This name is a synonym of Centaurea jacea subsp. gaudinii (Boiss. & Reut.) Gremli.
The record derives from TICA
(data supplied on 2012-02-11)
which reports it as a synonym (record 20F68195-CDA4-45A2-B40B-35709A065777).
This name record (from TICA) was not included in version 1 of The Plant List. It is possible the same name was included from a different data source, to check this you can search for Centaurea amara in version 1 of The Plant List.