Rhododendron 'Anna Rose Whitney', which is van Veen hybrid introduced by William Whitney and documented as R. griersonianum x 'Countess of Derby', 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.
'Anna Rose Whitney', which has 'Broughtonii', 'Pink Pearl', and 'Countess of Derby'
as ancestors, is the pollen parent of 'Hurricane'; however, like many (semi)fertile triploids 'Anna Rose Whitney' is reluctant to produce viable seedlings as either a seed or pollen parent.
In the case of triploid 'Anna Rose Whitney', a suspected diploid crossed with a tetraploid produced a triploid indicating that normal reduced meiosis most likely occurred for both parents. In other words, 'Anna Rose Whitney' having 39 chromosomes received 13 chromosomes from the suspected diploid R. griersonianum and 26 chromosomes from the tetraploid 'Countess of Derby'.
Summary of Ploidy Levels
Diploid 'Hurricane',
Triploid 'Broughtonii',
Triploid 'Pink Pearl',
Triploid 'Anna Rose Whitney',
Tetraploid 'Countess of Derby'
Source: Whitney Nursery
John and Sally Perkins
