Inheritance of apricot growth habit in breeding materials

Tree architecture is controlled by training systems that require a lot of effort and labor-intensive pruning operations. The reduced tree habit and small canopy make all agro-technical procedures easier and are objectives in the breeding programs of all fruit species. The aim of our study was to trace the inheritance of the main growth characteristics: tree habit, angle of branching, internode length, one-year-old shoot coloration, length and thickness in two apricot hybrid families. The progenies of the parental combinations 'Modesto' x 'Harcot' and 'Harlayne' x 'Harcot' were planted in 2011 in a breeding orchard at the Fruit Growing Institute - Plovdiv, Bulgaria. In both hybrid families, the ratio between the hybrids with upright to upright to spreading tree habit was approximately 1:1. With a higher frequency in the 'Harlayne' x 'Harcot' progeny were the hybrids with a smaller angle of branching compared to the parental cultivars. The internode length was segregating in both hybrid generations. In 'Modesto' x 'Harcot' hybrid family the number of hybrids with shorter internodes than those of the parental cultivars was small. In the other parental combination, the biggest was the group of hybrids that resemble 'Harcot' - with internode length between 1.75 and 2.00 cm. During the first two years of the study, the growth of the hybrids was intense and the one-year-old shoots were long to medium long with medium thickness for both hybrid families. The one-year-old shoot color was variable in the three years of observations. The parental combination 'Harlayne' x 'Harcot' is more perspective for future breeding schemes aiming to a reduced growth habit.