There's a famous geographic distinction in China where the north historically had wheat as a staple and the south had rice. This means different regional cuisines, but there is even a claim that it's led to other cultural differences:

http://advances.sciencemag.org/content/4/4/eaap8469

I wonder if your grandmother has any awareness that rice is a traditional staple crop only in the southern parts of Asia. Around the world, you could find more rice cultivation in tropical areas and more wheat cultivation in temperate areas... although the historical dividing line in China is still some ways north of the Tropic of Cancer.