Development of a population-based threshold model of conidial germination for analysing the effects of physiological manipulation on the stress tolerance and infectivity of insect pathogenic fungi
Development of a population-based threshold model of conidial germination for analysing the effects of physiological manipulation on the stress tolerance and infectivity of insect pathogenic fungi
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DOI：
10.1111/j.1462-2920.2006.01055.x
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发表时间：
2006-09-01
影响因子：
5.1
通讯作者：
Chandler, D.
中科院分区：
文献类型：
--
作者：
Andersen, M.;Magan, N.;Chandler, D.
昆虫病原真菌正被用作害虫的生物防治剂，但在水供应减少的环境中，它们的效果可能很差。在这项研究中，潜在的提高生物防治通过生理操纵真菌接种进行了研究。通过在水分胁迫条件下培养球孢白僵菌、蕈状芽孢杆菌、长孢芽孢杆菌、绿僵菌和烟状拟青霉，使其产生的分生孢子浓度增加。采用广义线性模型描述了不同水分活度（水活度，a(w)）条件下分生孢子萌发的时间过程，在大多数情况下，降低萌发介质的水分活度会延迟萌发的开始，而不影响萌发时间的分布。在生理调控下，绿僵菌、蕈状芽孢菌、长孢菌和烟状芽孢菌的萌发速度在a(w)水平范围内加快。然而，生理处理对孢子萌发的影响与分生孢子渗透物含量之间的关系因真菌种类而异。发芽率（以发芽时间倒数表示）与萌发培养基的a(w)之间存在线性关系，但真菌种类和生理操作对萌发的a(w)阈值没有显著影响。在绿僵菌的生物试验中，生理处理后的分生孢子在寄主甜瓜棉蚜（Aphis gossypii）表面的萌发速度更快，即使在初始高相对湿度后降低，真菌毒力也会增加。综上所述，生理调控可能会导致田间生物防治的改善，但真菌种类/分离物的选择将是关键。此外，本研究中使用的基于群体的阈值模型，根据生理时间（也称为hydrotime）考虑发芽，可能在真菌学和环境微生物学中具有普遍应用。
Entomopathogenic fungi are being used as biocontrol agents of insect pests, but their efficacy can be poor in environments where water availability is reduced. In this study, the potential to improve biocontrol by physiologically manipulating fungal inoculum was investigated. Cultures of Beauveria bassiana, Lecanicillium muscarium, Lecanicillium longisporum, Metarhizium anisopliae and Paecilomyces fumosoroseus were manipulated by growing them under conditions of water stress, which produced conidia with increased concentrations of erythritol. The time-course of germination of conidia at different water activities (water activity, a(w)) was described using a generalized linear model, and in most cases reducing the water activity of the germination medium delayed the onset of germination without affecting the distribution of germination times. The germination of M. anisopliae, L. muscarium, L. longisporum and P. fumosoroseus was accelerated over a range of a(w) levels as a result of physiological manipulation. However, the relationship between the effect of physiological manipulation on germination and the osmolyte content of conidia varied according to fungal species. There was a linear relationship between germination rate, expressed as the reciprocal of germination time, and a(w) of the germination medium, but there was no significant effect of fungal species or physiological manipulation on the a(w) threshold for germination. In bioassays with M. anisopliae, physiologically manipulated conidia germinated more rapidly on the surface of an insect host, the melon cotton aphid Aphis gossypii, and fungal virulence was increased even when relative humidity was reduced after an initial high period. It is concluded that physiological manipulation may lead to improvements in biocontrol in the field, but choice of fungal species/isolate will be critical. In addition, the population-based threshold model used in this study, which considered germination in terms of physiological time, also called hydrotime, could have general application in mycology and environmental microbiology.