Formation of appressoria by two species of lepidopteran-pathogenic Entomophthorales

2002 ◽  
Vol 80 (2) ◽  
pp. 220-225 ◽  
Author(s):  
Ann E Hajek ◽  
Melanie J Filotas ◽  
Debbie C Ewing
Keyword(s):  
Fungal Pathogens ◽  
Surface Hydrophobicity ◽  
Infection Process ◽  
Appressorium Formation ◽  
Entomophaga Maimaiga ◽  
Lepidopteran Larvae ◽  
Chemical Stimuli ◽  
Fungi Infection ◽  
Germ Tubes

Fungal pathogens frequently form appressoria, specialized hyphal swellings on the surfaces of hosts. Production of appressoria by two entomophthoralean species that infect lepidopteran larvae, Entomophaga maimaiga Humber, Shimazu & Soper and Furia gastropachae (Raciborski) Filotas, Hajek & Humber, was investigated in vitro 6–8 h after conidial discharge. Entomophaga maimaiga appressoria were elongate, irregularly swollen structures located adjacent to the conidium or at the ends of short germ tubes. The highest percentages of appressoria were formed on hard surfaces such as polystyrene (21.5 ± 4.6%) and mylar (22.2 ± 4.3%). Nutrients or chemical stimuli were not required for appressorial formation but could stimulate growth as germ tubes. The contribution of surface hydrophobicity to appressorium formation was questionable; while appressoria were formed on hydrophobic surfaces, they were also formed to a lesser extent on glass, which is hydrophilic. When conidia of F. gastropachae were exposed to similar substrates and conditions, appressoria were never made, supporting the hypothesis that stimuli for appressorium formation can be species specific.Key words: appressorium, entomopathogenic fungi, infection process, Entomophthorales.

Early interactions, adhesion, and establishment of the infection court by Erysiphe graminis

1995 ◽  
Vol 73 (S1) ◽  
pp. 609-615 ◽  
Author(s):  
Ralph L. Nicholson ◽  
Hitoshi Kunoh
Keyword(s):  
Hydrophobic Surface ◽  
Surface Hydrophobicity ◽  
Infection Process ◽  
Erysiphe Graminis ◽  
Hydrophilic Surface ◽  
Colletotrichum Graminicola ◽  
Appressorium Formation ◽  
Barley Leaf ◽  
Powdery Mildew Pathogen ◽  
Suitable Substratum

The establishment of a fungal pathogen on the surface of its host is essential to the success of the infection process. For many fungi, establishment on the host is an active process that may depend on recognition of the host surface through chemical or topographic signals. Events that allow for establishment may be considered to represent the "preparation of the infection court" by the pathogen. This sometimes involves the adhesion of the pathogen to the host and possibly the alteration of the host's surface topography or chemistry. Adhesion is often presumed to be a single, chemically mediated event associated with germ tube or appressorium formation. However, adhesion of ungerminated propagules may also occur, and evidence suggests that it is mediated by the release of adhesive materials directly from the propagule upon contact with a suitable substratum. Fungi may require either a hydrophobic or a hydrophilic surface to initiate the infection process. The barley powdery mildew pathogen, Erysiphe graminis, requires a hydrophilic surface for appressorium formation, yet the barley leaf is extremely hydrophobic. The problem is resolved by the release of an exudate from conidia that makes the hydrophobic leaf surface hydrophilic. In contrast, Colletotrichum graminicola requires a hydrophobic surface for the initiation of its infection process. Ungerminated conidia of this fungus release materials that allow for the rapid adhesion of conidia, which ensures that germination and appressorium formation occur, initiating the infection process. For both fungi, these events happen well in advance of germination and establish the pathogen at the site of the infection court. Key words: adhesion, cuticle, cutinase, surface hydrophobicity, infection process.

scholarly journals Effect of Pyrisoxazole on Colletotrichum scovillei Infection and Anthracnose on Chili

