WIDENING OF GENETIC-VARIATION IN BARLEY BREEDING PROGRAMS - EXPERIENCES FROM COMPOSITE CROSSES TO NORDIC BARLEY BREEDING POPULATIONS

The establishment, breeding and;selection procedures of long-term popu lation breeding methods used in barley breeding are briefly outlined. Composite crosses (CC) are described as an example of long-term barley bulk populations. Experimental studies on compositional changes withi n CCs are discussed to show how plant breeders can utilize the effects of natural selection. Genetic variability and changes in adaptedness of CCs are surveyed, and thus their significance to breeding populatio ns and genetic conservation. Finally, an ongoing barley population bre eding project is presented. The aim of the Nordic project is to form g ene pools with a high level of resistance to various barley diseases. During the establishment phase the effects of exotic germplasm on the expression of agricultural traits in adapted barleys is studied.