'Horizon Monarch' OP is a Diploid

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

'Orange Leopard' is a Diploid

Rhododendron 'Orange Leopard', 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 'Orange Leopard', a diploid crossed with a tetraploid produced a diploid indicating that supper reduced meiosis most likely occurred for the tetraploid parent. In other words, 'Orange Leopard' 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

'Stony Brook' is a Diploid

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

'Rendezvous' is a Diploid

Rhododendron 'Rendezvous', which is a Hachmann hybrid documented as 'Marinus Koster' X R. degronianum ssp. yakushimanum, 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.

The hybridization efforts by John and Sally Perkins indicated that 'Rendezvous' was most likely a diploid.

Rhododendron 'Marinus Koster', which was determined to be a tetraploid, is the seed parent of the diploid 'Rendezvous'. This seems to indicate that 'Marinus Koster' only provided 1x gamete (13 chromosomes) to 'Rendezvous'.

'Marinus Koster' is the pollen parent to 'Point Defiance', which was determined to be a tetraploid using flow cytometry by Dr. Thomas Ranney, J.R. Jones, and Nathan Lynch. 'Anna', which was determined to be a diploid, is the seed parent of 'Point Defiance'.

Summary of Ploidy Levels

Diploid 'Anna',
Diploid 'Rendezvous',
Tetraploid 'Marinus Koster',
Tetraploid 'Point Defiance'

Source: John and Sally Perkins

John and Sally Perkins