IN VITRO MUTAGENESIS FOR THE IMPROVEMENT OF VEGETATIVELY PROPAGATED PLANTS

摘要

A number of important crops such as banana, plantain, cassava, potato, sweet potato and sugar cane are propagated from corms, tubers and stem cuttings. Some of these plants do not produce seed, and often the size of the propagule is too big to treat large populations with mutagens. In vitro techniques allow mutagenic treatment of large numbers and multiplication of the selected genotypes in a small space and short duration under disease free conditions. After treatment with mutagens, the chimeral tissues can be separated into mutated and non-mutated sectors without loss of plants, which may occur in conventional propagation. Somaclonal variation among plants regenerated from callus and cell suspension cultures may provide additional variation to that induced through mutagenesis. In vitro methods allow induction and expression of recessive mutations in the haploids, producing homozygous doubled haploids. The availability of simple, efficient and rapid techniques for screening large plant populations for desired traits is an essential component of plant breeding. In vitro culture techniques allow selection of the desired variants from large populations of cells and plants. This may be achieved by manipulating the medium composition, e.g. selection for tolerance to salinity and drought, and by co-culturing the plant tissues with pathogens or their toxins, as in the case of selection for disease resistance. The variants thus selected can be subjected to selection in the glasshouse or field. Even though the occurrence of desired mutations is empirical and random, the combination of in vitro and mutation techniques can speed up the breeding of vegetatively propagated plants.