Rhododendron 'Stony Brook', which is a Werner Brack hybrid documented as 'Voluptuous' x 'Point Defiance', has been determined to be a diploid 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.
In the case of diploid 'Stony Brook', a diploid crossed with a tetraploid produced a diploid indicating that supper reduced meiosis most likely occurred for the tetraploid parent. In other words, 'Stony Brook' having 26 chromosomes received 13 chromosomes from the diploid 'Voluptuous' and 13 chromosomes from the tetraploid 'Point Defiance'. Tetraploids usually contribute 26 chromosomes to their offspring.
Three seedlings were ploidy tested from the Brack cross of 'Voluptuous' x 'Point Defiance'. 'Orange Leopard' and 'Stony Brook' tested as diploid. An unnamed seedling tested as triploid. This indicates that the offspring of a given cross can have different ploidy levels from one offspring to another.
Summary of Ploidy Levels
Diploid 'Orange Leopard',
Diploid 'Stony Brook',
Diploid 'Voluptuous',
Triploid Seedling of 'Voluptuous' x 'Point Defiance',
Tetraploid 'Point Defiance'
Source: Werner Brack
John and Sally Perkins
