中国白粉菌的四个新记录分类群

报道了中国白粉菌科Erysiphaceae的四个新记录分类群,即:寄生于大刺儿菜上的梅厄白粉菌日本变种Erysiphemayoriivar.japonica,寄生于铺地委陵菜上的瑟门白粉菌Erysiphethuemenii,寄生于美女樱上的马鞭草高氏白粉菌Golovinomycesverbenae以及寄生于牻牛儿苗和老鹳草属上的老鹳草新白粉菌Neoerysiphegeranii。研究标本保存在赤峰学院菌物标本室(CFSZ)。     

Susceptibility to powdery mildew of wheat plants deficient in copper

Summary Wheat plants were grown in deep pots at three levels of copper nutrition in an open-sided glasshouse where they were subject to natural infection by powdery mildew. Plant growth and the degree of infection of each leaf were assessed weekly throughout the life of the plants.During the middle phase of growth especially — from tillering to anthesis — severity of infection of leaves was decreased by increasing the level of copper supply. Stems of copper-deficient plants were also severely infected. In these plants serious disease was sustained until final harvest. The results are discussed in relation to known and speculative roles of copper in plants.     

Conidial germination in the filamentous fungus Fusarium graminearum

The ascomycetous fungus Fusarium graminearum is an important plant pathogen causing Fusarium head blight disease of wheat and barley. To understand early developmental stages of this organism, we followed the germination of macroconidia microscopically to understand the timing of key events. These events, recorded after suspension of spores in liquid germination medium, included spore swelling at 2h, germination tube emergence and elongation from conidia at 8h and hyphal branching at 24h. To understand changes in gene expression during these developmental changes, RNA was isolated from spores and used to interrogate the F. graminearum Affymetrix GeneChip. RNAs corresponding to 5813 genes were detected in fresh spores and 5146, 5249 and 5993, respectively, in spores incubated in germination medium after 2, 8 or 24h (P<0.001). Gene expression data were used to predict the cellular and physiological state of each developmental stage for known processes. Predictions were confirmed microscopically for several previously unreported developmental events such as manifestation of peroxisomes in fresh spores and nuclear division resulting in binuclear cells within macroconidia prior to spore germination. Knowledge of stage-specific gene expression and changes in gene expression levels between developmental stages are an important first step to understanding the molecular mechanisms responsible for spore germination and development.     

白粉菌交配型位点基因结构及分子系统学关系

白粉菌是一类植物专性寄生真菌,广泛分布于世界各地,可引起多种植物白粉病。开展白粉菌交配型基因研究可以为全面认识白粉菌的生活史循环和系统演化提供证据。本研究以子囊菌中已报道的10种MAT基因和4种侧翼基因的氨基酸序列为种子序列,采用生物信息学方法在21个白粉菌基因组中进行氨基酸同源性分析,探索MAT基因及其侧翼基因的种类和线性排布。结果表明,21个白粉菌基因组中有10个属于MAT1-1型,包含MAT1-1-1和MAT1-1-3两种基因;10个属于MAT1-2型,仅包含MAT1-2-1基因;在Erysiphe pulchra的基因组中同时存在MAT1-1-1、MAT1-1-3、MAT1-2-1;而4种侧翼基因SLA2、APC5、APN2和CoxVia在21个白粉菌基因组中均存在。21个菌株中有两个菌株Blumeria graminis f. sp. hordei RACE1和Golovinomyces orontii的MAT基因和4种侧翼基因分布在同一个scaffold,其余菌株MAT基因和侧翼基因均不在同一scaffold出现。本研究分别分析了具有MAT1-1和MAT1-2的菌株中MAT基因和4种侧翼基因的排列关系,同时根据9个菌株的MAT基因注释信息,推测了其他菌株的MAT基因结构。结果表明,同属白粉菌的MAT基因结构相同,属间MAT基因结构差异明显。以从白粉菌基因组中获得的MAT1-1-1、MAT1-1-3和MAT1-2-1 3种MAT基因序列分别构建系统发育树,发现布氏白粉菌属Blumeria、白粉菌属Erysiphe和戈洛文白粉菌属Golovinomyces分别形成独立分枝,且白粉菌属与戈洛文白粉菌属形成姊妹群,这与前人对白粉菌系统发育关系的研究结果一致。本研究得到的白粉菌MAT基因种类、分布及其结构的相关结果为进一步实验提供了理论依据,为探究白粉菌的系统发育提供了新的思路。     

