Flow cytometric analysis of the different ploidy levels observed in the genus Ulex L Faboideae-Genisteae in Brittany (France)

A controversy arose in the last decade concerning the identity of U. gallii and the ploidy of gorses in Brittany. To determine, for a wide number of samples, the ploidy levels of indigenous or recently introduced gorses in Brittany, we used the flow cytometric method on DAPI fluorescent nuclear suspensions, together with size measurements of stomata and dry pollen grains. All plants belonged to the section Neowillkommia of the genus Ulex. They were found to form a polyploid series with 2x, 4x and 6x levels. All U. minor were diploid. All U. europaeus ssp. europaeus and all U. gallii, except a single specimen out of 65, were hexaploid. This specimen had cell dimensions very close to that of U. europaeus ssp. latebracteatus which is a tetraploid. Tissue-specific augmentation was found in Rhizobium-containing cells of root nodules and within the endosperm of immature seeds. The 2C DNA content of U. europaeus ssp. europaeus was estimated at 90 % that of Pisum sativum, so weighing about 7.7 pg/2C. Neither U. gallii nor U., europaeus ssp. europaeus showed any difference in their ploidy level between erect and prostrate ecotypes. The taxonomic and nomenclatural consequences are discussed.