wheat berry vs food grain

wheat berry and food grain both are nouns.

Word	Noun	Adjective	Verb	Adverb
wheat berry	Yes	No	No	No
food grain	Yes	No	No	No

As nouns, food grain is a hypernym of wheat berry; that is, food grain is a word with a broader meaning than wheat berry:

wheat berry: grains of common wheat; sometimes cooked whole or cracked as cereal; usually ground into flour
food grain: foodstuff prepared from the starchy grains of cereal grasses

Other hypernyms of wheat berry include cereal, grain.

wheat berry (noun)	food grain (noun)
grains of common wheat; sometimes cooked whole or cracked as cereal; usually ground into flour	foodstuff prepared from the starchy grains of cereal grasses
a grain of wheat