Studies of the powdery-mildew fungus, Leveillula taurica, on green pepper. II. Light and electron microscopic observation of the infection process

1979 ◽  
Vol 57 (22) ◽  
pp. 2501-2508 ◽  
Author(s):  
Hitoshi Kunoh ◽  
Mitsuru Kohno ◽  
Sadayoshi Tashiro ◽  
Hiroshi Ishizaki
Keyword(s):  
Powdery Mildew ◽  
Light And Electron Microscopy ◽  
Host Cells ◽  
Outer Cell ◽  
Lipid Bodies ◽  
Powdery Mildew Fungus ◽  
Green Pepper ◽  
Ultrastructural Studies ◽  
Leveillula Taurica ◽  
Powdery Mildew Fungi

Almost all ultrastructural studies of powdery-mildew fungi have been focused on the epiparasitic fungi. In this paper, one of the endoparasitic powdery-mildew fungi, Leveillula taurica (Lev.) Arn., on green pepper (Capsicum annuum L. var. angulosum Mill.) leaves was investigated by light and electron microscopy. Most germinated conidia formed a lobed adhesion body (similar to the appressorium in morphology but different in function) before stomatal invasion. The track of the adhesion body on the leaf epidermis was depressed, and no cuticular perforations were observed in it. After stomatal invasion, infection hyphae grew extensively into the intercellular spaces of the leaves and formed haustoria in the spongy- and palisade-parenchyma cells. The haustorium was flask shaped with a neck arising from the intercellular hypha. The overall profiles of the haustorium resembled those of epiphytic powdery-mildew fungi of other authors; the haustorium was composed of a nucleate central body and many anucleate lobes, and the entire structure was bounded by an extrahaustorial membrane. Papillae consisting of three distinct regions formed against the outer cell walls at the site of penetration. The most obvious alteration in infected host cells was a marked increase in the number of large lipid bodies. Lipid bodies increased in number with time after haustorial formation. They appeared first in the host cytoplasm near the extrahaustorial membrane, then in the extrahaustorial matrix and haustorial body.

scholarly journals The partial duplication of an E3-ligase gene in Triticeae species mediates resistance to powdery mildew fungi

2017 ◽  
Author(s):  
Jeyaraman Rajaraman ◽  
Dimitar Douchkov ◽  
Stefanie Lück ◽  
Götz Hensel ◽  
Daniela Nowara ◽  
...  
Keyword(s):  
Powdery Mildew ◽  
E3 Ligase ◽  
Defense Responses ◽  
Duplication Event ◽  
Stable Gene ◽  
Cellular Functions ◽  
Powdery Mildew Fungus ◽  
Crop Species ◽  
Powdery Mildew Fungi ◽  
Plant Pathogen Interactions

ABSTRACTIn plant-pathogen interactions, components of the plant ubiquitination machinery are preferred targets of pathogen-encoded effectors suppressing defense responses or co-opting host cellular functions for accommodation. Here, we employed transient and stable gene silencing-and over-expression systems in Hordeum vulgare (barley) to study the function of HvARM1 (for H. vulgare Armadillo 1), a partial gene duplicate of the U-box/armadillo-repeat E3 ligase HvPUB15 (for H. vulgare Plant U-Box 15). The partial ARM1 gene was derived from an ancient gene-duplication event in a common ancestor of the Triticeae tribe of grasses comprising the major crop species H. vulgare, Triticum aestivum and Secale cereale. The barley gene HvARM1 contributed to quantitative host as well as nonhost resistance to the biotrophic powdery mildew fungus Blumeria graminis, and allelic variants were found to be associated with powdery mildew-disease severity. Both HvPUB15 and HvARM1 proteins interacted in yeast and plant cells with the susceptibility-related, plastid-localized barley homologs of THF1 (for Thylakoid formation 1) and of ClpS1 (for Clp-protease adaptor S1) of Arabidopsis thaliana. The results suggest a neo-functionalization HvARM1 to increase resistance against powdery mildew and provide a link to plastid function in susceptibility to biotrophic pathogen attack.

scholarly journals Characterization of Powdery Mildew Caused by Leveillula taurica on Calla Lily in California

