Defence reactions of Hordeum chilense accessions to three formae speciales of cereal powdery mildew fungi

2000 ◽  
Vol 78 (12) ◽  
pp. 1561-1570 ◽  
Author(s):  
D Rubiales ◽  
T LW Carver
Keyword(s):  
Powdery Mildew ◽  
Leaf Surface ◽  
Penetration Resistance ◽  
Blumeria Graminis ◽  
Epidermal Cells ◽  
Hordeum Chilense ◽  
Adult Plant ◽  
Formae Speciales ◽  
Abaxial Leaf Surface ◽  
Stomatal Complexes

The histology of resistance to infection by Blumeria graminis DC Speer f.sp. hordei, Blumeria graminis f.sp. tritici, and Blumeria graminis f.sp. avenae was studied in 15 accession lines of Hordeum chilense. All were highly resistant to all formae speciales. There were small differences in spore germination rates and the morphological normality of germlings formed on the different lines. Relatively large differences between accessions were detected in terms of penetration resistance and the frequency with which attacked epidermal cells died. Greater penetration resistance was expressed by epidermal cells of the seventh-formed leaves than by earlier leaves, indicating that penetration resistance is a component of adult plant resistance in H. chilense. Epidermal cells overlying vascular tissues (long epidermal cells) were more resistant to penetration than cells adjacent or close to stomatal complexes. In a limited examination involving two accession lines, epidermal cells on the abaxial leaf surface of one line were more penetration resistant than those on the adaxial surface; the other line was highly resistant on both surfaces. However, in the few cases where long cells and abaxial cells were penetrated, the frequency of associated cell death was lower than in short cells or on the adaxial leaf surface. This is consistent with the macroscopic observation that the few colonies formed on H. chilense were often close to the mid-rib and more frequent on the abaxial leaf surface. The data support the view that H. chilense offers a valuable source of powdery mildew resistance for cultivated cereals.Key words: Blumeria graminis, Erysiphe graminis, powdery mildew, disease resistance, histology, Hordeum chilense.

scholarly journals Superoxide and Hydrogen Peroxide Play Different Roles in the Nonhost Interaction of Barley and Wheat with Inappropriate formae speciales of Blumeria graminis

2004 ◽  
Vol 17 (3) ◽  
pp. 304-312 ◽  
Author(s):  
Marco Trujillo ◽  
Karl-Heinz Kogel ◽  
Ralph Hückelhoven
Keyword(s):  
Hydrogen Peroxide ◽  
Host Defense ◽  
Superoxide Anion ◽  
Penetration Resistance ◽  
Blumeria Graminis ◽  
Microscopic Level ◽  
Hypersensitive Cell Death ◽  
Formae Speciales ◽  
Cell Death Response ◽  
Wall Appositions

Nonhost resistance of cereals to inappropriate formae speciales of Blumeria graminis is little understood. However, on the microscopic level, nonhost defense to B. graminis is reminiscent of host defense preventing fungal development by penetration resistance and the hypersensitive cell death response (HR). We analyzed histochemically the accumulation of superoxide anion radicals (O2•¯) and hydrogen peroxide (H2O2) at sites of B. graminis attack in nonhost barley and wheat. Superoxide visualized by subcellular reduction of nitroblue tetrazolium accumulated in association with successful fungal penetration in attacked cells and in cells neighboring HR. In contrast, H2O2 accumulated in cell wall appositions beneath fungal penetration attempts or in the entire epidermal cell during HR. The data provide evidence for different roles and sources of superoxide and H2O2 in the nonhost interaction of cereals with inappropriate formae speciales of B. graminis.

scholarly journals Effect of Fungicide Mobility and Application Timing on the Management of Grape Powdery Mildew

Plant Disease ◽  
2020 ◽  
Vol 104 (4) ◽  
pp. 1167-1174 ◽  
Author(s):  
Brent Warneke ◽  
Lindsey D. Thiessen ◽  
Walter F. Mahaffee
Keyword(s):  
Powdery Mildew ◽  
Leaf Surface ◽  
Quality Standards ◽  
Pinot Noir ◽  
Abaxial Surface ◽  
Phenological Stages ◽  
Application Timing ◽  
Abaxial Leaf Surface ◽  
Detached Leaves ◽  
Grape Powdery Mildew

