Thanks for the info! This is a topic where I know what I don’t know is vastly greater than what I do know. So, I love that you’re on this site and willing to share your expertise 
I have to stop by and buy you a beer or twenty the next time I’m on the west coast 
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Is it your opinion that somaclonal variations and somatic mutations are the same (or have the same result) but are from different causes? With the former mainly caused by newly induced mutations from some TC processes, and the latter caused by unnaturally extended plant age through vegetative cloning?
Assuming plants are pathogen-free, it sounds like you think epigenetic changes through histone modification (H3K9 methylation) and DNA methylation may be the primary causes of clonal decay (affecting genetic fidelity, which negatively affects vigor and secondary metabolite biosynthesis) - so-called ‘genetic drift.’ And in contrast, somaclonal variations and somatic mutations are less likely to be the cause. If so, that’s also what John Brunstein (Ph.D. in biochemistry) believes and what other molecular biologists and geneticists I have listened to think. But other researchers have recently found measurable clonal decay caused by somatic mutation-induced genetic mosaicism from vegetative cloning, albeit with significant caveats:
Assuming clonal decay of old clone-only strains that growers report is primarily caused by epigenetic changes, what is your opinion of active and passive DNA demethylation and histone demethylation, and the implication of their cross-talk, through TC regeneration as a whole-genome ‘reset’ to revert the unwanted epigenetic changes? I’m currently looking for TC labs that can do demethylation. Also, from the limited papers I have (thus far) read on the subject, it seems like advances in tissue culture understanding and processes avoid inducing somaclonal variation; is that correct?