In this context, rice is a main or crucial element or food of something (i.e. diet, country, person).
Staple foods of the United States are corn, wheat, and rice. Staple food of Mexico is corn, it is used in many of the popular dishes in Mexico. Staple foods of Italy are fish, cheese, pork, and corn.
The staple food of Manipur : Rice, fish curry, Iromba
The staple food of Karnataka is rice.
The staple food of Delhi is rice.
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