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1
Ho, Wai-Hong, Teik-Khiang Goh, Kevin D. Hyde, and I. John Hodgkiss. "Studies of conidial anatomy and conidiogenesis in Sporoschisma nigroseptatum using light and electron microscopy." Canadian Journal of Botany 76, no. 9 (September 1, 1998): 1614–23. http://dx.doi.org/10.1139/b98-109.
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The results of an ultrastructural study of the conidial anatomy and conidiogenesis in Sporoschisma nigroseptatum are presented. The development of the conidial chain involves endogenous conidial ontogeny, apical wall-building, and retrogressive conidial delimitation followed by cessation of apical wall-building, then replacement ring wall-building of additional retrogressively delimited conidia, and extrusion of the true conidial chain through the terminal aperture of the conidiogenous cell. Maturation of conidia involves deposition of two inner wall layers and formation of five distosepta. Conidial chains secede schizolytically. No proliferation of the conidiogenous cell occurs and the conidium is delimited by a cross wall that is discontinuous with the periclinal wall. Each conidium has polar plug-and-socket-like structures that are interlocked between adjacent conidia along the conidial chain. Similar plug-and-socket-like structures are also seen in other Sporoschisma species. The taxonomy of Chalara is also briefly discussed with reference to patterns of conidial wall-building.Key words: Chalara, conidial chain, conidial ontogeny, ultrastructures.
2
Sommartya, Tharmmasak, and M. K. Beute. "Temperature Effects on Germination and Comparative Morphology of Conidia for Thai and USA Isolates of Cercosporidium personatum1,2." Peanut Science 13, no. 2 (July 1, 1986): 67–70. http://dx.doi.org/10.3146/i0095-3679-13-2-6.
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Abstract Ten isolates of Cercosporidium personation (Cp) were collected from seven geographical areas in Thailand and the USA. Four USA and 6 Thai isolates were cultured on a susceptible peanut genotype, NC 3033, to produce conidia for all studies. Conidial germination was determined after 12, 24, and 48 h at 16–36 C. Percent germination of conidia for all populations were greatest at 16–20 C. At 30 and 32 C, 58 and 22% of conidia from Thai isolates germinated, respectively. Only 33 and 6% of conidia from USA isolates germinated at 30 and 32 C. Only Thai isolates germinated at 36 C. No differences were observed among isolates for conidial length or number of septa per conidium. Conidia of all isolates, however, were longer and had more septa than previously reported. Conidial length in this study ranged from 16–90 um and number of septa per conidium ranged from 1–11. Conidia with furcate branching were observed with both Thai and USA isolates. Forked conidia produced normal germtubes either intercalary or terminally and all three terminal cells produced germ tubes.
3
Wong, M. KM, E. BG Jones, M. A. Abdel-Wahab, D. WT Au, and L. LP Vrijmoed. "Ultrastructure of conidiogenesis and appendage ontogeny in the coelomycete Bartalinia robillardoides." Canadian Journal of Botany 81, no. 11 (November 1, 2003): 1083–90. http://dx.doi.org/10.1139/b03-100.
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Conidiogenesis and conidial appendage ontogeny of the coelomycete Bartalinia robillardoides Tassi was studied at the light microscope, scanning electron microscope, and transmission electron microscope levels. Conidiogenesis in B. robillardoides is holoblastic. Appendage ontogeny begins as a cellular outgrowth of the apical and the basal cells of the young conidium, the former developing prior to the basal appendage. Conidia detach from the conidiogenous cells schizolytically. Mature conidial cell walls comprise two layers: an outer electron-dense layer, 3038 nm, and an inner less electron-dense layer, 100125 nm. The apical appendages arise from an outgrowth of the apical cell, which then branches to form the appendages. The single basal appendage arises from the junction between the basal cell of the conidium and the conidiogenous cell prior to conidial detachment from the conidiogenous cell, as an outgrowth of the conidial cell wall. Conidial appendage ontogeny is compared with those of other coelomycetes.Key words: Annellidic, appendage ontogeny, coelomycetes, holoblastic.
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Thomas, Stephen W., Mikkel A. Glaring, Søren W. Rasmussen, Julia T. Kinane, and Richard P. Oliver. "Transcript Profiling in the Barley Mildew Pathogen Blumeria graminis by Serial Analysis of Gene Expression (SAGE)." Molecular Plant-Microbe Interactions® 15, no. 8 (August 2002): 847–56. http://dx.doi.org/10.1094/mpmi.2002.15.8.847.
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The fungal pathogen Blumeria graminis f. sp. hordei develops on the barley leaf via distinct, morphologically well-defined stages. After landing on a host plant, the conidia rapidly germinate to form a primary germ tube. Subsequently, an appressorial germ tube emerges from the conidium and differentiates an appressorium from which penetration of the host cell wall is attempted. We have used serial analysis of gene expression to provide a measurement of messenger RNA contents in ungerminated conidia, during conidial germination, and during appressorium formation. The resulting data provide a resource for the characterization of changes in transcript accumulation during early development of B. graminis.
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Hall, Alison A., Lene Bindslev, Jacques Rouster, Søren W. Rasmussen, Richard P. Oliver, and Sarah J. Gurr. "Involvement of cAMP and Protein Kinase A in Conidial Differentiation by Erysiphe graminis f. sp. hordei." Molecular Plant-Microbe Interactions® 12, no. 11 (November 1999): 960–68. http://dx.doi.org/10.1094/mpmi.1999.12.11.960.
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Erysiphe graminis f. sp. hordei, the causal agent of barley powdery mildew, is an obligate biotroph. On arrival on the host, a primary germ tube (PGT) emerges from the conidium. An appressorial germ tube (AGT) then appears, forms an appressorium, and effects host penetration. Such developmental precision may be due to multiple, plant-derived signals and to endogenous tactile and chemical signals. The transduction mechanism remains obscure. The isolation of an expressed sequence tag (EST) homologue of the catalytic subunit of cyclic AMP (cAMP)-dependent protein kinase A (PKA) enabled the corresponding gene to be characterized and the transcript to be identified in conidia and in PGT and AGT stage spores. cAMP-dependent PKA activity was detected in ungerminated conidia. These data suggest that PKA and cAMP are involved in conidial development. To substantiate this we exploited the responses of developing conidia to various surfaces, including exposure to the host leaf (fully inductive to AGT formation), cellulose membrane (semi-inductive), and glass (non-inductive). Assessment of fungal development, following application of exogenous cAMP or cAMP analogues, revealed that, at different concentrations and on different surfaces, cAMP either promoted or inhibited conidial differentiation. Various PKA inhibitors were tested for their effect on PKA activity and conidial development. A negative correlation was established between PKA inhibition in vitro and fungal development in vivo. Taken collectively, these data suggest that PKA and cAMP play a role in conidial differentiation in this obligate, plant-pathogenic fungus.
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Hayer, Kimran, Malcolm Stratford, and David B. Archer. "Structural Features of Sugars That Trigger or Support Conidial Germination in the Filamentous Fungus Aspergillus niger." Applied and Environmental Microbiology 79, no. 22 (August 30, 2013): 6924–31. http://dx.doi.org/10.1128/aem.02061-13.
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ABSTRACTThe asexual spores (conidia) ofAspergillus nigergerminate to produce hyphae under appropriate conditions. Germination is initiated by conidial swelling and mobilization of internal carbon and energy stores, followed by polarization and emergence of a hyphal germ tube. The effects of different pyranose sugars, all analogues ofd-glucose, on the germination ofA. nigerconidia were explored, and we define germination as the transition from a dormant conidium into a germling. Within germination, we distinguish two distinct stages, the initial swelling of the conidium and subsequent polarized growth. The stage of conidial swelling requires a germination trigger, which we define as a compound that is sensed by the conidium and which leads to catabolism ofd-trehalose and isotropic growth. Sugars that triggered germination and outgrowth includedd-glucose,d-mannose, andd-xylose. Sugars that triggered germination but did not support subsequent outgrowth includedd-tagatose,d-lyxose, and 2-deoxy-d-glucose. Nontriggering sugars includedd-galactose,l-glucose, andd-arabinose. Certain nontriggering sugars, includingd-galactose, supported outgrowth if added in the presence of a complementary triggering sugar. This division of functions indicates that sugars are involved in two separate events in germination, triggering and subsequent outgrowth, and the structural features of sugars that support each, both, or none of these events are discussed. We also present data on the uptake of sugars during the germination process and discuss possible mechanisms of triggering in the absence of apparent sugar uptake during the initial swelling of conidia.
7
Son, Hokyoung, Myung-Gu Kim, Kyunghun Min, Jae Yun Lim, Gyung Ja Choi, Jin-Cheol Kim, Suhn-Kee Chae, and Yin-Won Lee. "WetA Is Required for Conidiogenesis and Conidium Maturation in the Ascomycete Fungus Fusarium graminearum." Eukaryotic Cell 13, no. 1 (November 1, 2013): 87–98. http://dx.doi.org/10.1128/ec.00220-13.
