Two kinds of wild wheat have grown in the open deciduous oak woodland in the northern part of the Fertile Crescent for several thousand years: Einkorn Wheat Triticum monococcum and Emmer Wheat Triticum dicoccum. Both came into cultivation together with barley. Just before the time of the Romans, the Naked Bread Wheat or Hard Wheat Triticum durum started replacing the hulled varieties. This then became the favorite type of wheat for bread and macaroni. Spelt is a sub-member of the Triticum aestivum species.

In New Revised Standard Version, updated edition and some other versions, the generic Hebrew word bar has been rendered “wheat” in Jeremiah 23:28 et al. This is legitimate, since the grain referred to by bar was probably wheat. However, it might be better to say “grain” in these passages.

The most important early wheat for the Israelites was emmer, probably the only wheat known in Egypt, and referred to in Hebrew as chittah. However, according to Hepper (Baker Encyclopedia of Bible Plants: Flowers and Trees, Fruits and Vegetables, Ecology. Baker Book House, 1992), the seven-headed wheat of the Egyptian king’s dream (Genesis 41:5ff.) suggests that there may also have been Triticum turgidum (rivet wheat) in the emmer group. The Hebrew word kusemeth probably refers to a type of emmer wheat that the Egyptians called swt.

Wheat is a type of grass like rice and barley, growing to around 75 centimeters (2.5 feet) in height and having a head with many small grains in rows.

Bread made from wheat was the staple food for the people of ancient Israel, so God punished them by breaking “the staff of bread” (see, for example, Ezekiel 4:16).

If wheat is unfamiliar, translators can transliterate from a major language in non-rhetorical contexts (for example, English witi, Portuguese trigo, French ble or froment, Swahili ngano, Arabic kama/alkama). The transliteration may add a generic tag such as “grain.” The New Testament passages are mostly rhetorical, opening the possibility for a metaphorical equivalent.

Source: Each According to its Kind: Plants and Trees in the Bible (UBS Helps for Translators)