The imagery of scripture, prayer and the witness of tradition is consistent in the centrality of bread formed by wheat and wine from the fruit of the vine. Blessed rice cakes are not substitutes for the body and blood of Christ, and are never to be used in worship. Chicago liturgist Gabe Huck noted that the issue of using wheat for Communion bread has long been a point of contention among Asian Catholics who would rather use their staple food, rice, for Communion. The universal church should be sensitive to cultural nuances, Huck said. Wheat is not their food.
Rice is their food.
The Richardsons and others said they knew of priests who make exceptions. It could be going on. I don't know. That would not be valid matter. That would indeed not be a valid sacrament if it were rice flour.