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ABSTRACTFusarium graminearum, a prominent fungal pathogen that infects major cereal crops, primarily utilizes asexual spores to spread disease. To understand the molecular mechanisms underlying conidiogenesis inF. graminearum, we functionally characterized theF. graminearumortholog ofAspergillus nidulanswetA, which has been shown to be involved in conidiogenesis and conidium maturation. Deletion ofF. graminearumwetAdid not alter mycelial growth, sexual development, or virulence, but thewetAdeletion mutants produced longer conidia with fewer septa, and the conidia were sensitive to acute stresses, such as oxidative stress and heat stress. Furthermore, the survival rate of aged conidia from theF. graminearumwetAdeletion mutants was reduced. ThewetAdeletion resulted in vigorous generation of single-celled conidia through autophagy-dependent microcycle conidiation, indicating that WetA functions to maintain conidial dormancy by suppressing microcycle conidiation inF. graminearum. Transcriptome analyses demonstrated that most of the putative conidiation-related genes are expressed constitutively and that only a few genes are specifically involved inF. graminearumconidiogenesis. The conserved and distinct roles identified for WetA inF. graminearumprovide new insights into the genetics of conidiation in filamentous fungi.
8
Oichi, W., Y. Matsuda, T. Nonomura, H. Toyoda, L. Xu, and S. Kusakari. "Formation of Conidial Pseudochains by Tomato Powdery Mildew Oidium neolycopersici." Plant Disease 90, no. 7 (July 2006): 915–19. http://dx.doi.org/10.1094/pd-90-0915.
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The formation of conidial pseudochains by the tomato powdery mildew Oidium neolycopersici on tomato leaves was monitored using a high-fidelity digital microscope. Individual living conidiophores that formed mature conidial cells at their apex were selected for observation. The conidial cells were produced during repeated division and elongation by the generative cells of the conidiophores. Under weak wind conditions (0.1 m/s), these conidial cells did not separate from each other to produce a chain of conidial cells (pseudochain). The pseudochains dropped from the conidiophores once four conidial cells were connected. The conidiophores resumed conidium production, followed by another cycle of pseudochain formation. The formation of pseudochains by tomato powdery mildew was not influenced by the ambient relative humidity. On the other hand, the conidial cells produced were easily wind dispersed without forming pseudochains when conidiophores were exposed to stronger winds (1.0 m/s). The present study successfully demonstrated that the pathogen required wind to disperse progeny conidia from the conidiophores and produced conidial pseudochains when the wind was below a critical level, independent of high relative humidity as reported previously.
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Wasylnka, Julie A., and Margo M. Moore. "Adhesion of Aspergillus Species to Extracellular Matrix Proteins: Evidence for Involvement of Negatively Charged Carbohydrates on the Conidial Surface." Infection and Immunity 68, no. 6 (June 1, 2000): 3377–84. http://dx.doi.org/10.1128/iai.68.6.3377-3384.2000.
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ABSTRACT Invasive lung disease caused by Aspergillus species is a potentially fatal infection in immunocompromised patients. The adhesion of Aspergillus fumigatus conidia to proteins in the basal lamina is thought to be an initial step in the development of invasive aspergillosis. The purpose of this study was to determine the mechanism of adhesion of A. fumigatus conidiospores to basal-lamina proteins and to determine whether conidia possess unique adhesins which allow them to colonize the host. We compared conidia from different Aspergillus species for the ability to bind to purified fibronectin and intact basal lamina. Adhesion assays using immobilized fibronectin or type II pneumocyte-derived basal lamina showed that A. fumigatus conidia bound significantly better than those of other Aspergillus species to both fibronectin and intact basal lamina. Neither desialylation nor complete deglycosylation of fibronectin decreased the binding of A. fumigatus conidia to fibronectin, suggesting that oligosaccharides on fibronectin were not involved in conidiospore binding. Further evidence for this hypothesis came from experiments using purified fragments of fibronectin; A. fumigatusconidia preferentially bound to the nonglycosylated 40-kDa fragment which contains the glycosaminoglycan (GAG) binding domain. Negatively charged carbohydrates, including dextran sulfate and heparin, as well as high-ionic-strength buffers, inhibited binding of A. fumigatus conidia to both fibronectin and intact basal lamina, suggesting that negatively charged carbohydrates on the surface of the conidium may bind to the GAG binding domain of fibronectin and other basal-lamina proteins. These data provide evidence for a novel mechanism of conidial attachment whereby adherence to fibronectin and other basal-lamina proteins is mediated via negatively charged carbohydrates on the conidial surface.
10
Scheper, Reiny W. A., Lizelle Vorster, Lauren Turner, Rebecca E. Campbell, Kate Colhoun, Danielle McArley, Rosalind Murti, et al. "Lesion development and conidial production of Neonectria ditissima on apple trees in four New Zealand regions." New Zealand Plant Protection 72 (July 26, 2019): 123–34. http://dx.doi.org/10.30843/nzpp.2019.72.302.
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This study examined incubation period, lesion length and conidial release in Neonectria ditissima (European canker) in four New Zealand regions in relation to climatic factors. Incubation period was studied on potted ‘Royal Gala’ trees inoculated with N. ditissima. One week after inoculation, symptomless trees were dispatched to Waikato, Hawke’s Bay, Tasman, Otago and positive controls remained in a glasshouse. Conidial release was studied in trees with lesions that were dispatched to the same regions. Rain traps were placed under each lesion and conidia quantified after each rain event. Disease progress and conidial production were examined in relation to weather. Lesions developed significantly slower in Otago and faster in Waikato and the glasshouse, compared with Tasman and Hawke’s Bay. Symptom development accelerated with increasing daily hours of 11–16°C and humidity (74.6–87.2% RH). The highest conidium counts occurred in Waikato and the lowest in Otago, while conidial production started earlier in Tasman than elsewhere. Temperature is the main driver for symptom development during the incubation period and rainfall is not required. Rainfall frequency drives conidial production.
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Khan, J., A. Qi, and M. F. R. Khan. "Fluctuations in Number of Cercospora beticola Conidia in Relationship to Environment and Disease Severity in Sugar Beet." Phytopathology® 99, no. 7 (July 2009): 796–801. http://dx.doi.org/10.1094/phyto-99-7-0796.
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Cercospora leaf spot, caused by Cercospora beticola, is the most damaging foliar disease of sugar beet in Minnesota (MN) and North Dakota (ND). Research was conducted to characterize the temporal progression of aerial concentration of C. beticola conidia in association with the environment and disease severity in sugar beet. In 2003 and 2004, volumetric spore traps were placed within inoculated sugar beet plots to determine daily dispersal of conidia at Breckenridge, MN, and St. Thomas, ND. Plots were rated weekly for disease severity. At both locations, conidia were first collected in early July 2003 and late June in 2004. Peaks of conidia per cubic meter of air were observed with maxima in late August 2003 and in early September 2004 at both locations. Peaks of airborne conidium concentration were significantly correlated with the average temperature of daily hours when relative humidity was greater than 87%. Weekly mean hourly conidia per cubic meter of air was significantly (P < 0.01) associated with disease severity during both years and across locations. This study showed that C. beticola conidial numbers may be used to estimate potential disease severity that, with further research, could be incorporated in a disease forecasting model to rationalize Cercospora leaf spot management.
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Subere, Cristita Verna. "Conidial Discharge of an Entomopathogenic Fungus Infecting the Cotton Leafhopper." Science and Humanities Journal 3, no. 1 (November 30, 2003): 16–27. http://dx.doi.org/10.47773/shj.1998.031.2.
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A laboratory experiment was conducted to determine the conidial discharge of Batkoa amrascae Keller & Villacarlos, an entomopathogenic fungus found infecting the cotton leafhopper on okra. Field and laboratoy-infected leafhopper cadavers were tested for the effect of light. The fungus from field-infected cadavers kept in the dark during sporulation produced and average of 26,372 conidia (29 hr. mean time conidial production), whereas those exposed to light had 5,290 conidia (33 hr. mean time conidial production). On the other hand, laboratory-infected cadavers exposed to light attained an average of 4,447 conidia while that of cadavers kept in the dark had 3,373 conidia, both had 28 hr mean time conidial production.
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Honda, Y., M. Z. Rahman, S. Z. Islam, and N. Muroguchi. "Leaf Spot Disease of Broad Bean Caused by Alternaria tenuissima in Japan." Plant Disease 85, no. 1 (January 2001): 95. http://dx.doi.org/10.1094/pdis.2001.85.1.95a.
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In April 1999, a leaf spot of broad bean (Vicia faba L.) was observed in commercial fields in Shimane prefecture of Western Japan. Lesions were concentric and brown in color. Older leaves were particularly affected. In later stages of the disease, plants defoliated as leaves blighted from margin to the center. Isolation was made from infected leaf tissue. The isolated fungus produced conidia on V8 medium (2) either in dark or under continuous irradiation of near ultraviolet radiation (NUV) from BLB fluorescent lamps. Conidial chains were unbranched or rarely formed a few lateral branches with a few conidia. The conidia of the fungus grown under continuous NUV were dark and smoothly tapered into the apical beak, and each conidium had a conspicuously thickened primary septum with a constriction of the conidial wall and often a darker median transverse septum. The conidia measured 21.2 to 45.5 μm (mean = 32.9 μm) × 7.3 to 17.7 μm (mean = 11.4 μm ) on V8 medium. Conidia produced on leaves and stem collected from field were similar in size and appearance. The fungus was identified as Alternaria tenuissima based on its cultural and morphological characteristics (2). An isolate was also sent to CABI Bioscience Identification Services (Egham, UK), which also identified the fungus as A. tenuissima. A conidial suspension (107 spores/ml) was prepared and used to inoculate detached leaves and intact plants of broad bean. Intact plants were inoculated by spaying with spore suspension and covered with polyethylene bags for maintaining high humidity. Detached leaves in moist petri dishes were inoculated with drops of spore suspension. Symptom developed on both detached and intact leaves 3 to 4 days after inoculation. Reisolating the pathogen from infected leaves completed Koch's postulates. In June 2000, the leaf spot was observed in all 15 fields surveyed in other areas of Shimane prefecture. In some fields, plants were defoliated and stems and pods were also infected. Isolates of A. tenuissima also were obtained from those fields. This pathogen has been isolated from other hosts in Japan (1). This is the first report of A. tenuissima on broad bean in Japan. References: (1) Anonymous. 2000. Common Names of Plant Diseases in Japan. The Phytopathological Society of Japan, Tokyo. (2) E. G. Simmon. Mycotaxon 37:79–119, 1990.
