CHAPTER III. Nomenclature of taxa according to their rank
SECTION 5. Names of taxa below the rank of species (infraspecific taxa)
The final epithet in the name of an infraspecific taxon may not repeat unchanged the epithet of the correct name of the species to which the taxon is assigned unless the two names have the same type.
The final epithet in the name of an infraspecific taxon may not repeat unchanged the epithet of the species name if that species name is illegitimate.
When Honda (in Bot. Mag. (Tokyo) 41: 385. 1927) published Agropyron japonicum var. hackelianum Honda under the illegitimate A. japonicum Honda (1927), which is a later homonym of A. japonicum (Miq.) P. Candargy (1901), he did not validly publish an autonym “A. japonicum var. japonicum” (see also Art. 55 Ex. 3).