ESTIMATION OF DNA CONTENT IN THE GENUS GLADIOLUS (BOTANICAL SPECIES AND HYBRIDS)

The nuclear DNA content has been assessed using flow cytometry of DAPI-stained ⁽¹⁾ nuclei for 2 Mediterranean gladiolus species, 21 South-African species and 16 interspecific hybrids of Gladiolus (and Homoglossum) derived from the south African types. A collection of 38 hybrids between cultivated gladiolus and botanical types, used as parents in a breeding program for selection of winter flowering varieties, as well as 67 genotypes selected from further interprogeny crosses also were analysed. All these genotypes were maintained in our germplasm collection. The flow cytometry approach enabled a rapid and reproducible characterisation of somatic material in term of DNA content. The DNA content of Gladiolus genotypes was estimated from the known DNA content of the Gerbera cultivar ‘Fredonzelle’ which was used as an internal standard. Flow cytometry results showed a large variation in the DNA content between the studied botanical diploid species, up to a difference of 53 % between G. gracilis and G. angustus. Relation between DNA content and ploidy level was confirmed on several genotypes, using chromosomal counting on root tips. For the interspecific hybrids selected from interprogeny crosses, the estimated ploidy levels fluctuated from 3x to 4, 5 and 6x. It was also possible to detect some mistakes in term of labelling inside genotypes of the collection. Moreover, the technique should be useful for very early identification of interspecific hybrids.

⁽¹⁾ Chemical name used: 4',6-diamidino-2-phenylindole (DAPI)