Why have wheat and corn been used as commodity money in the past while strawberries and lettuce have not?

the causes of the dust bowls were severe droughts,   lands became dry and hard, temperature was higher than usual, hot and dry conditions killed crops, high winds. because of those factors, the winds kicked up dry soil and created clouds of dust.

the speech revealed that eastern european countries were no threat to their neighbors, which led to the creation of the truman doctrine i think this might be correct.