If your were able to grow a dozen of your green corn plants to maturity.
you could then self-pollinate them. On growing the resulting seed, you
might have segregation of white seedlings among one or more of the
populations. Plant the seed of each ear in a separate row and
self-pollinate 10 green plants in the row(s) with white seedlings. You
will then have an ongoing supply of seed for class use. I suppose it's
possible none will so segregate -- maybe several loci are involved and
the numbers would be too low to catch the rare white plant.