Plant Disease ◽  
2020 ◽  
Vol 104 (2) ◽  
pp. 551-559
Author(s):  
Y. Y. Gao ◽  
X. X. Li ◽  
L. F. He ◽  
B. X. Li ◽  
W. Mu ◽  
...  
Keyword(s):  
Inhibitory Activity ◽  
Infection Process ◽  
Appressorium Formation ◽  
Baseline Sensitivity ◽  
Sensitivity Curves ◽  
Half Maximal Effective Concentration ◽  
Colletotrichum Scovillei ◽  
Feasible Alternative

Anthracnose caused by Colletotrichum scovillei is one of the most destructive diseases affecting chili production. Disease control mainly relies on conventional fungicides, and repeated exposure to single-site mode-of-action fungicides may pose a risk for the development of resistant isolates within the population. Our previous study suggested that pyrisoxazole has strong inhibitory activity against C. scovillei in vitro. However, the effects of pyrisoxazole on the C. scovillei infection process and the performance of pyrisoxazole in the field remain unclear. In this study, pyrisoxazole exhibited strong inhibitory activity against the mycelial growth, appressorium formation, and appressorium diameter of C. scovillei, with half maximal effective concentration values of 0.1986, 0.0147, and 0.0269 μg/ml, respectively, but had no effect on sporulation, even at the highest concentration of 1.6 μg/ml. The baseline sensitivity curves were unimodal with a long right-hand tail. The in vivo data showed that pyrisoxazole provided both preventive and curative activity against anthracnose on chili. Pyrisoxazole decreased the incidence of anthracnose and reduced disease progress. The results of electron microscopy showed that pyrisoxazole can affect the C. scovillei infection process by altering mycelial morphology, degrading conidia and germ tubes, suppressing conidial germination and appressorium formation, and enhancing conidiophore production. Pyrisoxazole can be used to effectively control anthracnose under field conditions and increase chili yield; moreover, no phytotoxicity symptoms were observed after treatment. These results provide new insight into the mechanisms by which pyrisoxazole controls disease and suggest that pyrisoxazole is a feasible alternative for the management of anthracnose in chili.

scholarly journals Pecan Scab Fungus Lacks Substrate Specificity for Early Infection Stages

1996 ◽  
Vol 121 (5) ◽  
pp. 948-953 ◽  
Author(s):  
I.E. Yates ◽  
K.M.T. Cason ◽  
Darrell Sparks
Keyword(s):  
Substrate Specificity ◽  
Surface Hardness ◽  
Deionized Water ◽  
Dialysis Membrane ◽  
Appressorium Formation ◽  
Pecan Scab ◽  
Stomatal Guard Cells ◽  
Conidium Germination ◽  
Chemical Stimuli ◽  
Germ Tubes

Leaves and callus of pecan [Carya illinoinensis (Wangenh.) K. Koch], and glass, dialysis membrane, and agar were examined for capacity to support two of the earliest infection stages—conidium (spore) germination and appressorium formation—of Cladosporium caryigenum (Ellis & Langl.) Gottwald, the fungus causing pecan scab. Light and temperature effects on formation of germ tubes and appressoria were examined for conidia suspended in distilled-deionized water. Conidia formed germ tubes on all substrates and in distilled-deionized water; hence, conidia possessed endogenous materials required for germination and are independent of specific topographic or chemical stimuli. All substrates, except 2% water agar and water, sustained appressoria development, thus implicating regulation by surface hardness. More appressoria formed on leaf discs than on other substrates. Additionally, conidia formed appressoria with short germ tubes when near a leaf structural feature, such as stomatal guard cells. Thus, the pecan scab fungal isolate used in these experiments appeared to lack substrate specificity for forming germ tubes, but not appressoria, during the prepenetration stages of development. Conidium germination was maximized at about 25 °C and germination did not respond to light.

scholarly journals APPRESSORIUM FORMATION IN THE PECAN SCAB FUNGUS

HortScience ◽  
1992 ◽  
Vol 27 (6) ◽  
pp. 627f-627
Author(s):  
K.M.T. Cason ◽  
I.E. Yates
Keyword(s):  
Germ Tube ◽  
Light And Electron Microscopy ◽  
Preliminary Evidence ◽  
Tube Length ◽  
Dialysis Membrane ◽  
Appressorium Formation ◽  
Pecan Scab ◽  
Germ Tubes