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Iqbal, S. H. "Further studies on efficiency of artificial foam in trapping conidia of Ingoldian fungi." Canadian Journal of Botany 73, no. 8 (August 1, 1995): 1176–85. http://dx.doi.org/10.1139/b95-127.
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Artificial foam traps conidia of rare species in rich communities of freshwater hyphomycetes as efficiently as it traps conidia in a community showing poor species composition with low conidial numbers. A large number of conidia, particularly the tetraradiate ones, are lost from the stream water as it passes through rapids and waterfalls. Addition of a detergent results in greater loss of conidia in the effluent water. The trapping of conidia in the foam concentrate and their loss while passing through the rapids and waterfalls is not related to conidial concentration. It may be influenced by water chemistry. Key words: artificial foam, conidia, Ingoldian fungi.
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Yang, Jun, Xiaoyan Zhao, Jing Sun, Zhensheng Kang, Shengli Ding, Jin-Rong Xu, and You-Liang Peng. "A Novel Protein Com1 Is Required for Normal Conidium Morphology and Full Virulence in Magnaporthe oryzae." Molecular Plant-Microbe Interactions® 23, no. 1 (January 2010): 112–23. http://dx.doi.org/10.1094/mpmi-23-1-0112.
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In Magnaporthe oryzae, pyriform conidia are the primary inoculum and the main source for disease dissemination in the field. In this study, we identified and characterized the COM1 gene that was disrupted in three insertional mutants producing slender conidia. COM1 encodes a putative transcription regulator unique to filamentous ascomycetes. The com1 disruption and deletion mutants had similar defects in conidium morphology and were significantly reduced in virulence on rice and barley seedlings. Microscopic examination revealed that the Δcom1 mutants were defective in appressorium turgor generation, penetration, and infectious growth. COM1 was expressed constitutively in M. oryzae. The Com1 protein had putative helix-loop-helix structures and three predicted nuclear localization signal sequences. In transformants expressing COM1335-613–enhanced green fluorescent protein fusion constructs, fluorescence signals were observed in the nucleus. Our data indicated that the COM1 gene may encode a novel transcription regulator that regulates conidial development and invasive growth in M. oryzae.
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Úrbez-Torres, José R., Emilie Bruez, José Hurtado, and Walter D. Gubler. "Effect of Temperature on Conidial Germination of Botryosphaeriaceae Species Infecting Grapevines." Plant Disease 94, no. 12 (December 2010): 1476–84. http://dx.doi.org/10.1094/pdis-06-10-0423.
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Germination of conidia of eight botryosphaeriaceous fungi infecting grapevines was evaluated after 2, 4, 6, 12, and 24 h incubation under eight different temperatures (5, 10, 15, 20, 25, 30, 35, and 40°C). The effect of temperature on conidial germination was also evaluated in different stages (hyaline versus pigmented conidia) of the species Lasiodiplodia theobromae. Conidial germination of Botryosphaeriaceae species infecting grapevines was significantly affected by temperature. Overall, conidial germination increased significantly with longer incubation times, especially from 2 to 12 h. In most cases, germination of conidia was not significantly different between 12 and 24 h incubation. Conidia of botryosphaeriaceous species did not germinate (with the exception of Botryosphaeria dothidea and Neofusicoccum parvum) at 5°C, and only B. dothidea, Diplodia seriata, and L. theobromae showed high levels of conidial germination at 40°C. Optimum conidial germination temperatures (defined as the temperature in which germination reached at least 50% in the shortest incubation time) were 25°C for B. dothidea and Dothiorella iberica, 25 to 30°C for Spencermartinsia viticola, 30°C for Diplodia corticola, D. mutila, D. seriata, N. parvum, and hyaline L. theobromae, and 40°C for pigmented L. theobromae conidia. Successful conidial germination of species of Botryosphaeriaceae infecting grapevines was always observed between 10 and 35°C with the exception of Dothiorella iberica and pigmented L. theobromae conidia, neither of which germinated at 35 and 10°C, respectively. Results of this study show conidia of botryosphaeriaceous species infecting grapevines to be capable of germination under a broad range of temperatures including those considered to be extreme, which may explain the success of these species as grapevine pathogens throughout most of the grape-growing areas in both Northern and Southern Hemispheres.
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Valsecchi, Isabel, Emmanuel Stephen-Victor, Sarah Sze Wah Wong, Anupama Karnam, Margaret Sunde, J. Iñaki Guijarro, Borja Rodríguez de Francisco, et al. "The Role of RodA-Conserved Cysteine Residues in the Aspergillus fumigatus Conidial Surface Organization." Journal of Fungi 6, no. 3 (August 26, 2020): 151. http://dx.doi.org/10.3390/jof6030151.
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Immune inertness of Aspergillusfumigatus conidia is attributed to its surface rodlet-layer made up of RodAp, characterized by eight conserved cysteine residues forming four disulfide bonds. Earlier, we showed that the conserved cysteine residue point (ccrp) mutations result in conidia devoid of the rodlet layer. Here, we extended our study comparing the surface organization and immunoreactivity of conidia carrying ccrp-mutations with the RODA deletion mutant (∆rodA). Western blot analysis using anti-RodAp antibodies indicated the absence of RodAp in the cytoplasm of ccrp-mutant conidia. Immunolabeling revealed differential reactivity to conidial surface glucans, the ccrp-mutant conidia preferentially binding to α-(1,3)-glucan, ∆rodA conidia selectively bound to β-(1,3)-glucan; the parental strain conidia showed negative labeling. However, permeability of ccrp-mutants and ∆rodA was similar to the parental strain conidia. Proteomic analyses of the conidial surface exposed proteins of the ccrp-mutants showed more similarities with the parental strain, but were significantly different from the ∆rodA. Ccrp-mutant conidia were less immunostimulatory compared to ∆rodA conidia. Our data suggest that (i) the conserved cysteine residues are essential for the trafficking of RodAp and the organization of the rodlet layer on the conidial surface, and (ii) targeted point mutation could be an alternative approach to study the role of fungal cell-wall genes in host–fungal interaction.
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Sridhar, K. R., and Felix Bärlocher. "Viability of aquatic hyphomycete conidia in foam." Canadian Journal of Botany 72, no. 1 (January 1, 1994): 106–10. http://dx.doi.org/10.1139/b94-015.
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The viability of aquatic hyphomycete conidia trapped in foam was estimated with tetrazolium bromide. In fresh foam, 76 – 91% of all conidia had at least one viable cell; in old foam, these values were 20 – 43%. The average number of viable cells per conidium was higher in fresh than in old foam. Laboratory-produced conidia of Heliscus lugdunensis and Articulo-spora tetracladia had much higher numbers of viable cells than field-collected conidia. Viability as defined in this study (at least one viable cell per conidium) proved to be an excellent predictor of ability to germinate. Conidia of four species (two Canadian and two Indian strains) did not survive for more than 24 d when exposed to −17 °C, or to freeze – thaw cycles. Persistence of conidia through unfavourable conditions therefore seems limited. Key words: aquatic hyphomycetes, conidia, viability, germination.
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Verma, O. P., and V. N. Pathak. "Conidial germination in Claviceps fusiformis Lov. in relation to physical and ontogenic factors." Acta Mycologica 21, no. 2 (August 20, 2014): 265–70. http://dx.doi.org/10.5586/am.1985.021.
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Influence of certain physical and ontogenic factors on germination of conidiu of <i>Clariceps fusiformls</i> Lov., the incitant of pe rl miller (<i>Pennisetum americanum </i>(L.) Leeke) ergot. was investigated. Maximum germination of conidia was recorded at 24 C and l0% RH. The germination was completely checked in washed conidia. Increasing dilution of honeydew with sterile water as well as drying of conidia for more than 30 minutes caused significant reduction in their germination. Conidia up to the age of 3 days gave significantly more germination than older conidia.
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Horowitz Brown, S., R. Zarnowski, W. C. Sharpee, and N. P. Keller. "Morphological Transitions Governed by Density Dependence and Lipoxygenase Activity in Aspergillus flavus." Applied and Environmental Microbiology 74, no. 18 (July 25, 2008): 5674–85. http://dx.doi.org/10.1128/aem.00565-08.
