Adventitious Bud Formation on Isolated Leaves and its Significance for Mutation Breeding in Some Ornamental Plants

摘要

Since a mutation is a unicellular event, irradiation of a multicellular meristem results in the so-called diplontic selection. The competition between the mutated cell and the surrounding non-mutated cells is often lost by the mutated cell, causing a low frequency of mutated plants and a narrow mutation spectrum. When a mutated cell survives, chimeras are automatically formed because most spices consist of a number of fairly independent groups of cell layers. Both phenomena, diplontic selection and chimera formation, restrict the possibilities and the efficiency of mutation breeding. Such undesirable situation can be avoided by growing shoots or even complete plants from only one cell. After irradiation the resulting plants are either completely normal or solid mutants, in addition the number of mutated plants was considerably higher and the mutation spectrum wider (Broertjes, C., 1967, 1968 and Duron, M., 1992). It is therefore of utmost importance, in vegetative propagated plants, to look for or to develop method by which shoots or plants are obtained, which originate from only one cell. In vivo a great number of species are known in which the formation of adventitious buds can be stimulated on leaves of Begonia (Doorebos, J., Karper, J., 1975), Saintpaulia (Broertjes, C., 1968, 1972) and Streptocarpus (Broertjes, C., 1969). In general little is known about the number of cells, which take part in the formation of such buds. A cytological and histological study is one of the means of defining the exact number of which a few cases are reported (Haccius, B., and Lakshmanan, K., 1968). For the plant breeders a promising in vivo method is the adventitious bud technique using detached leaves. Many plant species can be stimulated to form adventitious buds on isolated leaves and in a number of cases it has been reported that only one cell was involved.