Genetic Mapping of Traits Important in Barley Breeding

Molecular markers were used for assessing genetic diversity in Finnish six-rowed barley and for mapping and tagging genes affecting traits important in barley breeding. Finnish six-rowed barley germplasm is narrow-based: twenty two released varieties are largely composed of only seven ancestors. The level of diversity in the RAPD markers has remained during barley breeding. Coancestry based on pedigree information and Jaccard’s index based on RAPD markers were not correlated. A doubled haploid progeny from a cross between two Finnish six-rowed barley varieties (Rolfi and Botnia) was used for linkage map construction and genetic mapping. The map covered only 654 cM, probably due to genetic similarity of the parental varieties. Segregation distortion was detected in several chromosomal regions. When a set of doubled haploid lines were tested for their anther culture response, associations between anther culture traits and markers were detected. Only some of the associated markers were located on the chromosomal regions with distorted segregation. Anther culture traits have not been mapped previously in barley. The Rolfi x Botnia linkage map was used for mapping agronomically important quantitative traits. From one to seven quantitative trait loci (QTLs) affecting each trait were detected. Many of these QTLs overlapped with QTLs found previously in other germplasm. Candidate loci were identified for QTLs affecting earliness and straw length. Clustering of QTLs was clear. Since many QTL clusters were situated in centromeric areas of the chromosomes, clustering may be explained by suppression of recombination. QTL x environment interactions and epistatic interactions were noted. To facilitate introgression of resistance genes into Finnish barley germplasm, genes for net blotch resistance were mapped and a gene for powdery mildew resistance was tagged with DNA-markers. Two genes controlling net blotch resistance in the Rolfi x CI9819 cross were found: one with a major effect on chromosome 6H and a second with a smaller epistatic effect on chromosome 5H. Information about QTLs underlying the genetic variation in agronomic traits can be utilized in barley breeding for mating design and selection. However, before using the putative QTLs in breeding, the exact locations and effects should be verified. Linked markers for net blotch and powdery mildew resistance may be used to speed up transfer of resistance from unadapted sources to the highly adapted elite Finnish barley germplasm.