Relating plant and pathogen development to optimise fungicide control of phoma stem canker (<Emphasis Type="Italic">Leptosphaeria maculans</Emphasis>) on winter oilseed rape (<Emphasis Type="Italic">Brassica</Emphasis><Emphasis Type="Italic">napus</Emphasis>)

In winter oilseed rape experiments at Rothamsted in 2000/01 to 2002/03 growing seasons, the severity of phoma stem canker epidemics in summer depended on the timing of phoma leaf spot epidemics in the previous autumn, and hence on the timing of Leptosphaeria maculans ascospore release. The first major release of L. maculans ascospores was earlier in 2000 (26 September) and 2001 (18 September) than in 2002 (21 October). Consequently, the autumn phoma leaf spot epidemic was also earlier in 2000 and 2001 than in 2002. The resulting stem canker epidemics were severe by harvest (July) in 2001 and 2002 but not in 2003. No correlation was found between the severity or duration of phoma leaf spotting (lesion days or lesion °C-days) and the subsequent severity of phoma stem canker epidemics. Rates of leaf production and loss were similar in the three growing seasons. Out of ca. 25 leaves produced on plants during each season, leaf numbers 10–14 generally remained on plants for the longest. Treatment with flusilazole + carbendazim in autumn decreased the severity of phoma leaf spotting for several weeks after treatment, decreased the severity of stem canker the following summer and increased yield significantly in 2001 and 2002 but not in 2003. The most effective timings for flusilazole + carbendazim application were when leaves 7–11 were present on most plants and at least 10% of plants were affected by phoma leaf spot. Two half-dose applications of fungicide reduced phoma stem canker and increased yield more than a single full dose application when phoma leaf spot epidemics were early (<800 °C-days after sowing).     

Introductions of non-native plant pathogens into Great Britain, 1970–2004

An analysis of records of plant pathogens first identified in Great Britain from 1970 to 2004 (inclusive) was undertaken to determine the numbers of new species that have become established over time. Results show that the numbers of newly recorded pathogens have not varied significantly. Of the 234 pathogens recorded for the first time between 1970 and 2004, 157 were fungi, 27 were oomycetes, 26 were viruses, 23 were bacteria, and one was a phytoplasma. Approximately 53% of pathogens were found on ornamental crops, 16% on horticultural crops, 15% on wild native species, 12% on agricultural crops, 2% on pasture plants and 2% on exotic forestry tree species. Where the origin of introductions was known or strongly suspected, 47% came from the Netherlands. About 38% of newly recorded pathogens with information on the location of first record were discovered in the South East region of England. Plant Pathologists regarded 19% of all new pathogens as important because of actual or potential economic/environmental losses. The results indicate that the numbers of new or important pathogens establishing in recent years are not increasing and that most new findings are associated with ornamental plants.     

中华真地鳖抗菌物质的抑菌活性测定

以研磨法从中华真地鳖五龄若虫体内提取得到抗菌物质,分别采用比浊法和菌碟法测定了其对多种细菌和植物病原真菌的抑菌活性。结果表明,该抗菌物质对大肠杆菌、金黄色葡萄球菌、白菜软腐菌和枯草芽孢杆菌等4种细菌生长均有一定的抑制作用,对数期延迟1~4h,菌的浓度、繁殖速度减缓。对7种植物病原真菌的抑菌试验表明,该抗菌物质对玉米茎基腐病菌、小麦根腐病菌、棉花枯萎病菌抑制效果较好,抑制率分别为50.0%、49.2%、45.2%;而对白菜黑斑病菌和玉米大斑病菌活性较差,抑制率仅为28.3%和24.5%。     

栽培防病措施对防治小麦白粉病的重要作用

为了解栽培措施对防治小麦白粉病的作用,通过不同栽培措施对病情产生不同影响的大量田间调查,明确了小麦早播、密播,过量水、肥条件下的旺苗和种植高度感病品种,都会加重小麦秋苗带菌量。短期播种、合理密植、视墒灌水、配方施肥、培育小麦壮苗及避免种植高感品种等均能减轻小麦秋苗带菌量。小麦秋苗带菌量大,则翌春病菌越冬菌源量也大。种植高感品种在田间有发病中心的作用。应把栽培防病措施规范化、科学化、制度化,以充分发     

Production and characterisation of monoclonal antibodies to cell wall components of the flax rust fungus

