紫花苜蓿白粉病病原菌鉴定及其生物学特性

【背景】白粉病是影响苜蓿产量和品质的主要真菌病害之一,引起紫花苜蓿白粉病的病原有3种:蓼白粉菌(Erysiphe polygoni DC.)、豆科内丝白粉菌(Leveillula leguminosarum Golov.)和豌豆白粉菌(Erysiphe pisi DC.)。【目的】系统研究紫花苜蓿白粉病病原菌的生物学特性,以及分生孢子和闭囊壳的形态特征,明确宁夏地区紫花苜蓿白粉病病原种类。【方法】采用室内盆栽法调查病害发生和闭囊壳形成条件,利用气象站自动获取数据,采用光学显微镜观察病原菌特征,采用水琼脂玻片法观察病原菌分生孢子萌发特性。【结果】紫花苜蓿白粉病发生的温度范围为20-24℃,湿度范围为40%-60%,形成闭囊壳的条件为温度20-25℃、湿度70%左右,闭囊壳的形成大约需要42 d。分生孢子以向基式的产孢方式在分生孢子梗上产孢,成熟的分生孢子卵圆形或椭圆形,大小为(29-46)×(12.5-21.0)μm。闭囊壳黑褐色,球形或近球形,直径71-135μm,具有大量附属丝,少数为不规则分枝1-2次。闭囊壳内含有4-6个子囊,子囊倒棒型或卵圆形,具柄,大小为(58-90)×(29...     

亚蔬中心绿豆品种(系)抗白粉病评价

采用苗期人工接种鉴定法,在大棚种植条件下对12个亚蔬中心(AVRDC)绿豆品种白粉病抗性进行了鉴定评价。结果显示,VC1560C、V4785和VC2768A三个品种高抗(HR)白粉病,VC6173-14、V1132为中抗(MR)白粉病品种。其它品种对白粉病表现高度感病。在田间种植条件下对亚蔬中心16个抗豆象回交9代品系(BC9)进行了成株期白粉病抗性鉴定。与对照感病品种 VC1973、VC1178A 相比,VC6459-3-6-37和 VC6458-6-3-16对白粉病具有一定抗性,但白粉病感染程度仍很严重,其它14个 BC9品系均对白粉病表现高度感病。     

Resistance to oat powdery mildew in Britain and Europe: a review

The evolution of virulence in UK oat powdery mildew (Blumeria graminis f.sp. avenae) populations is presented along with comparative information on the deployment of resistant cultivars. Virulence frequencies have followed classical gene‐for‐gene principles, and there are no effective resistance genes currently deployed in cultivars grown in the UK. The incidence of powdery mildew in continental Europe and pathogen variation is reviewed as well as other strategies for the control of this disease. New resistant sources have been identified and are being used in breeding programmes throughout Europe.     

Changes in protein abundance during powdery mildew infection of leaf tissues of Cabernet Sauvignon grapevine (Vitis vinifera L.)

A comparative analysis of differentially expressed proteins in a susceptible grapevine (Vitis vinifera ‘Cabernet Sauvignon’) during the infection of Erysiphe necator, the causal pathogen of grapevine powdery mildew (PM), was conducted using iTRAQ. The quantitative labeling analysis revealed 63 proteins that significantly changed in abundance at 24, 36, 48, and 72 h post inoculation with powdery mildew conidiospores. The functional classification of the PM‐responsive proteins showed that they are involved in photosynthesis, metabolism, disease/defense, protein destination, and protein synthesis. A number of the proteins induced in grapevine in response to E. necator are associated with the plant defense response, suggesting that PM‐susceptible Cabernet Sauvignon is able to initiate a basal defense but unable to restrict fungal growth or slow down disease progression.     

Effect of certain plant extracts and fungicides against powdery mildew disease of Grapevines in Upper Egypt

The efficiency of azadirachtin, jojoba oil, Reynoutria sachalinensis, azoxystrobin + difenoconazole, kresoxim methyl, propiconazole and sulphur in controlling powdery mildew disease of Grapevines caused by Uncinula necator (Schlecht.) was evaluated during 2015 and 2016 seasons. Laboratory study showed that all the tested plant extracts and fungicides significantly (p < 0.05) reduced germination of conidia of the causal pathogen. Spraying of the extracts on vine trees significantly (p < 0.05) decreased the disease severity (D.S. %) compared with infected control. The tested plant extracts as well as fungicide have high effect in disease reduction; no significant differences (p < 0.05) in the disease reduction were found in the effect of the extracts between tested compounds in both seasons. Moreover, treatment of trees with Reynoutria extract exhibited the highest increment in peroxidase activity (PO), polyphenol-oxidase (PPO) activity and phenol content compared to other treatments after 9 days from spraying.     