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ABSTRACT Aspergillus flavus differentiates to produce asexual dispersing spores (conidia) or overwintering survival structures called sclerotia. Results described here show that these two processes are oppositely regulated by density-dependent mechanisms and that increasing the cell density (from 101 to 107 cells/plate) results in the lowest numbers of sclerotial and the highest numbers of conidial. Extract from spent medium of low-cell-density cultures induced a high-sclerotium-number phenotype, whereas high-cell-density extract increased conidiation. Density-dependent development is also modified by changes in lipid availability. Exogenous linoleic acid increased sclerotial production at intermediate cell densities (104 and 105 cells/plate), whereas oleic and linolenic acids inhibited sclerotium formation. Deletion of Aflox encoding a lipoxygenase (LOX) greatly diminished density-dependent development of both sclerotia and conidia, resulting in an overall increase in the number of sclerotia and a decrease in the number of conidia at high cell densities (>105 cells/plate). Aflox mutants showed decreased linoleic acid LOX activity. Taken together, these results suggest that there is a quorum-sensing mechanism in which a factor(s) produced in dense cultures, perhaps a LOX-derived metabolite, activates conidium formation, while a factor(s) produced in low-density cultures stimulates sclerotium formation.
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Larena, I., P. Melgarejo, and A. De Cal. "Production, Survival, and Evaluation of Solid-Substrate Inocula of Penicillium oxalicum, a Biocontrol Agent Against Fusarium Wilt of Tomato." Phytopathology® 92, no. 8 (August 2002): 863–69. http://dx.doi.org/10.1094/phyto.2002.92.8.863.
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Production of conidia of Penicillium oxalicum (ATCC number pending), a biocontrol agent of Fusarium oxysporum f. sp. lycopersici, was tested in liquid and solid fermentation. P. oxalicum produced 250-fold more conidia in solid than in liquid fermentation at 30 days after inoculation of substrate. Solid fermentation was carried out in plastic bags (600 cm3) especially designed for solid fermentation (VALMIC) containing 50 g of peat/vermiculite (PV) (1:1, wt/wt) with 40% moisture, sealed, sterilized, and then inoculated with 1 ml of a conidial suspension of P. oxalicum (105 conidia g-1 dry substrate), sealed again, and incubated in darkness at 20 to 25°C for 30 days. Addition of amendments to PV in a proportion of 0.5 (wt/wt) significantly increased conidial production of P. oxalicum. The best production was obtained on PV plus meal of cereal grains (barley) or leguminous seeds (lentil) (100-fold higher). Conidial production obtained after 5 days of inoculation was similar to that obtained at 30 days. However, viability of conidia produced in PV plus lentil meal was 35% higher than that of conidia produced in PV plus barley meal. Changes in proportions (1:1:0.5, wt/wt/wt; 1:1:1, wt/wt/wt; 1:0.5:0.5, wt/wt/wt; 1:1:0.5, vol/vol/vol) of components of the substrate (peat/vermiculite/lentil meal) did not enhance production or viability of conidia. Optimal initial moisture in the substrate was 30 to 40%. At lower moistures, significant reductions of production of conidia were observed, particularly at 10%. There was a general decline in the number of conidia in bags with time of storage at -80, -20, 4, and 25°C, or at room temperature (range from 30 to 15°C), with the highest decline occurring from 60 to 180 days. Conidial viability also was reduced with time, except for conidia stored at -20°C. Fresh conidia produced in solid fermentation system or those conidia stored at -20°C for 180 days reduced Fusarium wilt of tomato by 49 and 61%, respectively.
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Sabuquillo, P., A. De Cal, and P. Melgarejo. "Dispersal Improvement of a Powder Formulation of Penicillium oxalicum, a Biocontrol Agent of Tomato Wilt." Plant Disease 89, no. 12 (December 2005): 1317–23. http://dx.doi.org/10.1094/pd-89-1317.
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Sugars, polyalcohols, inorganic salts, and detergents were added to conidia of Penicillium oxalicum at three different points of the production-formulation process to improve water dispersal. Effects also were tested on conidial germination and production. Conidial germination without additives ranged from 51 to 79%. Additives did not reduce conidial germination except for 50% polyethylene glycol (PEG) 300 and 10% CaCl2. Sunflower oil and sodium alginate, sucrose (0.5, 15, 30, and 60%), D-sorbitol (30 and 60%), glycerol (2, 5, 20, and 30%), 30% PEG 300, CaCl2 (0.01 to 1%), Tween 20 (0.01, 0.02, 0.5, and 1%), and Tween 80 (0.01 to 1%) enhanced conidial germination. Production without additives ranged from 0.57 to 4.58 conidia × 108 g-1 substrate. Additives did not affect conidial production except for reduction by 60% D-sorbitol, 60% fructose, and 10% CaCl2. Conidial dispersal in water improved when 1.5% sodium alginate was added to substrate in bags before production, and when 1.5% sodium alginate, 60% sucrose, 60% D-sorbitol, 60% fructose, 5 to 20% PEG 8000, or 20% glycerol were added to conidia before drying. Dispersal of dried conidia was enhanced with 1% Tween 20, 1% Tween 80, 1% Trition X-100, 10% Agral, and 1.5% sunflower oil. Two P. oxalicum formulations (conidial suspensions maintained with 60% sucrose or 1.5% sodium alginate for 10 min before drying) significantly reduced tomato wilt caused by Fusarium spp. under greenhouse conditions and, in a preliminary trial, by Verticillium spp. in a field assay.
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Fisher, B. M., T. A. Taylor, L. M. Flórez-Palacios, D. I. Hedderley, and R. W. A. Scheper. "Freezing and melting conditions affect the viability of Neonectria ditissima conidia." New Zealand Plant Protection 69 (January 8, 2016): 319. http://dx.doi.org/10.30843/nzpp.2016.69.5922.
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Different freezing and melting conditions of conidial suspensions of Neonectria ditissima were examined to determine optimal longterm storage conditions Four concentrations of glycerol two freezing temperatures and three melting methods were compared using two isolates RS305p with singlecelled conidia and RS324p with multicelled conidia After 10 months conidia of RS305p had significantly higher germination rates than those of RS324p Glycerol added to conidial suspensions before freezing reduced the germination rate significantly Suspensions frozen at 80C had significantly higher germination rates than those at 20C Defrosting in a 20C water bath resulted in significantly higher germination rates than defrosting in ice water However freezing for 10 months at 80C without glycerol reduced the conidial germination rate of RS324p from 65 before freezing to 8 In contrast the conidial germination rate of RS305p frozen in the same conditions increased from 15 to 74 More research is needed to determine optimal storage conditions
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Wang, Bing, Bao-Hua Li, Xiang-Li Dong, Cai-Xia Wang, and Zhen-Fang Zhang. "Effects of Temperature, Wetness Duration, and Moisture on the Conidial Germination, Infection, and Disease Incubation Period of Glomerella cingulata." Plant Disease 99, no. 2 (February 2015): 249–56. http://dx.doi.org/10.1094/pdis-04-14-0361-re.
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Glomerella leaf spot (GLS) caused by Glomerella cingulata is a newly emergent disease that results in severe defoliation and fruit spots. Currently, GLS is not effectively controlled in China due to a lack of understanding of its epidemiology. Therefore, the effects of temperature, wetness duration, and moisture on conidial germination, infection, and the disease incubation period of GLS were examined by inoculating cv. Gala apple leaves with a conidial suspension and performing in vitro germination assays. Conidia could germinate and form appressoria at temperatures ranging from 5 to 35°C, with an optimum temperature of 27.6°C. The germination of conidia required free water or a nearly saturated relative humidity, with only a few conidia germinating and forming appressoria when the RH was less than 99%. The conidial germination dynamics at 10, 25, and 30°C were well represented by three logistic models. The infection of cv. Gala apple leaves by conidia occurred at temperatures ranging from 15 to 35°C. The minimum wetness duration required for infection by conidia at different temperatures was described using a polynomial equation, and the lowest minimum wetness duration was 2.76 h, which occurred at 27.6°C according to the polynomial. Successful infection by conidia was represented by the number of lesions per leaf, which increased with extended wetness durations at the conidial infection stage for six tested temperatures, with the exception of 10°C, when the minimum wetness durations were satisfied. The associations of successfully infected conidia with wetness duration at temperatures of 15, 20, 25, and 30°C were described by four logistic models. Conidia infections developed into visible lesions at temperatures ranging from 15 to 30°C, and the shortest incubation period of 2 days was observed at 25°C. These data and models can be used to construct forecasting models and develop effective control systems for Glomerella leaf spot.
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Fu, Ci, Asuma Tanaka, and Stephen J. Free. "Neurospora crassa 1,3-α-glucan synthase, AGS-1, is required for cell wall biosynthesis during macroconidia development." Microbiology 160, no. 8 (August 1, 2014): 1618–27. http://dx.doi.org/10.1099/mic.0.080002-0.
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The Neurospora crassa genome encodes two 1,3-α-glucan synthases. One of these 1,3-α-glucan synthase genes, ags-1, was shown to be required for the synthesis of 1,3-α-glucan in the aerial hyphae and macroconidia cell walls. 1,3-α-Glucan was found in the conidia cell wall, but was absent from the vegetative hyphae cell wall. Deletion of ags-1 affected conidial development. Δags-1 produced only 5 % as many conidia as the WT and most of the conidia produced by Δags-1 were not viable. The ags-1 upstream regulatory elements were shown to direct cell-type-specific expression of red fluorescent protein in conidia and aerial hyphae. A haemagglutinin-tagged AGS-1 was found to be expressed in aerial hyphae and conidia. The research showed that 1,3-α-glucan is an aerial hyphae and conidia cell wall component, and is required for normal conidial differentiation.
