fixed onto the soil surface. Symptoms in garlic trap plots located in the vicinity of infected debris, started in March and developed during April–May to reach disease incidence close to 100%, final disease severity values being lower in 1993 and 1995 than in 1994 and 1996. Whereas daily concentrations of ascospores were rather erratic, with 30% of captures between 0 and 6 h, conidia showed a daily periodicity with highest concentrations between 12 and 18 h, with a pronounced peak between 14 and 16 h, and lowest values at night. Ascospore release occurred mainly in February and March. It coincided with rainfall periods, 14 h with vapour pressure deficit 5 mb and solar radiation <145 W m^–2 on the current day of the capture. In contrast, greatest captures of conidia started in late April and were prevalent in May, and were associated with rainfall in days previous to the capture in which rather high temperature occurred and solar radiation was 109–345 W m^–2. Among the weather variables considered, rainfall appeared directly related to the aerial concentration of ascospores and conidia. The role of relative humidity seemed essential when rainfall did not occur. There was a relationship between conidia concentration in the air and number of hours with temperature in the range 12–21 °C. Ascospore production was not essential for infections to take place, since primary infection from conidia may occur and disease can develop from them readily.     

Molecular characterization of A2 and D strains of Soybean mosaic virus, which caused a recent virus outbreak in soybean cultivar Sachiyutaka in Chugoku and Shikoku regions of Japan

Coat protein sequences of two isolates in strain A₂ and five isolates in strain D of Soybean mosaic virus (SMV), which caused a recent mosaic outbreak in soybeans (cv. Sachiyutaka) in Chugoku and Shikoku in Japan, were compared to published data on 15 other Asian-origin isolates. Sequence comparison and cluster analysis showed that SMV isolates of strain A₂ from these districts were closely related, as were those of strain D, but strains A₂ and D were not. Thus, the two strains may have different origins and be carried through seed transmission.     

基于mtCOI基因序列的我国云南省和缅甸、柬埔寨草地贪夜蛾种群遗传多样性分析

为制定有效的草地贪夜蛾防控措施,分别自缅甸、柬埔寨和我国云南省采集4、2和8个种群共542个草地贪夜蛾样品,基于mtCOI基因序列分析这14个种群的遗传多样性指数、遗传分化系数及基因流。结果表明,缅甸草地贪夜蛾种群的单倍型多样性指数和平均核苷酸差异数分别介于0.273～0.396和4.643～6.727之间,高于我国云南省的草地贪夜蛾种群,分别介于0.047～0.214和0.791～3.636之间;除ZT种群、LS种群和TO种群外,其它11个种群的Fu’s F均为显著正值,表明缅甸、柬埔寨和我国云南省的草地贪夜蛾种群未经历种群扩张事件;在14个种群中,LS种群与其它种群分化较明显,TK种群、MY种群、CP种群、MS种群和KY种群有效迁入个数和有效迁出个数之和较高,分别为699.41、682.50、855.76、684.56和701.31,推测这5个种群在草地贪夜蛾基因交流中起着类似"中转站"的作用。     

Luteoforol,a flavan 4-ol,is induced in pome fruits by prohexadione-calciumand shows phytoalexin-like properties against <Emphasis Type="Italic">Erwinia amylovora</Emphasis>and other plant pathogens

Treatments with prohexadione-calcium led to lowered incidence of fire blight, scab and other diseases in pome fruit trees and other crop plants. In addition to acting as a growth regulator, prohexadione-calcium interferes with flavonoid metabolism and induces the accumulation of the 3-deoxycatechin luteoliflavan in shoots of pome fruit trees. Luteoliflavan does not possess any remarkable antimicrobial activity. Therefore luteoforol, its unstable and highly reactive precursor, has been tested in vitro for its bactericidal and fungicidal activities. Luteoforol was found to be highly active against different strains of Erwinia amylovora, the causal agent of fire blight, and all other bacterial and fungal organisms tested. Phytotoxic effects were also observed in pear plantlets. The results obtained indicate that prohexadione-calcium induces luteoforol as an active principle with non-specific biocidal properties. It is proposed that luteoforol is released upon pathogen attack from its cellular compartment and inhibits further disease development by destroying pathogen cells as well as by inducing a hypersensitive-like reaction in the host plant tissue. This mechanism would be closely analogous to the one known for structurally related phytoalexins in sorghum.     

