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APPLICATIONS OF GENETIC ENGINEERING TO PLANTAND ANIMAL PRODUCTIONJoachim Schroder and Jeff SchellMax-Planck-Institut fur PflanzenzuchtungD-5000 Koln 30 FRGABSTRACTThe main limitations of conventional plant and animal breeding are the lengthof time required to produce new, useful varieties and the relatively mall genepool available for sexual crossings. In plants, the length of time can be reducedby employing haploid tissue cultures and plants. Elimination of undesirablephenotypes and selection of genetic variants is thereby simplified, and thediploid state can be restored, providing the breeder with suitable material forfurther crossings. Somatic hybridization of plant cells is a first step toenlarge the available gene pool. Protoplasts from sexually incompatible plantscan thus fused to form a new genetic unit which contains the genomes of bothparent plants. The direct introduction of genes as DNA molecules with help ofgene vectors represents a system of minimal interference with existing, stablegenomes. With dicotyledonous plants, the Ti-plasmid system is available fordirect transfer of genes, and improvement of crop plants can be expected in thenear future. Gene vectors for monocotyledonous plants and preferably also forchloroplasts and mitochondria need to be developed. With animals, recentdevelopments indicate that genetic engineering has become a feasible project,although many fundamental problems remained to be solved. Both with plants andanimals, the chief limitation for progress in genetic engineering is insufficientknowledge on structure, function, and regulation of genes.KEYWORDS: haploid tissue cultures, somatic cell hybridization, crown gall,Ti-plasmids, T-DNA, gene vectors, genetic engineering.INTRODUCTIONConventional plant and animal breeding has been of great importance in thelast decades for the production of better and more useful plants and animals, andthere is little doubt that it will continue this role in the future. However, italso has limitations. It takes a long time to produce new and better varieties(with plants for example between eight and 30 years), and the gene pool availablefor new combinations is limited by the fact that under normal conditions onlyclosely related species can be crossed sexually. The vast pool of potentiallyvaluable genes in other organisms cannot be tapped by conventional breedingtechniques.563