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Viruega, J. R., J. Moral, L. F. Roca, N. Navarro, and A. Trapero. "Spilocaea oleagina in Olive Groves of Southern Spain: Survival, Inoculum Production, and Dispersal." Plant Disease 97, no. 12 (December 2013): 1549–56. http://dx.doi.org/10.1094/pdis-12-12-1206-re.
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Olive scab caused by the mitosporic fungus Spilocaea oleagina is the most important foliar disease of olive. Limited information is available on pathogen survival and disease epidemiology; however, this information is essential for development of new control strategies. Pathogen survival and inoculum production on infected olive leaves and conidial dispersal were evaluated during 4 years in an olive orchard of the susceptible ‘Picual’ in southern Spain. Infected leaves in the tree canopy were important for pathogen survival and conidia production. The number of conidia per square centimeter of scab lesion and their viability varied greatly throughout the seasons and between years; conidial density in lesions was highest (about 1 to 5 × 105 conidia cm–2) from November to February in favorable years. Conidial density declined sharply in other periods of the year (becoming zero in summer) or in less favorable years. The pathogen did not form new conidia in scab lesions, although some pseudothecia-like structures and chlamydospores were detected on fallen leaves. Under humid conditions, the pathogen could not be detected on fallen leaves after 3 months because the leaves were colonized by saprophytic fungi. The dispersal of conidia as a function of distance from infected leaves in the tree canopy was well described by an exponential model which, together with the lack of conidia in a Burkard spore trap, showed that conidia were mainly rain-splash dispersed. Some trapped conidia were attached to olive leaf trichomes, suggesting that detached trichomes might enhance wind dispersal of conidia.
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Byrne, J. M., M. K. Hausbeck, and B. D. Shaw. "Factors Affecting Concentrations of Airborne Conidia of Oidium sp. Among Poinsettias in a Greenhouse." Plant Disease 84, no. 10 (October 2000): 1089–95. http://dx.doi.org/10.1094/pdis.2000.84.10.1089.
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Atmospheric concentrations of Oidium sp. conidia in two research greenhouses containing infected poinsettias were monitored to investigate the role of environment in prompting conidial release and dissemination. Hourly concentrations of conidia of Oidium sp. were estimated using a Burkard volumetric spore sampler. The influence of temperature on disease development was studied by placing healthy poinsettias in each greenhouse for 7-day periods, removing them, and recording the days to the appearance of the first colony. When averaged over 5 December to 1 June, atmospheric conidial concentrations in greenhouse (GH) 2 were greatest during 1000 to 1800 hours with a peak (325 conidia/m3/h) occurring at 1200 hours. In GH 11, peak concentrations occurred at 1300 hours (65 conidia/m3/h) and 1600 hours (75 conidia/m3/h). Large numbers of conidia were sampled (≥100/m3) within 1-h periods, indicating conidial release events (CREs). Fluctuations in relative humidity (RH) (either positive or negative) prompted CREs. In both greenhouses, the highest number of CREs (up to 23) occurred following RH fluctuations of 5 to 15%. Watering resulted in an immediate increase (≤25%) followed by a rapid decrease in RH (≤32%) beginning 1 to 2 h later. In GH 2 and GH 11, 89 and 48%, respectively, of the CREs occurred within 3 h following greenhouse watering. When greenhouse temperatures exceeded 25°C for 21 days in May (GH 2) and 19 days in March (GH 11), atmospheric conidial concentrations were reduced 80 and 75% from the previous months, respectively.
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Chauvet, Eric, and Keller Suberkropp. "Temperature and Sporulation of Aquatic Hyphomycetes." Applied and Environmental Microbiology 64, no. 4 (April 1, 1998): 1522–25. http://dx.doi.org/10.1128/aem.64.4.1522-1525.1998.
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ABSTRACT Temperature appears to be an important factor affecting the occurrence and distribution of aquatic hyphomycetes, the dominant leaf litter-decomposing fungi in streams. We compared conidium production by eight species of aquatic hyphomycetes grown on yellow poplar leaves in stream-simulating microcosms at three temperatures (15, 20, and 25°C). The greatest conidium production occurred at 15°C for one species, 20°C for two species, and 25°C for two species. Two species produced similar numbers of conidia at 20 and 25°C, and one species produced similar numbers of conidia at all three temperatures. Linear growth rates were determined on malt extract agar. Six species had the same pattern of temperature responses for growth on malt extract agar as for sporulation on leaves, as shown by the positive correlations between the two parameters at the three temperatures. The species examined also exhibited differences in number of conidia produced from a similar amount of leaf material at a given temperature. These differences appeared to be due primarily to differences in individual conidium mass (determined by weighing conidia produced from cultures), as shown by the relationship of the type Y = k/X (r 2 = 0.96), where Y is the number of conidia produced, X is the individual conidium mass in milligrams, and k is a constant empirically determined to be 2.11. This finding supports the hypothesis that aquatic hyphomycetes allocate similar amounts of their resources to reproduction but vary with respect how these resources are partitioned into reproductive units (conidia).
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Byrne, J. M., M. K. Hausbeck, and R. Hammerschmidt. "Conidial Germination and Appressorium Formation of Colletotrichum coccodes on Tomato Foliage." Plant Disease 81, no. 7 (July 1997): 715–18. http://dx.doi.org/10.1094/pdis.1997.81.7.715.
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Conidial germination and infection processes of Colletotrichum coccodes were quantified on foliage of processing tomatoes (Lycopersicon esculentum Mill.). The abaxial surface of two opposing terminal leaflets removed from a fully expanded leaf at the 4th to 5th node was inoculated with 10-μl droplets of C. coccodes conidial suspension. Leaflets were incubated for 2 to 24 h in 2-h intervals at 25°C under high relative humidity. Explants with the conidial droplet were fixed, cleared, and preserved for microscopic observation. The percentage of germinated conidia and those with unmelanized and melanized appressoria was determined for each leaf disk. Conidial germination increased linearly with time (R2 = 0.73) (P = 0.001), maximizing (68.3%) 24 h after inoculation. The percentage of germinated conidia with unmelanized appres-soria peaked 6 h after inoculation (38.3%). Melanized appressoria formation followed a linear trend (R2 = 0.74) (P = 0.001), maximizing (62.0%) 24 h after inoculation. Infection vesicles were produced in 2.7% of conidia by 22 h, indicating successful infection.
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Gamliel-Atinsky, E., A. Sztejnberg, M. Maymon, D. Shtienberg, and S. Freeman. "Inoculum Availability and Conidial Dispersal Patterns of Fusarium mangiferae, the Causal Agent of Mango Malformation Disease." Phytopathology® 99, no. 2 (February 2009): 160–66. http://dx.doi.org/10.1094/phyto-99-2-0160.
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Inoculum availability and conidial dispersal patterns of Fusarium mangiferae, causal agent of mango malformation disease, were studied during 2006 and 2007 in an experimental orchard. The spatial pattern of primary infections in a heavily infected commercial mango orchard corresponded with a typical dispersal pattern caused by airborne propagules. Malformed inflorescences were first observed in mid-March, gradually increased, reaching a peak in May, and declined to negligible levels in August. The sporulation capacity of the malformed inflorescences was evaluated during three consecutive months. Significantly higher numbers of conidia per gram of malformed inflorescence were detected in May and June than in April. Annual conidial dissemination patterns were evaluated by active and passive trapping of conidia. A peak in trapped airborne conidia was detected in May and June for both years. The daily pattern of conidial dispersal was not associated with a specifically discernable time of day, and an exponential correlation was determined between mean relative humidity (RH) and mean number of trapped conidia. Higher numbers of conidia were trapped when RH values were low (<55%). This is the first detailed report on airborne dispersal of F. mangiferae, serving as the primary means of inoculum spread.
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Filonow, Alexander B. "Adhesion of decay-causing fungal conidia in wounds ofMalus×domestica'Golden Delicious' apple fruit is influenced by wound age." Canadian Journal of Botany 82, no. 2 (February 1, 2004): 265–72. http://dx.doi.org/10.1139/b03-149.
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Wounds are the primary site in apple fruit for infection by conidia of Botrytis cinerea Pers.:Fr. and Penicil lium expansum Link & Thom. The effects of wound shape, wound age, and chemical properties of the wound on conidial adhesion in wounds of Malus ×domestica Borkh. 'Golden Delicious' fruit were investigated. Adhesion was measured after dislodging conidia from wounds using a sonication probe above the wound. In all experiments, conidial adhesion responses were similar for both fungi. Conidial adhesion in puncture wounds was not different from adhesion in slice wounds. Wound age, however, profoundly affected conidial adhesion. Conidia of both fungi exhibited 78.1%91.9% adhesion in freshly made wounds of both shapes compared with 37.7%56.6% in 1-d-old wounds. Conidial adhesion increased as wound age increased from 1 to 5 d. Exposure of 1- and 2-d-old wounds to butyl acetate, a volatile constituent of apple fruit, increased conidial adhesion compared with nonexposed wounds. This finding, in addition to results from the histochemical analyses of wounds, the quantification of sugars and total phenolics in water diffusates from wounds, and the measurement of conidial adhesion to wound diffusates, suggested that conidial adhesion in wounds was influenced by altered surface chemistry of wounds as they aged.Key words: apple fruit wounds, decay-causing fungi, fungal spore adhesion, mycoactive acetate esters, wound aging, wound decay.