Morphological and phylogenetic comparisons amongst powdery mildews on Catalpa in the UK

Three species of powdery mildew, Erysiphe elevata, E. catalpae, and Neoerysiphe galeopsidis were identified on Catalpa species in England in 2004. A new disease record, N. galeopsidis was the first Catalpa mildew to appear (in June), but it was later out-competed by E. elevata that caused the most serious damage. Both mildews also attacked C. speciosa, C. ×erubescens and a new host, ×Chitalpa tashkentensis, a Chilopsis × Catalpa hybrid. No powdery mildew was detected on C. bungei, C. ovata, or C. fargesii. Identifications of the pathogens using morphological data were fully supported by DNA analysis yielding characteristic rDNA ITS sequences. The sequences placed E. catalpae within the E. aquilegiae clade. The sequences for E. elevata from southern England and France closely matched those from Hungary and North America, confirming the recent spread of this pathogen from the USA. It eventually overran N. galeopsidis and its sudden appearance in the UK could be due to greater aggressiveness and to the production of more ascomata especially during autumns with delayed leaf fall as in 2001. A further species, Oidium hiratae (i.e. Podosphaera sp.), though described from a 1978 UK collection on C. bignonioides, was not detected in the field.     

Conidial germination in the filamentous fungus Fusarium graminearum.

The ascomycetous fungus Fusarium graminearum is an important plant pathogen causing Fusarium head blight disease of wheat and barley. To understand early developmental stages of this organism, we followed the germination of macroconidia microscopically to understand the timing of key events. These events, recorded after suspension of spores in liquid germination medium, included spore swelling at 2h, germination tube emergence and elongation from conidia at 8h and hyphal branching at 24h. To understand changes in gene expression during these developmental changes, RNA was isolated from spores and used to interrogate the F. graminearum Affymetrix GeneChip. RNAs corresponding to 5813 genes were detected in fresh spores and 5146, 5249 and 5993, respectively, in spores incubated in germination medium after 2, 8 or 24h (P<0.001). Gene expression data were used to predict the cellular and physiological state of each developmental stage for known processes. Predictions were confirmed microscopically for several previously unreported developmental events such as manifestation of peroxisomes in fresh spores and nuclear division resulting in binuclear cells within macroconidia prior to spore germination. Knowledge of stage-specific gene expression and changes in gene expression levels between developmental stages are an important first step to understanding the molecular mechanisms responsible for spore germination and development.     

Inoculum production and long-term conservation methods for cucurbits and tomato powdery mildews

The behaviour of cucurbit powdery mildews (Podosphaera xanthii and Golovinomyces cichoracearum) and tomato powdery mildew (Oidium neolycopersici) infesting detached cotyledons of Lagenaria leucantha cv. ‘Minibottle’ was studied in order to develop an easy culture method for pure inoculum production. High spore production was found with a combination of mannitol (0.1 m), sucrose (0.02 m) and agar (8 g l⁻¹) in the cotyledon survival medium. Sporulation on cotyledons and viability of conidia were affected by the age of culture for the three species of powdery mildew tested. The age of cotyledons had also an impact of the spore production. This method was used to produce large amounts of inoculum for P. xanthii, G. cichoracearum and O. neolycopersici and enable the development of other species of powdery mildew like Leveillula taurica. Freezing conidia in liquid nitrogen enabled the long-term conservation of P. xanthii without any loss of virulence. The same method was unsuccessful with G. cichoracearum, and L. taurica and partly successful with O. neolycopersici.     

