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1.
Until recently, Erysiphe pisi was thought to be the only causal agent of powdery mildew in pea, but recent studies showed that other species such as Erysiphe trifolii and Erysiphe baeumleri can also cause this disease. Three genes, er1, er2 and Er3, conferring resistance to E. pisi have been reported so far in pea. Previous studies showed that E. trifolii and E. baeumleri were able to overcome er1 resistance, but whether er2 and Er3 were effective against E. trifolii was not known. In this study, pea accessions carrying these three genes were evaluated for resistance to E. trifolii under controlled conditions at 20 and 25 °C. In addition, these accessions were also evaluated under field conditions in Spain and in India. Analysis of the ribosomal DNA (rDNA) internal transcribed spacer (ITS) sequences showed that E. trifolii was the causal agent of powdery mildew symptoms in lines carrying er1 in Spain and that this pathogen was also present in India. Our results showed that E. trifolii was able to overcome er1 and shows that this pathogen can also overcome Er3 resistance in some conditions. In contrast, er2 provided high level of resistance against E. trifolii in all conditions and locations studied. Temperature affected the expression of Er3 against E. trifolii, but not of er1 or er2. The pea accession JI2480, containing er2, was highly resistant and JI2302 containing er1 was susceptible to E. trifolii at both temperatures, whereas P660-4 containing Er3 was resistant at 20 °C but susceptible at 25 °C. The present study also identified sources of resistance effective against both E. pisi and E. trifolii.  相似文献   

2.
During the past years, nrDNA ITS sequences have supported the identification of many powdery mildew fungi because comprehensive analyses showed that differences in these sequences have always correlated with the delimitation of different species and formae speciales of the Erysiphales. Published data, obtained using direct sequencing of the PCR products, suggested that even one to five nucleotide differences in the ITS sequences delimit different, albeit closely related, species, and/or indicate differences in host range patterns. Here we show that such differences in the ITS sequences can be detected even in a single sample of a powdery mildew fungus. We sequenced the ITS region in 17 samples, representing six powdery mildew species, both directly and after cloning the PCR products. Among these, samples of O. longipes exhibited two or three, samples of O. neolycopersici three or four, those of an Oidium sp. from Chelidonium majus up to seven, and a sample of another Oidium sp. from Passiflora caerulea two different ITS types determined after cloning. No ITS nucleotide polymorphisms were found in samples of O. lycopersici and Erysiphe aquilegiae. This suggests that some powdery mildew taxa are more variable at the ITS level than others. Thus, although the ITS sequences determined by direct sequencing represent robust data useful in delimitation and phylogenetic analysis of distinct species of the Erysiphales, these need to be used with precaution, and preferably determined after cloning, especially when dealing with closely related taxa at species and sub-species levels. With this method a hitherto undetected genetic diversity of powdery mildews can be revealed.  相似文献   

3.
Since 2003, Torenia fournieri plants grown for experimental purposes were repeatedly infected by powdery mildew in a laboratory in Hungary. Based on morphological characteristics, the pathogen belonged to the mitosporic genus Oidium subgen. Reticuloidium, the anamorph stage of Golovinomyces. The rDNA ITS sequence was identical to that of two other powdery mildew fungi, infecting Arabidopsis and Veronica, respectively, in different parts of the world. According to a previous phylogenetic analysis of ITS and 28S rDNA sequences, those two powdery mildews belong to a recently evolved group of Golovinomyces characterized by multiple host range expansions during their evolution. Both the ITS sequence and the morphological data indicate that the powdery mildew anamorph infecting Torenia also belongs to this group. It is likely that the powdery mildew infections of the experimental T. fournieri plants, native to south-east Asia, were the result of a very recent host range expansion of a polyphagous Golovinomyces because (i) T. fournieri is absent from our region, except as an experimental plant grown in the laboratory, (ii) the powdery mildew fungus infecting this exotic plant belongs to a group of Golovinomyces where host range expansion is a frequent evolutionary scenario, (iii) cross-inoculation tests showed that this pathogen is also able to infect other plant species, notably A. thaliana and tobacco, and (iv) no Golovinomyces species are known to infect T. fournieri anywhere in the world. Although host range expansion has often been proposed as a common evolutionary process in the Erysiphales, and also in other biotrophic plant pathogens, this has not been clearly demonstrated in any case studies so far. To our knowledge, this is the first convincing case of a host range expansion event in the Erysiphales.  相似文献   

