啤酒花潜隐类病毒研究进展

啤酒花潜隐类病毒在啤酒花上的感染较普遍,且一般不产生明显症状,给生产带来一定损失。对于该类病毒病害,较为可行的控制措施是实行检疫控制其扩展和培育与栽培无类病毒苗。较为系统地综述了国内外啤酒花潜隐类病毒的分布与危害、生物学特性、基因组结构与序列分析、检测方法及防治与控制等方面的研究进展。     

Effect of soil inoculum level and environmental factors on potato powdery scab caused by Spongospora subterranea

The effects of soil inoculum level and three environmental factors (soil type, soil moisture regime and temperature) on the incidence and severity of powdery scab caused by Spongospora subterranea were investigated in potato plants grown under controlled environmental conditions. Symptoms of powdery scab on tubers were assessed visually, after which DNA was extracted from tuber peelings and quantified in a real-time polymerase chain reaction assay using primers and a TaqMan® probe specific to S. subterranea to establish tuber infection levels. Soil inoculum concentration of S. subterranea did not significantly affect the incidence and severity of either tuber infection or powdery scab symptoms at maturity. No significant differences in disease incidence and severity were found between sandy, loamy and clay soils, although the two lighter soils yielded more powdery scab than clay soil. Constant dampness of the soil resulted in significantly more disease than a fluctuating moisture regime. Infection and disease levels were high at all three temperatures tested (9, 12 and 17°C), but symptoms were most severe at 12°C. The percentage of plants with infected tubers did not increase after tuber initiation, although the amount of S. subterranea DNA detected in tubers and the severity of powdery scab symptoms increased in mature plants. Latent tuber infections were found to be common, especially under conditions suboptimal for disease development. This new information may be important for the prevention of powdery scab in potato-growing areas around the world.     

Hippeastrum mosaic virus and another filamentous virus in Eucharis grandiflora

Two viruses were found in mosaic-diseased plants ofEucharis grandiflora in a glasshouse of the laboratory. One virus with a normal particle length of 733 nm caused local lesions onHyoscyamus niger and mosaic symptoms in leaves of healthy-lookingEucharis andHippeastrum plants. On the basis of its host range, physical properties and serology it was identified asHippeastrum mosaic virus, a member of the potyvirus group. This was confirmed by the presence of spherical nuclear inclusions and pinwheels in different tissues of diseasedEucharis plants. The second virus with a normal particle length of 598 nm was present in both healthy-looking and mosaic-diseasedEucharis plants, and it inconsistently induced local lesions onGomphrena globosa. According to its morphology and its reaction onGomphrena, it might be identical or related toHippeastrum latent virus. Crystal-like inclusions were observed in the cytoplasm of cells of both healthy-looking and mosaic-showingEucharis leaves. As no virus-free seedlings ofEucharis were available, the virus nature of these inclusions could not be established.     

Potato latent virus: a proposed new species in the genus Carlavirus

A previously undescribed carlavirus, potato latent virus (PotLV), was found infecting the potato cultivar Red La Soda imported from the USA. The particles were filamentous and slightly curved, with modal lengths of 530 and 670 nm. The 11 kDa protein encoded downstream from the coat protein contained a 'zinc-finger' motif characteristic of carlaviruses, and RT–PCR using a carlavirus-specific primer gave a PCR product of 857 bp. Antibodies produced to PotLV did not detect other carlaviruses when used in ELISA and the coat-protein nucleic acid sequence of PotLV showed < 67% similarity with the other carlaviruses tested. The closest similarity was with the Andean strain of potato virus S. Unusually for a carlavirus, PotLV systemically infected Nicotiana bigelovii , N. glutinosa , N. rustica , N. tabacum and Physalis floridana .     

A review of the known unknowns in the early stages of septoria tritici blotch disease of wheat

Septoria tritici blotch (STB) disease of wheat is caused by the fungal pathogen Zymoseptoria tritici. It is the most important foliar disease of wheat in western Europe and affects wheat cultivation worldwide. The combination of intensive fungicide usage, a polycyclic asexual life cycle and an active sexual cycle has led to the emergence of fungal strains resistant/tolerant to all the major classes of fungicides used in its control. The hallmark of this disease is a long, symptomless latent phase that precedes the onset of visible symptoms. Understanding the processes that occur during the symptomless phase of infection is paramount in developing alternative strategies for disease control; however, large gaps in our knowledge of the disease remain. The known unknowns of the latent stage of infection can be summarized in three questions. Does the fungus initiate or manipulate host defences to trigger programmed cell death in order to facilitate nutrient acquisition or is the host acting exclusively? Does the fungus feed during both the latent phase and the necrotrophic phase like a true hemibiotroph? Does the long latent phase serve a beneficial function for the fungus or is it simply an artefact of evolution? This review aims to distil observations made during studies that have directly or indirectly contributed to answering these questions and points towards their most likely answers.     

