QTL Mapping of the Narrow-Branch "pendula" Phenotype in Norway Spruce (picea Abies L. Karst.)

Pendula-phenotyped Norway spruce has a potential forestry interest for high-density plantations. This phenotype is believed to be caused by a dominant single mutation. Despite the availability of RAPD markers linked to the trait, the nature of the mutation is yet unknown. We performed a quantitative trait loci (QTL) mapping based on two different progenies of F1 crosses between pendula and normal crowned trees using NGS technologies. Approximately 25% of all gene bearing scaffolds of Picea abies genome assembly v1.0 were mapped to 12 linkage groups and a single QTL, positioned near the center of LG VI, was found in both crosses. The closest probe markers placed on the maps were positioned 0.82 cm and 0.48 cm away from the Pendula marker in two independent pendula-crowned x normal-crowned wild-type crosses, respectively. We have identified genes close to the QTL region with differential mutations on coding regions and discussed their potential role in changing branch architecture.