Grape powdery mildew (GPM) fungicide programs consist of 5 to 15 applications, depending on region or market, in an attempt to achieve the high fruit quality standards demanded by the market. Understanding how fungicides redistribute and targeting redistributing fungicide to critical crop phenological stages could improve fungicide protection of grape clusters. This study evaluated fungicide redistribution in grapevines from major fungicide groups labeled for GPM control. Translaminar and xylem redistribution was examined by placing fungicide-impregnated filter disks on the adaxial or abaxial leaf surface of detached leaves for 10 min and then incubating for 48 h before inoculating the abaxial surface with conidia. Vapor redistribution used Teflon disks sprayed with fungicides and placed on the abaxial leaf surface of detached leaves 48 h before inoculation. Disease development was rated 10 days later. Translaminar movement through calyptra was tested using flowering potted vines. All fungicides tested redistributed through at least one mechanism. Fungicide timing at critical phenological stages (early, mid, and late bloom) was assessed in small plots of cultivar Pinot noir vines. The application of trifloxystrobin, quinoxyfen, or fluopyram at different bloom stages showed that applications initiated at end of bloom resulted in the lowest berry infection probabilities of 0.073, 0.097, and 0.020, respectively. The results of this study suggest that integrating two carefully timed applications of redistributing fungicides initiated at end of bloom into a fungicide program may be an effective strategy for wine grape growers in western Oregon to produce fruit with low GPM infection.

scholarly journals Structures of Heracleum sosnovskii Manden. stem and leaves releasing photodermatosis-causing substances

2012 ◽  
Vol 67 (4) ◽  
pp. 25-32 ◽  
Author(s):  
Elżbieta Weryszko-Chmielewska ◽  
Mirosława Chwil
Keyword(s):  
Fluorescence Microscopy ◽  
Human Skin ◽  
Leaf Surface ◽  
Epidermal Cells ◽  
Secretory Structures ◽  
Intense Fluorescence ◽  
Abaxial Leaf Surface ◽  
Stems And Leaves

In its stems and leaves, <em>Heracleum sosnovskii</em> Manden. contains furanocoumarins, which exert a phototoxic effect on humans. The aim of the investigations was to describe the external secretory structures of the epidermis and internal secretory tissues in organs responsible for emission of secretion that is toxic to human skin. The study was conducted using light and fluorescence microscopy. On the stems and leaves, various types of secretory trichomes with dispersed or deposited secretion were found. The trichomes were most abundant on the abaxial leaf surface. Epidermal cells and the secretion present on the trichomes exhibited intense fluorescence, which may indicate the presence of furanocoumarins in the tissue and trichome secretions.

scholarly journals First Report of Powdery Mildew of Greenhouse Pepper Caused by Leveillula taurica in Canada

Plant Disease ◽  
1999 ◽  
Vol 83 (8) ◽  
pp. 781-781 ◽  
Author(s):  
R. F. Cerkauskas ◽  
J. Brown ◽  
G. Ferguson ◽  
S. Khosla
Keyword(s):  
Powdery Mildew ◽  
Leaf Surface ◽  
Morphological Characteristics ◽  
Chili Pepper ◽  
Width Ratio ◽  
Old Field ◽  
First Report ◽  
Leveillula Taurica ◽  
Plastic Bags ◽  
Abaxial Leaf Surface