Plant Disease ◽  
2002 ◽  
Vol 86 (2) ◽  
pp. 187-187 ◽  
Author(s):  
S. T. Koike ◽  
P. Beckman
Keyword(s):  
Powdery Mildew ◽  
Cross Sections ◽  
Late Summer ◽  
Tomato Plants ◽  
Leveillula Taurica ◽  
Calla Lily ◽  
Initial Symptoms ◽  
Humidity Chamber ◽  
Advanced Stages ◽  
Powdery Mildew Fungi

Spring calla lily (Zantedeschia spp.), also known as colored or miniature calla, has markedly increased in popularity in recent years, and the production acreage in the central coast counties of California (Monterey, Santa Cruz, and San Benito), therefore, has significantly increased. Commercial plantings of calla lily (Z. albo maculata and Z. rehmannii hybrids) in California have been infected with a powdery mildew for several years, with the disease particularly evident in late summer and fall. In 2001, powdery mildew was again prevalent, and the pathogen was examined in detail. Initial symptoms consisted of chlorotic, circular-to-oval leaf lesions with diffuse margins. As the disease progressed, white sporulation became visible on lesions. In advanced stages of the disease, the center tissue of lesions turned necrotic. For any such lesion, both the corresponding adaxial and abaxial sides of the leaf always exhibited the symptoms of the disease and developed sporulation of the pathogen. Epidermal strips from both sides of leaves and leaf cross sections were mounted in drops of lactophenol and aniline blue and examined with a light microscope. These preparations showed that epiphytic mycelium was absent and all conidiophores developed from endophytic mycelium and emerged through stomata. Conidiophores carried single or sometimes two conidia and were sometimes branched. Hyaline, single-celled conidia were dimorphic. Primary (terminal) conidia were lanceolate with distinct apical points and measured (58-) 67 to 78 (-81) × 14 to 22 μm. Secondary conidia were ellipsoid-cylindric and measured (56-) 58 to 72 × 17 to 22 μm. For both conidial types, length to width ratios were greater than three. Based on these characters, the pathogen was identified as Leveillula taurica (anamorph Oidiopsis taurica). Cleistothecia were not observed. To test whether the calla lily pathogen could infect another known host of L. taurica, diseased calla lily leaves were gently pressed against leaves of potted tomato (Lycopersicon esculentum) plants (2). Inoculated tomato plants were kept in a humidity chamber for 48 h and maintained in a greenhouse (24 to 26°C). After 12 days, chlorotic lesions appeared on inoculated tomato leaves, and sporulation of L. taurica was observed on the lesions. Uninoculated control tomato plants did not develop powdery mildew. To our knowledge, this is the first report of powdery mildew, caused by L. taurica, on calla lily in North America. This disease has been reported on calla lily in South Africa, Spain, Taiwan, Turkey, and Zimbabwe (1,3,4). References: (1) Y.-K. Chen et al. Ann. Phytopathol. Soc. Jpn. 62:580, 1996. (2) J. C. Correll et al. Plant Dis. 71:248, 1987. (3) K. A. Hirata. Host Range and Geographic Distribution of the Powdery Mildew Fungi. Japan Scientific Society Press, Tokyo, 1986. (4) E. Sezgin et al. J. Turkish Phytopathol. 13:111, 1984.

scholarly journals Host-Induced Gene Silencing in Barley Powdery Mildew Reveals a Class of Ribonuclease-Like Effectors

2013 ◽  
Vol 26 (6) ◽  
pp. 633-642 ◽  
Author(s):  
Clara Pliego ◽  
Daniela Nowara ◽  
Giulia Bonciani ◽  
Dana M. Gheorghe ◽  
Ruo Xu ◽  
...  
Keyword(s):  
Powdery Mildew ◽  
Gene Silencing ◽  
Transcript Abundance ◽  
Powdery Mildew Fungus ◽  
Host Cell Death ◽  
Barley Powdery Mildew ◽  
Biotrophic Pathogens ◽  
Powdery Mildew Fungi ◽  
Bona Fide ◽  
Do So

