贵州魔芋软腐病菌多基因分子鉴定及其致病力分析

为明确贵州魔芋软腐病菌种类?致病力及分布特点, 采用组织分离法对贵州主要魔芋种植区软腐病样进行病原菌分离, 对icdA, mdh, mtlD, proA, rpoS 等5个管家基因进行了扩增?序列测定, 分别用单基因和多基因联合系统发育树对病菌进行鉴定, 同时采用组织块接种方法测定了不同菌株的致病力?通过组织分离法共分离魔芋软腐病菌株47株; 采用5个管家基因进行分子鉴定, 将病菌分别鉴定为海芋果胶杆菌Pectobacterium aroidearum?胡萝卜果胶杆菌Pectobacterium carotovorum和方中达迪基氏菌Dickeya fangzhongdai 3个种, 其中海芋果胶杆菌P.aroidearum为贵州魔芋软腐病主要致病菌, 占分离菌株的70%, 广泛分布在多个地区; 其次为方中达迪基氏菌D. fangzhongdai, 占分离菌株的28%, 也普遍存在于贵州各魔芋种植区; 胡萝卜果胶杆菌P. carotovorum最少, 占分离菌株的2%?致病力测定结果表明, 菌株间致病力存在一定的差异, 其中海芋果胶杆菌不同菌株之间致病力差异较大, 低?中?高致病力菌株都有, 方中达迪基氏菌差异较小, 仅有中?高致病力菌株?本研究确定了贵州魔芋软腐病菌种类?致病力及在贵州的分布特点, 首次报道了海芋果胶杆菌?方中达迪基氏菌是贵州魔芋软腐病的主要病原菌, 进一步加深了对魔芋软腐病及其发生流行的认识, 为软腐病的科学防控提供了科学依据?     

玉米灰斑病菌致病性分化研究

从我国玉米品种资源中首次成功筛选出9个具有广泛血缘代表性的自交系,即沈137,78599-1,Mo17,478,C8605-2,E28,598,Va35,K12,作为玉米灰斑病菌的生理分化鉴别寄主;8个主栽品种,即沈试29,沈试31,铁单9,掖单13,丹413,丹玉18,沈农87,东单54,作为辅助鉴别寄主,从而确定了玉米灰斑病菌生理分化鉴别寄主体系。采用田间成株期鉴定,高粱粒灌心法进行接种,根据在鉴别寄主上的发病等级,将采自北方玉米主产区的23个玉米灰斑病菌菌株划分成5个致病类型。研究表明,我国玉米灰斑病菌存在一定程度的致病性分化,通过病级评价可将23个玉米灰斑病菌菌株分成5个致病类型,其中致病类型I为强致病类型,致病类型IV为弱致病类型,Ⅱ,Ⅲ2组致病类型介于两者之间,而致病类型V属于不确定类型。研究结果为我国玉米品种抗性鉴定、灰斑病流行监测和品种合理布局提供了理论依据。     

大理州“红阳”猕猴桃真菌性枝干的发生与病原鉴定

以大理州"红阳"猕猴桃枝干为试材,采用田间调查法调查病原菌对其危害状况,对采集的10份病样采用常规组织分离法分离病原,单孢纯化法获得病原菌,采用形态和分子法鉴定病原种类,以期明确大理州"红阳"猕猴桃枝干病害的发生状况及危害病原。结果表明:大理州"红阳"猕猴桃枝干病害发生严重,病株率高达69.6%,5个采样点共分离得到15个菌株,其中以链格孢菌(Alternaria alternata)、厚坦镰刀菌(Fusarium chlamydosporum)、小新壳梭孢菌(Neofusicoccum parvum)和间座壳属中一种(Diaporthe bohemiae)共4类病原菌出现频率最高,是优势种,分离率分别为55.6%、52.4%、49.8%和50.1%。利用柯赫氏法则对分离所得的所有菌株进行致病性测定,证实了优势菌株对猕猴桃茎杆的致病性,进一步明确了引起大理州猕猴桃茎杆的病原真菌。     

The Ecological Concept of Costs of Induced Systemic Resistance (ISR)