Pecan scab, caused by the fungus Cladosporium caryigenum (Ell. et Lant) Gottwald, produces more damage to pecan than all other diseases and insects combined. Early events during infection are critical to disease establishment and to expression of host resistance, but have not been examined previously. Objectives of this research were to determine if there is regulation of appressorial formation and if it is related to resistance. Pre-infectional host-pathogen interactions were studied in vivo (on leaves) and in vitro (on callus, dialysis membrane, and agar) with light and electron microscopy. Leaves, callus tissue, dialysis membranes, and agar were inoculated with scab conidia and were incubated under conditions optimum for germination. Conidia germinate and produce a germ tube on agar and dialysis membrane, but appressoria are not formed. Appressoria form on pecan callus, but germ tubes are long. Long germ tubes are often associated with resistant disease reactions. In vivo, appressoria form readily, but germ tube length varies depending on the location of the spore on the leaf surface. Preliminary evidence indicates that surface topography affects induction of appressorium formation in the scab fungus.

Studies on Graminicolous Species of Phyllachora Fckl. I. Ascospores - their liberation and germination

1963 ◽  
Vol 11 (2) ◽  
pp. 117 ◽  
Author(s):  
DG Parbery
Keyword(s):  
Spore Germination ◽  
Germ Tube ◽  
Leaf Surface ◽  
Individual Species ◽  
Appressorium Formation ◽  
Rain Splash ◽  
First Time ◽  
Germ Tubes ◽  
Appressorium Development

The process of ascospore liberation is a moderately active one. Discharged ascospores collect on the host leaf surface in white, glutinous masses and are believed to be dispersed by rain splash. Ascospores of all species examined germinated in 2-12 hr at 14°C under laboratory conditions, but there were indications that the process was more rapid in the field. The pattern for spore germination and appressorium formation was similar for the six species studied. Each ascospore produced a single germ tube which, in 2-6 hr after germination began, formed an appressorium initial in the form of a swelling at its apex. Appressoria were completely developed 6-12 hr later. The process of appressorium development is described for species of Phyllachora for the first time. The swelling at the apex of the germ tube extended back along the germ tube towards the ascspore. In some species, e.g. P. cornispora, the entire germ tube was converted into an appressorium which consequently was sessile. In other species, such as P. parilis, only approximately half of the germ tube developed into appressorium. In P. parilis, temperatures greater than 26°C inhibited appressorium formation. Instead of producing appressoria, germ tubes continued to grow and became long and flexuous. Germination did not occur at temperatures of 30°C or greater. Evidence suggested that while contact with a surface was not necessary to initiate appressorium formation, contact with a grass leaf surface was required for appressoria to develop normally. The morphology of appressoria of individual species of Phyllachora was usually variable when these structures developed in vitro but constant and distinct when they developed on the host. Among the species examined three basic morphological types of appressoria were recognized.

scholarly journals In vitro Study of Secreted Aspartyl Proteinases Sap1 to Sap3 and Sap4 to Sap6 Expression in Candida albicans Pleomorphic Forms

2012 ◽  
Vol 61 (4) ◽  
pp. 247-256 ◽  
Author(s):  
MONIKA STANISZEWSKA ◽  
MAŁGORZATA BONDARYK ◽  
KATARZYNA SIENNICKA ◽  
ANNA KUREK ◽  
JACEK ORŁOWSKI ◽  
...  
Keyword(s):  
Candida Albicans ◽  
Human Serum ◽  
Associated Factors ◽  
In Vitro Study ◽  
Infection Process ◽  
Detection Level ◽  
Aspartic Proteases ◽  
Germ Tubes ◽  
Pleomorphic Cells

