5 resultados para Paecilomyces
em QUB Research Portal - Research Directory and Institutional Repository for Queen's University Belfast
Resumo:
The effects of temperature (5-50°C), water availability (0.998-0.88 water activity, aw), and aw × temperature interactions (15-45°C) on growth of three entomogenous fungi, Beauveria bassiana, Metarhizium anisopliae, and Paecilomyces farinosus, were evaluated on a Sabouraud dextrose-based medium modified with the ionic solute KCl, the non-ionic solute glycerol, and an inert solute, polyethylene glycol (PEG) 600. The temperature ranges for growth of B. bassiana, M. anisopliae, and P. farinosus were 5-30, 5-40, and 5-30°C, and optimum growth temperatures were 25, 30, and 20°C, respectively. All three species grew over a similar aw range (0.90-0.998) at optimum temperatures for growth. However, there were significant interspecies variations in growth rates on media modified with each of the three aw-modifying solutes. Growth aw optima ranged between 0.99 and 0.97 on KCl-, glycerol-, and PEG 600-modified media for M. anisopliae and P. farinosus. B. bassiana grew optimally at 0.998 aw, regardless of aw. Comprehensive two-dimensional profiles of aw × temperature relations for growth of these three species were constructed for the first time. The results are discussed in relation to the environmental limits that determine efficacy of entomogenous fungi as biocontrol agents in nature. © 1999 Academic Press.
Resumo:
The growth and conidial physiology of the entomopathogenic fungi Beauveria bassiana, Metarhizium anisopliae, and Paecilomyces farinosus were studied under different conditions. The effects of culture age (up to 120 days), temperature (5 to 35°C), and pH (2.9 to 11.1) were determined. Growth was optimal at pH 5 to 8 for each isolate and between 20 and 35°C, depending on the isolate. The predominant polyol in conidia was mannitol, with up to 39, 134, and 61 mg g of conidia-1 for B. bassiana, M. anisopliae, and P. farinosus, respectively. Conidia of M. anisopliae contained relatively small amounts of lower-molecular-weight polyols and trehalose (less than 25 mg g-1 in total) in all treatments. Conidia of B. bassiana and P. farinosus contained up to 30, 32, and 25 mg of glycerol, erythritol, and trehalose, respectively, g-1, depending on the treatment. Conidia of P. farinosus contained unusually high amounts of glycerol and erythritol at pH 2.9. The apparent effect of pH on gene expression is discussed in relation to the induction of a water stress response. To our knowledge, this is the first report of polyols and trehalose in fungal propagules produced over a range of temperature or pH. Some conditions and harvesting times were associated with an apparent inhibition of synthesis or accumulation of polyols and trehalose. This shows that culture age and environmental conditions affect the physiological quality of inoculum and can thereby determine its potential for biocontrol.
Resumo:
The insect pathogen Beauveria bassiana, Metarhizium anisopliae and Paecilomyces farinosos can be effective biocontrol agents when relative humidity (RH) is close to 100%. At reduced water availability, germination of propagules, and therefore host infection, cannot occur. Cultures of B. bassiana, M. anisopliae and P. farinosus were grown under different conditions to obtain conidia with a modified polyol and trehalose content. Conidia with higher intracellular concentrations of glycerol and erythritol germinated both more quickly and at lower water activity (a(w)) than those from other treatments. In contrast, conidia containing up to 235.7 mg trehalose g-1 germinated significantly (P < 0 05) more slowly than those with an equivalent polyol content but less trehalose, regardless of water availability. Conidia from control treatments did not germinate below 0.951 - 0.935 a(w) (≡ 95.1 - 93.5% RH). In contrast, conidia containing up to 164.6 mg glycerol plus erythritol g-1 germinated down to 0.887 a(w) (≡ 88.7% RH). These conidia germinated below the water availability at which mycelial growth ceases (0.930 - 0.920 a(w)). Germ tube extension rates reflected the percentage germination of conidia, so the most rapid germ tube growth occurred after treatments which produced conidia containing the most glycerol and erythritol. This study shows for the first time that manipulating polyol content can extend the range of water availability over which fungal propagules can germinate. Physiological manipulation of conidia may improve biological control of insect pests in the field.
