Maize has more human induced genetic diversity than any higher order organism. There are many "heritage" maize varieties grown for various reasons - my favorite is a type of popcorn that grows very small kernels (search for "tinybutmighty popcorn"). That said, this seems like mostly an advertisement for a brand of bourbon whiskey. Most of the specialty maize varieties have a similar origin story, usually with some dr…
While maize has some of the widest genetic variation Out there, in practice I think it is paradoxically the most frequent monocrop you will see. Lots of genetic options but each field will have almost no genetic diversity.