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Meyer, Robert J., and James S. Plaskowitz. "Scanning Electron Microscopy of Conidia and Conidial Matrix of Trichoderma." Mycologia 81, no. 2 (March 1989): 312. http://dx.doi.org/10.2307/3759718.
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Meyer, Robert J., and James S. Plaskowitz. "Scanning Electron Microscopy of Conidia and Conidial Matrix of Trichoderma." Mycologia 81, no. 2 (March 1989): 312–17. http://dx.doi.org/10.1080/00275514.1989.12025665.
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Canel, Romina Soledad, Sofìa Guerrissi, Vanesa Ludemann, Viviana Renaud, Jorge Ricardo Wagner, Federico Laich, Gabriela Mónaco, and Mariana Sanchez. "Microbiological and Sensory Characteristics of Mould-Ripened Salami under Different Packaging Conditions." Food technology and biotechnology 57, no. 1 (2019): 87–96. http://dx.doi.org/10.17113/ftb.57.01.19.5803.
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The preservation of mould-ripened salami was investigated during 48 days at 19-20 °C under different packaging conditions: (i) high barrier film filled with air, 100 % N2 or under vacuum, (ii) biaxially oriented polypropylene film, (iii) microperforated polyethylene film and (iv) unpackaged. Sensory, texture profile, physicochemical and microbiological analyses were performed. Fungal quantification revealed two data groups. In group 1 (consisting of salami in microperforated polyethylene film, biaxially oriented polypropylene film and unpackaged) the conidium viability was relatively constant. In group 2 (salami preserved in high barrier film filled with air, 100 % N2 or under vacuum) the conidium viability decreased due to the absence of oxygen and the high carbon dioxide volume fraction. SEM micrographs showed micromorphological changes in fungal structure; microperforated polyethylene film, biaxially oriented polypropylene film and unpackaged conditions preserved the conidial morphology, while high barrier film filled with air, 100 % N2 or vacuum conditions collapsed the hyphae and most of the conidia. Salami packed in microperforated polyethylene film and biaxially oriented polypropylene film showed the most acceptable organoleptic characteristics and lower hardness and chewiness values after packaging.
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Hsiang, Tom, R. L. Edmonds, and C. H. Driver. "Conidia of Heterobasidion annosum from Tsuga heterophylla forests in western Washington." Canadian Journal of Botany 67, no. 4 (April 1, 1989): 1262–66. http://dx.doi.org/10.1139/b89-164.
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Heterobasidion annosum produces conidia abundantly in culture; however, since conidiophores are rare in nature, conidia are usually considered to have little or no role in dispersal. Heterokaryotic mycelia of H. annosum produce both heterokaryotic and homokaryotic conidia, whereas basidiospores are homokaryotic. This difference was exploited to assess the relative prevalence of these spore types in western hemlock forests of western Washington state. Two out of 10 spores trapped on selective media were found to give rise to heterokaryotic mycelia identified by the presence of clamp connections. However, homokaryotic conidia could not be distinguished from basidiospores by this method, so two approaches were taken in the laboratory: examining conidia for number of nuclei and determining frequency of clamp connections in conidial cultures. Both methods indicated that from a single heterokaryotic mycelium, half of the conidial progeny were homokaryotic and the other half heterokaryotic. Thus the presence of two heterokaryotic conidia in 10 spores implied that conidia may make up a third to a half of the aerial spore load of H. annosum in western hemlock forests of western Washington state.
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Inglis, G. D., D. L. Johnson, and M. S. Goettel. "FIELD AND LABORATORY EVALUATION OF TWO CONIDIAL BATCHES OF BEAUVERIA BASSIANA (BALSAMO) VUILLEMIN AGAINST GRASSHOPPERS." Canadian Entomologist 129, no. 1 (February 1997): 171–86. http://dx.doi.org/10.4039/ent129171-1.
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AbstractThe efficacy of two production batches of conidia of Beauveria bassiana (Balsamo) Vuillemin that showed differential field efficacy in 1992 (GHA 92) and 1994 (GHA 94) were compared against grasshoppers in the laboratory and field. Conidia of GHA 92 and GHA 94 exhibited good germination (> 92%) by 24 h, but the rate of germination was slower for GHA 94 than for GHA 92. Although both conidial batches were highly virulent (LD50 < 6 × 103 conidia per nymph) against nymphs of Melanoplus sanguinipes (Fabricius) (Orthoptera: Acrididae) in the laboratory, GHA 92 was slightly more virulent than GHA 94. Conidia were applied to field populations of grasshoppers in a 1.5% emulsifiable oil-emulsion amended with 4% clay at a volume of 112 L/ha. There were no differences between GHA 92 and GHA 94 in the deposition of spray droplets on water-sensitive papers or of conidia on leaves and coverslips (2.4 × 10 to 4.1 × 10 cfu/cm2). All grasshopper nymphs collected from plots sprayed with conidia of GHA 92 and GHA 94 were equally infested with B. bassiana; conidial populations averaged 3.5 × 103 to 4.3 × 103 cfu/nymph. Conditions were hot, dry, and sunny, and regardless of the batch, persistence of conidia was equally short on both leaves and grasshoppers. Neither treatment of B. bassiana significantly reduced field populations nor did either impact differentially on specific grasshopper taxa. However, among grasshoppers collected immediately after conidial application and maintained in cages in the greenhouse, over 80% died of infection with B. bassiana. For both conidial treatments, the prevalence of disease in caged grasshoppers decreased with the sampling date but the onset of mycosis always occurred 3–4 days after collection. This study indicates that environmental conditions in the field and not pathogen virulence or targeting were responsible for the poor efficacy of B. bassiana against grasshoppers.
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García-Madrid, Luz, María Huizar-López, Leopoldo Flores-Romo, and Alfonso Islas-Rodríguez. "Trichophyton rubrum manipulates the innate immune functions of human keratinocytes." Open Life Sciences 6, no. 6 (December 1, 2011): 902–10. http://dx.doi.org/10.2478/s11535-011-0060-6.
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AbstractEvasion or subversion of host immune responses have been shown for a variety of microorganisms, and this might be the case for Trichophyton rubrum, the most common pathogenic fungus causing chronic dermatophytosis in humans. Keratinocytes, the main epidermal cells, have important roles as a first defense against microbial challenges in local immune reactions. Epidermal keratinocytes express several Toll-like receptors and produce host defense peptides, cytokines and chemokines in response to various stimuli. We analyzed the expression of Toll-Like receptor TLR2, TLR4, TLR6, and Human Beta Defensin (HBD)-1, HBD-2, Interleukin IL-1b and IL-8 production, when exposing primary keratinocyte cultures to T. rubrum. We observed changes in size and granularity of keratinocytes stimulated with either whole conidia or conidial homogenates compared to other treatments. Intact conidia decreased keratinocytes’ TLR2 and TLR6 expression without affecting that of TLR4, while conidial homogenates increased the expression of these three receptors. Interestingly, whole conidia decreased HBD-1 and HBD-2 production, whereas conidial homogenate increased it. No changes were observed in IL-1b and IL-8 production after stimulation with conidia or conidial homogenate. CONCLUSIONS. Our results suggest that: 1) Keratinocytes can recognize and respond to cell wall components of T. rubrum; 2) Viable intact conidia inhibit TLR-2 and TLR6 expression and decrease HBD-1 and HBD-2 production; 3) Conidial homogenate from T. rubrum increases the expression of TLR2, TLR4 and TLR6 and induces HBD-1 and HBD-2 production; 4) Therefore, innate immune functions of keratinocytes as the first level of local skin immunity are apparently manipulated by T. rubrum, likely to ensure its establishment, persistence and survival.
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Inglis, G. D., G. M. Duke, P. Kanagaratnam, D. L. Johnson, and M. S. Goettel. "PERSISTENCE OF BEAUVERIA BASSIANA IN SOIL FOLLOWING APPLICATION OF CONIDIA THROUGH CROP CANOPIES." Memoirs of the Entomological Society of Canada 129, S171 (1997): 253–63. http://dx.doi.org/10.4039/entm129171253-1.
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AbstractThe influence of three formulations, water, oil, and a 5% oil emulsion, and two crops, alfalfa and crested wheatgrass, on the deposition and subsequent persistence of Beauveria bassiana (Balsamo) Vuillemin conidia in soil was investigated. The alfalfa canopy was considerably denser than that of wheatgrass. Leaf area indices for alfalfa ranged from 1.8 to greater than 2, those for wheatgrass ranged from 0.24 to 0.55. Initial populations of conidia averaged 1.2 × 103 to 2.6 × 104 colony-forming units (cfu) per gram of dry weight of soil under alfalfa, and 5.5 × 103 to 3.4 × 104 cfu per gram of soil under wheatgrass. There was no consistent influence of formulation or application method (high or ultra low volume) on penetration of conidia through the canopy of either crop. However, conidial populations under wheatgrass were larger than those under alfalfa in two of three trials. After 225–272 days (over winter), substantial populations (87 to 4.3 × 104 cfu/g) were recovered from soil. Although conidial densities decreased over time, reductions in population size over this period were generally less than one order of magnitude; neither crop nor formulation consistently influenced conidial persistence. In most instances, a rapid decrease in conidial populations was observed within approximately 20 days but thereafter, the rates of population decline abated. The initial decrease in conidial numbers did not appear to be related to precipitation. This study demonstrates that substantial numbers of B. bassiana conidia infiltrate crop canopies, are deposited on the soil surface, and subsequently persist in a clay–loam soil. The aerial application of B. bassiana conidia to vegetated roadsides may prove useful for the management of ovipositing grasshoppers and emerging nymphs.
