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J K Pell - One of the best experts on this subject based on the ideXlab platform.
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a novel computerised image analysis method for the measurement of production of conidia from the aphid pathogenic fungus Erynia neoaphidis
Fems Microbiology Letters, 2003Co-Authors: Tony Jo Bonner, J K Pell, Simon N. GrayAbstract:A semi-automated method has been developed for the quantification and measurement of conidia discharged by the aphid pathogen Erynia neoaphidis. This was used to compare conidiation by E. neoaphidis-mycosed pea aphid cadavers, mycelial plugs cut from agar plates, mycelial pellets from shake flasks and by mycelial pellets from different phases of liquid batch fermenter culture. Aphid cadavers discharged significantly more and significantly smaller conidia than plugs or pellets. The volume of conidia discharged was stable over the period of discharge (80 h), but more detailed analysis of the size frequency distribution showed that more very small and very large conidia were discharged after 5 h incubation than after 75 h incubation. Biomass harvested at the end of the exponential growth phase in batch fermenter culture produced significantly more conidia than biomass from any other growth phase. The implications of these findings for the development of production and formulation processes for E. neoaphidis as a biological control agent are discussed.
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aerodynamic diameter of conidia of Erynia neoaphidis and other entomophthoralean fungi
Fungal Biology, 2002Co-Authors: J K Pell, Farhad Hemmati, Alastair H Mccartney, M L DeadmanAbstract:The aerodynamic diameter, da, of conidia produced in vivo and in vitro by the entomopathogenic fungus Erynia neoaphidis were estimated using an impaction method. The estimated values of da for conidia produced in vivo were smaller than those produced in vitro: in vivo the values of da for primary and secondary conidia were between 16 and 18 μm (equivalent fall speed, Vs, 0.8–1.0 cm s−1); for in vitro produced conidia da values were between 28 and 31 μm (Vs, 2.4–3 cm s−1). For conidia produced by field collected cadavers the value of da, was estimated to be similar to that for conidia produced in vivo in the laboratory. The aerodynamic diameter of primary conidia of Conidiobolus obscurus (strain X39) and Zoophthora radicans (strain NW250) produced in vivo were also measured using the same method. The values of da for these two species were 45 and 17 μm (Vs, 6.2 and 0.9 cm s−1) respectively. Implications for dispersal of E. neoaphidis are discussed. The physical diameters of the test spores were measured microscopically and compared with the aerodynamic diameters.
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Apparent competition between two species of aphid via the fungal pathogen Erynia neoaphidis and its interaction with the aphid parasitoid Aphidius ervi
2002Co-Authors: Pope T, J K Pell, Croxson E, Godfray Hcj, Cb MullerAbstract:1. Motivated by a community study on aphids and their fungal pathogens, three hypotheses were tested experimentally to investigate the influence of the fungal pathogen, Erynia neoaphidis Remaudière and Hennebert, on aphid population and community ecology. 2. Field experiments were performed in 2 years to test whether two susceptible aphid species on different host plants might interact through the shared fungal pathogen. No strong pathogen-mediated indirect interactions (apparent competition) between populations of pea aphid Acyrthosiphon pisum Harris and nettle aphid Microlophium carnosum Buckton were detected. 3. In the first of the field experiments, pea aphids exposed to the fungus showed a weak tendency to produce more winged dispersal morphs than control populations not exposed to the fungus. In a laboratory test, however, no support was found for the hypothesis that the presence of volatiles from fungus-infected cadavers promotes production of winged offspring. 4. The response of the pea aphid parasitoid Aphidius ervi Halliday to colonies containing hosts infected 1 and 3 days previously was assessed. Wasps initiated fewer attacks on 1-day-old infected colonies than on healthy colonies, with the numbers on 3-day-old fungus-infected colonies intermediate
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conidial discharge in the aphid pathogen Erynia neoaphidis