Obligate biotrophic pathogens of plants must circumvent or counteract defenses to guarantee accommodation inside the host. To do so, they secrete a variety of effectors that regulate host immunity and facilitate the establishment of pathogen feeding structures called haustoria. The barley powdery mildew fungus Blumeria graminis f. sp. hordei produces a large number of proteins predicted to be secreted from haustoria. Fifty of these Blumeria effector candidates (BEC) were screened by host-induced gene silencing (HIGS), and eight were identified that contribute to infection. One shows similarity to β-1,3 glucosyltransferases, one to metallo-proteases, and two to microbial secreted ribonucleases; the remainder have no similarity to proteins of known function. Transcript abundance of all eight BEC increases dramatically in the early stages of infection and establishment of haustoria, consistent with a role in that process. Complementation analysis using silencing-insensitive synthetic cDNAs demonstrated that the ribonuclease-like BEC 1011 and 1054 are bona fide effectors that function within the plant cell. BEC1011 specifically interferes with pathogen-induced host cell death. Both are part of a gene superfamily unique to the powdery mildew fungi. Structural modeling was consistent, with BEC1054 adopting a ribonuclease-like fold, a scaffold not previously associated with effector function.

scholarly journals The Parauncinula polyspora Draft Genome Provides Insights into Patterns of Gene Erosion and Genome Expansion in Powdery Mildew Fungi

mBio ◽  
2019 ◽  
Vol 10 (5) ◽  
Author(s):  
Lamprinos Frantzeskakis ◽  
Márk Z. Németh ◽  
Mirna Barsoum ◽  
Stefan Kusch ◽  
Levente Kiss ◽  
...  
Keyword(s):  
Powdery Mildew ◽  
Defense Mechanism ◽  
Repetitive Sequences ◽  
Draft Genome ◽  
Model Systems ◽  
Powdery Mildew Fungus ◽  
Evolutionary Trajectory ◽  
Reproduction Strategy ◽  
Powdery Mildew Fungi ◽  
Fungal Genes

ABSTRACT Due to their comparatively small genome size and short generation time, fungi are exquisite model systems to study eukaryotic genome evolution. Powdery mildew fungi present an exceptional case because of their strict host dependency (termed obligate biotrophy) and the atypical size of their genomes (>100 Mb). This size expansion is largely due to the pervasiveness of transposable elements on 70% of the genome and is associated with the loss of multiple conserved ascomycete genes required for a free-living lifestyle. To date, little is known about the mechanisms that drove these changes, and information on ancestral powdery mildew genomes is lacking. We report genome analysis of the early-diverged and exclusively sexually reproducing powdery mildew fungus Parauncinula polyspora, which we performed on the basis of a natural leaf epiphytic metapopulation sample. In contrast to other sequenced species of this taxonomic group, the assembled P. polyspora draft genome is surprisingly small (<30 Mb), has a higher content of conserved ascomycete genes, and is sparsely equipped with transposons (<10%), despite the conserved absence of a common defense mechanism involved in constraining repetitive elements. We speculate that transposable element spread might have been limited by this pathogen’s unique reproduction strategy and host features and further hypothesize that the loss of conserved ascomycete genes may promote the evolutionary isolation and host niche specialization of powdery mildew fungi. Limitations associated with this evolutionary trajectory might have been in part counteracted by the evolution of plastic, transposon-rich genomes and/or the expansion of gene families encoding secreted virulence proteins. IMPORTANCE Powdery mildew fungi are widespread and agronomically relevant phytopathogens causing major yield losses. Their genomes have disproportionately large numbers of mobile genetic elements, and they have experienced a significant loss of highly conserved fungal genes. In order to learn more about the evolutionary history of this fungal group, we explored the genome of an Asian oak tree pathogen, Parauncinula polyspora, a species that diverged early during evolution from the remaining powdery mildew fungi. We found that the P. polyspora draft genome is comparatively compact, has a low number of protein-coding genes, and, despite the absence of a dedicated genome defense system, lacks the massive proliferation of repetitive sequences. Based on these findings, we infer an evolutionary trajectory that shaped the genomes of powdery mildew fungi.

