Prospects and perspectives in mutation breeding.

Induction of mutations, primarily a method of generating variation, can contribute to plant improvement when combined with selection, or recombination and selection, or with other methods of manipulating genetic variation. As a source of variability, induced mutations supplement naturally occurring variation. When specific mutants are selected following mutagenic treatments it is highly likely that a number of mutational changes will have occurred in the selected genotype. Hence, although most of the mutant varieties released so far have resulted from mutation and direct selection, the future trend will be for increasing use of mutants in association with recombination. Whereas induced mutations are generally regarded as random events, there are suggestions of some mutational specificity in response to different mutagenic agents and treatments. The best immediate prospects for increasing specificity lie in the manipulation of the selection environment. Biochemical selection applied to large number of plant cells in culture to locate mutations in specific biosynthetic pathways and the subsequent regeneration of whole plants offers great prospect for reducing the cost of breeding programs and altering the amount or composition of a desired end or intermediate product. Mutations in conbination with other techniques of genetic engineering will constitute the tools of the plant breeders of the future. Their present role in plant breeding has been established. They have advantages in certain situations, disadvantages in others. Greater understanding will lead to their more widespread use.