4.
Since 2001, several isolates of Blumeria graminis, the causal agent of cereal powdery mildew, maintained on detached leaves at the John Innes Centre, Norwich, UK, have spontaneously become infected with an unknown filamentous fungus whose mycelia have quickly overgrown the powdery mildew colonies and destroyed them completely. A total of five isolates of the contaminant were obtained and identified as Paecilomyces farinosus based on morphological characteristics and rDNA ITS sequence data. To determine whether these P. farinosus isolates can be considered as biocontrol agents (BCAs) of powdery mildews, we studied the interactions between P. farinosus and the following four powdery mildew species: B. graminis f.sp. hordei infecting barley, Oidium neolycopersici infecting tomato, Golovinomyces orontii infecting tobacco and Podosphaera fusca infecting cucumber. The powdery mildew colonies of all these four powdery mildew species were quickly destroyed by P. farinosus in leaf cultures but neither conidial suspensions nor cell-free culture filtrates of P. farinosus isolates could suppress the spread of powdery mildew infections on diseased barley, tomato, tobacco or cucumber plants in the greenhouse. It is concluded that P. farinosus cannot be considered as a promising BCA of powdery mildew infections although it can destroy powdery mildew colonies in detached leaf cultures and can be a menace during the maintenance of such cultures of cereal, apple, cucurbit and tomato powdery mildew isolates.  相似文献   

5.
In March 1999, we found prairie gentian (Eustoma grandiflorum) infected with powdery mildew in a greenhouse in Oita Prefecture, Japan. Morphological observation revealed that the causal fungus belongs to the mitosporic genus Oidium subgenus Pseudoidium [teleomorph: Erysiphe sensu Braun and Takamatsu (2000)]. Precise taxonomic position of the fungus, however, is uncertain due to lack of the perfect stage. We determined the nucleotide sequence of the rDNA ITS region of the fungus. Comparison of the sequence with those obtained from DNA databases of this fungal group revealed that the sequence is identical to those of powdery mildews from garden four-o'clock (Mirabilis jalapa) and broad bean (Vicia faba). Inoculation of an isolate from garden four-o'clock caused mildew on prairie gentian and broad bean, suggesting that the prairie gentian mildew originates from garden four-o'clock or broad bean. Molecular phylogenetic analysis indicated a close relationship of this fungus to Erysiphe baeumleri on Vicia spp. and E. trifolii on Trifolium pratense. From these results, we propose that prairie gentian mildew diverged from a Fabaceae-parasitic ancestor. Received 14 March 2002/ Accepted in revised form 28 May 2002  相似文献   

6.
To determine whether Ca2+ promotes powdery mildew penetration, Ca2+-treated barley coleoptiles were inoculated with conidia of pathogenic and nonpathogenic fungi. Penetration efficiency of the pathogenic powdery mildew Blumeria graminis was enhanced by Ca2+ treatment, but that of the necrotrophic pathogen Helminthosporium sp. remained unaffected. Similarly, when actin-dependent penetration resistance is suppressed with cytochalasin A, Ca2+ treatment specifically enhanced penetration of the nonpathogenic powdery mildew Erysiphe pisi but not that of other nonpathogens. Calmodulin inhibitors suppressed the promotive effect of Ca2+ on B. graminis penetration. These results suggest that barley powdery mildew specifically requires Ca2+ and calmodulin for penetration.  相似文献   

