This name is a synonym of Rhododendron mekongense var. rubrolineatum (Balf. f. & Forrest) Cullen.
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 12304909) with original publication details: Notes Roy. Bot. Gard. Edinburgh 12(57–58): 160–162 1920.
This name was in version 1 of The Plant List, record tro-12304909, and has not been changed.