Fungal Biology, 2001Co-Authors: J K Pell, Farhad Hemmati, Alastair H Mccartney, S J Clark, M L DeadmanAbstract:The patterns of conidial discharge of Erynia neoaphidis were measured from three species of aphids: nettle aphid (Microlophium carnosum), grain aphid (Sitobion avenae) and pea aphid (Acyrthosiphon pisum). The effects of release height, morph of aphid and temperature on the horizontal and vertical discharge of conidia were studied. Numbers of conidia deposited in the dorsal and lateral directions were distributed with distance in truncated bell shaped patterns. Discharge distances ranged from 2 to 11 mm and half the conidia caught travelled further than 5 mm. There was little difference in the horizontal dispersal patterns of conidia when ejected from cadavers of different morphs of the same species, or from different species. The weight of infected aphids showed little correlation with discharge patterns. Values of maximum discharge distance, Dm, were generally between 6 and 9 mm. Temperature had a significant effect on conidia discharged from the dorsal surface of apterous A. pisum cadavers. Dm was greater at 18 °C than at 10 or 25 °. Vertical discharge distances for conidia released from A. pisum cadavers ranged between about 2 and 8 mm. The maximum height to which conidia were projected vertically was not affected by temperature. However, the average height tended to be greater at 18 °. Half of the conidia reached heights of about 3.5 mm while the maximum heights reached were about 8 mm. The initial speeds of conidia were estimated from measured discharge distances. The results suggest that conidia of E. neoaphidis may be ejected at speeds of about 8 ms−1.
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airborne concentrations of conidia of Erynia neoaphidis above cereal fields
Fungal Biology, 2001Co-Authors: Farhad Hemmati, J K Pell, Alastair H Mccartney, M L DeadmanAbstract:The temporal pattern of release and dispersal of inoculum of plant and insect pathogenic fungi play an important role in the spread of disease. Airborne concentrations of primary and secondary conidia of Erynia neoaphidis released from the rose-grain aphid Metopolophium dirhodum were monitored at the edge of two winter wheat crops on IACR-Rothamsted Experimental Farm between May and September in 1996 and 1997. Hourly average temperature and humidity were recorded at each spore trap site and daily totals of rain and sunshine hours and daily average wind speed recorded about 1.6 km from the monitoring sites. No airborne conidia were found in 1996, but large numbers were trapped at the two sites in 1997. They were present from mid-June until early August, reaching peak concentrations on 17–18 July. Concentrations were usually highest during the night and in the early morning (01:00-07:00 h GMT) and were generally low during the day. On the 3 days when significant numbers of conidia were caught in the afternoon, daytime relative humidity was high (about 89%) and day-time temperature low (about 16°C). Night-time conditions nearly always favoured the production of conidia. This suggests day to day variation in airborne conidium concentrations may be affected more by underlying biological factors than environmental conditions.
Urs Tuor - One of the best experts on this subject based on the ideXlab platform.
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infection of macrosiphum euphorbiae with mycelial preparations of Erynia neoaphidis in a greenhouse trial
Fungal Biology, 2000Co-Authors: P. A. Shah, Markus Aebi, Urs TuorAbstract:Experimental preparations (alginate granules and mycelial mats) of the entomopathogenic Erynia neoaphidis were assessed for their capacity to cause infections in populations of Macrosiphum euphorbiae on pepper plants, in a greenhouse trial performed over 14 d. The dried preparations contained hyphal cells, which upon rehydration produced conidiophores and ejected ballistospores. Applications of alginate granules and mycelial mats on soil were more rapid in causing infections in the host population compared with foliar applications. On the last sample date, infection rates of 10–14% were obtained with foliar applications of E. neoaphidis as alginate granules and mycelial mats, respectively. With soil applications of E. neoaphidis granules and mats, infections were 23–36% after 14 d. From all sample dates, 183 cadavers were found on pepper plants treated with E. neoaphidis and 37 (= 20%) exhibited external sporulation after overnight incubation. Comparisons were also made with single foliar sprays of Beauveria bassiana (Mycotrol WPr) and the systemic insecticide pymetrozine (Chess WPg), the latter being the only treatment to significantly reduce aphid numbers during the trial period. Treatment with B. bassiana resulted in good initial infection rates (50–60%) which declined over the period and reached the same infection level as E. neoaphidis treatments at the end of the trial. With B. bassiana , a total of 81 cadavers were found, of which 62 (= 77%) sporulated.