7.
In pea, two single recessive genes, er1 and er2, have been identified for resistance to powdery mildew caused by Erysiphe pisi, but little is known about their mode of action. Pea accessions carrying the genes er1 or er2 and other accessions displaying resistance to powdery mildew in the field were studied. In accessions carrying gene er1, epidermal cell penetration was prevented and very few haustoria or colonies were formed. Under controlled conditions, er1 conferred complete or almost complete resistance to the fungal isolates used and this resistance was not associated with macroscopically visible necrosis. Under field conditions these accessions developed a low level of disease. Resistance in line JI2480 (carrying er2) increased with temperature and leaf age, and complete resistance was expressed only at high temperature (25 °C) or in mature leaves. This resistance was based mainly on post-penetration cell death, complemented by a reduction of percentage penetration success in mature leaves. Combining the resistance provided by gene er1 and by line JI2480 into new cultivars is likely to increase their level of resistance and enhance durability of the protection.  相似文献   

8.
Cashew powdery mildew is presently the most important disease of cashew trees in all Brazilian growing regions. Although it was described over a century ago, it had never threatened the Brazilian cashew industry until the first decade of the 21st century. Morphological and pathogenic evidence indicated the possibility of different pathogen species being involved in early and late types of cashew powdery mildew. This study was designed to elucidate this issue by comparing two different powdery mildew fungi occurring on cashew plants in Brazil according to the morphological characteristics, phylogenetic relationships with closely related powdery mildew fungi and pathogenic relationships. Based on morphology, molecular phylogenetics and pathogenicity on cashew, it was shown that two species of powdery mildew specimens are without question associated with cashew trees. One species, which infects young immature tissues such as shiny leaves, flowers and young fruits, is Erysiphe quercicola, while Erysiphe necator is associated exclusively with mature leaves. This is the first report of both E. quercicola and E. necator causing cashew powdery mildew, and the first detection of E. necator on cashew.  相似文献   

9.
<正>刺槐(Robinia pseudoacacia L.)又名洋槐,属蝶形花科刺槐属的落叶乔木。原生于北美洲,现被广泛引种到亚洲、欧洲等地。刺槐白粉病是刺槐叶部、嫩枝病害,能降低叶片光合作用,严重的引起叶部畸形、茎尖和枝梢枯死。Braun最早记载中国刺槐白粉病病原菌为Microsphaera subtrichotoma~([1,2])。刺槐白粉病在日本也有报道,引起白粉病的病原菌为Erysiphe  相似文献   

10.
南宁市桑白粉病病原菌种类鉴定   总被引：2，自引：0，他引：2  
桑白粉病是桑树的重要病害,分为桑里白粉病和桑表白粉病。通过形态特征观察和ITS、D1/D2序列分析,明确桑里白粉病的病原菌为桑生球针壳Phyllactinia moricola;桑表白粉病的病原菌为桑白粉菌Erysiphe mori。桑钩丝壳Uncinula mori是桑白粉菌的异名。  相似文献   

11.
The powdery mildew Erysiphe pisi var. pisi, complete with its teleomorph, has been observed on faba beans ( Vicia faba cultivars) for the first time in Britain. It appeared in a glasshouse on Syrian lines of fodder bean and English cultivars of broad bean. It also infected tare ( Vicia sativa ) and sweet pea ( Lathyrus odoratus ), but not edible pea ( Pisum sativum ), ornamental lupin ( Lupinus polyphyllus ), French bean ( Phaseolus vulgaris ) or sainfoin ( Onobrychis viciaefolia ). Inoculations in a glasshouse showed that another strain of E. pisi var. pisi found on outdoor everlasting pea ( Lathyrus latifolius ) was also capable of affecting faba bean, and was distinguished by its ability to infect edible pea. A third strain found on outdoor ornamental lupin infected only lupin. E. pisi var. pisi was shown to be morphologically and pathogenically distinct from the Erysiphe sp. newly affecting tomatoes in Britain.  相似文献   

