GENETIC-ENGINEERING AND PLANT-BREEDING, ESPECIALLY CEREALS

Over the last 5000 years cereals have been bred for food, feed, and be verages by selection of spontaneous mutations and random hybrids. Sinc e the turn of the century, crosses with defined parents, and since 192 7 artificially induced mutations, have been used to create variability on which selection of new varieties is based. It is pointed out that hybrid corn and transfer of rust-resistant genes from wild species int o chromosomes of bread wheat was preceded by decades of basic research . Genetic transformation is an additional tool for the breeder to intr oduce novel genes in a rational manner and will complement but not rep lace the existing efficient breeding methods. Genetic transformation h as been demonstrated in maize, rice, and wheat, while techniques to ob tain transgenic barley plants are still being developed. Our present k nowledge on the endosperm-specific expression of storage proteins and the modulation of this expression by transcriptional activators is rev iewed. Breeding strategies for altered protein quality and for proanth ocyanidin-free malting barley are presented. Engineering of an improve d malt enzyme, a heat stable (1-3,1-4)-beta-glucanase, is described. T he enzyme is expected to survive, like alpha-amylases, the kilning pro cess and has been shown to act efficiently in the mashing process for the elimination of water-soluble beta-glucans which impede filtration of wort. The engineered enzyme is expressed in transformed aleurone pr otoplasts and secreted from these cells and thus shown to be operation al in the tissue, where it is expected to work. Hormone-regulated prom oters for the expression of genes acting during grain development and malting have been characterized. Prospects for the production of polyh ydroxyalkanoates and cyclodextrins in cereal grains are discussed.