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drying and storage procedures for formulated and unformulated mycelia of the aphid pathogenic fungus Erynia neoaphidis
Fungal Biology, 2000Co-Authors: P. A. Shah, Markus Aebi, Urs TuorAbstract:Mycelial preparations of Erynia neoaphidis were tested under different drying and storage conditions. For unformulated mycelial discs and formulated alginate granules, sporulation was best maintained if drying at 20–22 °C was performed at 60 or 90% r.h. rather than an ambient humidity of 30%. Storage experiments were performed on preparations dried at 90% r.h. for 72 h. Estimates for a 50% decline in sporulation with storage time (ST 50 ) were computed if there were statistically significant fits using exponential or non-parametric linear regression. For mycelial discs, values of ST 50 were between 36–39 d when maintained at 10° with silica gel or 20% r.h., and 14–26 d when kept at 10° and 35% r.h. or with silica gel and 15 or 20°. For alginate granules, ST 50 values of 6–9 d were obtained at 10° and 20–55% r.h. A 5- to 9-fold increase in sporulation was produced with granules containing 2% w/v sucrose and 5% w/v starch compared to granules without additives. Elevated humidities are recommended for drying E. neoaphidis mycelia and viability of dried preparations is best maintained if they are stored at 10° compared with 15 or 20°.
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biological characteristics of selected Erynia neoaphidis isolates
Fungal Biology, 2000Co-Authors: H Sierotzki, P. A. Shah, Markus Aebi, F Camastral, Urs TuorAbstract:Four isolates of the entomopathogenic fungus Erynia neoaphidis , from different hosts and locations in Switzerland, were distinguished by their DNA fragment banding pattern obtained by RAPD-PCR. The isolates differed in sporulation and germination rates, but not in virulence (overall mean LD 50 16 conidia mm −2 ) against the aphid Acyrthosiphon pisum. The sporulation rate was 6 to 24 conidia mm −2 10 min −1 . On nutrient agar, 24–73% of the conidia produced secondary conidia and 32–68% produced germ-tubes on polystyrene. Differentiation of primary into secondary conidia or germ-tubes is possibly dependent on the presence of free water on the contact surface; on a dry surface, conidia germinated mostly with a germ-tube, whereas on a wet surface the conidia produced a secondary conidium. Experimental support is provided for the claim that, in addition to LD 50 values, features such as sporulation rate, spore germination, capacity to form secondary conidia and intraspecific variation should be considered in selecting isolates of E. neoaphidis for biocontrol agents.
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production factors involved in the formulation of Erynia neoaphidis as alginate granules
Biocontrol Science and Technology, 1999Co-Authors: P. A. Shah, Markus Aebi, Urs TuorAbstract:Granular formulations of the aphid-pathogenic fungus Erynia neoaphidis were produced by entrapping mycelia in alginate polysaccharide polymers. Four Swiss isolates were compared for the numbers of conidia discharged from the surface of alginate granules in standardized laboratory assays and two were considered to be suitable for further development. Conidiation was achieved from granules produced using nozzle diameters of 2.0. 1.0 and 0.5 mm from glass burettes or a novel vibrating tip apparatus. The mean diameters of dried granules varied from 0.5 to 1.8 mm. The addition of sucrose, potato starch or chitin in alginate solutions significantly improved the numbers of discharged conidia. W ith freshly produced granules, there was a 14.2- fold increase in sporulation from 6.3 to 89.7 conidia mm - 2 using 2% (w/v) sucrose. Increases of 1.6-to 2.3-fold, from 11.0 to 17.7 and 25.2 conidia mm - 2, were observed using 5% (w/v) starch or chitin respectively. The overnight drying of granules in a laminar flow hood ...
