Mapping of QTLs for Yield and Alpha Acid Content in Hop

Hop breeding is a lengthy process due to the dioecious nature of hop, producing highly heterozygous offspring and only female plants are of commercial interest. Molecular approaches have therefore been developed to support conventional hop breeding programmes. We studied the effects of quantitative trait loci (QTLs) and determined map locations for alpha-acid content and yield in hop, using amplified fragment length polymorphism (AFLP) and microsatellite markers (SSRs). Genetic linkage maps were constructed from a mapping population consisting of 111 progeny from a double pseudo-testcross. A total of 194 markers were located on the 20 linkage groups (LGs) of the maternal and paternal maps, covering total map lengths of 706 and 616 cM, respectively. Due to the presence of common biparental SSR markers, homology of LGs between parental maps could be inferred. The progeny segregated quantitatively for alpha-acid content and yield determined in the years from 2002 - 2006. Several putative QTLs were determined and the results are discussed from the point of view of implementation of a marker-assisted selection (MAS) programme in hop.