12.
Podosphaera macularis, the causal agent of hop powdery mildew, is known to produce chasmothecia (formerly cleistothecia) in eastern North America and Europe. Ascocarps have not yet been reported from the Pacific Northwestern region of North America. Reasons for the apparent absence of chasmothecia in the Pacific Northwest were unknown. This study established that P. macularis is heterothallic and ascocarp ontogeny, maturation, dehiscence and ascospore infection proceed similarly to other powdery mildew fungi. Genome sequencing of a MAT1‐1 isolate revealed the structure of the MAT1 locus and presence of MAT1‐1‐3, demonstrating further similarities to other powdery mildew fungi. PCR assays with primers designed from conserved domains of the MAT1 idiomorphs were developed to characterize the frequency of idiomorphs in populations of P. macularis. Amongst 317 samples of P. macularis collected during 2012 and 2013 from the Pacific Northwest only the MAT1‐1 idiomorph was found. In contrast, among 56 samples from the eastern United States and Europe, MAT1‐1 and MAT1‐2 idiomorphs were detected at equivalent frequencies. At temperatures representative of late season conditions in the Pacific Northwest, chasmothecia formed readily when a Pacific Northwest MAT1‐1 isolate was paired with a MAT1‐2 isolate collected from outside the region. Although these findings do not encompass all climatic, geographic or temporal barriers that could inhibit the formation of chasmothecia, the current absence of the ascigerious stage of P. macularis in the Pacific Northwest could be explained by the absence of the MAT1‐2 mating type idiomorph.  相似文献   

13.
To clarify the relationship between the phylogeny and infectivity of isolates of Podosphaera fuliginea s. lat. (= Sphaerotheca fuliginea s. lat.) from cosmos and cucumber, more than 50 powdery mildew isolates from these two plants were subjected to nucleotide sequencing or PCR-RFLP analysis of the rDNA internal transcribed spacer (ITS) region and cross-inoculation tests. The isolates from both cosmos and cucumber are genetically monotypic, and there are six nucleotide substitutions in the rDNA ITS region between isolates from cosmos and cucumber. Cross-inoculation tests of these isolates revealed that isolates from cosmos are not pathogenic on cucumber. Although isolates from cucumber produced conidia on leaves of cosmos in the laboratory, the conidial density was much lower than that from isolates from cosmos. This result, as well as the fact that the cucumber strain was not isolated from cosmos in fields, suggests that isolates from cucumber do not infect cosmos in the field. Therefore, powdery mildews on cosmos and cucumber can be regarded to have become specialized for their hosts both genetically and pathogenically. The present study reconfirms the close relationship between phylogeny and infectivity of powdery mildew fungi. Host specialization may be a trigger that causes genetic divergence of powdery mildew fungi. Received 28 June 2000/ Accepted in revised form 4 September 2000  相似文献   

14.
In 2002, a powdery mildew with catenate conidia lacking fibrosin bodies was found on cucumber in a greenhouse in Kanagawa Prefecture, Japan. Morphological observation revealed that the fungus belongs to Oidium subgenus Reticuloidium, anamorph of the genus Golovinomyces. Molecular phylogenetic analyses of the nucleotide sequences of the rDNA ITS regions and D1/D2 domains of the 28S rDNA indicated that the fungus belongs to the clade of G. orontii with other Golovinomyces fungi from a wide range of host plants, suggesting that the fungus was newly transported from abroad. Because there has been no prior report of cucumber powdery mildew caused by Reticuloidium, further research on the physiology, epidemiology, control and resistant cucumber varieties is required.  相似文献   