Transition from round budding cells to long hyphal forms and production of secreted aspartic proteases (Saps) are considered virulence-associated factors of Candida albicans. Although plenty of data dealing with Saps involvement in the infection process have been published, Saps expression by the different pleomorphic forms as well as the capacity of C. albicans filaments to express Sap1-6 under serum influence are poorly investigated. In this study, we used immunofluorescence and immunoelectron microscopy for the detection of Sap1-6 isoenzymes in C. albicans pleomorphic cells (blastoconidia, germ tubes, pseudohyphae, true hyphae) grown in Sap-inductive human serum and Sap non-inductive medium - yeast extract-peptone-glucose (YEPD). Isoenzymes were below the detection level in all blastoconidial cells grown in YEPD for 18 h. Sap1-6 expression was hardly detected in C. albicans cells cultivated in serum for 20 min. Increasing level of Sap1-6 expression was observed when C. albicans was incubated for 2, 6 and 18 h in serum corresponding to the development of germ tubes, pseudohyphae and true hyphae. The expression of Sap1-3 in pseudohyphae and true hyphae was more intensive compared to Sap4-6. Thus, we could show that human serum induced hyphae formation and the expression of Sap1-6 were co-regulated.

scholarly journals In Vitro and In Vivo Antifungal Activity of Sorbicillinoids Produced by Trichoderma longibrachiatum

2021 ◽  
Vol 7 (6) ◽  
pp. 428
Author(s):  
Men Thi Ngo ◽  
Minh Van Nguyen ◽  
Jae Woo Han ◽  
Myung Soo Park ◽  
Hun Kim ◽  
...  
Keyword(s):  
Late Blight ◽  
Culture Filtrate ◽  
Fungal Pathogens ◽  
Gray Mold ◽  
Trichoderma Longibrachiatum ◽  
Chemical Structures ◽  
Natural Agents ◽  
Blight Disease

In the search for antifungal agents from marine resources, we recently found that the culture filtrate of Trichoderma longibrachiatum SFC100166 effectively suppressed the development of tomato gray mold, rice blast, and tomato late blight. The culture filtrate was then successively extracted with ethyl acetate and n-butanol to identify the fungicidal metabolites. Consequently, a new compound, spirosorbicillinol D (1), and a new natural compound, 2′,3′-dihydro-epoxysorbicillinol (2), together with 11 known compounds (3–13), were obtained from the solvent extracts. The chemical structures were determined by spectroscopic analyses and comparison with literature values. The results of the in vitro antifungal assay showed that of the tested fungal pathogens, Phytophthora infestans was the fungus most sensitive to the isolated compounds, with MIC values ranging from 6.3 to 400 µg/mL, except for trichotetronine (9) and trichodimerol (10). When tomato plants were treated with the representative compounds (4, 6, 7, and 11), bisvertinolone (6) strongly reduced the development of tomato late blight disease compared to the untreated control. Taken together, our results revealed that the culture filtrate of T. longibrachiatum SFC100166 and its metabolites could be useful sources for the development of new natural agents to control late blight caused by P. infestans.

scholarly journals The Use of Essential Oils from Thyme, Sage and Peppermint against Colletotrichum acutatum

Plants ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 114
Author(s):  
Armina Morkeliūnė ◽  
Neringa Rasiukevičiūtė ◽  
Lina Šernaitė ◽  
Alma Valiuškaitė
Keyword(s):  
Essential Oils ◽  
Fungal Pathogens ◽  
Control Plant ◽  
Antimicrobial Activities ◽  
Plant Diseases ◽  
Colletotrichum Acutatum ◽  
Low Toxicity ◽  
Colletotrichum Spp ◽  
Biological Protection

The Colletotrichum spp. is a significant strawberry pathogen causing yield losses of up to 50%. The most common method to control plant diseases is through the use of chemical fungicides. The findings of plants antimicrobial activities, low toxicity, and biodegradability of essential oils (EO), make them suitable for biological protection against fungal pathogens. The aim is to evaluate the inhibition of Colletotrichum acutatum by thyme, sage, and peppermint EO in vitro on detached strawberry leaves and determine EO chemical composition. Our results revealed that the dominant compound of thyme was thymol 41.35%, peppermint: menthone 44.56%, sage: α,β-thujone 34.45%, and camphor: 20.46%. Thyme EO inhibited C. acutatum completely above 200 μL L−1 concentration in vitro. Peppermint and sage EO reduced mycelial growth of C. acutatum. In addition, in vitro, results are promising for biological control. The detached strawberry leaves experiments showed that disease reduction 4 days after inoculation was 15.8% at 1000 μL L−1 of peppermint EO and 5.3% at 800 μL L−1 of thyme compared with control. Our findings could potentially help to manage C. acutatum; however, the detached strawberry leaves assay showed that EO efficacy was relatively low on tested concentrations and should be increased.

