Gluten is a mix of proteins that are produced in some grains, such as wheat. Rice does not naturally contain gluten in its grains. However, scientists have used a method which induced mutations in rice plants and successfully created a strain of rice that produces gluten. The method involved exposing plants, seeds, or pollen to radiation. The resulting plants were then grown and tested for different traits.

Due to mutation.

Explanation:

Due to mutation, the rice plants are able to produce gluten like other grain crops such as wheat etc. In this mutation, change occurs in a DNA sequence of the rice plant by exposing the plant to ionized radiation. Due to this radiation, change occurs in the DNA of rice plant and the rice plant is able to produce gluten like wheat plant. So mutation is a very useful method for producing substances which a plant can't produce in its normal condition.