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Method To Immobilize the Aphid-Pathogenic Fungus Erynia neoaphidis in an Alginate Matrix for Biocontrol
Applied and environmental microbiology, 1998Co-Authors: P. A. Shah, Markus Aebi, Urs TuorAbstract:Erynia neoaphidis is an important fungal pathogen of aphid pests worldwide. There have been few reported attempts to formulate this natural agent for use in biocontrol. In the current study, factors involved in the immobilization of E. neoaphidis hyphae in an alginate matrix were investigated. Hyphae of two isolates cultured in liquid medium were 220 to 620 μm in length and 7 to 19 μm in diameter with a 74 to 83% cytoplasmic content. The optimal concentration of low-viscosity sodium alginate for production of conidia from entrapped hyphae was 1.5% (wt/vol), and 0.1 and 0.25 M calcium chloride were equally suitable for use as the gelling solution. Alginate beads were rinsed with 10% sucrose after gelling. However, beads should not be left for longer than 40 min in 0.1 M calcium chloride or 10% sucrose to prevent a 10% loss in conidial production. A 40% (vol/vol) concentration of fungal biomass produced significantly more conidia than either 20% or the standard concentration of 10%. This effect persisted even after beads were dried overnight in a laminar flow hood and stored at 4°C for 4 days. Conidia from freshly produced alginate beads caused 27 to 32% infection in Pea aphids as determined by standardized laboratory bioassays. This finding was not significantly different from infections in aphids inoculated with fresh mycelial mats or plugs from Petri dish cultures. In conclusion, algination appears to be a promising technique for utilizing E. neoaphidis in the biocontrol of aphid pests.
Farhad Hemmati - One of the best experts on this subject based on the ideXlab platform.
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aerodynamic diameter of conidia of Erynia neoaphidis and other entomophthoralean fungi
Fungal Biology, 2002Co-Authors: J K Pell, Farhad Hemmati, Alastair H Mccartney, M L DeadmanAbstract:The aerodynamic diameter, da, of conidia produced in vivo and in vitro by the entomopathogenic fungus Erynia neoaphidis were estimated using an impaction method. The estimated values of da for conidia produced in vivo were smaller than those produced in vitro: in vivo the values of da for primary and secondary conidia were between 16 and 18 μm (equivalent fall speed, Vs, 0.8–1.0 cm s−1); for in vitro produced conidia da values were between 28 and 31 μm (Vs, 2.4–3 cm s−1). For conidia produced by field collected cadavers the value of da, was estimated to be similar to that for conidia produced in vivo in the laboratory. The aerodynamic diameter of primary conidia of Conidiobolus obscurus (strain X39) and Zoophthora radicans (strain NW250) produced in vivo were also measured using the same method. The values of da for these two species were 45 and 17 μm (Vs, 6.2 and 0.9 cm s−1) respectively. Implications for dispersal of E. neoaphidis are discussed. The physical diameters of the test spores were measured microscopically and compared with the aerodynamic diameters.
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conidial discharge in the aphid pathogen Erynia neoaphidis
Fungal Biology, 2001Co-Authors: J K Pell, Farhad Hemmati, Alastair H Mccartney, S J Clark, M L DeadmanAbstract:The patterns of conidial discharge of Erynia neoaphidis were measured from three species of aphids: nettle aphid (Microlophium carnosum), grain aphid (Sitobion avenae) and pea aphid (Acyrthosiphon pisum). The effects of release height, morph of aphid and temperature on the horizontal and vertical discharge of conidia were studied. Numbers of conidia deposited in the dorsal and lateral directions were distributed with distance in truncated bell shaped patterns. Discharge distances ranged from 2 to 11 mm and half the conidia caught travelled further than 5 mm. There was little difference in the horizontal dispersal patterns of conidia when ejected from cadavers of different morphs of the same species, or from different species. The weight of infected aphids showed little correlation with discharge patterns. Values of maximum discharge distance, Dm, were generally between 6 and 9 mm. Temperature had a significant effect on conidia discharged from the dorsal surface of apterous A. pisum cadavers. Dm was greater at 18 °C than at 10 or 25 °. Vertical discharge distances for conidia released from A. pisum cadavers ranged between about 2 and 8 mm. The maximum height to which conidia were projected vertically was not affected by temperature. However, the average height tended to be greater at 18 °. Half of the conidia reached heights of about 3.5 mm while the maximum heights reached were about 8 mm. The initial speeds of conidia were estimated from measured discharge distances. The results suggest that conidia of E. neoaphidis may be ejected at speeds of about 8 ms−1.
