One seedling of Rhododendron cumberlandense orange X Rhododendron atlanticum 'Marydel', which is a Sally and John Perkins hybrid, has been determined to be a triploid 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.
This seedling of Rhododendron cumberlandense orange X Rhododendron atlanticum 'Marydel' looks remarkably similar to the tetraploid pollen parent 'Marydel' differing primarily in having a small yellow blotch.
To date this seedling has proven sterile as both a seed parent and a pollen parent.
In the case of this triploid (39 chromosomes), a diploid crossed with a tetraploid produced a triploid indicating normal meiosis occurred where the diploid contributed a 1x gamete (13 chromosomes) and the tetraploid contributed a 2x gamete (26 chromosomes).
Summary of Ploidy Levels
Diploid Rhododendron cumberlandense,
Triploid One seedling of Rhododendron cumberlandense X Rhododendron atlanticum 'Marydel',
Tetraploid Rhododendron atlanticum,
Tetraploid Rhododendron atlanticum 'Marydel'
Source: East Fork Nursery
John and Sally Perkins
