This (longer) version [0] is more precise (e.g. Historia Civilis' one mentions "messengers sent out to call reinforcement", while on [0] it correctly states that about 15,000 cavalry units were sent out to call reinforcements).
So yes, corn existed in Europe long before Columbus.
Romans would not have gone out for corn, though. They had the word 'granum', from which we derived 'grain'.
The use of the word "corn" to refer exclusively to maize and not other cereal grains is a quirk of North American English that apparently has also spread to Oceania, but is not shared by much of the rest of the English-speaking world.