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.

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 Biological Control of Celery Powdery Mildew Disease Caused by Erysiphe heraclei DC In Vitro and In Vivo Conditions

Plants ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 2342
Author(s):  
Hamada F. A. Ahmed ◽  
Mahmoud F. Seleiman ◽  
Adel M. Al-Saif ◽  
Maha A. Alshiekheid ◽  
Martin L. Battaglia ◽  
...  
Keyword(s):  
Powdery Mildew ◽  
Disease Severity ◽  
Germ Tube ◽  
The Other ◽  
Biocontrol Agents ◽  
Tube Length ◽  
Conidia Germination ◽  
Germ Tube Length

The present study aimed to investigate the potentiality of certain biocontrol agents, namely Bacillus subtilis, B. pumilus, B. megaterium, Pseudomonas fluorescens, Serratia marcescens, Trichoderma album, T. harzianum and T. viride, as well as the synthetic fungicide difenoconazole to control celery powdery mildew caused by Erysiphe heraclei DC, in vitro (against conidia germination and germ tube length of E. heraclei) and in vivo (against disease severity and AUDPC). In vitro, it was found that the antifungal activity of the tested biocontrol agents significantly reduced the germination percentage of the conidia and germ tube length of the pathogen. The reduction in conidia germination ranged between 88.2% and 59.6% as a result of the treatment with B. subtilis and T. album, respectively compared with 97.1% by the synthetic fungicide difenoconazole. Moreover, the fungicide achieved the highest reduction in germ tube length (92.5%) followed by B. megaterium (82.0%), while T. album was the least effective (62.8%). Spraying celery plants with the tested biocontrol agents in the greenhouse significantly reduced powdery mildew severity, as well as the area under the disease progress curve (AUDPC), after 7, 14, 21 and 28 days of application. In this regard, B. subtilis was the most efficient followed by B. pumilus, S. marcescens and B. megaterium, with 80.1, 74.4, 73.2 and 70.5% reductions in disease severity, respectively. In AUDPC, reductions of those microorganisms were 285.3, 380.9, 396.7 and 431.8, respectively, compared to 1539.1 in the control treatment. On the other hand, the fungicide difenoconazole achieved maximum efficacy in reducing disease severity (84.7%) and lowest AUDPC (219.3) compared to the other treatments. In the field, all the applied biocontrol agents showed high efficiency in suppressing powdery mildew on celery plants, with a significant improvement in growth and yield characteristics. In addition, they caused an increase in the concentration of leaf pigments, and the activities of defense-related enzymes such as peroxidase (PO) and polyphenol oxidase (PPO) and total phenol content (TPC). In conclusion, the results showed the possibility of using tested biocontrol agents as eco-friendly alternatives to protect celery plants against powdery mildew.

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.

Effects of Probiotics in the Management of Infected Chronic Wounds: From Cell Culture to Human Studies

2020 ◽  
Vol 15 (3) ◽  
pp. 193-206
Author(s):  
Brognara Lorenzo ◽  
Salmaso Luca ◽  
Mazzotti Antonio ◽  
Di M. Alberto ◽  
Faldini Cesare ◽  
...  
Keyword(s):  
Chronic Wounds ◽  
Animal Experiments ◽  
Multidrug Resistant ◽  
Preliminary Evidence ◽  
Human Studies ◽  
In Vivo Studies ◽  
Resistant Bacteria ◽  
Keywords Probiotics

Background: Chronic wounds are commonly associated with polymicrobial biofilm infections. In the last years, the extensive use of antibiotics has generated several antibiotic-resistant variants. To overcome this issue, alternative natural treatments have been proposed, including the use of microorganisms like probiotics. The aim of this manuscript was to review current literature concerning the application of probiotics for the treatment of infected chronic wounds. Methods: Relevant articles were searched in the Medline database using PubMed and Scholar, using the keywords “probiotics” and “wound” and “injuries”, “probiotics” and “wound” and “ulcer”, “biofilm” and “probiotics” and “wound”, “biofilm” and “ulcer” and “probiotics”, “biofilm” and “ulcer” and “probiotics”, “probiotics” and “wound”. Results: The research initially included 253 articles. After removal of duplicate studies, and selection according to specific inclusion and exclusion criteria, 19 research articles were included and reviewed, accounting for 12 in vitro, 8 in vivo studies and 2 human studies (three articles dealing with animal experiments included also in vitro testing). Most of the published studies about the effects of probiotics for the treatment of infected chronic wounds reported a partial inhibition of microbial growth, biofilm formation and quorum sensing. Discussion: The application of probiotics represents an intriguing option in the treatment of infected chronic wounds with multidrug-resistant bacteria; however, current results are difficult to compare due to the heterogeneity in methodology, laboratory techniques, and applied clinical protocols. Lactobacillus plantarum currently represents the most studied strain, showing a positive application in burns compared to guideline treatments, and an additional mean in chronic wound infections. Conclusions: Although preliminary evidence supports the use of specific strains of probiotics in certain clinical settings such as infected chronic wounds, large, long-term clinical trials are still lacking, and further research is needed.

scholarly journals Staphylococcus aureus Serves as an Iron Source for Pseudomonas aeruginosa during In Vivo Coculture

2005 ◽  
Vol 187 (2) ◽  
pp. 554-566 ◽  
Author(s):  
Lauren M. Mashburn ◽  
Amy M. Jett ◽  
Darrin R. Akins ◽  
Marvin Whiteley
Keyword(s):  
Staphylococcus Aureus ◽  
Pseudomonas Aeruginosa ◽  
Pathogenic Bacteria ◽  
Iron Acquisition ◽  
Low Oxygen ◽  
Dialysis Membrane ◽  
Opportunistic Human Pathogen ◽  
The Impact