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airborne concentrations of conidia of Erynia neoaphidis above cereal fields
Fungal Biology, 2001Co-Authors: Farhad Hemmati, J K Pell, Alastair H Mccartney, M L DeadmanAbstract:The temporal pattern of release and dispersal of inoculum of plant and insect pathogenic fungi play an important role in the spread of disease. Airborne concentrations of primary and secondary conidia of Erynia neoaphidis released from the rose-grain aphid Metopolophium dirhodum were monitored at the edge of two winter wheat crops on IACR-Rothamsted Experimental Farm between May and September in 1996 and 1997. Hourly average temperature and humidity were recorded at each spore trap site and daily totals of rain and sunshine hours and daily average wind speed recorded about 1.6 km from the monitoring sites. No airborne conidia were found in 1996, but large numbers were trapped at the two sites in 1997. They were present from mid-June until early August, reaching peak concentrations on 17–18 July. Concentrations were usually highest during the night and in the early morning (01:00-07:00 h GMT) and were generally low during the day. On the 3 days when significant numbers of conidia were caught in the afternoon, daytime relative humidity was high (about 89%) and day-time temperature low (about 16°C). Night-time conditions nearly always favoured the production of conidia. This suggests day to day variation in airborne conidium concentrations may be affected more by underlying biological factors than environmental conditions.
Simon N. Gray - One of the best experts on this subject based on the ideXlab platform.
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a novel computerised image analysis method for the measurement of production of conidia from the aphid pathogenic fungus Erynia neoaphidis
Fems Microbiology Letters, 2003Co-Authors: Tony Jo Bonner, J K Pell, Simon N. GrayAbstract:A semi-automated method has been developed for the quantification and measurement of conidia discharged by the aphid pathogen Erynia neoaphidis. This was used to compare conidiation by E. neoaphidis-mycosed pea aphid cadavers, mycelial plugs cut from agar plates, mycelial pellets from shake flasks and by mycelial pellets from different phases of liquid batch fermenter culture. Aphid cadavers discharged significantly more and significantly smaller conidia than plugs or pellets. The volume of conidia discharged was stable over the period of discharge (80 h), but more detailed analysis of the size frequency distribution showed that more very small and very large conidia were discharged after 5 h incubation than after 75 h incubation. Biomass harvested at the end of the exponential growth phase in batch fermenter culture produced significantly more conidia than biomass from any other growth phase. The implications of these findings for the development of production and formulation processes for E. neoaphidis as a biological control agent are discussed.
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a model to explain the growth kinetics of the aphid pathogenic fungus Erynia neoaphidis in liquid culture
Fungal Biology, 1997Co-Authors: Simon N. Gray, Paul MarkhamAbstract:A mathematical model is presented which qualitatively describes the growth kinetics of the aphid-pathogenic Erynia neoaphidis in liquid culture. An essential feature of the model is that it allows for the presence of a toxic component within the growth medium which may be broken down by an extracellular enzyme released by the biomass. In this investigation, the toxin was oleic acid which had previously been shown to be essential for the growth of E. neoaphidis , but only at low concentration. The model reproduces a number of unusual features of the kinetics of growth of E. neoaphidis in liquid culture. These include: the requirement for a high inoculum concentration to successfully initiate growth in liquid culture; failure to grow in continuous culture under conditions similar to those supporting successful batch culture; a reduced growth yield in continuous culture compared to batch culture; a depressed apparent specific growth rate in continuous culture compared to batch culture and, deviation from the usual exponential decrease of biomass concentration during washout. Through the development of the model, and the application of predictions derived from it to the laboratory situation, continuous culture of E. neoaphidis was achieved for the first time.