First record of dill powdery mildew caused by Erysiphe heraclei DC in Egypt

In Egypt, powdery mildew was observed for the first time on dill plants, during annual disease surveys of March–May 2003 and 2005. Typical symptoms of powdery mildew of dill plant (Anethum graveolens L.) were observed in Gharbeia Governorate. Symptoms of powdery mildew became common on leaves, stems inflorescences and fruits as white irregular areas. These symptoms appeared at vegetative and early flowering stages then gradually increased through fruiting and pre-maturity stages. Samples of infected leaflets, stem, inflorescences and fruits were collected for examination by light and scanning electron microscope (SEM). Microscopic examination revealed that conidiophores were short, erect–69 × 6–10 μm in dimension, conidia were observed without conspicuous fibrosin bodies singly, elliposid to ovoid 25–33 × 10–16 μm in dimension, and the length to width ratio of conidia ranged from 1.7 to 2.0 and were produced singly. Cylindrical foot cells (22.0 × 8.0 μm) were followed by one or two shorter cells (12.5 × 7.5 μm). In spring, the sexual stage (cleistothecia) appeared on infected leaves and stems in spherical, gregarious measures 105–117 (111) × 100– 87.5 μm in diameter. Each cleistothecium contained (2–4) round to ovoid asci, 45–55 (50) × 45–25 (35) μm in dimension. The ascus contained (3–4) ellipsoid to ovoid ascospores, 20–17.5 × 15–10 (13.2) μm. Cleistothecia appendages are simple myceloid branched tips measuring 80–200 (140) μm in length and 3–5 (4) μm in diameter. Based on the observations of the morphology of its anamorph and teleomorph stages, the causal agent of dill powdery mildew was identified as Erysiphe heraclei which is reported for the first time in Egypt.     

Polyamines in discrete regions of barley leaves infected with the powdery mildew fungus, Erysiphe graminis

The concentrations of putrescine, spermidine and spermine and the activities of arginine decarboxylase (ADC; EC 4.1.1.19) and ornithine decarboxylase (ODC: EC 4.1.1.17) were determined in discrete regions of barley leaves ( Hordeum vulgare L. cv. Golden Promise) infected with the powdery mildew fungus ( Erysiphe graminis f.sp. hordei Marchal). Polyamine concentrations and the activities of both enzymes were always greatest within the region surrounding the fungal pustule, with the lowest values always being found in the region furthest away from the pustule. Although the concentrations of the three amines and ADC and ODC activities within the fungal pustule were always less than values from the zone surrounding the pustule, these differences were never significant. Polyamine concentrations and ODC activity were not significantly reduced, and ADC activity remained unchanged in mildewed leaves with all surface fungal growth removed. It would appear therefore that not only does most of the increase in amines and ODC activity reside in the leaf itself, but that very little of this increase is due to fungal growth and sporulation. Furthermore, it seems possible that the increase in polyamines in mildewed barley could be involved in 'green-island' formation, where regions around mildew pustules remain green and physiologically active while the rest of the leaf senesces.     

Phylogenetic relationships ofMicrosphaera andErysiphe sectionErysiphe (powdery mildews) inferred from the rDNA ITS sequences

The genusMicrosphaera has been considered to be derived from sectionErysiphe of the genusErysiphe by a single event. Cleistothecial appendages are the most distinct difference between the two genera and have an important role for overwintering. To understand the phylogenetic relationship betweenErysiphe sectionErysiphe andMicrosphaera more precisely, phylogenetic trees were constructed using the nucleotide sequences of the rDNA ITS region from 11Erysiphe (sectionErysiphe) and 16Microsphaera taxa. The phylogenetic trees indicated the close relationship between the two genera. However, the generaErysiphe (sectionErysiphe) andMicrosphaera did not group into separate monophyletic lineages; instead, they formed several small clusters that were mixed together. This result suggests that the differentiations of the genera occurred two or more times independently. This also supports the idea that appendage morphology does not always accurately reflect the phylogeny of the powdery mildews because the morphology of appendages may evolve convergently under the selection pressure of their particular biotopes (host plants). Contribution No. 144 from the Laboratory of Plant Pathology, Mie University.     

The current systematics and taxonomy of the powdery mildews (Erysiphales): an overview

A brief survey of the current systematics and taxonomy of powdery mildews (Erysiphales) is given with special focus on new characters used for taxonomic purposes as well as new approaches, methods and techniques. The structure of the family Erysiphaceae based on phylogenetic results is summarized, and the current, strongly increased number of powdery mildew taxa in a planned new monographic treatment of this fungal group is given and compared with the old monograph from 1987.     

