Widening of Genetic Variation in Barley Breeding Programmes: Experiences from Composite Crosses to Nordic Barley Breeding Populations

The establishment, breeding and selection procedures of long-term population 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 within 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 populations and genetic conservation. Finally, an ongoing barley population breeding project is presented. The aim of the Nordic project is to form gene 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.