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in vitro germination of single conidia of the aphid pathogenic fungus Erynia neoaphidis and phenotypic variation among sibling strains
Fems Microbiology Letters, 1991Co-Authors: Simon N. Gray, Neil Wilding, Paul MarkhamAbstract:A simple method has been developed for triggering the germination of isolated Erynia neoaphidis conidia in vitro. This was used to obtain genetically pure monoconidial isolates of the fungus for the first time in vitro. The phenotypes of such isolated were characterized on the basis of colony radial growth rate, colony peripheral growth zone width, specific growth rate and aphid-infectivity. Significant differences were demonstrated between isolates from a single parental colony for the first two of these characteristics, suggesting that several different genotypes could be derived from a single field isolate.
P. A. Shah - One of the best experts on this subject based on the ideXlab platform.
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infection of macrosiphum euphorbiae with mycelial preparations of Erynia neoaphidis in a greenhouse trial
Fungal Biology, 2000Co-Authors: P. A. Shah, Markus Aebi, Urs TuorAbstract:Experimental preparations (alginate granules and mycelial mats) of the entomopathogenic Erynia neoaphidis were assessed for their capacity to cause infections in populations of Macrosiphum euphorbiae on pepper plants, in a greenhouse trial performed over 14 d. The dried preparations contained hyphal cells, which upon rehydration produced conidiophores and ejected ballistospores. Applications of alginate granules and mycelial mats on soil were more rapid in causing infections in the host population compared with foliar applications. On the last sample date, infection rates of 10–14% were obtained with foliar applications of E. neoaphidis as alginate granules and mycelial mats, respectively. With soil applications of E. neoaphidis granules and mats, infections were 23–36% after 14 d. From all sample dates, 183 cadavers were found on pepper plants treated with E. neoaphidis and 37 (= 20%) exhibited external sporulation after overnight incubation. Comparisons were also made with single foliar sprays of Beauveria bassiana (Mycotrol WPr) and the systemic insecticide pymetrozine (Chess WPg), the latter being the only treatment to significantly reduce aphid numbers during the trial period. Treatment with B. bassiana resulted in good initial infection rates (50–60%) which declined over the period and reached the same infection level as E. neoaphidis treatments at the end of the trial. With B. bassiana , a total of 81 cadavers were found, of which 62 (= 77%) sporulated.
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drying and storage procedures for formulated and unformulated mycelia of the aphid pathogenic fungus Erynia neoaphidis
Fungal Biology, 2000Co-Authors: P. A. Shah, Markus Aebi, Urs TuorAbstract:Mycelial preparations of Erynia neoaphidis were tested under different drying and storage conditions. For unformulated mycelial discs and formulated alginate granules, sporulation was best maintained if drying at 20–22 °C was performed at 60 or 90% r.h. rather than an ambient humidity of 30%. Storage experiments were performed on preparations dried at 90% r.h. for 72 h. Estimates for a 50% decline in sporulation with storage time (ST 50 ) were computed if there were statistically significant fits using exponential or non-parametric linear regression. For mycelial discs, values of ST 50 were between 36–39 d when maintained at 10° with silica gel or 20% r.h., and 14–26 d when kept at 10° and 35% r.h. or with silica gel and 15 or 20°. For alginate granules, ST 50 values of 6–9 d were obtained at 10° and 20–55% r.h. A 5- to 9-fold increase in sporulation was produced with granules containing 2% w/v sucrose and 5% w/v starch compared to granules without additives. Elevated humidities are recommended for drying E. neoaphidis mycelia and viability of dried preparations is best maintained if they are stored at 10° compared with 15 or 20°.
