Spontaneous mutations-"sports"-played an essen tial role in the breeding of new cultivars. Their low-frequency limits effective breeding since the breeding process is accidental and more extensive compared with seed propagated plants (Abbot and Atkin, 1987).Application ofradiation enhances dras tically the frequency of somatic mutations from which useful traits may be selected. A mutation is a one cell event but multicellular apices generally con sist of a number of rather autonomous groups of cell layers such as L] (epidermis), L2(subepidermis) in the so-called tunica and L3 in the corpus and have a number ofmeristematic cells in each layer. Mutagen esis applied to multicellular structures like buds gives rise to mericlinal or sectorial chimeras. However, homohistont shoots can be obtained after several propagation cycles of axillary buds. Irradiation of apical promeristems and high doses increase the probability of occurrence of large mutated sectors and irradiation of adventitious buds that are derived from single, epidermal cells generates homohistont mutants (Broertjes and Van Harten, 1988). Vegeta tive single cell descending propagules offer. a possi bility for early screening and fast propagation of mutants for the breeding of commercially improved cultivars.