In this Daf. Rebbe Meir holds you are not obligated to separate Challah from maaser sheni dough as it is not considered yours but Hashems. So to by matazah and esrog which have to be yours. Cam a kohein use maaser sheni challah for his matzah as it can't ever be eaten outside of yerushalyim. What is the source you can't use the loaves of a Todah of wafers of a nazir for matazah.