In vitro selection for disease resistance in potato and barley

Strategies for the incorporation of resistances in crop plants are increasingly demanding a quantitative approach. With such an approach, procedures for rapid and reproducible screening are necessary. The paper describes to what extent in vitro cell procedures might permit selection of disease-resistant types from within existing variation. Examples are also given for the production of new variability and for the incorporation of haploids in resistance-breeding programmes. Our results with potato and barley are outlined with regard to the rapid introduction of resistance to such viruses as potato virus X, potato virus Y, potato leafroll virus and barley yellow mosaic virus, and fungi such as Phytophthora and Fusarium. In potato, haploid calli and protoplasts are used in screening for resistance. In barley, the work concentrates on somatic cells and isolated microspores. Futhermore, starting from immature embryos, suspension cultures were established and single-cell suspensions achieved. Regeneration from isolated microspores became possible after preconditioning the medium with ovaries. Under these conditions, the regeneration rate was high enough to use this system for selection. Fusaric acid was applied as a selection agent, calli which survived 0.2 mM furasic acid being selected. This concentration is toxic to unselected material. In this procedure, the advantages of a single-cell system are combined with those of haploidy. (author)