In 1999, powdery mildew on cvs. Oberon and Triple 4 of greenhouse pepper (Capsicum annum L.) and cv. FireFlame of chili pepper was reported simultaneously in two commercial greenhouses at two separate locations, Leamington and Vineland, geographically separated by 290 km, in southern Ontario. Losses of 10 to 15% each in the 2 and 3.1 ha greenhouse pepper operations were noted. The greenhouse pepper industry in Canada consists of 89.4 ha with sales of $43.6 million (Canadian). Lesions appeared as a white, powdery coating on the abaxial leaf surface only, generally on the lower foliage of pepper plants, while diffuse chlorotic spots were present at corresponding locations on the adaxial surface. In chili pepper, this chlorosis was restricted to interveinal tissue, causing the leaves to have a somewhat netted appearance. In some cases, pale yellow spots appeared on the adaxial portion of the affected foliage during later stages of disease development. No cleistothecia were observed. Pyriform and cylindrical, hyaline, single-celled conidia were present in equal numbers. Both conidia had a network of crests and granules containing tiny, thornlike projections on the surface. These projections were also evident on the lower half of conidiophores. Pyriform conidia ranged in length from 61.6 to 84.0 μm (mean = 70.8, SE = 0.7) and in width from 14.0 to 25.8 μm (mean = 21.1, SE = 0.4, n = 50), with a mean length to width ratio of 3.4. Cylindrical conidia ranged in length from 54.9 to 80.1 μm (mean = 66.3, SE = 0.9) and in width from 15.7 to 24.1 μm (mean = 18.6, SE = 0.3, n = 50), with a mean length to width ratio of 3.1. Short conidial chains borne on conidiophores consisted of a pyriform conidium first followed by cylindrical conidium. Stomatal penetration and extensive endophytic mycelial growth in the mesophyll layer were evident in foliar tissue cleared with glacial acetic acid:EtOH (1:2) and stained with lactophenol cotton blue. To confirm pathogenicity, conidia from infected pepper leaves were dusted onto the water-misted abaxial leaf surface of 41-day-old greenhouse pepper cvs. Cubico and Edison, and onto the similarly treated adaxial leaf surface of 58-day-old field pepper cv. Renegade. Plants were enclosed in plastic bags for 24 h on a bench. Control plants were treated identically but not inoculated. Inoculated plants developed foliar powdery mildew symptoms, including sporulation similar to that of naturally infected plants. Occurrence of the fungus on the abaxial surface of pepper foliage, presence of endophytic mycelium, and the morphological characteristics of the imperfect state confirm the identity of the fungus. This is the first report of Leveillula taurica (Lév.) G. Arnaud on pepper in Canada. Reference: J. Palti. Bot. Rev. 54:423, 1988.

scholarly journals Leaf surface of two understorey shrubs Rudgea Decipiens Müll. Arg. and Rudgea macrophylla Benth. (Rubiaceae)

Rodriguésia ◽  
1993 ◽  
Vol 45-49 (71-75) ◽  
pp. 7-13 ◽  
Author(s):  
André Mantovani ◽  
Ricardo Cardoso Vieira
Keyword(s):  
Environmental Factors ◽  
Atlantic Forest ◽  
Leaf Surface ◽  
Epidermal Cells ◽  
Surface Features ◽  
Unusual Pattern ◽  
Abaxial Leaf Surface ◽  
Surface Correlations

ABSTRACT MICROMORPHOLOGICAL CHARACTERISTICS OF LEAF SURFACE OF TWO SPECIES OF RUDGEA ARE PRESENTED. THE STUDY WAS BASED ON MATERIAL FROM THE UNDERSTOREY OF ATLANTIC FOREST. SPECIAL ATTENTION IS PAID TO THE OCCURENCE OF SMOOTH AND STRIATED CUTICLE, TO PARACYTIC STOMATA,(SOME OF WHICH EXIHBIT AN UNUSUAL PATTERN IN THE ARRANGEMENT OF THE SURROUNDING EPIDERMAL CELLS) AND TO PAPILLAE, WHICH ARE IRREGULARLY DISTRIBUTED ON THE ABAXIAL LEAF SURFACE. CORRELATIONS BETWEEN THE LEAF SURFACE FEATURES AND ENVIRONMENTAL FACTORS ARE DISCUSSED.