Resumo:
Beauveria bassiana, Metarhizium anisopliae and Paecilomyces farinosus were grown on Sabouraud Dextrose Agar (SDA) modified with KCl to give a range of water activity (a(w)) from 0.938 to 0.998. Growth of all three species was optimal at 0.983 a(w) and growth occurred over the a(w) range tested. Acyclic sugar alcohol (polyol) and trehalose content of conidia was determined by HPLC and found to vary with species and a(w). Conidia of B. bassiana and P. farinosus were found to contain totals of 1.5% and 2.3% polyols respectively at 0.998 a(w), and double these amounts at <0.950 a(w). Conidia of M. anisopliae contained from 5.7% to 6.8% polyols at each a(w) tested. In conidia of all three species the predominant polyol was mannitol. The lower molecular weight polyols, arabitol and erythritol, were found to accumulate at reduced a(w). Small amounts of glycerol were present in conidia of each species; <15% total polyols. Conidia of B. bassiana and M. anisopliae contained about 0.5% trehalose from 0.970 to 0.998 a(w), but only trace amounts below 0.950 a(w). Conidia of P. farinosus contained 2.1% trehalose at 0.998 a(w) and this decreased to <0.1% below 0.950 a(w). Potential to manipulate the endogenous reserves of conidia of these biological control agents to enhance viability and desiccation tolerance is discussed.
Resumo:
The entomopathogenic fungi Beauveria bassiana, Metarhizium anisopliae and Paecilomyces farinosus were cultured on solid agar media containing different carbohydrate components (glycerol, glucose, trehalose or starch) at concentrations of ≤ 142.7 g added carbon 1-1 for 30 d at 25°C. The water activity (a(w)) of the media ranged from 0.925 to 0.998. Growth of M. anisopliae and P. farinosus was stimulated between 0.975 and 0.995 a(w) on glucose media and that of P. farinosus at 0. 975 a(w) on glycerol media. At < 0.970 a(w), growth of each fungal species was significantly reduced (P < 0.05). Polyhydroxy alcohols (polyols) and trehalose were extracted from conidia produced on different media and quantified using HPLC. Total polyol content of conidia produced on glucose media varied between 5.2 and 52.2 mg g-1 for B. bassiana, 77.3 and 90.3 mg g-1 for M. anisopliae, and 26.7 and 76.1 mg g-1 for P. farinosus. The amounts of specific polyols in conidia varied significantly from media of different glucose concentrations. Mannitol was the predominant polyol in conidia of all three species, with conidia of M. anisopliae, for example, containing as much as 75.2 mg mannitol g-1 when cultured on glucose media. The amount of the lower molecular mass polyols glycerol and erythritol was greater in conidia produced on glucose media with > 50.0 g added carbon 1-1 than that in conidia produced at lower glucose concentrations. Conidia contained between 10.8 and 20.8 mg glycerol plus erythritol g-1 on glucose media with 142.7 g added carbon 1-1, depending on species. Conversely, conidia of B. bassiana and P. farinosus contained maximum amounts of trehalose ( ≤ 23.5 mg g-1) when produced on glucose media with < 50.0 g added carbon l-1, and trehalose content was considerably less at higher glucose concentrations. There were accumulations of glycerol and erythritol in conidia of all three species when grown on glycerol media with > 25.0 g added carbon 1-1; conidia of B. bassiana contained up to 154.0 mg glycerol plus erythritol g-1. hen B. bassiana and P. farinosus were grown on trehalose media, conidia contained up to 222.1 mg trehalose g-1. By contrast, conidia of M. anisopliae contained < 17.0 mg trehalose g-1 under all conditions tested. The water availability of solutions of different polyols is discussed in relation to their potential to act in osmotic adjustment during germination. The ability to manipulate polyol and trehalose content of fungal propagules may be critical in enhancing the storage life and efficacy of biological control agents.