I'm thinking key to subsistence agriculture would be diversity: for hybrid vigor, disease resistance, productivity when conditions are right for only some crops, pollinators, and likely other benefits.
There was some interesting research a while back with relatively isolated communities and their customary diets, and how that affected some aspects of appearance and of health of the population. Groups that really existed with subsistence and nomadic hunter gatherer had good facial symmetry, strong bones, clear skin, some apparent disease resistance. Isolated groups that relied on subsistence farming but had developed an appetite for more highly processed Western diet and shunned some of their more traditional food stuff: these people showed stranger physiognomy, skin afflictions and allergies, more distorted growth patterns of teeth and bones, etc.This was noted worldwide. I recall some were in Scotland and some were in the Aussie Outback, but there were many other groups, too.
Groups like the Saami and probably Andaman islanders may have limited diets, but they traditionally find a balance of nutrition whether they primarily eat caribou or coconuts. That may mean eating bark or grubs or entrails.
So if you selectively seed five different types of beans in the woods and wilds, maybe two will make it through several years with reseeding (at a guess) and selectively plant several different native grapes, of which only some will have fruit or leaves you find palatable, and have fallen logs and growing trees that support saprophytic fungi of your choice, then you have a start toward independent subsistence.