Episode 167: Genetic Degradation in Propagation: Why Plants Change Over Time
In this episode of the Cannabis Cultivation and Science Podcast, host Tad Hussey sits down with Dr. Grey Monroe and PhD candidate Matthew Davis from UC Davis to discuss their groundbreaking PNAS paper, Genome degradation in plant tissue culture. For decades, cannabis growers have reported a phenomenon known as genetic drift or maternal decline, where long-held mother plants or clonal lines seemingly lose their vigor, yield, or terpene profiles over time. This conversation provides a definitive look into the biological mechanisms driving these changes.
While traditional field-grown cuttings maintain incredibly high genetic integrity, the guests explain how certain high-intensity lab cloning environments break a plant's natural DNA repair mechanisms. Crucially, the extreme 3000 percent plus mutation rates, chromosome duplications, and activated jumping genes observed in their study were caused by somatic embryogenesis, a process where single cells are forced through rapid, artificial generational cycling. The authors emphasize that this differs fundamentally from organized meristem tip culture, which is the predominant method used in cannabis for viroid cleaning. The episode bridges the gap between academic orchard research and commercial cannabis cultivation, exploring how operators can use strategic genetic screening to protect their elite cultivars before mass micropropagation.
J. Grey Monroe is an Associate Professor in the Department of Plant Sciences and the Genome Center at UC Davis. His lab studies how mutations arise across genomes, DNA repair, epigenomics, and genome evolution in plants, with applications in crop improvement and protection. Lab website: https://monroelab.org/ Email: gmonroe@ucdavis.edu
Matthew Davis is a fifth year PhD candidate in the Plant Biology Graduate Group co-advised by Grey Monroe and Pat J. Brown. His research focuses on somatic mutation in orchard crops, an understudied genetic process that directly affects one of California’s largest agricultural industries.
Bluesky: @davismw.bsky.social
Email: mtdavis@ucdavis.edu
Research Links and Resources
Peer-Reviewed Paper: https://www.pnas.org/doi/10.1073/pnas.2530182123 Shorter general audience article: https://www.ucdavis.edu/blog/not-all-clones-are-created-equal Slightly longer general audience article: https://www.plantsciences.ucdavis.edu/news/davis-monroe-somatic-mutations