Regulation of resistance and susceptibility in wheat–powdery mildew pathosystem with exogenous cytokinins

Dose–response relationship between resistance of wheat seedlings (Triticum aestivum, cultivar Zarya) to Erysiphe graminis f. sp. tritici Marchal. (Syn. Blumeria graminis), a causal organism of wheat powdery mildew and exogenous zeatin has been investigated. Two-week-old seedlings were inoculated with the pathogen. Zeatin or zeatinriboside were added to the nutrient solution immediately after inoculation. The dose–response curve of cytokinin in the most cases was multiphasic, with peaks of increased susceptibility occurring at 0.25–1.5 and 1.5–9 μM cytokinin, separated by a region of increased resistance at 0.5–3 μM cytokinin. The change in mineral nutrition or simultaneous treatment with thidiazuron revealed alterations of the dose–response curve ranging from a curve with maximum of resistance to a curve with maximum of susceptibility. Both multiphase nature of dose–response and its variability were proposed as possible explanations for earlier observed discrepancies in experimental data on modification of disease resistance by cytokinins. A mathematical model for two metabolic processes with substrate inhibition connected in-series was suggested to explain the multiphase dose–response. In this model, the product of the first reaction was used as substrate for the second reaction. Numerical experiments showed the changes in the shape of dose–response curve with changes in parameters dependent of cytokinin metabolism.     

Evaluation of biocontrol agents and potassium silicate for the management of powdery mildew of zucchini

Investigations were conducted under greenhouse and field conditions to evaluate the effects of potential biocontrol agents (BCAs) and soluble silicon (Si) on powdery mildew of zucchini caused by Podosphaera xanthii. Five BCAs were applied as foliar sprays to zucchini leaves and Si was drenched weekly into the rhizosphere of these plants.In the greenhouse, all BCAs provided significant control of powdery mildew with fungal isolates, reducing disease levels by up to 90%. Si alone reduced powdery mildew by as much as 35% and improved the efficacy of most of the biocontrol agents. Higher disease pressure reduced the efficacy of Si on powdery mildew but did not affect the performance of the BCAs. In the field, a disease reduction of 10–70% was achieved by BCAs and Si. Lower temperatures and high humidity ranges were suitable for optimal performances. The efficacy of the bacterial BCA, Serratia marcescens – B15 and silicon diminished at temperatures above 25 °C. The fungal BCAs (Clonostachys rosea – EH and Trichothecium roseum – H20) were better suited to higher temperatures (25–30 °C) and were tolerant of low RH values. Application of K₂SiO₂ to zucchini roots increased the level of Si in the leaves, which was responsible for suppression of the disease.     

Hyperparasites of the genus shape Ampelomyces on powdery mildew fungi in Serbia

From 1982 to 1996, in Serbia, 229 species of plants infected with powdery mildew were collected. Seventy-five species had hyperparasites of the genus Ampelomyces. Distribution analysis showed that hyperparasitism was greatest on plants from the families Asteraceae, Apiaceae and Fabaceae. Ampelomyces was not found on the family Poaceae. It was reported for the first time on the families Amygdalaceae, Cornaceae, Grossulariaceae, Plantaginaceae, Rhamnaceae and other 37 plant species. Hyperparasites of the genus Ampelomyces were found on 33 different species of fungi that are causal agents of powdery mildews. They are reported for the first time on nine species. Pycnidial size varied in the range 45–106 × 25.5–40.5 μm and conidia from 4.5–10.5 × 2.5–4.8 μm. This revised version was published online in June 2006 with corrections to the Cover Date.     

