Thanks for your comments on this Jogro.
You're welcome. Here are
my functional/colloquial definitions of the two main medical cannabis subtypes:
"Indica": A variety of medical
cannabis sativa exhibiting traits typically associated with subcontinental (ie India, Afghanistan, Pakistan, etc) landrace strains. Classic indica strains typically exhibit short stature, bushy growth, broad leaf fingers, rapid maturation (eg 7-10 weeks flowering time), spicy/hash like scent, and narcotic-like medical effect.
"Sativa": A variety of medical
cannabis sativa exhibiting traits typically associated with tropical (eg Mexican, Columbian, Thai, Jamaican, African) landrace strains. Sativa strains are known for tall stature, open/branching growth, narrow leaf fingers, gradual flower maturation (eg 12-20+ weeks flowering time), floral/fruity scent, and cerebral/psychoactive medical effect.
Note that I said "variety" not "strain", since some of the so-called commercial "strains" are unstabilized hybrids that aren't really strains. Restricting this definition to "medical" varieties excludes hemp varieties (though these typically fall into the "sativa" definition above). Incidentally, the term "hemp" typically refers to cultivars bred to produce fiber and seeds, though some people use the term to refer to any wild strain, including ruderalis.
If you look at it THIS way, with a description of "75% indica" referring to its phenotype (ie which traits it expresses) rather than its precise genetic lineage, then the description becomes a bit more valuable, I think.
Now, as a though experiment, lets say I took an Afghan landrace strain and crossed it with a Thai landrace strain to create a 50-50% indica/sativa F1 hybrid generation. Then I crossed two 50-50 F1s to create an F2, did selection, crossed the selected F2s to create an F3, selected from the F3s then crossed them, and repeated these crosses until I ended my breeding project with a completely stable and effectively homogeneous inbred F10 generation.
What percentage indica/sativa genetics are these F10s?
50-50 since the original parents were an indica and a sativa, right? WRONG.
The correct answer is "impossible to determine".
The reason is that after the F1 generation, the genetic traits will tend to assort randomly in the offspring (not entirely, but that's a whole other discussion). What genetic percentage these stable F10s share with either parent depends almost entirely on how I did the selections!
If I were generating enough offspring to do true large-scale selections, and consistently selecting specifically for indica-like traits keeping only the indica-traits and discarding any sativa-like ones, I could have an F10 that was (in theory) greater than 99% indica, effectively indistinguishable from the original indica parent. Conversely, if I were selecting for sativa-like traits, the F10 could be 99% sativa. And again, depending on how I did the selection, I could have plants anywhere in between along the spectrum.
The point is, that even knowing the specific genetic lineage of a particular plant doesn't necessarily *by itself* tell you whether its an "indica" or not. You still have to see what it looks like, and that's why, I think, its better to think of these things as phenotypes (ie how a given plant conforms to the ideal conception of an "indica" or "sativa") rather than strict genetic measures.
Yes, ultimately the phenotypes and the genetics do correlate, but in practice you can't "measure" the genotypes (or at least not today), where as you can see the phenotypes.