Recurrent selection alternating with haploid steps - a rapid breeding procedure for combining agronomic traits in inbreeders.

Doubled haploid lines are increasingly used in practical breeding programs. Depending on the nature of the starting material as well as on the breeding aims, one or more haploid steps are recommended, and F1 hybrids or selfed progenies in later generations serve as starting material for the haploidization. It is demonstrated that one haploid step followed by selection in the greenhouse and in the field during the first androgenetic (A1) and two subsequent selfed generations (A2; A3) is the most efficient procedure, if characters from related varieties are to be combined. For breeding programs that include wild types or unrelated genotypes, recurrent selection alternating with several haploid steps is the most efficient. A prerequisite for successful application of this combination of repeated haploidization and selection steps alternating with backcrosses is an effective selection system. The different approaches are demonstrated on a winter barley breeding program, with the central aim of combining the qualitatively inherited character resistance to barley yellow mosaic virus with quantitatively inherited complexes, particularly yield.