(Mishnah): The following foods can be used (for the mitzvah of eating matzah on the first night) of Pesach -

Wheat, barley, spelt, oats and rye.

Demai (produce for which it is doubtful if its tithes were separated), Maaser Rishon that had its Terumah separated and Maaser Sheni or Hekdesh that were redeemed.

Kohanim may use Challah (the portion of dough separated for the Kohen) and Terumah.

However, one may not use -

Tevel (untithed produce), Maaser Rishon that had not had its Terumah separated, Maaser Sheni or Hekdesh that had not been redeemed,

If one made Matzos for Lachmei (bread brought with Korban) Todah or Rekikei (wafers brought with Korbanos) Nazir for himself; but if he made them to sell them [for these Korbanos but was not Makdish them] he may use them.

(Gemara - Mishnah in Challah): The verse states (Bamidbar 15, 19), "And when you shall eat from the bread of the land, you shall separate a Terumah to Hashem''. I would have said that all grains (even rice, millet or others) would be obligated in challa, the verse teaches "from the bread'', but not all breads.

If the verse teaches "from the bread'', but not all breads, I would only include wheat and barley. From where do we learn about other grains? "The beginning of your kneading'' - includes all others (similar) grains.

Quoting from R' Achva bar Zeira/ R' Yishmael: A Gezeira Shavah - It says "bread'' (Lechem Oni) about Pesach and it says "bread'' (MiLechem Ha'aretz) about Challah; just as the "bread'' mentioned with Pesach refers to grains that can become matzah and Chametz, so the "bread'' mentioned with Challah refers to grains that can become matzah and Chametz.

They checked and discovered that that only the five grains become matzah and Chametz; other grains only rot.