Three seedlings of Rhododendron 'Horizon Monarch' open pollinated, which were raised by Marc Colombel, have 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 the diploid seedling of 'Horizon Monarch' open pollinated, a tetraploid seed parent produced a diploid indicating that supper reduced meiosis most likely occurred for the tetraploid seed parent. In other words, the diploid seedling of 'Horizon Monarch' open pollinated having 26 chromosomes received only 13 chromosomes from the tetraploid 'Horizon Monarch'. Tetraploids usually contribute 26 chromosomes to their offspring.
Four seedlings were ploidy tested from seed collected by Marc Colombel from 'Horizon Monarch'. Three tested as diploid and one seedling tested as tetraploid. This indicates that the offspring of a given cross can have different ploidy levels from one offspring to another.
The 'Horizon Monarch' used to collect open pollinated seed by Marc Colombel ploidy tested as a tetraploid. This provides direct evidence that a tetraploid seed parent can produce diploid offspring in a single generation.
Summary of Ploidy Levels
Diploid 3 Seedlings of 'Horizon Monarch' open pollinated,
Tetraploid 1 Seedlings of 'Horizon Monarch' open pollinated,
Tetraploid 'Horizon Monarch'
Source Marc Colombel
John and Sally Perkins