甘草挥发性成分的气相色谱-质谱联用分析

[目的]对甘草挥发性成分进行研究。[方法]用水蒸气蒸馏法提取甘草中的挥发油,用气相色谱-质谱联用仪检测、直观推导式演进特征投影（HELP）解析所得的GC-MS数据。[结果]分离出39个峰,鉴定出31种成分,并测定了各组分的相对含量,其中含量最高的是二十酸（32．02％）。[结论]通过对甘草挥发油成分的研究,为甘草资源的进一步开发利用提供了试验依据,     

A comparative assessment of potential components of partial disease resistance to <Emphasis Type="Italic">Fusarium</Emphasis> head blight using a detached leaf assay of wheat,barley and oats

The relative resistance of 15 winter barley, three winter wheat and three winter oat cultivars on the UK recommended list 2003 and two spring wheat cultivars on the Irish 2003 recommended list were evaluated using Microdochium nivale in detached leaf assays to further understand components of partial disease resistance (PDR) and Fusarium head blight (FHB) resistance across cereal species. Barley cultivars showed incubation periods comparable to, and latent periods longer than the most FHB resistant Irish and UK wheat cultivars evaluated. In addition, lesions on barley differed from those on wheat as they were not visibly chlorotic when placed over a light box until sporulation occurred, in contrast to wheat cultivars where chlorosis of the infected area occurred when lesions first developed. The pattern of delayed chlorosis of the infected leaf tissue and longer latent periods indicate that resistances are expressed in barley after the incubation period is observed, and that these temporarily arrest the development of mycelium and sporulation. Incubation periods were longer for oats compared to barley or wheat cultivars. However, oat cultivars differed from both wheat and barley in that mycelial growth was observed before obvious tissue damage was detected under macroscopic examination, indicating tolerance of infection rather than inhibition of pathogen development, and morphology of sporodochia differed, appearing less well developed and being much less abundant. Longer latent periods have previously been related to greater FHB resistance in wheat. The present results suggest the longer latent periods of barley and oat cultivars, than wheat, are likely to play a role in overall FHB resistance if under the same genetic control as PDR components expressed in the head. However the limited range of incubation and latent periods observed within barley and oat cultivars evaluated was in contrast with wheat where incubation and latent periods were shorter and more variable among genotypes. The significance of the various combinations of PDR components detected in the detached leaf assay as components of FHB resistance in each crop requires further investigation, particularly with regard to the apparent tolerance of infection in oats and necrosis in barley, after the incubation period is observed, associated with retardation of mycelial growth and sporulation.     

Internal colonization pathways of potato plants by Erwinia carotovora ssp. atroseptica

Transmission of pectinolytic Erwinia species from infected mother tubers to daughter tubers has been studied mainly through detection tests, carried out at harvest, on limited samples of tubers produced by plants grown from artificially inoculated mother tubers. However, detection has not been performed on samples collected at different stages of crop development, in order to follow the contamination progress in different organs through the plants to the progeny tubers. In this study the bacterial contamination of progeny tubers was investigated by detecting Erwinia carotovora ssp. atroseptica in different symptomless plant organs (stolons, stems, progeny tubers) and in the parts with or without symptoms of diseased stems, collected at various stages of crop development. Infection levels in below- and above-ground organs of plants of two cultivars differing in their resistance to Erwinia, infected by either vacuum infiltration or sand wounding, were monitored throughout the growing season and at harvest using DAS-ELISA and PCR. Detection tests showed that healthy organs from symptomless plants were less frequently contaminated than symptomless organs from diseased plants, and that stolons were precociously and more frequently contaminated than stems and daughter tubers, irrespective of the health of the plant. Stem infections were shown to progress latently in the stem, bacteria usually being recovered 10–15 cm past visible lesions. In many cases, typical aerial stem-rot symptoms could be related to this upward movement of bacteria from the infected mother tuber. Daughter tubers without symptoms were shown to be frequently contaminated, usually at heel ends, suggesting internal contamination from mother tuber to progeny.     

猪伪狂犬病病毒潜伏感染检测方法研究进展

猪伪狂犬病是由伪狂犬病病毒引起的 ,是以仔猪的发病死亡和怀孕母猪繁殖障碍为特征的猪病 ,是危害养猪业的重要疫病之一。该病在世界上分布广泛 ,并有不断蔓延扩大的趋势。任何年龄的猪在耐过伪狂犬病病毒急性感染后均能形成潜伏感染 ,并可在体内终生潜伏 ,且不表现临床症状 ,在一定条件下 ,潜伏状态的病毒能被激活 ,引起复发性感染并向外散毒。这种伪狂犬病病毒潜伏 -激活循环机制决定了伪狂犬病病毒在猪群中的永远存在。猪一旦感染必须视为伪狂犬病病毒散播的潜在来源。因而对潜伏感染猪的剔除对于根除伪狂犬病病毒感染具有重要意义。国内外对潜伏感染的检测方法主要有鉴别血清学诊断、潜伏病毒的激活与检测、组织块培养技术、核酸探针技术以及PCR技术。本文主要综述了这几种方法的研究情况 ,并比较了其优缺点     

潜热在2013年5月26日青岛地区降水过程中的反馈作用

对2013年5月26—27日的青岛地区降水过程进行了数值模拟试验。结果表明,WRF中尺度模式能够较好地模拟此次暴雨天气,在暴雨过程中,受温带气旋缓慢移动的影响,造成了长时间的降水。其次,高低空急流的作用对暴雨发生发展起着重要作用;去除潜热“干”敏感试验验证了暴雨过程的正反馈作用。