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Read, S. J., S. T. Moss, and E. B. G. Jones. "Germination and development of attachment structures by conidia of aquatic Hyphomycetes: light microscope studies." Canadian Journal of Botany 70, no. 4 (April 1, 1992): 831–37. http://dx.doi.org/10.1139/b92-106.
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The time scales of conidial germination and production of postgermination attachment structures in species of the aquatic Hyphomycetes were investigated. The conidia of most species germinated within 2 h and formed appressoria within 6 h of settlement. Subsequent to settlement, appressoria were formed by all of the tetraradiate and branched conidia at the poles of the conidial arms. It is suggested that appressorium formation is an adaptation to aid fungal attachment to a substratum. Conidial germination was not influenced by the substratum; however, appressoria were both more numerous and more complex on a glass substratum. Mucilage was present on conidia, and mucilaginous sheaths were frequently observed to be associated with germ tubes and appressoria. The majority of species produced mucilages composed primarily of polysaccharide(s) with neutral or carboxyl functional groups. Key words: aquatic Hyphomycetes, germination, appressorium, attachment, settlement.
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Coertze, Sonja, and Gustav Holz. "Surface Colonization, Penetration, and Lesion Formation on Grapes Inoculated Fresh or After Cold Storage with Single Airborne Conidia of Botrytis cinerea." Plant Disease 83, no. 10 (October 1999): 917–24. http://dx.doi.org/10.1094/pdis.1999.83.10.917.
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Infection of grapes by different densities of airborne conidia of Botrytis cinerea was investigated on table grapes (cultivar Dauphine) harvested ripe (16°Brix) and inoculated fresh, or after SO2 treatment and 8-week storage at -0.5°C. Berries were detached at each inoculation and dusted with dry conidia in a settling tower. Following inoculation, the fresh berries were incubated for 24 h at high relative humidity (≥93%), or were overlaid with wet sterile paper towels. Cold-stored berries were incubated at high relative humidity. The effect of conidial density on surface colonization, penetration, and lesion formation was determined by surface sterilization, isolation, and freezing studies on fresh berries. Only symptom expression was determined on cold-stored berries. Fluorescence microscopy of skin segments showed that conidia were consistently deposited as single cells, and not in pairs or groups, on berry surfaces. Individual conidia, at all densities tested, readily infected the cold-stored berries and formed separate lesions after 2 days. Although the cold-stored berries were highly susceptible, lesion numbers were not related to conidial density at low inoculum dosages (0.67 to 2.60 conidia per mm2 berry surface). Lesion numbers tended to increase exponentially at higher dosages (3.24 to 3.88 conidia per mm2 berry surface). Individual conidia, however, did not induce any disease symptoms on fresh berries. Removal of the pathogen after 24-h incubation from the surface of fresh berries by ethanol, and subsequent incubation of excised skin segments revealed that, irrespective of the conidial density or the wetness regime, less than 2% of skin segments were penetrated. Furthermore, increasing densities of conidia did not lead to higher rates of surface colonization and skin penetration. The low incidence of disease caused on fresh berries and high disease incidence induced after prolonged cold storage indicated that infection was not governed by conidial density on berry surfaces, but by the level of host resistance.
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YANG, JING, JIAN-KUI (JACK) LIU, KEVIN D. HYDE, E. B. GARETH JONES, ZONG-LONG LUO, and ZUO-YI LIU. "Aquimonospora tratensis gen. et sp. nov. (Diaporthomycetidae, Sordariomycetes), a new lineage from a freshwater habitat in Thailand." Phytotaxa 397, no. 2 (March 15, 2019): 146. http://dx.doi.org/10.11646/phytotaxa.397.2.2.
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An interesting hyphomycetous taxon was collected on submerged wood in a freshwater stream in Trat Province, Thailand. It is morphologically similar to endophragmiella-like taxa, characterized by macronematous, mononematous conidiophores, monoblastic, enteroblastic conidiogenous cells and clavate to obovoid, septate brown conidia. The unique feature of this taxon is that the mature conidium often bears a young new conidial primordium which develops percurrently from a lower semi-transparent cell and they secede simultaneously. Phylogenetic analyses of a combined LSU, SSU and RPB2 sequence data support the placement of this fungus together with Platytrachelon and close to the family Papulosaceae within Diaporthomycetidae, Sordariomycetes. A new genus is introduced to accommodate the new taxon as Aquimonospora. The novel species Aquimonospora tratensis is described and illustrated and is compared with other morphologically similar taxa.
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Cox, ML, and JAG Irwin. "Conidium and appressorium variation in Australian isolates of the Colletotrichum gloeosporioides group and closely related species." Australian Systematic Botany 1, no. 2 (1988): 139. http://dx.doi.org/10.1071/sb9880139.
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Australian collections of the Colletotrichum gloeosporioides group and closely related species were studied to assess the suitability of existing taxonomic criteria and to examine the possibility of using alternative characters in the delimitation of taxa within the group. Conidia produced on free hyphae in slide cultures were consistently more variable than those produced in conidiomata in pure culture. Because of this, only dimensions of conidia from conidiomata should be used in taxonomic work. Appressorium morphology but not size was a useful addition to existing taxonomic criteria, with some isolates producing only unlobed or slightly lobed appressoria and others deeply lobed appressoria. On the basis of dimensions of conidia produced in conidiomata and appressorium morphology three biological groups emerge: isolates with mean conidial widths between 3.0 and 4.2 µm, with either unlobed or slightly lobed appressoria; isolates with mean conidial widths between 4.5 and 5.5 µm, with unlobed or slightly lobed appressoria; and isolates with conidial widths between 4.5 and 5.5 µm, with obviously lobed appressoria. Hyphal conidiogenesis appears to be useful in delimiting taxa only in C. crassipes where hyphal conidia were borne on branched conidiophores that were relatively short and stout. All other collections examined produced hyphal conidia on long, unbranched conidiophores, indistinguishable from normal hyphae.
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Melouk, H. A., and J. L. Sherwood. "Effect of peanut mottle virus on reaction of peanut cv. Tamnut 74 to Cercospora arachidicola." Peanut Science 13, no. 1 (January 1, 1986): 31–33. http://dx.doi.org/10.3146/i0095-3679-13-1-9.
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Abstract Two-week old seedlings of Tamnut 74 peanut were inoculated with peanut mottle virus (PMV) or left nontreated, and four weeks later were sprayed with a conidial suspension of Cercospora arachidicola (2 × 104 conidia/mL) prior to placement in a polyethylene enclosure in a growth chamber (22–30 C, 100% RH). After three weeks, number of lesions/leaflet, leaflet area (mm2), necrotic area (mm2)/leaflet, percent necrotic area, conidial density (conidia/mm2) of necrotic area), and conidia/leaflet, was determined on four leaflets for each of 12 PMV-infected and 12 virus-free plants. Conidia/leaflet (one important parameter in evaluating reaction of peanut genotypes to C. arachidicola), lesions/leaflet, area of lesion, and leaflet area was reduced on PMV-infected plants compared to virus-free plants in each of 4 experiments. Similarly, necrotic area/leaflet were reduced in 3 of 4 experiments. Conidia/mm2 of necrotic area was reduced in 2 of 4 experiments. PMV was not detected in conidia of C. arachidicola from PMV infected plants by inoculation to a PMV indicator host, serology, electron microscopy or electrophoresis.
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Marr, Kieren A., Michael Koudadoust, Michele Black, and S. Arunmozhi Balajee. "Early Events in Macrophage Killing ofAspergillus fumigatus Conidia: New Flow Cytometric Viability Assay." Clinical Diagnostic Laboratory Immunology 8, no. 6 (November 1, 2001): 1240–47. http://dx.doi.org/10.1128/cdli.8.6.1240-1247.2001.
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ABSTRACT Detailed investigations of macrophage phagocytosis and killing ofAspergillus fumigatus conidia have been limited by technical difficulties in quantifying fungal uptake and viability. In order to study early events in cell pathogen ingestion and killing, we developed a new flow cytometry assay that utilizes the fungus-specific viability dye FUN-1. Metabolically active A. fumigatusconidia accumulate orange fluorescence in vacuoles, while dormant or dead conidia stain green. After incubation within THP-1 cells, recovered conidia are costained with propidium iodide (PI) to discriminate between dormant and dead cells. Flow cytometric measurements of FUN-1 metabolism and PI uptake provide indicators of conidial viability, dormancy, and death. Conidial phagocytosis and killing are also assessed by measurement of green and orange FUN-1 fluorescence within the THP-1 cell population. Compared to previously described methods, this assay has less error introduced by membrane permeability changes and serial dilution of filamentous fungal forms. Results suggest that the THP-1 cells kill conidia rapidly (within 6 h) after exposure. Conidia that are preexposed to human serum are ingested and killed more quickly than are nonopsonized conidia.
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Mims, C. W., M. A. Rogers, and C. G. Van Dyke. "Ultrastructure of conidia and conidium germination in the plant pathogenic fungus Alternaria cassiae." Canadian Journal of Botany 75, no. 2 (February 1, 1997): 252–60. http://dx.doi.org/10.1139/b97-027.