15.
Previous works indicated a considerable variation in the pathogenicity, virulence, and host range of Oidium neolycopersici isolates causing tomato powdery mildew epidemics in many parts of the world. In this study, rDNA internal transcribed spacer (ITS) sequences, and amplified fragment length polymorphism (AFLP) patterns were analyzed in 17 O. neolycopersici samples collected in Europe, North America, and Japan, including those which overcame some of the tomato major resistance genes. The ITS sequences were identical in all 10 samples tested and were also identical to ITS sequences of eight previously studied O. neolycopersici specimens. The AFLP analysis revealed a high genetic diversity in O. neolycopersici and indicated that all 17 samples represented different genotypes. This might suggest the existence of either a yet unrevealed sexual reproduction or other genetic mechanisms that maintain a high genetic variability in O. neolycopersici. No clear correlation was found between the virulence and the AFLP patterns of the O. neolycopersici isolates studied. The relationship between O. neolycopersici and powdery mildew anamorphs infecting Aquilegia vulgaris, Chelidonium majus, Passiflora caerulea, and Sedum alboroseum was also investigated. These anamorphs are morphologically indistinguishable from and phylogenetically closely related to O. neolycopersici. The cross-inoculation tests and the analyses of ITS sequences and AFLP patterns jointly indicated that the powdery mildew anamorphs collected from the above mentioned plant species all represent distinct, but closely related species according to the phylogenetic species recognition. All these species were pathogenic only to their original host plant species, except O. neolycopersici which infected S. alboroseum, tobacco, petunia, and Arabidopsis thaliana, in addition to tomato, in cross-inoculation tests. This is the first genome-wide study that investigates the relationships among powdery mildews that are closely related based on ITS sequences and morphology. The results indicate that morphologically indistinguishable powdery mildews that differed in only one to five single nucleotide positions in their ITS region are to be considered as different taxa with distinct host ranges.  相似文献   

16.
Pycnidial fungi belonging to the genus Ampelomyces are common intracellular mycoparasites of powdery mildews worldwide. Some strains have already been developed as commercial biocontrol agents (BCAs) of Erysiphe necator and other powdery mildew species infecting important crops. One of the basic, and still debated, questions concerning the tritrophic relationships between host plants, powdery mildew fungi, and Ampelomyces mycoparasites is whether Ampelomyces strains isolated from certain species of the Erysiphales are narrowly specialized to their original mycohosts or are generalist mycoparasites of many powdery mildew fungi. This is also important for the use of Ampelomyces strains as BCAs. To understand this relationship, the nuclear ribosomal DNA internal transcribed spacer (ITS) and partial actin gene (act1) sequences of 55 Ampelomyces strains from E. necator were analyzed together with those of 47 strains isolated from other powdery mildew species. These phylogenetic analyses distinguished five major clades and strains from E. necator that were present in all but one clade. This work was supplemented with the selection of nine inter-simple sequence repeat (ISSR) markers for strain-specific identification of Ampelomyces mycoparasites to monitor the environmental fate of strains applied as BCAs. The genetic distances among strains calculated based on ISSR patterns have also highlighted the genetic diversity of Ampelomyces mycoparasites naturally occurring in grapevine powdery mildew. Overall, this work showed that Ampelomyces strains isolated from E. necator are genetically diverse and there is no indication of strict mycohost associations in these strains. However, these results cannot rule out a certain degree of quantitative association between at least some of the Ampelomyces lineages identified in this work and their original mycohosts.  相似文献   

17.
This study examines the effects of a vegetable fungicide on sugar beet powdery mildew (Erysiphe betae) and cucumber powdery mildew (Erysiphe cichoracearum). The formulations consisting of a dispersion of Brassicaceae meal in vegetable or mineral oils on infected leaves of sugar beet, reared in the greenhouse, and of musk melons cultivated under plastic tunnels, were tested in comparison to each oil taken separately. Both formulations containing Brassicaceae meals, caused 94% of conidia to be distorted while for the untreated group only 2% were distorted. Furthermore, the leaf area infected by E. betae was 56% for untreated plants and 2.7 and 9.9% respectively, for plants treated with meal containing mineral and vegetable oil. Vegetable oil considered separately or with Brassicaceae meals showed no phytotoxicity, while the formulations based on mineral oil showed a significantly lower fresh and dry weight on tomato plants. The low level or absence of phytotoxicity of plants treated with vegetable oil formulations suggests that to improve the efficacy of powdery mildew control, they could be used mixed with sulphur. The efficiency of the vegetable formulations in the powdery mildew control observed during these trials encourages further investigation on other parasitic fungi and foliar pathogens.  相似文献   