Micromorphology of Johnsongrass (Sorghum halepense) Leaves

Weed Science ◽  
1993 ◽  
Vol 41 (4) ◽  
pp. 583-589 ◽  
Author(s):  
Chester G. Mcwhorter ◽  
Clark Ouzts ◽  
Rex N. Paul
Keyword(s):  
Leaf Surface ◽  
Epicuticular Wax ◽  
Epidermal Cells ◽  
Sorghum Halepense ◽  
Single Type ◽  
Cork Cell ◽  
Silica Cell ◽  
Stomatal Complexes ◽  
Epicuticular Wax Crystals ◽  
Wax Crystals

Adaxial and abaxial epidermal surfaces of johnsongrass leaves were studied to determine which cells contribute to leaf microroughness. Cork-silica cell (CSC) pairs, three types of prickles, macrohairs, bicellular trichomes, stomata, and ordinary short and long epidermal cells were found and described. CSC pairs made up about 22% of all cells and probably contribute more to microroughness than any other single type because each cork cell produces 11 ± 3 wax filaments that are up to 100 μm long. Bicellular trichomes represented 4 to 5% of the total cells but decreased leaf roughness by secreting a type of mucilage that covers microscopic wax crystals. Stomatal complexes comprised 15 to 18% of all cells and contributed to leaf roughness because they are slightly recessed below the leaf surface. Long prickles occur primarily over veins and represent less than 1% of all cells. Small prickles were present primarily on adaxial surfaces and represent only 3% of all cells. Macrohairs were the largest appendages, 237 ± 104 μm, but they represent far less than 1% of all cells and occur primarily over veins. Ordinary short cells comprised 6 to 13% of all cells. Long cells were most common (41%) of all cells. Short and long cells contribute to leaf roughness because the surface is often convex. A typical johnsongrass leaf may contain more than 25 million appendages on each surface that increase the roughness already caused by epicuticular wax crystals.

scholarly journals The Barley Apoptosis Suppressor Homologue Bax Inhibitor-1 Compromises Nonhost Penetration Resistance of Barley to the Inappropriate Pathogen Blumeria graminis f. sp. tritici

2004 ◽  
Vol 17 (5) ◽  
pp. 484-490 ◽  
Author(s):  
Ruth Eichmann ◽  
Holger Schultheiss ◽  
Karl-Heinz Kogel ◽  
Ralph Hückelhoven
Keyword(s):  
Cell Death ◽  
Laser Scanning ◽  
Penetration Resistance ◽  
Suppressor Gene ◽  
Blumeria Graminis ◽  
Epidermal Cells ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Over Expression ◽  
Enhanced Expression

BAX inhibitor-1 (BI-1) proteins have been characterized as suppressors of programmed cell death in mammals and plants. The barley BI-1 is a suppressor of nonspecific background resistance and mlo-mediated penetration resistance to the biotrophic fungal pathogen Blumeria graminis f. sp. hordei when overexpressed in epidermal cells of barley. We report here that BI-1 expression is also slightly up-regulated during interaction with the inappropriate wheat pathogen Blumeria graminis f. sp. tritici. Significantly, over-expression of BI-1 in single epidermal cells of barley by microprojectile-mediated transformation rendered cells susceptible to penetration by inappropriate B. graminis f. sp. tritici. The degree of transgene-induced accessibility to B. graminis f. sp. tritici was thereby similar to the effect achieved by overexpression of the defense suppressor gene Mlo and could not be further enhanced by double expression of both BI-1 and Mlo. Confocal laser scanning microscopy was used to locate a functional green fluorescing GFP:BI-1 fusion protein in endomembranes and the nuclear envelope of barley epidermal cells. Together, enhanced expression of barley BI-1 suppresses penetration resistance to B. graminis f. sp. tritici, linking barley nonhost resistance with cell death regulation.

scholarly journals First Report of Powdery Mildew of Kenaf Caused by Leveillula taurica in South Africa

Plant Disease ◽  
2001 ◽  
Vol 85 (8) ◽  
pp. 923-923
Author(s):  
W. J. Swart ◽  
J. Terblanche
Keyword(s):  
South Africa ◽  
Powdery Mildew ◽  
Seed Quality ◽  
Leaf Surface ◽  
Hibiscus Cannabinus ◽  
First Report ◽  
Leveillula Taurica ◽  
Abaxial Leaf Surface ◽  
Extensive Growth ◽  
Northwest Province