The Occurrence of dsRNA Species in Apparently Healthy and Virus-infected Ribes Cultivars, and Evidence That One Such Species Originates from a Member of the Virus Family Totiviridae

Analysis was made of dsRNA in 37 cultivars and species of Ribes, that were healthy, naturally affected with the virus-like diseases, blackcurrant yellows, blackcurrant infectious variegation, gooseberry veinbanding or blackcurrant reversion, or graft-inoculated with scions from such diseased plants. Various dsRNA species, differing in size (from ca. 2 to 11kbp), number and staining intensity in gels, were detected in some or all assays of all plants, including those held as virus-tested stock. In different plant tissues from individual plants, the dsRNA species were usually similar in size and number but, in some sources, the dsRNA profile from flowers and/or bark differed greatly from the profiles of dsRNA obtained from leaves. No dsRNA species were associated consistently with any of these diseases. A 499kbp cDNA probe was obtained that in Northern blot analysis was specific to a ca. 5kbp dsRNA species present in the blackcurrant cv. Baldwin. It also detected a similarly sized dsRNA species in plants of many other blackcurrant cultivars, but it did not react with a similarly sized dsRNA species in redcurrant and gooseberry tissues. The 156 amino acid sequence encoded by the cDNA was very similar to sequences in the RNA-directed RNA polymerases of virus species in the family Totiviridae, especially Saccharomyces cerevisiae viruses L-1 and L-A. The significance of these findings and the possible origin of these dsRNA species are discussed.     

甘肃省甘谷县小麦条锈菌群体遗传结构分析

为明确我国小麦条锈菌Puccinia striiformis f. sp. tritici主要越夏地区的群体遗传结构及演变情况,利用SSR荧光检测技术,对甘肃省甘谷县2013—2015年期间连续5个小麦生长季采集的141株小麦条锈菌单孢系基因组DNA进行分子标记分析,对小麦条锈菌季节亚群的遗传多样性进行分析。结果表明,甘谷地区小麦条锈菌的遗传多样性丰富,有效等位基因数为1.71,Shannon信息指数为0.66,2014年秋季(2014A)亚群体的基因型多样性低于其余亚群体。分子变异方差分析结果显示,小麦条锈菌季节亚群体间变异仅占21%,变异主要出现在亚群体内部,表明甘谷地区各季节亚群体间遗传分化水平差异较小,小麦条锈菌群体在一个小范围内基本能维持稳定状态。主坐标分析(PCoA)、遗传分化、基因流以及共享基因型分析均表明2014年秋季(2014A)亚群体的遗传结构与相邻季节亚群体存在一定差异,表明越夏过程对甘谷地区个别年份小麦条锈菌群体周年稳定性造成较大的影响,越冬过程对小麦条锈菌群体的影响相对较小,春季受外来菌源干扰的可能性较低。     

Induction of peroxidase, scopoletin, phenolic compounds and resistance in Hevea brasiliensis by elicitin and a novel protein elicitor purified from Phytophthora palmivora

Elicitin and a new protein 75 kDa elicitor were purified from the culture filtrate of Phytophthora palmivora, a pathogen of Hevea brasiliensis (rubber plant). Elicitin was obtained by using a one step of DEAE cellulose chromatography and the new elicitor was obtained by two steps of chromatography: a DEAE cellulose column followed by a hydrophobic column. Both elicitors were stable to heat and a wide range of pH values, but were sensitive to ProteaseK. Both elicitors induced scopoletin, peroxidase isozymes (with substrate o-dianisidine and scopoletin) and total phenolic compounds in cell suspension of H. brasiliensis with similar kinetics. In addition, both elicitors induced peroxidase enzyme (o-dianisidine), total phenolic compounds and enhanced local resistance against P. palmivora on young rubber tree seedlings. However, the increase of peroxidase enzyme and total phenolic compounds in rubber tree seedlings was different from those in cell suspension. Furthermore, during the expression of local resistance the zoospore of P. palmivora induced the peroxidase enzyme (o-dianisidine) more rapidly and with higher level than the control plants. H. brasiliensis is more responsive to the new elicitor than elicitin in triggering defense responses. That is the new elicitor was active at a concentration lower than those required for elicitin, about a 30-fold decrease for activation defense responses in cell suspension. For induction of peroxidase enzyme (o-dianisidine), phenolic compounds and local resistance of rubber plants against P. palmivora, the 75 kDa protein was active at about a 2-fold lower concentration when compared to elicitin.     

Disease levels in winter wheat,rye and triticale grown on soil artificially inoculated withCephalosporium gramineum

Field experiments with winter cereals grown on soil inoculated withC. gramineum showed that wheat and rye cultivars possess some resistance to the pathogen, while the triticale cultivars were the most susceptible. Higher tolerance of the tested wheat cultivars was connected mainly with slow development of disease symptoms; rye cultivars had, on average, lower percentages of plants infected byC. gramineum. The greatest variation in susceptibility toC. gramineum occurred among the selected cultivars of triticale.     

