seed grain vs seed corn

seed grain and seed corn both are nouns.

Word	Noun	Adjective	Verb	Adverb
seed grain	Yes	No	No	No
seed corn	Yes	No	No	No

As nouns, seed grain and seed corn are synonyms defined as:

seed grain and seed corn: good quality seeds (as kernels of corn) that are reserved for planting

seed grain (noun)	seed corn (noun)
good quality seeds (as kernels of corn) that are reserved for planting	good quality seeds (as kernels of corn) that are reserved for planting