Diploid Tsutsusi Rhododendron Species

In the paper "Flow Cytometric Analysis of Ploidy in Rhododendron (subgenus Tsutsusi)", S. De Schepper1, L. Leus, M. Mertens, E. Van Bockstaele, and M. De Loose found 6 Rhododendron species of section Tsutsusi to be diploid.

In the paper "Ploidy Levels and Relative Genome Sizes of Diverse Species, Hybrids, and Cultivars of Rhododendron", Jeff R. Jones, Thomas G. Ranney, Nathan P. Lynch, and Stephen L. Krebs found 1 Rhododendron species of section Tsutsusi to be diploid. Results from this paper are denoted by ^j.

Triploids hybrid evergreen azaleas from these 2 papers are also listed here.

Diploid

Rhododendron indicum
Rhododendron kiusianum
Rhododendron mucronatum
Rhododendron noriakianum
Rhododendron scabrum
Rhododendron simsii
Rhododendron stenopetalum ‘Linearifolium’ ^j

Triploid

'Crimson Majesty' ^j
'Euratom'
'Euratom Orange'
'Red Wing'

Mixaploid

'Casablanca Tetra'

'Briggs Red Star' is a Tetraploid

Rhododendron 'Briggs Red Star', which is a chemically treated 'The Honourable Jean Marie de Montague' produced by Briggs, 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.

Ranney, Jones, and Lynch found 'Brigg's Red Star' to be a 2x + 4x mixaploid which breeds as a tetraploid having tetraploid pollen.

Summary of Ploidy Levels

Diploid 'The Honourable Jean Marie de Montague',
Tetraploid 'Brigg's Red Star'

Source: Ned Brockenbrough

John and Sally Perkins