Sylleptic branching in winter-headed apple (Malus × domestica) trees: accession-dependent responses and their relationships with other tree architectural characteristics

Well-feathered apple trees are essential for commercial orchards to optimize yields. However, most cultivars do not form these sylleptic branches readily in commercial nurseries due to high apical dominance. Several treatments exist to promote their formation in the nurseries, one of which is heading. However, not all cultivars are expected to react similarly to these treatments. We studied the branching response of 155 genotypes following heading and its relation to other architectural traits as a function of the cultivar’s genetic background. Trees were grown for two consecutive years after grafting in a nursery, and the main axes were headed in the winter following growth in year 1. After heading, a single shoot was retained when growth resumed in the second year. Plant architectural traits such as growth of the main shoot, internode length, sylleptic branching, etc. were measured before and after heading and were statistically compared using a mixed model. This model showed the effe...