Natural occurrence of ampelomyces intracellular mycoparasites in mycelia of powdery mildew fungi

This is the first extensive investigation that quantifies natural mycoparasitic relationships in the phyllosphere. The presence of Ampelomyces spp. was quantified in naturally occurring powdery mildew fungi collected in Hungary and Romania between 1992 and 1995. A total of 570 samples was studied representing 27 species (nine genera) of the Erysiphaceae infecting 41 host plant genera. The incidence of Ampelomyces spp., determined as the proportion of samples in which intracellular pycnidia were present, varied between 4.3 and 68.8% in the host fungal genera studied. The intensity of mycoparasitism, defined as a percentage of the powdery mildew mycelia parasitized by Ampelomyces , ranged from 0.15 to 65%. Both the incidence and the intensity of mycoparasitism showed the lowest values in Blumeria graminis (DC.) Speer collected from wild and cultivated monocotyledons, while the highest values were found in Arthrocladiella mougeotii (Lév.) Vassilkov infecting Lycium halimifolium Mill. plants. The paper reports for the first time the natural occurrence of Ampelomyces in Sawadaea bicornis (Wallr.:Fr.) Homma on maple.     

两种不同白粉病抗性野生蔷薇内生真菌群落结构

【背景】白粉病是蔷薇、月季等观赏植物的主要病害,提高其白粉病抗性是花卉产业亟待解决的难题。内生菌在增强植物抗病性能方面的益处已经得到证实。大理紫花是一种白粉病高抗野生蔷薇,而七姐妹是一种高感野生蔷薇,目前对两者在内生菌群落结构及功能方面的异同尚不清楚。【目的】对比研究白粉病高抗和高感两种野生蔷薇内生菌群落组成的异同,探索内生菌在宿主植物白粉病抗性中可能发挥的生态学功能,为蔷薇白粉病防治提供新思路。【方法】通过传统的内生真菌分离培养方法,结合形态学特征和分子生物学分析确定所获菌株的分类地位,对白粉病高抗和高感两种野生蔷薇内生真菌群落组成进行对比分析。【结果】从两种不同白粉病抗性野生蔷薇的2 880个组织块中,共分离得到2 003株内生真菌,其中从大理紫花得到1 333株,从七姐妹得到670株。它们分属于链格孢属(Alternaria)、炭角菌属(Xylaria)和拟盘多毛孢属(Pestalotiopsis)等30个分类单元。其中链格孢(A. alternata)、平头刺盘孢(C. truncatum)和拟茎点霉(Phomopsis amygdali)为两种蔷薇在白粉病暴发各时期的共有优势菌,而盘毛孢(Seimatosporium sp.)、鬼伞(Coprinellus sp.)和球毛壳菌(Chaetomium globosum)等则只存在于大理紫花或七姐妹一种植物中。【结论】在白粉病暴发进程中,白粉病高抗野生蔷薇大理紫花与高感蔷薇七姐妹的内生真菌多样性及群落结构明显不同。且随着时间的推移,七姐妹的内生真菌多样性逐渐增加,而大理紫花的却逐渐减少。但在各采样时间点,高抗蔷薇内生真菌的数量和平均定殖率均明显高于高感蔷薇(P0.05,卡方检验)。大理紫花中存在一些特有和优势内生真菌,它们在大理紫花白粉病抗性中的功能有待进一步深入研究。     

PCR primers useful for nucleotide sequencing of rDNA of the powdery mildew fungi

Four PCR primers that are useful to determine the nucleotide sequences of the rDNA of the powdery mildew fungi were newly designed. These primers provide both enough stability to work on a wide range of powdery mildews and enough specificity to eliminate contaminating DNA by PCR. DNA sequences of the rDNA ITS region were successfully obtained from specimens that were contaminated by other fungi. In addition, sequence results of the 18S and 28S rDNA were dramatically improved by using these primers in most of the specimens examined.     

Linkage of the hordein loci Hor1 and Hor2 with the powdery mildew resistance loci Ml-k and Ml-a on Barley chromosome 5

Summary The linkage relationship among the loci Hor1, Hor2, Ml-k and Ml-a on the short arm of chromosome 5 was studied by progeny testing the F₂ generation of two crosses. The loci Hor1 and Hor2 code for polypeptides of the storage protein hordein (prolamin) and the loci Ml-k and Ml-a determine the resistance reaction with some powdery mildew fungi cultures. The order of the loci is Ml-k, Hor1, Ml-a, and Hor2, the first named being nearest the centromere. The recombination percentage between Hor1 and Hor2 was determined in the F₁ and F₂ generations in both crosses, the combined estimate being 7.4±0.9 per cent. The recombination percentage estimated between Ml-k and Hor1 was 4.0±1.3, between Hor1 and Ml-a, 5.3±1.1, and between Ml-a and Hor2, 6.1±1.2. The estimates involving the Ml- loci were all probably a little too high.     