ABSTRACT Pseudomonas aeruginosa is a gram-negative opportunistic human pathogen often infecting the lungs of individuals with the heritable disease cystic fibrosis and the peritoneum of individuals undergoing continuous ambulatory peritoneal dialysis. Often these infections are not caused by colonization with P. aeruginosa alone but instead by a consortium of pathogenic bacteria. Little is known about growth and persistence of P. aeruginosa in vivo, and less is known about the impact of coinfecting bacteria on P. aeruginosa pathogenesis and physiology. In this study, a rat dialysis membrane peritoneal model was used to evaluate the in vivo transcriptome of P. aeruginosa in monoculture and in coculture with Staphylococcus aureus. Monoculture results indicate that approximately 5% of all P. aeruginosa genes are differentially regulated during growth in vivo compared to in vitro controls. Included in this analysis are genes important for iron acquisition and growth in low-oxygen environments. The presence of S. aureus caused decreased transcription of P. aeruginosa iron-regulated genes during in vivo coculture, indicating that the presence of S. aureus increases usable iron for P. aeruginosa in this environment. We propose a model where P. aeruginosa lyses S. aureus and uses released iron for growth in low-iron environments.

scholarly journals Toxin Production by Pseudomonas Tolaasii Paine

1973 ◽  
Vol 26 (2) ◽  
pp. 509 ◽  
Author(s):  
NG Nair ◽  
PC Fahy
Keyword(s):  
Toxin Production ◽  
Nutrient Broth ◽  
Dialysis Membrane ◽  
Pseudomonas Tolaasii ◽  
Brown Discoloration

Evidence is presented for the production of toxin in vitro and in vivo by P. tolaasii. Nutrient broth suspensions of P. tolaasii placed on detached mushroom sporophores but separated by a dialysis membrane caused brown discoloration and slightly sunken lesions.

scholarly journals A note on the antibiotic properties of Bacillus subtilis against Colletotrichum trifolii

2005 ◽  
Vol 73 (1) ◽  
pp. 31-36 ◽  
Author(s):  
Y. Douville ◽  
J.G. Boland
Keyword(s):  
Bacillus Subtilis ◽  
Disease Incidence ◽  
Suppressive Effect ◽  
Mechanisms Of Action ◽  
Colletotrichum Trifolii ◽  
Growth Room ◽  
A Cell ◽  
Germ Tubes

The influence and mechanisms of action of Bacillus subtilis on Colletotrichum trifolii, a causal agent of anthracnose of alfalfa (Medicago sativa), were studied in vivo and in vitro. In growth room conditions, a cell-free culture filtrate of B. subtilis significantly reduced disease incidence and severity on alfalfa seedlings from 56% to 16% and from 2.0 to 1.2, respectively. Treatment of seedlings with washed cell suspensions of B. subtilis had no influence on disease. Applications of crude filtrate on alfalfa leaflets inoculated with C. trifolii were associated with reduced germination of conidia, lysis of conidia, and reduced formation of appressoria. Under in vitro conditions, crude filtrate reduced germination of conidia, and induced lysis of conidia and the formation of inflated germ tubes on germinating conidia. An antibiotic of the iturin family, iturin D, was tentatively identified as the active compound responsible for the suppressive effect of B. subtilis on C. trifolii.

scholarly journals Germ Tubes and Proteinase Activity Contribute to Virulence of Candida albicans in Murine Peritonitis

1999 ◽  
Vol 67 (12) ◽  
pp. 6637-6642 ◽  
Author(s):  
Marianne Kretschmar ◽  
Bernhard Hube ◽  
Thomas Bertsch ◽  
Dominique Sanglard ◽  
Renate Merker ◽  
...  
Keyword(s):  
Candida Albicans ◽  
Bowel Perforation ◽  
Tube Length ◽  
Triple Mutant ◽  
Liver And Pancreas ◽  
Organ Specific ◽  
Secreted Aspartyl Proteinase ◽  
Pepstatin A

ABSTRACT Peritonitis with Candida albicans is an important complication of bowel perforation and continuous ambulatory peritoneal dialysis. To define potential virulence factors, we investigated 50 strains of C. albicans in a murine peritonitis model. There was considerable variation in their virulence in this model when virulence was measured as release of organ-specific enzymes into the plasma of infected mice. Alanine aminotransferase (ALT) and α-amylase (AM) were used as parameters for damage of the liver and pancreas, respectively. The activities of ALT and AM in the plasma correlated with invasion into the organs measured in histologic sections and the median germ tube length induced with serum in vitro. When the activity of proteinases was inhibited in vivo with pepstatin A, there was a significant reduction of ALT and AM activities. This indicates that proteinases contributed to virulence in this model. Using strains ofC. albicans with disruption of secreted aspartyl proteinase gene SAP1, SAP2, SAP3, orSAP4 through SAP6 (collectively referred to asSAP4-6), we showed that only a Δsap4-6 triple mutant induced a significantly reduced activity of ALT in comparison to the reference strain. In contrast to the Δsap1, Δsap2, and Δsap3 mutants, the ALT induced by the Δsap4-6 mutant could not be further reduced by pepstatin A treatment, which indicates that Sap4-6 may contribute to virulence in this model.

scholarly journals Novel Dissolution Approach for Tacrolimus-Loaded Microspheres Using a Dialysis Membrane for in Vitro–in Vivo Correlation

2019 ◽  
Vol 67 (5) ◽  
pp. 467-475 ◽  
Author(s):  
Masanori Kaihara ◽  
Kazuhiro Hojo ◽  
Tomokazu Tajiri ◽  
Atsushi Kambayashi ◽  
Takatsune Yoshida ◽  
...  
Keyword(s):  
Dialysis Membrane

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.

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