Determination of genetic loci in the control network of grapevine flowering

The study of grapevine phenological traits such as flowering and ripening time has become increasingly important in the past few years. With regard to climate change, cultivars with delayed flowering and ripening characteristics may be more advantageous in viticulture. However, genetic markers for these traits applicable for marker-assisted breeding are sparse. Even though homologs of genes that control flowering time have already been identified and characterized in model plants, our overall knowledge about which genetic factors are involved in the complex control of flowering time in Vitis remains very limited. A mapping population consisting of 150 F1 individuals derived from the cross of the early-flowering genotype ‘Calardis Musqué’ and late-flowering cultivar ‘Villard Blanc’ was used for quantitative trait locus (QTL) detection of the flowering-time trait. For this purpose, vines were phenotyped in 11 seasons for the date of full bloom. QTL analysis led to the identification of several genomic regions, and epistatic effects between the identified loci were observed. The QTLs could be verified in a large extended population of ‘Calardis Musqué’ × ‘Villard Blanc’.