Plants can be vegetatively propagated either in vivo or in vitro. These vegetative propagation techniques are commonly applied for cloning of plants that have highly segregating seeds, long juvenility or are parthenocarpic. Plants such as pineapples and bananas for example, are vegetatively propagated because it is not preferable to have seeded fruits. In pineapple, leaf budding has been shown to be a good way of mass propagating in vivo (Fig. 1). An average of 15 leaf-buds can be obtained from a single crown. Meanwhile, suckers have traditionally been used to propagate banana. However, the rate of in vivo propagation through suckers or leaf budding is not sufficiently rapid and does not have growth uniformity for commercial scale production. Therefore, micropropagation through tissue culture techniques is developed and has been very instrumental in improving the rate of clonal propagation as well as the quality of both pineapple and banana seedlings.
For fruit trees such as durian (Durio zibethinus), mango, rambutan, ciku (Achras sapota L.) and citrus, budding and marcotting are the traditional methods for propagation. Other methods such as stem cutting and cleft grafting have been successfully developed for duku langsat (Lansium domesticum), durian and ciku. These are important development not only for clonal propagation of new varieties but also useful for a genetic improvement program of these fruit trees.
An efficient vegetative propagation system whether in vivo or in vitro is very pertinent prerequisite for genetic improvement procedures of such plants which have long juvenility, difficult sexual compatibility, and sterility. Physical and chemical mutagen treatments can induce mutations on the growing points of these vegetatively propagated plants. The mutated sectors on these treated tissues can then be grown and isolated from the non-mutated sectors through a series of vegetative propagation procedures either in vitro or in vivo. Many useful mutant cultivars with improved agronomic characteristics have been developed through this methodology.
The advent of tissue culture technology enables small and easily handled amount of tissue to be treated. Excised stem tips or callus growing on standard nutrient medium in a test tube for examples, could be treated and the explants grown to maturity and evaluated for useful mutations. Advanced in vitro manipulations such as somatic embryogenesis and single cell cultures also reduce the problem of chimerism often encountered in the induction of mutations on vegetatively propagated plants.

The varietal improvement activities in Malaysia have adopted both approaches of in vivo and in vitro vegetative propagation for mutagenesis in plants such as banana, orchids and other foliage ornamentals. The objectives are to develop varieties that have better agronomic characteristics such as high yield, disease resistance or tolerance, better and attractive flower colour, longer shelf life and good plant architecture.