Kenaf (Hibiscus cannabinus L.) is a fast-growing, bamboo-like annual plant belonging to the Malvaceae. The stem, which ranges from 1.5 to 4 m, presents a source of high-quality cellulose fibers. The plant is being investigated in South Africa with a view to commercial production. In April 2001, at least 50% of 4- to 5-month-old kenaf plants grown from seed in trials near Rustenburg, Northwest Province, South Africa, were observed as having powdery mildew. Signs included extensive growth of white, superficial mycelium and emergent conidiophores on the abaxial leaf surface, followed by partial defoliation. On older leaves, the abaxial leaf surface was completely covered by powdery mildew, and chlorotic and necrotic patches were clearly visible on the adaxial surface. Symptoms were observed on all five planted cultivars (Everglades 41, Cuba 108, El Salvador, SF459, and Tainung 2), and no difference in disease severity was noted among cultivars. Leveillula taurica (Lév.) Arnaud (anamorph Oidiopsis taurica [Lév.] Salmon) was subsequently identified by the presence of endophytic mycelia, often branched conidiophores, and dimorphic conidia borne singly or in short chains (1). In 100 measurements of each type, pyriform conidia averaged 69 ± 5 × 18 ± 2 μm and cylindrical conidia averaged 62 ± 6 × 16 ± 2 μm. The teleomorph was not observed. The source of L. taurica for this reported outbreak is unknown, and powdery mildew was not observed in a field of mature cotton (Gossypium hirsutum L.) growing within 10 m of the kenaf plot. L. taurica was reported on kenaf in Texas in 1992 (2) and in Italy in 1995 (3). The pathogen can cause significant losses in seed yield and reduce seed quality in susceptible kenaf cultivars. Although L. taurica has been reported from Hibiscus sabdariffa in Egypt (4), to our knowledge this is the first report of the pathogen occurring on kenaf in Africa. References: (1) H. J. Boesewinkel. Bot Rev. 46:167, 1980. (2) C. G. Cook and J. L. Riggs. Plant Dis. 79:968, 1995. (3) S. Frisullo et al. Inf. Fitopatol. 45:37–41, 1995. (4) M. Khairy, et al. Phytopathol. Medit. 10:269–271, 1971.

scholarly journals Barley RIC157 is involved in RACB-mediated susceptibility to powdery mildew

2019 ◽  
Author(s):  
Stefan Engelhardt ◽  
Michaela Kopischke ◽  
Johanna Hofer ◽  
Katja Probst ◽  
Christopher McCollum ◽  
...  
Keyword(s):  
Powdery Mildew ◽  
Fungal Infection ◽  
G Protein ◽  
Blumeria Graminis ◽  
Epidermal Cells ◽  
Scaffold Proteins ◽  
Cell Periphery ◽  
Dependent Manner ◽  
Susceptibility Function

AbstractSuccessful pathogens often benefit from certain cellular host processes. For the biotrophic ascomycete fungus Blumeria graminis f.sp. hordei (Bgh) it has been shown that barley RACB, a small monomeric G-protein (ROP, RHO of plants), is required for full susceptibility to fungal penetration. The susceptibility function of RACB probably lies in its role in cell polarisation, which may be co-opted by the pathogen for invasive ingrowth of its haustorium. However, the actual mechnism of how RACB supports the fungal penetration success is little understood. RIC proteins are considered scaffold proteins which can interact directly with ROPs via a conserved CRIB motif. Here we describe a yet uncharacterised RIC protein, RIC157, which can interact directly with RACB. We could show that RIC157 undergoes a recruitment from the cytoplasm to the cell periphery in the presence of activated RACB. During fungal infection, RIC157 and activated RACB colocalise at the penetration site, particularly at the haustorial neck. In a RACB-dependent manner, transiently overexpressed RIC157 renders barley epidermal cells more susceptible to fungal penetration. We conclude that RIC157 promotes fungal penetration into barley epidermal cells via its function as downstream executor in RACB-signaling.

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