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biological characteristics of selected Erynia neoaphidis isolates
Fungal Biology, 2000Co-Authors: H Sierotzki, P. A. Shah, Markus Aebi, F Camastral, Urs TuorAbstract:Four isolates of the entomopathogenic fungus Erynia neoaphidis , from different hosts and locations in Switzerland, were distinguished by their DNA fragment banding pattern obtained by RAPD-PCR. The isolates differed in sporulation and germination rates, but not in virulence (overall mean LD 50 16 conidia mm −2 ) against the aphid Acyrthosiphon pisum. The sporulation rate was 6 to 24 conidia mm −2 10 min −1 . On nutrient agar, 24–73% of the conidia produced secondary conidia and 32–68% produced germ-tubes on polystyrene. Differentiation of primary into secondary conidia or germ-tubes is possibly dependent on the presence of free water on the contact surface; on a dry surface, conidia germinated mostly with a germ-tube, whereas on a wet surface the conidia produced a secondary conidium. Experimental support is provided for the claim that, in addition to LD 50 values, features such as sporulation rate, spore germination, capacity to form secondary conidia and intraspecific variation should be considered in selecting isolates of E. neoaphidis for biocontrol agents.
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production factors involved in the formulation of Erynia neoaphidis as alginate granules
Biocontrol Science and Technology, 1999Co-Authors: P. A. Shah, Markus Aebi, Urs TuorAbstract:Granular formulations of the aphid-pathogenic fungus Erynia neoaphidis were produced by entrapping mycelia in alginate polysaccharide polymers. Four Swiss isolates were compared for the numbers of conidia discharged from the surface of alginate granules in standardized laboratory assays and two were considered to be suitable for further development. Conidiation was achieved from granules produced using nozzle diameters of 2.0. 1.0 and 0.5 mm from glass burettes or a novel vibrating tip apparatus. The mean diameters of dried granules varied from 0.5 to 1.8 mm. The addition of sucrose, potato starch or chitin in alginate solutions significantly improved the numbers of discharged conidia. W ith freshly produced granules, there was a 14.2- fold increase in sporulation from 6.3 to 89.7 conidia mm - 2 using 2% (w/v) sucrose. Increases of 1.6-to 2.3-fold, from 11.0 to 17.7 and 25.2 conidia mm - 2, were observed using 5% (w/v) starch or chitin respectively. The overnight drying of granules in a laminar flow hood ...
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Method To Immobilize the Aphid-Pathogenic Fungus Erynia neoaphidis in an Alginate Matrix for Biocontrol
Applied and environmental microbiology, 1998Co-Authors: P. A. Shah, Markus Aebi, Urs TuorAbstract:Erynia neoaphidis is an important fungal pathogen of aphid pests worldwide. There have been few reported attempts to formulate this natural agent for use in biocontrol. In the current study, factors involved in the immobilization of E. neoaphidis hyphae in an alginate matrix were investigated. Hyphae of two isolates cultured in liquid medium were 220 to 620 μm in length and 7 to 19 μm in diameter with a 74 to 83% cytoplasmic content. The optimal concentration of low-viscosity sodium alginate for production of conidia from entrapped hyphae was 1.5% (wt/vol), and 0.1 and 0.25 M calcium chloride were equally suitable for use as the gelling solution. Alginate beads were rinsed with 10% sucrose after gelling. However, beads should not be left for longer than 40 min in 0.1 M calcium chloride or 10% sucrose to prevent a 10% loss in conidial production. A 40% (vol/vol) concentration of fungal biomass produced significantly more conidia than either 20% or the standard concentration of 10%. This effect persisted even after beads were dried overnight in a laminar flow hood and stored at 4°C for 4 days. Conidia from freshly produced alginate beads caused 27 to 32% infection in Pea aphids as determined by standardized laboratory bioassays. This finding was not significantly different from infections in aphids inoculated with fresh mycelial mats or plugs from Petri dish cultures. In conclusion, algination appears to be a promising technique for utilizing E. neoaphidis in the biocontrol of aphid pests.