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Transmission electron microscopy of plunge-frozen and freeze-substituted samples was used to examine germinating conidia of Alternaria cassiae, a plant pathogenic fungus used as a biological control agent for sicklepod (Cassia obtusifolia). Hydrated conidia on small pieces of dialysis membrane were incubated for 1, 2, or 3 h on the surface of corn meal agar prior to fixation. Conidia were large, darkly pigmented, and surrounded by a thick, two-layered wall. Each conidium was divided by transverse and longitudinal septa into multiple cells, a few of which sometimes appeared necrotic. Each septum tapered to a small central pore region with which Woronin bodies were associated. Each healthy cell of a conidium contained a typical complement of cellular organelles including multiple nuclei. With the exception of lipid bodies, all the various organelles were well preserved by plunge freezing and freeze substitution. Evidence of germ tube development was visible by 2 h post-incubation and well-developed germ tubes were present by 3 h. Two modes of germ tube development were observed. In the less common mode germ tubes developed inside conidia and grew internally through one or more adjacent cells before emerging from the conidium surface. Cells penetrated by internal germ tubes appeared necrotic. In the more common mode of germination, germ tubes developed directly from the conidium surface. Multiple germ tubes usually arose from each conidium and grew out in all directions. Germ tubes that contacted the underlying dialysis membrane continued to grow along its surface. Extracellular material was produced in association with developing germ tubes and coated the sides of germinated conidia and covered germ tubes growing along membranes. Key words: transmission electron microscopy, cryofixation, freeze substitution, germ tube development.
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Rizkie, Lilian, Siti Herlinda, Suwandi ., Chandra Irsan, Susilawati ., and Benyamin Lakitan. "KERAPATAN DAN VIABILITAS KONIDIA BEAUVERIA BASSIANA DAN METARHIZIUM ANISOPLIAE PADA MEDIA IN VITRO PH RENDAH." JURNAL HAMA DAN PENYAKIT TUMBUHAN TROPIKA 17, no. 2 (October 1, 2017): 119. http://dx.doi.org/10.23960/j.hptt.217119-127.
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Conidial density and viability of Beauveria bassiana and Metarhizium anisopliae grown on the low-pH in vitro medium. Liquid bioinsecticide with active ingredient from conidial entomopathogenic fungus has major constraints, namely short shelf life due to declining conidial viability and density is caused by low pH in the bioinsecticide carrier. This experiment aimed to measure the loss of conidial viability and density of Beauveria bassiana and Metarhizium anisopliae isolates grown on in vitro medium with low pH. Entomopathogenic fungus isolates were used as much as 28 isolates grown on in vitro medium at low pH, namely pH 5, 4, 3, and 2. The results showed that the fungus isolate that had the highest conidial density on in vitro medium at pH 5 was found on isolates of B. bassiana with code BPcMs (2.583 x 109 conidia mL-1), while the lowest one was found on isolates of B. bassiana with code of BWS Pantura (0.825x109 conidia mL-1). All isolate conidial density from in vitro medium with pH 2 decreased regularly. Conidial density of BPcMs isolate decreased to 2.483 x 109conidia mL-1, as well as BWS Pantura isolate also decreased to 0.425x109 conidia mL-1. The highest conidial viability at pH 5 was found on isolates of B. bassiana with code of BPcMs (51.572%), while the lowest conidial viability was found on isolate of B. bassiana with BTmPc code (15.040%). At pH 2, almost isolates tested had low conidial viability. The conidial viability of isolates BPcMs decreased to 47.037%%, while the isolates BTmPc also decreased to 12.778%. Therefore, the lower of the pH of the in vitro medium was, the lower of conidial viability and density of B. bassiana and M. anisopliae was
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Kramer, John P. "Entomophthora muscae — moisture as a factor affecting its transmission and conidial germination." Acta Mycologica 16, no. 1 (August 20, 2014): 133–39. http://dx.doi.org/10.5586/am.1980.009.
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The role played by moisture in the transmission of <i>Entomophthora muscae</i> and in the germination of its conidia was investigated. A majority of adult house flies exposed to conidial showers that fell upon surfaces covered with droplets of condensation acquired the parasite, while no flies exposed to conidial showers that fell upon dry surfaces did so. A microscopical study of conidial showers showed that germination was practically non-existent on dry surfaces while a vast majority of conidia that fell upon a droplet-covered surface germinated. A method for the <i>in vivo</i> culture of <i>E. muscae</i> was developpd and 11 serial passages of the fungus were achieved. Resting spores rather than conidia became the dominant form produced in the cadavers, and flies in a twelfth group remained unifected.
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Dyke, C. Gerald Van, and Charles W. Mims. "Ultrastructure of conidia, conidium germination, and appressorium development in the plant pathogenic fungus Colletotrichum truncatum." Canadian Journal of Botany 69, no. 11 (November 1, 1991): 2455–67. http://dx.doi.org/10.1139/b91-305.
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Nongerminating conidia of Colletotrichum truncatum were coated with copious amounts of a finely fibrillar extracellular matrix. This matrix spread out onto the dialysis membrane used as a substrate in this study. Each thin-walled conidium contained a single nucleus that underwent mitosis 1–2 h following placement of aqueous suspensions of conidia on membranes. A septum subsequently developed near the middle of the conidium, creating two uninucleate cells. Just prior to or during septum development a germ tube emerged laterally, usually near one end of the conidium. The nucleus moved into the germ tube and underwent mitosis. One daughter nucleus remained in the germ tube, the other moved back into the conidium. Developing germ tubes appeared to produce large amounts of electron-dense, fibrillar material that coated their surfaces. This material blended into the remnants of the matrix initially coating conidia and could not be clearly differentiated from the latter material. Germ tubes grew to various lengths before forming appressoria. Appressorium differentiation began shortly after the germ-tube tip curved sharply. A septum developed to delimit the tip that differentiated into a swollen appressorium. By 6 h following initial hydration of conidia, appressoria were melanized and the surrounding extracellular material had condensed onto their surfaces, forming an electron-dense coating that appeared to stick appressoria to dialysis membranes. A tiny penetration peg developed from an apparently wall-less region on the underside of the mature appressorium and, in some instances, grew a short distance into the dialysis membrane. Key words: electron microscopy, freeze substitution, conidia, appressoria.
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Ment, Dana, Galina Gindin, Asael Rot, Victoria Soroker, Itamar Glazer, Shimon Barel, and Michael Samish. "Novel Technique for Quantifying Adhesion of Metarhizium anisopliae Conidia to the Tick Cuticle." Applied and Environmental Microbiology 76, no. 11 (April 2, 2010): 3521–28. http://dx.doi.org/10.1128/aem.02596-09.
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ABSTRACT The present study describes an accurate quantitative method for quantifying the adherence of conidia to the arthropod cuticle and the dynamics of conidial germination on the host. The method was developed using conidia of Metarhizium anisopliae var. anisopliae (Metschn.) Sorokin (Hypocreales: Clavicipitaceae) and engorged Rhipicephalus annulatus (Say) (Arachnida: Ixodidae) females and was also verified for M. anisopliae var. acridum Driver et Milner (Hypocreales: Clavicipitaceae) and Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae) larvae. This novel method is based on using an organic solvent (dichloromethane [DCM]) to remove the adhered conidia from the tick cuticle, suspending the conidia in a detergent solution, and then counting them using a hemocytometer. To confirm the efficacy of the method, scanning electron microscopy (SEM) was used to observe the conidial adherence to and removal from the tick cuticle. As the concentration of conidia in the suspension increased, there were correlating increases in both the number of conidia adhering to engorged female R. annulatus and tick mortality. However, no correlation was observed between a tick's susceptibility to fungal infection and the amount of adhered conidia. These findings support the commonly accepted understanding of the nature of the adhesion process. The mechanism enabling the removal of the adhered conidia from the host cuticle is discussed.
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Leandro, L. F. S., M. L. Gleason, F. W. Nutter, S. N. Wegulo, and P. M. Dixon. "Strawberry Plant Extracts Stimulate Secondary Conidiation by Colletotrichum acutatum on Symptomless Leaves." Phytopathology® 93, no. 10 (October 2003): 1285–91. http://dx.doi.org/10.1094/phyto.2003.93.10.1285.
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Conidial suspensions of Colletotrichum acutatum were prepared in 1:27, 1:45, and 1:81 (wt/vol) dilutions of an extract of strawberry (cv. Tristar) flowers or leaves in water. Strawberry leaves and plastic coverslips were sprayed with the conidial suspensions, incubated at 25°C and continuous wetness for 48 h, and the number of conidia and appressoria were counted. In another experiment, leaves and coverslips were sprayed with a conidial suspension in water, incubated for 72 h to establish C. acutatum populations, and placed in a growth chamber under dry conditions for up to 6 weeks. At each sampling time, leaves and coverslips were sprayed with flower extracts, leaf extracts, or water, incubated for 48 h at 25°C and continuous wetness, and the number of conidia and appressoria were counted. Flower extracts significantly (P ≤ 0.05) increased the number of conidia on leaves and coverslips compared with water, both when conidia were applied with the extracts and when the extracts were applied to C. acutatum populations exposed to dryness for up to 2 weeks. Application of flower extracts resulted in up to 10- and 16-fold increases in conidia on leaves and coverslips, respectively. Number of conidia increased more when exposed to flower extracts than to leaf extracts. Production of appressoria was not significantly affected by flower or leaf extracts. Our results suggest that inoculum levels of C. acutatum on foliage may increase during flowering of strawberry plants.