Rhododendron 'Taurus', which is a Frank Mossman hybrid documented as 'The Honourable Jean Marie de Montague' x R. strigillosum, 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.
Frank Mossman considered Rhododendron 'Taurus' to be his one standout hybridizing achievement.
Rhododendron 'Taurus', although reluctant to be a parent, appears to be both seed and pollen fertile. Werner Brack raised several seedlings from open pollinated seed collected from a 'Taurus' in his garden. The 'Taurus' in the Brack garden was tested and shown to be a triploid. This provides direct evidence that a triploid Rhododendron can indeed set viable seed.
A seedling of a Jack Rosenthal cross of Rhododendron yakushimanum x 'Taurus' was, also, determined to be a triploid.
In the case of the triploid 'Taurus', a diploid crossed with a diploid produced a triploid indicating that unreduced meiosis most likely occurred for one of the diploid parents. In other words, 'Taurus' having 39 chromosomes most likely received 13 from one diploid parent and 26 chromosomes from the other diploid parent.
Rhododendron 'Taurus' was also determined to be a triploid using flow cytometry by Dr. Thomas Ranney, J.R. Jones, and Nathan Lynch.
Rhododendron 'Grace Seabrook', which is also documented as 'The Honorable Jean Marie de Montague' x R. strigillosum, has been determined to be a triploid.
Rhododendron 'The Honorable Jean Marie de Montague', although a diploid, is documented as the parent of several triploids indicating 'The Honorable Jean Marie de Montague' may throw more unreduced gametes than most diploids.
Summary of Ploidy Levels
Diploid 'The Honourable Jean Marie de Montague',
Triploid 'Grace Seabrook',
Triploid 'Taurus',
Triploid A seedling of Rhododendron yakushimanum x 'Taurus'
Source: Greer Gardens
Source: Werner Brack
John and Sally Perkins