Plant defence is thought to provide benefits for the defended plants. Theoretical concepts must, therefore, explain why there is variation in defensive traits, which naively might be assumed to be present constitutively in fixed high amounts. Explanations are mainly based on the assumption of fitness costs. Investment in defence is thought to reduce the fitness of plants in enemy-free environments. Fitness costs often result from allocation costs, i.e. allocation of limited resources to defence, which then cannot be used for growth or other fitness-relevant processes. This theoretical concept can provide a useful tool for the interpretation of induced plant responses against pathogens, named induced systemic (or systemic acquired) resistance (ISR or SAR). Phenotypic plasticity, leading to induced responses, might have evolved mainly to reduce costs, since investment in defence is restricted to situations actually requiring defence. ISR can incur allocation costs and other, indirect costs, which ultimately may lead to fitness costs. Evolution of any defensive trait depends on both what a plant ideally 'should do and what it actually 'is able to do. Costs of defence constrain its expression. This might have important influences on the evolution of plant defensive traits, as well as on the exploitation of natural defences in agricultural crop protection.     

新疆两种野生葱浸提液对几种植物病原真菌的抑制作用

新疆野生葱属植物资源十分丰富,本文就其中两个具有浓烈辛辣气味的种－长喙葱和滩地韭的组织浸提液对棉花,番茄等主要作物病害病原真菌生长的抑制特性进行了研究。试验结果显示：长喙葱浸提液对镰孢菌,轮枝菌,丝核菌及疫霉菌的生长具有明显抑制效果,其10、20和50倍稀释液对丝核菌12h的抑菌率分别为100％,94％,80％,而其10、20倍稀释液对镰孢菌12h的抑菌率分别为100％、72．2％,滩地韭浸提液能抑制镰孢菌,轮枝菌的生长,但不影响丝核菌的生长,两类浸提液的抑菌效果均受温度影响。并随稀释倍数和作用时间的增加而减弱,长喙葱浸提液在4℃冷藏室内放置10d和在121℃条件下放置30min都会丧失长喙葱浸提液经透析去除小分子化合物,其上清液、沉淀都无抑菌作用,说明抑菌有效成分属小分子化合物。     

Production,survival and evaluation of solid-substrate inocula ofConiothyrium minitans againstSclerotinia sclerotiorum

Coniothyrium minitans grew on all ten solid-substrates (barley, barley-rye-sunflower, bran-vermiculite, bran-sand, maizemed-perlite, millet, oats, peat-bran, rice and wheat) tested, producing high numbers of germinable pycnidiospores (1.9–9.3×10⁸ g^–1 air dry inocula). All solid substrate inocula survived better in the laboratory at 5 and 15 °C than at 30 °C for at least 64 weeks.In pot bioassays carried out in the glasshouse and field, soil incorporations of each inoculum almost completely inhibited carpogenic germination ofS. sclerotiorum. In the field bioassay, no sclerotia were recovered after 38 weeks fromC. minitans-treated pots compared to 56% from control pots. In the glasshouse bioassay, 9–30% of sclerotia were recovered after 20 weeks fromC. minitans-treated pots, but 88–100% of these were infected by the antagonist. The antagonist also spread to infect sclerotia in control pots.In larger scale glasshouse trials, single preplanting soil-incorporations of five inocula (barley-ryesunflower, maizemeal-perlite, peat-bran, rice and wheat) controlled Sclerotinia disease in a sequence of lettuce crops, with only small differences between the types of inocula tested. At harvest,C. minitans reduced sclerotial populations on the soil surface and over 74% of sclerotia recovered fromC. minitans-treated plots were infected by the antagonist.C. minitans survived in soil in all solid-substrate inocula-treated plots for at least 39 weeks at levels of 10⁴–10⁵ colony forming units cm^–3 soil and spread to infect over 36% of sclerotia recovered from control plots.     

