VARIATIONS IN THE TOTAL NUCLEAR-DNA CONTENT IN AFRICAN COFFEA SPECIES(RUBIACEAE)

Laser flow cytometry has been used to estimate total nuclear DNA conte nt for seventy-five Coffea accessions, corresponding to sixteen diploi d species (2 n = 22) and C arabica (tetraploid, 2 n = 44). Nuclei were isolated and stained by propidium iodine (DNA intercaling dye). 2C-va lues ranging from 0.9 to 1.9 pg per nucleus have been estimated for Co ffea species. Three species native of East Africa (C sessiliflora, C r acemosa and C pseudozanguebariae) had the smallest genome size (about 1 pg per nucleus). Species native of the African evergreen forest (C h umilis, C. sp. Moloundou and C liberica) had the highest diploid DNA c ontent (1.6 pg). The genome size of the tetraploid C arabica, native o f Ethiopia, was 2.5 pg. In most species, variation in 2C-values (up to 25 %) was also recorded. Results are compared with data from other an giosperm species and are discussed in terms of their evolutionary sign ificance.