"(cumberlandense X lutem) not" is a Diploid

Three seedlings of Rhododendron "(cumberlandense X lutem) not" have been determined to be a diploid using flow cytometry by

Dr. João Loureiro, Dr. Silvia Castro, José Cerca Oliveira, 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.

Ploidy testing indicates that Rhododendron luteum may not be the pollen parent of this hybrid.

Summary of Ploidy Levels

Diploid Rhododendron cumberlandense,
Diploid 3 Seedlings of "(cumberlandense X luteum) not",
Tetraploid Rhododendron luteum

Source: Bruce Clyburn

John and Sally Perkins

atlanticum X (atlanticum X molle) is a Tetraploid

Four seedlings of Rhododendron atlanticum X (Rhododendron atlanticum X Rhododendron molle) have been determined to be a tetraploid using flow cytometry by

Dr. João Loureiro, Dr. Silvia Castro, José Cerca Oliveira, 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.

These seedlings do show the influence of Rhododendron molle or maybe Rhododendron luteum. Successful 4X X 2X crosses in deciduous azaleas are rare.

Summary of Ploidy Levels

Diploid Rhododendron molle,
Tetraploid Rhododendron atlanticum,
Tetraploid Rhododendron luteum,
Tetraploid 4 Seedlings of Rhododendron atlanticum X (Rhododendron atlanticum X Rhododendron molle)

Source: Bruce Clyburn

John and Sally Perkins

Rhododendron arborescens X Rhododendron calendulaceum is a Triploid

One seedling of Rhododendron arborescens X Rhododendron calendulaceum has been determined to be a triploid 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 arborescens is diploid species. Rhododendron calendulaceum is a tetraploid species.

In the case of these triploid (39 chromosomes), a diploid crossed with a tetraploid produced a triploid indicating normal meiosis occurred where the diploid contributed a 1x gamete (13 chromosomes) and the tetraploid contributed a 2x gamete (26 chromosomes).

Summary of Ploidy Levels

Diploid Rhododendron arborescens,
Triploid 5 seedlings from Rhododendron occidentale SM189 X Rhododendron calendulaceum 'Colossus',
Tetraploid Rhododendron calendulaceum

Source: Bruce Clyburn

John and Sally Perkins

occidentale SM189 X calendulaceum 'Colossus' is a Triploid

Five seedlings of Rhododendron occidentale SM189 X Rhododendron calendulaceum 'Colossus' have been determined to be a triploid 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 occidentale is diploid species. Rhododendron calendulaceum is a tetraploid species.

In the case of these 5 triploids (39 chromosomes), a diploid crossed with a tetraploid produced a triploid indicating normal meiosis occurred where the diploid contributed a 1x gamete (13 chromosomes) and the tetraploid contributed a 2x gamete (26 chromosomes).

Summary of Ploidy Levels

Diploid Rhododendron occidentale,
Triploid 5 seedlings from Rhododendron occidentale SM189 X Rhododendron calendulaceum 'Colossus',
Tetraploid Rhododendron calendulaceum

Source: Bruce Clyburn

John and Sally Perkins

Rhododendron canadense is a Diploid

Rhododendron canadense 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.

Rhododendron canadense was also determined to be a diploid using flow cytometry by Dr. Thomas Ranney, J.R. Jones, and Nathan Lynch. The Ranney research involved several samples from diverse wild populations including samples from Salem, New Hampshire.

Read Ploidy Level of Rhododendron canadense

Summary of Ploidy Levels

Diploid Rhododendron canadense,
Diploid Rhododendron canadense var. album
Diploid Rhododendron canadense 'Osku's Showy'

Source: Arnold Arboretum Accession Number: 199-2006-C
Source: Bruce Clyburn
Source: John and Sally Perkins
Source: Kristian Theqvist

John and Sally Perkins