变温干燥固体发酵产物对球孢白僵菌分生孢子性能的影响

Influence of different drying temperatures for solid substrate after fermentation on conidia characteristics of the entomopathogenic fungus Beauveria bassiana

【目的】评价球孢白僵菌固体发酵产物的干燥温度对产后分生孢子性能的影响。【方法】采用28℃和35℃组合的7种恒温或变温处理干燥发酵产物,分析收获的分生孢子质量。【结果】变温干燥可显著降低产后孢子粉的杂菌污染。干燥温度对活孢率和孢子萌发速度影响不一致。35℃恒温干燥5h后活孢率与新鲜孢子无明显差异,但萌发中时缩短了9.3%。干燥处理提高了孢子对高温和紫外辐射的耐受性。适当的变温干燥比恒温干燥有利于增强孢子抗逆性。干燥温度影响分生孢子胞内海藻糖积累,但其含量与抗逆性无直接相关性。优化干燥温度可提高产后分生孢子毒力。在370～450孢子/mm2剂量下,经28℃24h后升至35℃干燥2h或35℃恒温干燥5h的分生孢子对桃蚜的致死中时分别比新鲜孢子缩短了10.6h和7.5h。【结论】球孢白僵菌固体发酵产物的干燥温度是影响产后孢子粉杂菌污染、孢子活力、抗逆性和毒力的重要因素。

[Objective] This study was to evaluate the effect of drying temperature for solid substrate after fermentation on conidia characteristics of entomopathogenic fungus Beauveria bassiana. [Methods] Seven constant or varied temperatures between 28℃ and 35℃ were designed for drying the solid substrate and the quality of harvested conidia was analyzed. [Results] The results showed that the drying treatments at varied temperatures significantly decreased bacterial contamination in the harvested conidia powder. The conidia viability and germination speed were varied with different drying treatments. After drying at 35℃ for 5 h, there was no significant difference in viability between the dried and fresh conidia, while the median germination time （9.6 h） of the dried conidia was shortened by 9.3%. The tolerance of conidia to heat and UV radiation was increased by drying treatment. Compared to the drying treatment at a constant temperature at 28℃ or 35℃, some varied temperature treatments were in favor of enhancing the stress tolerance of conidia. Drying treatments influenced accumulation of trehalose in harvested conidia, while neither heat resistance nor UV tolerance of conidia was obvious correlation with trehalose level. Optimizing drying temperature could increase the virulence of B. bassiana. After drying at 28℃ for 24 h and then 35℃ for 2 h or at 35℃ for 5 h, the LT50s to Myzuspersicae at the dose of 370-450 conidia/mm^2 were shortened by 10.6 h and 7.5 h, respectively. [Conclusion] The results suggested that the drying temperature for post-fermentation solid substrate has an important influence on bacterial contamination in the harvested conidia powder, spore viability, stress tolerance and virulence in B. bassiana.