Erwinia amylovora hrpN mutants,blocked in harpin synthesis,express a reduced virulence on host plants and elicit variable hypersensitive reactions on tobacco

Erwinia amylovora is the bacterium responsible for fire blight, a necrotic disease affecting many rosaceous plants and especially pear tree and apple tree. A protein named harpin, secreted through the Hrp secretion pathway and able to elicit an hypersensitive reaction (HR) on tobacco has recently been isolated. Mutants inhrpN, the gene encoding harpin were described as non pathogenic on immature pear fruit and unable to elicit an HR on tobacco [Weiet al., 1992; Wei and Beer, 1993]. In this paper, the phenotype on plant ofhrpN mutants was carefully determined.hrpN mutants expressed a weak but significant virulence on host plants. Furthermore, when infiltrated into tobacco leaf mesophyll, thehrpN mutants elicited varied responses that fluctuated from null reaction to full necrosis of the infiltrated area. These results show that harpin is not absolutely required neither for pathogenicity on host plant nor for elicitation of an hypersensitive reaction on tobacco. Furthermore, in all the tests performed, mutant blocked in harpin secretion remained non pathogenic and unable to elicit an HR on tobacco. This suggests that factor(s), different from harpin, involved both in pathogenicity and HR eliciting ability is (are) secreted through the Hrp secretion pathway.Abbreviations HR hypersensitive reaction - NSI necrosis severity index - CFU colonie forming units     

Production of phytotoxic metabolites by five species of Botryosphaeriaceae causing decline on grapevines, with special interest in the species Neofusicoccum luteum and N. parvum

In recent years an increasing number of species of Botryosphaeriaceae have been associated with grapevine decline worldwide. Five species isolated from declining grapevines in Spain (Botryosphaeria dothidea, Diplodia seriata, Dothiorella viticola, Neofusicoccum luteum and N. parvum) were checked for toxin production in liquid cultures. Cultural conditions for all fungi were adjusted to obtain optimal production of phytotoxic culture filtrates, by growing the fungi in steady liquid cultures of Czapek–Dox broth for different time intervals. Phytotoxicity of D. seriata and N. parvum reached a maximum after 14 days while the remaining species showed the highest phytotoxicity levels after 21 days in culture. All fungi produced hydrophilic high-molecular weight compounds with phytotoxic properties. In addition, N. luteum and N. parvum produced lipophilic low-molecular weight phytotoxins, not detected consistently among the remaining species. This led to a more exhaustive study on the phytotoxicity of N. luteum and N. parvum. Culture filtrates and corresponding extracts of both species were consistently highly phytotoxic in different assays. The gas-chromatography analysis of the acetylated O-methyl glycosides of the phytotoxic exopolysaccharides produced by N. parvum showed these substances to be composed mainly of glucose, mannose and galactose. Results suggest that phytotoxic metabolites could be involved in the virulence of both species in planta.     

Lonicera latent virus,a new carlavirus serologically related to poplar mosaic virus: some properties and inactivation in vivo by heat treatment

A virus with elongate particles (656 nm) was isolated from severalLonicera species. This virus, apparently belonging to the carlavirus group, is serologically distantly related to shallot latent virus and closely related to poplar mosaic virus. The inability to infect poplar and two other hosts of poplar mosaic virus characterizes the virus fromLonicera as a new virus which was namedLonicera latent virus.The virus was easily sap-transmissible but was not transmitted byMyzus persicae.Dilution end-point was about 10^–3, thermal inactivation between 65°C and 80°C and ageing in vitro 1–6 days.Heat treatment, combined with tip-rooting appeared to be a good method to eliminate the virus from severalLonicera species and cultivars.Samenvatting In verschillende soorten en cultivars van het geslachtLonicera (kamperfoelie) blijkt een virus voor te komen dat gemakkelijk door sapinoculatie kan worden overgebracht op kruidachtige planten.Een tegen gezuiverd virus bereid antiserum had een titer van ca. 4096. Er kon mee worden aangetoond dat het virus van kamperfoelie serologisch nauw verwant is met populieremozaïekvirus (Tabel 1). Het virus van kamperfoelie is echter niet in staat om populier,Phaseolus vulgaris Bataaf enVigna sinensis te infecteren en wordt mede daarom als een afzonderlijk virus beschouwd. Het wordt aangeduid als latent kamperfoelievirus (Lonicera latent virus) en behoort evenals populieremozaïekvirus tot de carlavirusgroep (aardappelvirus-S-groep).Het virus blijkt vrij gemakkelijk te kunnen worden geëlimineerd door besmette kamperfoelieplanten gedurende ongeveer zes weken een warmtebehandeling (37°C) te geven en daarna de uiterste toppen (1 cm) te stekken. Van verschillende cultivars werd op deze wijze virusvrij uitgangsmateriaal verkregen.