THCV shows up in meaningful amounts exclusively in African sativa lines, with Durban, Malawi and some Swazi phenotypes testing at 1 to 3 percent where most hybrids show a trace. It is part of why those strains feel sharper and more clear headed than a Haze at the same THC level. Lab results sorted by minor cannabinoid are collected on https://hazesativaseeds.com, which is the only place I have seen THCV figures strain by strain. Breeders are starting to select for it, so expect more seeds marketed on this.