Mustard seeds are small round seeds of various mustard plants. The seeds are usually about 1 or 2 mm in diameter. Mustard seeds may be coloured from yellowish white to black. They are an important spice in many regional foods. The seeds can come from three different plants: black mustard (Brassica nigra), brown Indian mustard (B. juncea) and white mustard (B. hirta/Sinapis alba). Black Mustard seeds have the most pungent taste, while white mustard seeds, which are actually yellow in colour, are the mildest. Brown mustard, which is actually dark yellow in color, has a pungent acrid taste.
In India it is cultivated mainly in Gujarat and Rajasthan