How often do tetraploids spontaneously arise from seedlings?
" In the framework of the IVIA triploid breeding program (Navarro et. al.), we have searched for tetraploids plants in seedling populations of 'Anana', 'Fairchild', 'Kara', 'Page', 'Saltemta', 'Simeto', 'Sunburst' and 'Tardivo di Ciaculli' mandarins, 'Afourer', 'Murcott' and 'Ortanique' tangors, 'Mapo'and 'Minneola' tangelos, 'Duncan' and 'Star Ruby' grapefruits and 'Sanguinelli' orange. Determination of ploidy level was made by flow cytometry and genetic analysis to confirm their genetic origin with 31 SSRs markers. Tetraploid plants were found in ail genotypes analyzed, except 'Salteiiita' and 'Simeto' mandarins, but the frequency of tetraploids varied with the genotype. 'Kinnow' mandarin produced the larger number of tetraploids plants (9.7%), whereas 'Page' mandarin produced the smaller percentage (0.5%). "
(Selection of spontaneous autotetraploid plants from Citrus polyembryonic cultivars, Pablo Aleza Gil, Patrick Ollitrault, Luis Navarro, Polytechnic University of Valencia, 2008 )