scholarly journals The Potential of Rhizoctonia-Like Fungi for the Biological Protection of Cereals against Fungal Pathogens

Plants ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 349
Author(s):  
Dominik Bleša ◽  
Pavel Matušinský ◽  
Romana Sedmíková ◽  
Milan Baláž
Keyword(s):  
Biological Control ◽  
Fungal Pathogens ◽  
Plant Pathogens ◽  
Higher Plants ◽  
Fusarium Culmorum ◽  
Suppressive Effect ◽  
Plant Production ◽  
Shoot Biomass ◽  
Organic Substrates

The use of biological control is becoming a common practice in plant production. One overlooked group of organisms potentially suitable for biological control are Rhizoctonia-like (Rh-like) fungi. Some of them are capable of forming endophytic associations with a large group of higher plants as well as mycorrhizal symbioses. Various benefits of endophytic associations were proved, including amelioration of devastating effects of pathogens such as Fusarium culmorum. The advantage of Rh-like endophytes over strictly biotrophic mycorrhizal organisms is the possibility of their cultivation on organic substrates, which makes their use more suitable for production. We focused on abilities of five Rh-like fungi isolated from orchid mycorrhizas, endophytic fungi Serendipita indica, Microdochium bolleyi and pathogenic Ceratobasidium cereale to inhibit the growth of pathogenic F. culmorum or Pyrenophora teres in vitro. We also analysed their suppressive effect on wheat infection by F. culmorum in a growth chamber, as well as an effect on barley under field conditions. Some of the Rh-like fungi affected the growth of plant pathogens in vitro, then the interaction with plants was tested. Beneficial effect was especially noted in the pot experiments, where wheat plants were negatively influenced by F. culmorum. Inoculation with S. indica caused higher dry shoot biomass in comparison to plants treated with fungicide. Prospective for future work are the effects of these endophytes on plant signalling pathways, factors affecting the level of colonization and surviving of infectious particles.

scholarly journals Biological control of strawberry crown rot, root rot and grey mould by the beneficial fungus Aureobasidium pullulans

BioControl ◽  
2021 ◽  
Author(s):  
Mudassir Iqbal ◽  
Maha Jamshaid ◽  
Muhammad Awais Zahid ◽  
Erik Andreasson ◽  
Ramesh R. Vetukuri ◽  
...  
Keyword(s):  
Root Rot ◽  
Fungal Pathogens ◽  
Aureobasidium Pullulans ◽  
Grey Mould ◽  
Lesion Size ◽  
Plant Diseases ◽  
Crown Rot ◽  
Whole Plants

AbstractUtilization of biocontrol agents is a sustainable approach to reduce plant diseases caused by fungal pathogens. In the present study, we tested the effect of the candidate biocontrol fungus Aureobasidium pullulans (De Bary) G. Armaud on strawberry under in vitro and in vivo conditions to control crown rot, root rot and grey mould caused by Phytophthora cactorum (Lebert and Cohn) and Botrytis cinerea Pers, respectively. A dual plate confrontation assay showed that mycelial growth of P. cactorum and B. cinerea was reduced by 33–48% when challenged by A. pullulans as compared with control treatments. Likewise, detached leaf and fruit assays showed that A. pullulans significantly reduced necrotic lesion size on leaves and disease severity on fruits caused by P. cactorum and B. cinerea. In addition, greenhouse experiments with whole plants revealed enhanced biocontrol efficacy against root rot and grey mould when treated with A. pullulans either in combination with the pathogen or pre-treated with A. pullulans followed by inoculation of the pathogens. Our results demonstrate that A. pullulans is an effective biocontrol agent to control strawberry diseases caused by fungal pathogens and can be an effective alternative to chemical-based fungicides.

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