Interspecific and intraspecific diversity in oak powdery mildews in Europe: coevolution history and adaptation to their hosts

Quercus has been reported as the genus with the largest number of attacking powdery mildews. In Europe, oak powdery mildew was rarely reported before 1907, when severe outbreaks were observed. These epidemics were attributed to the newly described species Erysiphe alphitoides, presumed to be of exotic origin. After the burst of interest following the emergence of the disease, research on this topic remained very limited. Interest in research was recently reactivated in response to the availability of molecular tools. This review summarizes current knowledge on the diversity of oak powdery mildews in Europe and their possible evolutionary relationships with European oaks. The most striking results are the evidence of cryptic diversity (detection in France of a lineage closely related to Erysiphe quercicola, previously thought to only have an Asian distribution), large host range (similarity of E. alphitoides and E. quercicola with powdery mildews of tropical plants) but also local adaptation to Quercus robur. These recent findings highlight the complexity of the history of oak powdery mildew in Europe and point to the question of host specialization and host jumps in the evolution of powdery mildew fungi.     

Biochemical genetics of powdery mildew resistance in pea

Summary A biochemical study on phenolic (total phenols and orthodihydroxy phenols) content and on the activities of phenol oxidizing enzymes (peroxidase and polyphenol oxidase) in pea cultivars resistant and susceptible to powdery mildew infection revealed that the resistant cultivars contained higher levels of phenolics and phenol-oxidizing enzymes than the susceptible ones. A further study of their F₁s, F₂s and backcross progenies suggested a high heritability for all biochemical traits. The correlation coefficients between the biochemical parameters and the disease index were also high. Both additive (d) and dominant () components were found to contribute to the inheritance of these constituents.Associate Professor (Genetics), Department of Basic Sciences     

Sources of powdery mildew resistance in barley landraces from morocco

A total of forty eight accessions of barley landraces from Morocco were screened for resistance to powdery mildew. Twenty two (46%) of tested landraces showed resistance reactions and thirty four single plant lines were selected. Eleven of these lines were tested in seedling stage with seventeen and another twenty three lines with twenty three isolates of powdery mildew respectively. The isolates were chosen according to the virulence spectra observed on the ‘Pallas’ isolines differential set. Line 229–2–2 was identified with resistance to all prevalent in Europe powdery mildew virulence genes. Lines 230–1–1, 248–1–3 showed susceptible reaction for only one and lines 221–3–2, 227–1–1, 244–3–4 for only two isolates respectively. Three different resistance alleles (Mlat, Mla6, and MLA14) were postulated to be present in tested lines alone or in combination. In thirty (88%) tested lines it was impossible to determine which specific gene or genes for resistance were present. Most probably these lines possessed alleles not represented in the ‘Pallas’ isolines differential set. The distribution of reaction type indicated that about 71% of all reaction types observed were classified as powdery mildew resistance (scores 0, 1 and 2). Majority (79%) of resistance reaction types observed in tested lines was intermediate resistance reaction type two and twenty three lines (68%) showed this reaction for inoculation with more than 50% isolates used. The use of new effective sources of resistance from Moroccan barley landraces for diversification of resistance genes for powdery mildew in barley cultivars was discussed.     

Three new records of powdery mildews found in Mexico with one genus and one new species proposed

Cystotheca lanestris on the new host Quercus canbyi, Microidium bauhiniicola on the new host Bauhinia macranthera and an undescribed species of Phyllactinia on Mimosa aculeaticarpa have recently been collected in Mexico. Analyses of morphological traits and molecular sequence data led to identifications of the causal agents of the powdery mildew diseases involved. Microidium bauhiniicola, hitherto only known from Argentina and Brazil, is new to Mexico. The phylogenetic analysis revealed an isolated position distant from Microidium indicating an undescribed genus, which is introduced as Bulbomicroidium gen. nov. Sequences derived from a Mexican specimen of C. lanestris on Quercus canbyi agree completely with other North American sequences, but differ from sequences retrieved from Asian collections, suggesting that C. lanestris in Asia is not conspecific with C. lanestris s. str. in North America. A new species of Phyllactinia on Mimosa malacophylla is morphologically similar to P. dalbergiae but readily distinguishable by differences in the asexual morph. Based on morphological peculiarities and results of molecular sequence analyses, this species is described as Phyllactinia mimosae sp. nov.