## 4 Selection of Host Species  
### Genetic Variability  
Genetic variability plays a critical role in the cultivation of _C. militaris_, significantly influencing the fungus's ability to adapt to various hosts and optimize the production of bioactive compounds. The genetic diversity within _C. militaris_ strains is substantial, resulting in variations in morphological and physiological traits that directly impact the fungus's infection efficiency, growth rate, and the synthesis of essential bioactive metabolites. This genetic diversity, which includes multiple chromosomes, is characterized by variations such as single nucleotide polymorphisms (SNPs) and insertions/deletions (indels), both of which drive phenotypic diversity [61]. Spontaneous mutations, sexual reproduction via spore-producing fruit bodies, and geographical isolation further contribute to this diversity, leading to local adaptations and, ultimately, speciation [62]. Understanding this genetic variability is crucial for cultivation practices, as different _C. militaris_ strains may exhibit better adaptation to specific hosts, enhancing both yield and the production of bioactivecompounds. Moreover, genetic diversity can provide resilience against environmental stresses, a vital factor for ensuring consistent and sustainable cultivation [31].  
The genetic basis for the production of bioactive compounds such as cordycepin and polysaccharides is well-established, with certain strains of _C. millitaris_ being naturally predisposed to higher levels of metabolite production. By selecting and cultivating these genetically superior strains, it is possible to optimize the synthesis of these valuable compounds, thereby improving the overall efficacy of _C. millitaris_-based products [30]. To harness this genetic variability, modern methodologies such as genome sequencing, quantitative trait loci (QTL) mapping, and CRISPR/Cas9 genetic engineering have been employed. These tools allow researchers to link specific genetic traits with desirable phenotypic characteristics, such as increased cordycepin production or enhanced growth rates, facilitating the targeted improvement of _C. millitaris_ strains [63]. For example, CRISPR/Cas9 has been successfully used to knock out or modify specific genes within the _C. millitaris_ genome, resulting in strains that exhibit improved resistance to environmental stressors or enhanced bioactive compound production. Such genetic modifications can be strategically applied to tailor _C. millitaris_ strains for specific medicinal or commercial purposes.  
Looking forward, future research in _C. millitaris_ cultivation is likely to focus on expanding genetic databases to identify additional markers linked to key traits, as well as refining genetic engineering techniques to achieve even more precise modifications. Advances in CRISPR/Cas9 technology, in particular, hold significant potential for the continued improvement of _C. millitaris_ strains. For instance, recent studies have demonstrated the utility of CRISPR/Cas9 in enhancing cordycepin production by targeting the biosynthetic pathways involved in nucleotide metabolism, which is directly linked to cordycepin synthesis. Another promising area of research involves the use of CRISPR/Cas9 to increase the efficiency of fungal adaptation to non-traditional hosts, such as synthetic media or agricultural by-products, thereby improving the sustainability of large-scale cultivation efforts. By focusing on these genetic engineering strategies, researchers can optimize the production of bioactive compounds in _C. millitaris_, making it a more viable and potent medicinal resource. These advancements underscore the critical importance of genetic understanding in maximizing the therapeutic potential of _C. millitaris_ and ensuring its commercial success.