该研究以实验室人工栽培模拟工业生产工艺，对蛹虫草菌株ZGCM进行重复传代培养，人为建立了1至7代的菌种退化梯度株系，以探究蛹虫草退化过程中的形态变化规律及其内在分子机制的变化。实验结果表明，ZGCM菌株自第2代开始退化，至第6代基本不产生子实体。培养基残糖含量随退化梯度菌种代际数目的上升而呈下降趋势，第5代与第1代相比下降了62.40%。培养基残余蛋白质含量在第2代下降后出现回升，提示蛹虫草菌株随着传代次数的上升，吸收外界氮源的能力持续下降。以qRT-PCR法测定过往报道中发现的14个转录水平变化趋势与蛹虫草退化代际数目呈线性相关的基因，结果表明仅有CCM_04090基因的表达量呈上升趋势，第5代与第1代相比提高了39.60%，与过往报道一致。其他基因均无显著变化。以HPLC法测定静置液体发酵液中的虫草素含量，发现其随着传代次数的上升而下降。静置发酵30 d时，第5代与第1代相比虫草素产量下降了74.56%。结果表明蛹虫草菌株退化会对子实体产量和虫草素含量等两大产品品质核心因素造成负面影响。

Repeated subculture of the Cordyceps militaris strain ZGCM was performed in the laboratory to simulate strain degeneration during industrial cultivation. A gradually degenerated strain line was built over seven generations to explore the morphological changes and internal molecular mechanisms of degeneration. The results showed that strain ZGCM degenerates from the second generation, with no fruiting bodies observed by the sixth generation. The residual sugar in the culture medium is reduced over each generation, with sugar content decreasing by 62.40 % in the fifth generation as compared to the first generation. Furthermore, the residual protein content of the medium increased after the second generation, suggesting that the ability of C. militaris to absorb nitrogen from external sources declines continuously. The transcription levels of 14 differentially expressed genes that were linearly related to C. militaris generation were measured using qRT-PCR. However, only the CCM_04090 gene showed increased expression with each generation, increasing by 39.60 % in the fifth generation as compared to the first generation, which is consistent with previous reports, and no significant changes were observed for other target genes. According to the HPLC results, cordycepin production exhibited a general decline over each generation and, after 30 days of fermentation, fifth generation cordycepin production decreased by 74.56 % as compared to the first generation. The results indicated that strain degeneration has a negative impact on not only the production of fruiting bodies, but also on cordycepin production, both of which are core quality indicators of C. militaris products.

广东省基础与应用基础研究基金项目（2019A1515110609）；广东省教育厅科研平台项目（2020KTSCX019）；江门市基础与应用基础重点项目（2020030103450009103）；中国博士后科学基金项目（2020M682731）