Rhododendron 'Platinum Pearl', which is a Harold Greer hybrid documented as 'Trude Webster' x R. fortunei ssp. discolor, 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.
'Platinum Pearl', which has 'Broughtonii', 'Pink Pearl', 'Cynthia', 'Countess of Derby', and 'Trude Webster' as ancestors, is the pollen parent of 'Gentle Giant'. 'Point Defiance', which has 'Marinus Koster' as an ancestor, is the seed parent of 'Gentle Giant'.
Notice 'Gentle Giant' represents the merging of 2 multi-generational polyploid lines, namely 1) 'Broughtonii' (3x), 'Pink Pearl' (3x), 'Countess of Derby (4x)' (polyploid), 'Trude Webster' (4x), 'Platinum Pearl' (3x), to 'Gentle Giant' (4x) and 2) 'Marinus Koster' (4x), 'Point Defiance' (4x), to 'Gentle Giant' (4x).
Summary of Ploidy Levels
Triploid 'Broughtonii',
Triploid 'Cynthia',
Triploid 'Pink Pearl',
Triploid 'Platinum Pearl',
Tetraploid 'Countess of Derby',
Tetraploid 'Gentle Giant',
Tetraploid 'Marinus Koster',
Tetraploid 'Point Defiance',
Tetraploid 'Trude Webster'
Source: Greer Gardens
John and Sally Perkins
