Durban
Breeding with the Durban is done with hand selected phenos that have been passed or traded back and forth for awhile.
Yet, now and then. Someone does the whole thing over again to produce things like Cookies strains and happily, The strains that cookies has produced it's self...
Buying a pack of Durban beans, and getting that over 30% pheno out of what? 10 beans? Good fucking luck! The strain it's self is nice and has good potency.
More strains then you think, owe their potency to Durban somewhere in it's past.
Durban is there but I think other sativa's like Colombian, Mexican, and some other South American sativa's are more integrated in today's hybrids. But let's not forget about the Thai sativa's which are all over the hybrid map.
With Indica's, Pakistani Chitral Kush is a main player as well. It's responsible for some of those wonderful colors. But there are many other indica varieties from the Pakistan/Afghanistan region and other parts of the world.
If you were to start breeding you couldn't go wrong starting with Durban, PCK, Columbian, Panama, Afghanistan, Thailand, and a couple other indica's. I say that because that's the path I'm taking with my
amateur breeding project. I'm biased and admit it.
Regardless, if you can get a real cut or seeds of any pure landrace strains you're likely going to get some good weed if you grown it right. Make a hybrid and those F1's can be fire.