Rhododendron 'Viscosepalum', which is 1842 Waterer hybrid often documented to be Rhododendron molle X Rhododendron viscosum, has been determined to be a tetraploid using flow cytometry by
Dr. João Loureiro, Dr. Silvia Castro, José Cerca, and Mariana Castro
Plant Ecology and Evolution Group,
Centre for Functional Ecology,
Department of Life Sciences,
Faculty of Science and Technology,
University of Coimbra, Portugal.
The Perkins' Pollen Based Ploidy Test indicated than 'Viscosepalum' was most likely a tetraploid.
Since Rhododendron molle and Rhododendron viscosum are both diploid species, the documented parentage of 'Viscosepalum' is questionable.
Rhododendron 'Daviesii', which is also documented to be Rhododendron molle X Rhododendron viscosum and was breed in the same time frame as 'Viscosepalum', has been determined using flow cytometry to be a triploid.
Summary of Ploidy Levels
Diploid Rhododendron molle,
Diploid Rhododendron viscosum,
Triploid Rhododendron 'Daviesii',
Tetraploid Rhododendron atlanticum,
Tetraploid Rhododendron 'Viscosepalum'
Source: John and Sally Perkins
John and Sally Perkins