Monoclonal antibodies have been raised against an haustorium-enriched sample prepared from flax leaves infected with the biotrophic flax rust pathogen Melampsora lini. The monoclonal antibodies were produced following conventional and co-immunisation procedures and the range of antibody specificities was compared. The preparation used as immunogen for the conventional protocol was a crude isolate of haustoria consisting of approx. 65% fungal haustoria, the other components being mainly mesophyll cells or cell wall and chloroplast fragments. Following hybridoma production, 40% of positive cell lines produced antibodies that reacted with haustoria and other fungal cells, but 60% bound to plant cells in the infected leaves. For the co-immunisation protocol, the preparation used for immunisation consisted of the crude isolate of haustoria mixed with serum raised against an haustorium-depleted leaf homogenate. In two fusions, 92-94% of the antibodies reacted with fungal cells, including 3 cell lines that localised specifically to the cell wall of haustoria. Only 6-8% of the antibodies produced via co-immunisation reacted with plant cells. The antigens targeted by the three haustorium-specific monoclonal antibodies are incorporated into the wall at early stages of haustorium development, remain in the wall throughout haustorium maturation, and are present in both compatible and incompatible interactions. The epitopes recognised by the monoclonal antibodies are oligosaccharide in nature and the antigens are highly resistant to extraction from the wall. These results highlight the value of the co-immunisation protocol for the production of monoclonal antibodies to specific components in an impure preparation and provide direct evidence for molecular differentiation within the wall of the haustorium of M. lini.     

桉树焦枯病病原菌特性的观察

对桉树焦枯病病原菌３种典型的５隔膜、３隔膜和１隔膜分生孢子进行了研究。５隔膜病原菌致病力最强，３隔膜次之，１隔膜较弱。匀菌剂菌毒清对３种病原菌有明显的抑制作用。     

Predicting the spread of postharvest disease in stored fruit,with application to apples

Postharvest diseases can cause considerable damage to harvested fruit in controlled atmosphere storage. Since there is a large cost associated with opening the storage rooms, regular assessment of damage levels is not feasible, and many experts agree on the need for a reliable predictive model. Presented here is a simulation model that predicts the overall incidence of disease in a bin of stored fruit as a function of initial infection levels and the fruit's susceptibility to fungal attack. Uninfected fruit tissue, infected fruit tissue, and fungal growth are modelled by a system of three ordinary differential equations. Simulations of the growth and spread of the pathogen in storage were conducted, with disease incidence measured monthly. The model provides insight into the dynamics of postharvest fungal disease, and forms the basis of a predictive model that could be used by packinghouses to determine how long a given crop of fruit can be stored before the infection risk rises above a predetermined tolerable level.     

Development of an international standard set of barley differential genotypes for Pyrenophora teres f. teres

International comparison of virulence profiles of Pyrenophora teres f . teres (Ptt), the cause of barley net blotch, is seriously restricted by inconsistencies in differential testers used among researchers. This paper reports an attempt to develop an appropriate set of differentials to standardize characterization of Ptt populations globally. Fourteen barley genotypes (Canadian Lake Shore (CLS), Harbin, c-8755, c-20019, Manchurian, Tifang, CI 9825, CI 5791, CI 9819, Beecher, CI 9214, Skiff, Prior and Corvette) were selected from among genotypes previously used as Ptt differentials. Three cultivars (Pirkka, Haruna Nijo and Harrington) were included to identify a universally susceptible control. Genotypes were inoculated with approximately 1000 Ptt isolates from Russia, Europe, Australia and Canada. The mean reaction frequency of genotypes ranged from highly resistant (CI 9819, CI 5791, c-8755 and CI 9825) to highly susceptible (Harrington, Haruna Nijo and Pirkka). The best differential abilities were demonstrated by Harbin, CLS, c-20019, Manchurian and Prior. Application of cluster analyses identified genotypes with similar reaction patterns, which supported a reduction of genotypes in the set. When combined with an algorithm comparing the ability of individual genotypes to discriminate among Ptt isolates, a further reduction of genotypes was justified. A new, concise set of barley genotypes for differentiating virulences in Ptt was formulated. It is proposed that these genotypes be adopted as the standard, international differential set to characterize and identify the virulence properties of Ptt populations across environments. The new Ptt differential set consists of the genotypes c-8755, c-20019, CI 5791, CI 9825, CLS, Harbin, Prior, Skiff and Harrington.     

Evaluation of Dutch elm disease susceptibility and pathogenicity of Ophiostoma ulmi using micropropagated elm shoots

Elm (Ulmus sp.) shoots from in vitro micropropagated plants were tested with Ophiostoma ulmi culture filtrates, at different dilutions to determine the susceptibility of different host clones to Dutch elm disease (DED). ‘Commelin’, a susceptible Dutch hybrid, showed a high wilting index but that of American elm was higher. Although U. pumila × japonica (Sapporo gold 2) was the most tolerant to spore inoculation, its wilting index was as high as that of ‘Commelin’. The absorption capacity and wilting index of the elm shoots showed consistent correlation to isolate effectiveness (as determined by inoculation experiments), to production of toxin (cerato-ulmin) and to filtrate dilution. This method could be used to assess the effectiveness of the different O. ulmi isolates and for the detection of elm genotypes that are highly susceptible to Dutch elm disease.     

我国杨树与溃疡病菌互作的病理学研究

杨树溃疡病是我国杨树人工林重大的生物灾害，危害越来越严重，本文从植物组织病理学、生理病理学和病理化学的角度深入系统地总结和评述了我国在杨树与溃疡病菌互作研究中所取得的进展和存在的问题，最后就该病害的未来的研究方向和研究内容作了展望。