First Report of Powdery Mildew on Potato Caused by Leveillula taurica in North America

2004 ◽  
Vol 5 (1) ◽  
pp. 15 ◽  
Author(s):  
Dean A. Glawe ◽  
Lindsey J. du Toit ◽  
Gary Q. Pelter
Keyword(s):  
North America ◽  
Middle East ◽  
Powdery Mildew ◽  
Russet Burbank Potato ◽  
Russet Burbank ◽  
The Other ◽  
Leveillula Taurica ◽  
Powdery Mildew Fungi ◽  
First Time ◽  
Made In

In August 2004, examination of powdery mildew-infected ‘Russet Burbank’ potato leaves from a furrow-irrigated field in Grant Co., WA, revealed two powdery mildew fungi, one referable to Erysiphe orontii and the other to Leveillula taurica (Lév.) G. Arnaud. Discovery of the two species sporulating together on diseased leaves is consistent with an observation made in the Middle East. This report documents, for the first time, L. taurica on potato in N. America and provides information on distinguishing it from E. orontii. Accepted for publication 9 December 2004. Published 14 December 2004.

scholarly journals Development and ultrastructure observations of secondary hyphae of Podosphaera leucotricha on apple cultivars of varying susceptibility to powdery mildew

2017 ◽  
Vol 38 (SI 2 - 6th Conf EFPP 2002) ◽  
pp. 425-428
Author(s):  
E. Rakhimova
Keyword(s):  
Electron Microscopy ◽  
Powdery Mildew ◽  
Light And Electron Microscopy ◽  
Dense Material ◽  
Podosphaera Leucotricha ◽  
Powdery Mildew Fungus ◽  
Full Complement ◽  
Apple Cultivars ◽  
Host Parasite

The development and ultrastructure feature of secondary hyphae of Podosphaera leucotricha were studied using light and electron microscopy. The percentage of development and length of secondary hyphae, differed in compatible and incompatible combinations. In compatible host-parasite combinations, hyphal cells of powdery mildew fungus contained a full complement of fungal organelles. There were differences of hyphal ultrastructure in compatible and incompatible host-parasite combinations, the main one was the appearance of dense material inside the nucleus, in the cytoplasm, and a few mitochondria.

scholarly journals Infection of papaya (Carica papaya) by four powdery mildew fungi

2021 ◽  
Vol 60 (1) ◽  
pp. 37-49
Author(s):  
Diána SERESS ◽  
Gábor M. KOVÁCS ◽  
Orsolya MOLNÁR ◽  
Márk Z. NÉMETH
Keyword(s):  
Powdery Mildew ◽  
New Record ◽  
Species Complex ◽  
Carica Papaya ◽  
Phylogenetic Analyses ◽  
Molecular Taxonomy ◽  
Podosphaera Xanthii ◽  
Powdery Mildew Fungus ◽  
Molecular Phylogenetic ◽  
Powdery Mildew Fungi

Papaya (Carica papaya L.) is an important fruit crop in many tropical and subtropical countries. Powdery mildew commonly affects this host, causing premature leaf loss, reduced yields and poor fruit quality. At least fifteen different fungi have been identified as the causal agents of papaya powdery mildew. Powdery mildew symptoms were detected on potted papaya plants growing in two locations in Hungary. This study aimed to identify the causal agents. Morphology of powdery mildew samples was examined, and sequences of two loci were used for molecular taxonomic identifications. Only anamophs were detected in all samples, and four morphological types were distinguished. Most samples had Pseudoidium anamorphs, while some were of the Fibroidium anamorph. Based on morphology and molecular taxonomy, the Fibroidium anamorph  was identified as Podosphaera xanthii. The Pseudoidium anamorphs corresponded to three different Erysiphe species: E. cruciferarum, E. necator and an unidentified Erysiphe sp., for which molecular phylogenetic analyses showed it belonged to an unresolved species complex of E. malvae, E. heraclei and E. betae. Infectivity of P. xanthii and E. necator on papaya was verified with cross inoculations. A review of previous records of powdery mildew fungi infecting papaya is also provided. Podosphaera xanthii was known to infect, and E. cruciferarum was suspected to infect Carica papaya, while E. necator was recorded on this host only once previously. No powdery mildew fungus belonging to the E. malvae/E. heraclei/E. betae species complex is known to infect papaya or any other plants in the Caricaceae, so the unidentified Erysiphe sp. is a new record on papaya and the Caricaceae. This study indicates host range expansion of this powdery mildew fungus onto papaya.

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