The language of the Book of Mormon is careful to always refer to the twelve in the New World as disciples and not Apostles. However, it is apparent from this verse that the calling of these twelve was identical to that of the Old World Apostles. Furthermore, Joseph Smith referred to these twelve as Apostles in an 1842 letter (History of the Church, 4:538). Therefore, whether they are called "Apostles" or "disciples" is a semantic argument of little significance, for they were both disciples and Apostles.
Joseph Fielding Smith
"While in every instance the Nephite twelve are spoken of as disciples, the fact remains that they had been endowed with divine authority to be special witnesses for Christ among their own people. Therefore, they were virtually apostles to the Nephite race, although their jurisdiction was, as revealed to Nephi, eventually to be subject to the authority and jurisdiction of Peter and the twelve chosen in Palestine (see Mormon 3:18-19). According to the definition prevailing in the world an apostle is a witness for Christ, or one who evangelizes a certain nation or people. 'A zealous advocate of a doctrine or cause.' Therefore the Nephite twelve became apostles, as special witnesses, just as did Joseph Smith and Oliver Cowdery in the Dispensation of the Fulness of Times." (Answer to Gospel Questions, 1:122 as taken from Latter-day Commentary on the Book of Mormon compiled by K. Douglas Bassett, p. 510-11)