Much of the Green Revolution depends on irrigation water pumped by diesel-fueled pumps. As you indicated, cheap fertilizer depends on cheap energy. Beyond that, the production and distribution of hybrid seeds depends on cheap energy.

Potable water generally has to be pumped, either from wells or through pipelines.

Thus both potable water and cheap food depend on cheap energy, and I do believe the poorest countries (such as Zimbabwe) will be the hardest hit by Peak Oil.

I do not think that production & distribution of seed requires large energy inputs.

Seed farms can be located within ox cart distance of most farmers. And even heavy trucks can move the minimal weight of seed (it varies by crop) a hundred miles or so "affordably".

Best Hopes,

Alan