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 wildtype 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.