18.
为西北农林科技大学小麦新育成品种（系）在黄淮麦区的大面积推广,该研究对83份西农新育成的小麦品种（系）进行苗期抗条锈病和白粉病鉴定,成株期抗条锈病、白粉病、叶锈病和赤霉病鉴定,并在田间自然环境下对其抗性进行鉴定及对相关抗病基因进行分子检测。结果显示,在苗期人工接种鉴定中,有63、29和16份小麦品种（系）分别对条锈菌Puccinia striiformis f.sp.tritici生理小种CYR32、CYR33和CYR34表现出抗性,9份小麦品种（系）对3个条锈菌生理小种均表现出抗性;有10、3和0份小麦品种（系）分别对白粉菌Blumeria graminis f.sp.tritici生理小种E15、E09和A13表现出抗性。在成株期人工接种鉴定中,有23、15、28和62份小麦品种（系）分别对条锈病、白粉病、叶锈病和赤霉病表现出抗性。在83份小麦品种（系）中有6份在苗期和成株期均对小麦条锈病表现出抗性。在田间抗性鉴定中,有57、6、65和40份小麦品种（系）分别对条锈病、白粉病、赤霉病及叶锈病表现出抗性。在83份小麦品种（系）中,3份含有Yr5基因,22份含有Yr9基因,3份含有Yr17基因,2份含有Pm24基因,14份含有Lr1基因,所占比例分别为3.6%、26.5%、3.6%、2.4%和16.8%。  相似文献   

19.
Hazelnut (Corylus avellana) is Turkey’s most valuable agricultural export, and an essential source of income for many families in the Black Sea Region. In spring 2013, hazelnut leaves, fruit clusters and shoots showing powdery mildew infection symptoms different from those observed previously were discovered in Giresun, Ordu and Trabzon provinces of Turkey. The disease has become epidemic throughout all hazelnut production areas spreading from east to west of the Black Sea Region over the subsequent years. Erysiphe corylacearum was identified as the causal agent of this new and highly destructive powdery mildew based on its morphological characteristics and analyses of DNA sequences of the internal transcribed spacer (ITS) and 28S regions of the ribosomal DNA. Pathogenicity of this species was examined in an infection test and proven for the first time. To our knowledge, this is the first report of E. corylacearum on Corylus avellana worldwide.  相似文献   

20.
利用28S rDNA D1/D2区和ITS rDNA序列鉴定甜瓜白粉病病原菌   总被引：2，自引：2，他引：0  
为了明确宁夏干旱带压砂甜瓜白粉病病原菌,从病原菌分生孢子中提取DNA,PCR扩增ITSrDNA和28S rDNA D1/D2区段,测序后进行BLAST比对.结果表明,病原菌的ITS rDNA和28SrDNA D1/D2序列与菜豆叉丝单囊壳白粉菌Podosphaera phaseoli、凤仙花又丝单囊壳白粉菌P.bal-saminae、菊科叉丝单囊壳白粉菌P.fwca、苍耳单囊壳白粉菌P.xanthii、瓜类单囊壳白粉菌P.fuligi-nea等叉丝单囊壳属Podosphaera的多个种的ITS rDNA和28S rDNA D1/D2序列之间相似度均大于99%,鉴定甜瓜白粉病病原菌为叉丝单囊壳属Podosphaera.  相似文献   

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