Prevalence of Faecal Pathogens in Calves of Racing Camels (Camelus dromedarius) in the United Arab Emirates

Tropical Animal Health and Production -     

Effects of Plant Defence Activators on Anthracnose Disease of Cashew

The plant defence activators acibenzolar-S-methyl (Benzo[1,2,3]thiadiazole-7-carbothioic acid-S-methyl ester, ASM), 2,6-dichloro-isonicotinic acid (DCINA), salicylic acid (SA), and dibasic potassium phosphate (K₂HPO₄) were tested for their ability to protect cashew (Anacardium occidentale) seeds and leaves from anthracnose disease caused by Colletotrichum gloeosporioides. No inhibition of the early stages of pathogen development was caused by concentrations equal to or lower than 1.1mM a.i. ASM, 1.2mM a.i. DCINA, 5mM SA and 50mM K₂HPO₄. Maximum reduction of the disease in detached leaves, without phytotoxic effects, was obtained with 0.07mM a.i. ASM and DCINA, 5mM SA, and 50mM K₂HPO₄, with a time interval of at least 72h between application of the activator and inoculation with the pathogen. On attached leaves, foliar sprays were slightly more efficient than soil drench treatments, with 5mM SA being the most effective treatment, while 50mM SA as well as 0.3mM a.i. ASM and DCINA caused phytotoxic effects. In field-grown plants, protection was conferred by a soil drench of concentrations as low as 12.6M a.i. ASM and DCINA and 2.6mM SA. These concentrations were not phytotoxic suggesting that plant defence activators have potential for control of anthracnose disease in the field.     

Effects of three esca-associated fungi on Vitis vinifera L.: II. Characterization of biomolecules in xylem sap and leaves of healthy and diseased vines

Secondary metabolites and host defense compounds were shown to occur in xylem sap, and leaves of Vitis vinifera cv. Italia and cv. Matilde naturally infected by the esca-associated fungi Phaeomoniella chlamydospora (Pch), Togninia minima (Tmi) and Fomitiporia mediterranea (Fme). Samples of xylem sap and leaves were collected from healthy vines and from vines showing severe symptoms of brown wood-streaking caused by Pch and Tmi, or from vines with symptoms of both brown wood-streaking and white rot caused by Fme. Xylem sap collection was carried out during the early spring of 2003 and 2004, corresponding to the phenological phases: (A) cotton bud; (B) green tip; (C) leaves out; (D) stretched out leaves; and (E) visible clusters. In the present work we have studied the accumulation of biomolecules (pentaketides and α-glucans), host defense compounds (benzaldehydes, benzoic acid and cinnamic acid derivatives, flavonols, flavanols, flavan-3-ol derivatives and stilbenes) at different stages of grapevine development. Accumulation and changes in total phenolics and recurring phenolics, and of three phytotoxic secondary metabolites (scytalone, isosclerone and pullulan) were analyzed by HPLC. On comparing results for cv. Italia and cv. Matilde, it can be seen that phenolic concentrations are strongly related to the cv.     

Effects of three esca-associated fungi on Vitis vinifera L.: III. Enzymes produced by the pathogens and their role in fungus-to-plant or in fungus-to-fungus interactions

When the esca-associated fungi Phaeomoniella chlamydospora (Pch), Togninia minima (Tmi) and Fomitiporia mediterranea (Fme) were grown in liquid stationary cultures, it was seen that they were able to live in media containing resveratrol (RES) or tannic acid (TA) as the sole carbon source and that the fungi were able to convert both compounds. Particular attention is paid here to detecting RES and TA conversion. Pch, Tmi and Fme were partially inhibited by RES or TA. Pch, Tmi and Fme produced extracellular tannase, laccase and peroxidase enzymes in liquid or agarized cultures, whether glucose was present or not. When colonies of Pch, Tmi and Fme were confronted, they showed spatially and temporally heterogeneous patterns of laccase and peroxidase activity. The results indicate the non-synergistic, competitive association of Pch and Tmi and the inhibition of Fme growth. Muconic acid, a well-known intermediate in a large number of lignin and phenol oxidative processes, can partly or completely inhibit the lignolytic agent Fme, but is tolerated by Pch and Tmi. An explanation for wood pigmentation patterns by Pch, Tmi and Fme is given.