Rhododendron 'Gentle Giant', which is a D. Sanders hybrid documented as 'Point Defiance' x 'Platinum Pearl', 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.
Rhododendron 'Gentle Giant' has as ancestors 'Broughtonii', 'Pink Pearl', 'Cynthia', 'Countess of Derby', 'Trude Webster', 'Platinum Pearl', 'Norman Gill', 'The Honourable Jean Marie de Montague', 'Anna', 'Marinus Koster', and 'Point Defiance'.
Both of the parents of 'Gentle Giant' have 'George Hardy' as an ancestor.
In the case of the tetraploid 'Gentle Giant', a tetraploid crossed with a triploid produced a tetraploid indicating that reduced meiosis most likely occurred for both parents. In other words, 'Gentle Giant' having 52 chromosomes received something similar to 26 chromosomes each from both the tetraploid 'Point Defiance' and the triploid 'Platinum Pearl'.
Rhododendron 'Gentle Giant' was also determined to be a tetraploid using flow cytometry by Dr. Thomas Ranney, J.R. Jones, and Nathan Lynch.
Summary of Ploidy Levels
Diploid 'Anna',
Diploid 'Norman Gill',
Diploid 'The Honourable Jean Marie de Montague',
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
