响应面设计优化莱氏绿僵菌SZCY固体发酵培养 条件及致病力测定

Optimization of the solid-state fermentation conditions of Metarhizium rileyi SZCY by response surface methodology and determination of the virulence

摘要:

【背景】莱氏绿僵菌(Metarhizium rileyi)对新入侵我国的草地贪夜蛾(Spodoptera frugiperda)具有较强的致病力和田间流行性，因此具备深入开发的价值。【目的】优化莱氏绿僵菌SZCY固态发酵培养条件，测定所产分生孢子对草地贪夜蛾幼虫的毒力，为提高该菌株分生孢子规模化生产奠定基础。【方法】采用单因素试验确定了相对适宜的固态培养基，利用Box-Behnken响应面法优化该菌株的固态培养基和发酵参数，同时评价不同条件下该菌所产分生孢子对草地贪夜蛾幼虫的毒力。【结果】去颖稻谷(rice)为莱氏绿僵菌SZCY菌株固相产孢最佳载体。培养温度、光周期及酵母浸粉含量是影响莱氏绿僵菌SZCY固态发酵产孢量的主要因素。莱氏绿僵菌SZCY固态发酵最佳工艺参数为温度22.83 ℃、光周期18.68 h L:5.32 h D、酵母浸粉4.98 g/100 g，在此条件下，莱氏绿僵菌在去颖稻谷固态培养基上的产孢量为5.65×10¹⁰孢子/g，用其制备浓度为10⁷孢子/mL的孢子悬浮液，对草地贪夜蛾3龄幼虫的LT₅₀为3.88 d。【结论】害虫生防真菌莱氏绿僵菌SZCY菌株以去颖稻谷为固态培养基的发酵培养条件，该条件下产孢量大且对草地贪夜蛾幼虫毒力强，具有广阔的开发应用前景。

Abstract:

[Background] The insect-pathogenic Metarhizium rileyi shows promising potential for controlling the virulent exotic Spodoptera frugiperda which infests crops, particularly maize. Thus, this fungal species should be further developed. [Objective] To optimize the solid-state fermentation conditions of M. rileyi SZCY, determine the virulence of the yielded conidia to S. frugiperda, and thus lay a basis for the large-scale production of the conidia. [Methods] The single-factor experiment and Box-Behnken design were used to optimize the solid-state fermentation medium factors and fermentation parameters. The virulence of the conidia yielded under different conditions to the 3rd instar larvae of S. frugiperda was evaluated. [Results] Husked rice was the best fermentation medium for SZCY, as the conidium yield was the highest. The culture temperature, photoperiod, and content of yeast extract powder were the main factors affecting the sporulation of SZCY in solid-state fermentation. The optimal fermentation parameters for solid-state fermentation are as follows: culture temperature of 22.83 ℃, photoperiod 18.68 h L:5.32 h D, and yeast extract powder of 4.98 g/100 g. Under these conditions, the conidium production of SZCY on husked rice was 5.65×10¹⁰ conidia/g and the LT₅₀of the suspension (10⁷ conidia/mL) for the 3rd instar larvae of S. frugiperda was 3.88 days. [Conclusion] The optimal medium for solid-state fermentation of SZCY was husked rice. With this medium and the optimal fermentation parameters, the conidium yield was higher and the yielded conidia show strong virulence to S. frugiperda. Therefore, SZCY should be further developed for biocontrol.