Unconventional methods in plant breeding.

There are three wass whereby unconventional methods of plant genetics can be used for applied plant breeding. 1. The time necessary for breeding by recombination can be shortened, making use of the discovery that plants can be obtained directly from the products of meiosis, the "Gonen." Two new cultivars bred in tobacco by this method already exist. 2. Microbiological methods may be applied to mutation and selection in haploid or dihaploid cell cultures. New cultivars bred by this method have not yet been published, but it should be possible to make use of this technique in plant breeding. 3. Somatic hybridization of plants by fusions of protoplasts or by uptake of nuclei and other organelles (plastids, mitochondria) or pure nucleic acids is another useful method. There exist up to now somatic hybrid plants (a) between mutants of the liverwort Sphaerocarpos donnellii, (b) some varieties of tobacco, and (c) two species of Nicotiana. All these hybrids can also be produced by conventional sexual hybridization. It is impossible to predict how often incompatibility for cross-fertilization can be surmounted by somatic hybridization, as incompatibility between two genomes must be restricted to the fertilization process, but it can work on any stage of the development of the hybrid.