There's not a lot of vitamin A in yams, so maybe GR2 is a better the option.
Why rice?
Uh, because rice is eaten and grown in more than a hundred countries, and it is the staple food for more than 3 billion people. When you look at the caloric intake of these people, rice provides 60%-70% of their total nutrition. These same people also happen to be the most affected by vitamin A deficiency. So, yeah, rice is a logical and exceptional choice. And given the resistance it has met by people who think it's better for their flagrant ignorance to prevail rather than for people to live, it's no wonder these companies aren't rushing to do the same for sorghum, teff, or any other product.
You should be asking that question to a mirror.
Rice cannot be grown in most of Africa. It will have to be imported.
Who will pay for it. These are impoverished people. They will not be able to grow their own. Even if someone drop shipped them the seeds to do so.
It’s simply too dry to grow rice there.
Ask Ethiopia what happens when you come to depend on foreign grains at the expense of growing your own. It only takes ONE disruption in that supply line and millions of people starve to death. Remember the photos from the late 1980’s?
Why not genetically engineer the gene into something that CAN and DOES grow in AFrica? Like Sorghum.
That that wasn’t done should give you pause.
Rice is not, in fact, a staple in much of Africa. I’ve lived there. It’s certainly not a historic crop there like Maize or Sorghum.
And yams have a bunch of beta carotene. Do not need to be imported by spending ready cash. And can be grown locally 12 months out of the year.
If you’re going to be ‘giving’ them the vitamin A or its precursors why not ‘give’ them cod liver oil capsules. That way they get both the vitamin A that doesn’t require any metabolic transmutation into an active form, AND you give them the dietary fat to metabolize it properly.
As far as fat content in rice, let’s see you give them brown rice. Poor people almost universally refuse to eat that. And it doesn’t store very long, particularly in hot humid countries, without cooling. Unless you’re into having them eat rancid foods.