No substantive amount of grain is grown in Hawaii for human consumption. Seed corn is grown here, though.
Hawaii has a unique opportunity for high volume production of gluten-free, “grain replacements” in the form of flour from canoe plants like ‘ulu/breadfruit, kalo/taro and u’ala/sweet potato, as well as cassava/tapioca and others. The flour can be used to make breads, noodles, cereals, etc.
There are also many additional value add products that can be made from ‘ulu in particular (i.e. adhesives, insect repellants).