白粉菌侵染对小麦叶片显微及超微结构的影响

通过半薄及超薄切片,比较了正常和受白粉菌感染的小麦叶片细胞的显微及超微结构的差异。观察结果发现：（1）受感染小麦叶肉细胞的细胞壁上局部沉积大量团状电子致密颗粒;（2）叶绿体形状由原来的椭圆形转变成圆形,叶绿体膜破裂;类囊体膨大,基粒片层排列疏松,同时,叶绿体内嗜饿性颗粒数量增加;（3）线粒体膜解体,内含物分散到了细胞质中。     

RFLP markers to identify the alleles on the Mla locus conferring powdery mildew resistance in barley

Summary To identify the mildew resistance locus Mla in barley with molecular markers, closely linked genomic RFLP clones were selected with the help of near-isogenic lines having the Pallas and Siri background. Out of 22 polymorphic clones 3 were located around the Mla locus on chromosome 5 with a distance of 5.1 + 2.9 cM (MWG 1H068), 4.2±1.7 cM (MWG 1H060) and 0.7 ± 0.7 cM (MWG 1H036), respectively. The polymorphic clone MWG 1H036 displayed the same RFLP pattern in both Pallas and Siri near-isogenic lines and in different varieties digested with six restriction enzymes possessing the same mildew resistance gene. The alleles of the Mla locus were grouped in 11 classes according to their specific RFLP patterns; 3 of these groups contain the majority of Mla alleles already used in barley breeding programs in Europe.     

In situ PCR technique based on pricking microinjection for cDNA cloning in single cells of barley coleoptile and powdery mildew pathogen

To clone cDNAs of mRNA specifically expressed at the infection sites, we applied the polymerase chain reaction (PCR) combined with pricking microinjection to barley coleoptile epidermis inoculated with powdery mildew pathogen. In essence, first-strand cDNAs were synthesized in situ the needle-pricked epidermal cells in which fungal haustoria had formed, and were subsequently amplified by PCR with synthetic primers. The amplified DNAs were subcloned into a plasmid vector for the construction of a cDNA library. The antisense RNAs were in vitro-transcribed from subcloned DNAs, labelled, and introduced into pathogen-invaded coleoptile epidermal cells by pricking microinjection. Target cell-specific cDNAs were identified by a specific in situ hybridization in the pathogen-invaded cells. This technique was also applied to the amplification and identification of cDNAs which were reverse-transcribed from mRNAs of targeted infection structures of the powdery mildew pathogens inoculated onto barley coleoptile epidermis.     

Rapid reorganization of microtubular cytoskeleton accompanies early changes in nuclear ploidy and chromatin structure in postmitotic cells of barley leaves infected with powdery mildew

Summary Post-mitotic epidermal cells of barley leaves were found to contain, in addition to cortical microtubules (CMTs), distinct arrays of endoplasmic microtubules (EMTs). These encircle nuclei and continuously merge into the CMT arrays that underly the plasmalemma. Detailed three-dimensional reconstruction of both types of MTs during fungal infection showed that profound and very rapid MT rearrangements occurred especially in the case of incompatible (resistant) barley-powdery mildew genotype combination. The most early MT responses, followed by their subsequent complete disintegration, were recorded around nuclei. These events might be relevant for the induction of such nuclear processes as onset of DNA synthesis and nuclear chromatin condensation. Observed pattern of early infection events, as well as less prominent responses in the case of compatible (susceptible) barley-powdery mildew genotype combination, both findings suggest that rapid reorganization of the MT cytoskeleton could be involved in recognition of the fungus by host cells and in the initiation of resistance responses in barley leaves. We hypothesize that the integrity and dynamics of the MT cytoskeleton, especially of its perinuclear part, might participate in control mechanisms involved in activation of resistance genes.Abbreviations CMTs cortical microtubules - EMTs endoplasmic microtubules - MT microtubules - PI propidium iodide - SC sensitive combination - RC resistant combination