Unité de Phytopathologie, Gembloux Agro-Bio Tech, Université de Liège, Gembloux, Belgium.
J Appl Microbiol. 2011 Feb;110(2):521-8. doi: 10.1111/j.1365-2672.2010.04908.x. Epub 2010 Dec 10.
To determine the effect of water activity (a(w) =0·880-0·960) and temperature (15-35°C) on the percentage of viable conidia and mycelial growth of three biocontrol agents effective against water hyacinth in Mali: Alternaria sp. isolate Mlb684, Fusarium sacchari isolate Mln799 and Cadophora malorum isolate Mln715.
The fungi were grown in vitro on plates containing potato dextrose agar medium at different a(w) values (glycerol being added to adjust the a(w)). The percentage of viable conidia and radial growth rate decreased with decreasing water activity. Statistical analysis showed a significant effect of a(w), temperature and the a(w) × temperature interaction on mycelial growth (P<0·0001). Water activity emerged as the factor exerting the greatest influence. Differences were observed between the fungi tested, the C. malorum appearing more tolerant to low a(w) and the F. sacchari more tolerant to high temperature (35°C). Growth models predicting the combined effect of a(w) and temperature were developed and response surfaces generated, showing fairly good agreement with the experimental values.
Our results confirm the previous finding that a(w) has a greater influence than temperature on fungal growth. Under most conditions, variation of environmental factors has a detrimental influence on the percentage of viable conidia and mycelial growth rate of fungal isolates.
The developed models may contribute to predicting the best environmental conditions for use of these fungi as effective biocontrol agents against water hyacinth.
确定水活度(a(w) =0·880-0·960)和温度(15-35°C)对 3 种防治水葫芦的生物防治剂(马里的Alternaria sp. 分离株 Mlb684、Fusarium sacchari 分离株 Mln799 和 Cadophora malorum 分离株 Mln715)的活孢子百分比和菌丝生长的影响。
在含有土豆葡萄糖琼脂培养基的平板上,在不同的水活度值(添加甘油以调节水活度)下体外培养真菌。活孢子百分比和径向生长速率随水活度的降低而降低。统计分析表明,水活度、温度和水活度×温度相互作用对菌丝生长有显著影响(P<0·0001)。水活度是影响最大的因素。测试的真菌之间存在差异,C. malorum 对低水活度的耐受性更强,F. sacchari 对高温(35°C)的耐受性更强。开发了预测水活度和温度综合效应的生长模型,并生成了响应面,与实验值相当吻合。
我们的结果证实了先前的发现,即水活度对真菌生长的影响大于温度。在大多数情况下,环境因素的变化对真菌分离物的活孢子百分比和菌丝生长速率有不利影响。
开发的模型可能有助于预测这些真菌作为防治水葫芦的有效生物防治剂的最佳环境条件。