Critics who claim that references to "wheat" in the Book of Mormon are anachronisms hold to an unjustified narrow view of what the word may have represented.
Wheat species commonly grown today are not known to have been present in the new world during Book of Mormon times. However, a similar plant call “amaranth” was present and was cultivated as leaf vegetables, cereals, and ornamental plants.
Amaranth has a similar nutritional profile to some grains. The Aztec Indians obtained up to 80% of their daily caloric needs from amanranth.
Amaranth is often called a "pseudograin" because it can be ground into flour like wheat or other seed grains, which biologically are grasses. Today, amaranth can be used to replace wheat flour in gluten-intolerant patients.
Amaranth was grown and used in Mexico at the time the Spaniards arrived.
Other possible pseudograins can be identified, but amanranth is the most likely candidate for “wheat” in the Book of Mormon.
As seen with multiple other anachronism accusations, it is impossible to prove something did not exist. The process becomes more difficult if the translation of languages is involved because it may be impossible to accurately identify the thing reportedly absent.