Rhododendron 'Horizon Monarch', which is a Ned Brockenbrough hybrid documented as 'Nancy Evans' x 'Point Defiance', 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 'Horizon Monarch' has as ancestors 'Anna', 'Hotei', 'Lem's Cameo', 'Nancy Evans', 'Norman Gill', 'The Honourable Jean Marie de Montague', 'Horizon Monarch', 'Marinus Koster', and 'Point Defiance'.
In the case of the tetraploid 'Horizon Monarch', a diploid crossed with a tetraploid produced a tetraploid indicating that unreduced meiosis may have occurred for the diploid parent. In other words, 'Horizon Monarch' having 52 chromosomes received something similar to 26 chromosomes from the diploid 'Nancy Evans' and 26 chromosomes from the tetraploid 'Point Defiance'.
Rhododendron 'Horizon Monarch' 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 'Hotei',
Diploid 'Lem's Cameo',
Diploid 'Nancy Evans',
Diploid 'Norman Gill',
Diploid 'The Honourable Jean Marie de Montague',
Triploid 'Steredenn',
Tetraploid 'Horizon Monarch',
Tetraploid 'Marinus Koster',
Tetraploid 'Point Defiance'
Source Marc Colombel
John and Sally Perkins
