Inheritance of vigour tree in F1 apple interspecific hybrids

Abstract

In ornamental apple breeding process, the vigour of the tree is an important characteristic, this trait being analyzed in selection of seminal descendants obtained by hybridization. The vigour of the apple trees was studied in 25 interspecific hybrids F1 belonging to different Malus ornamental species, used as maternal or paternal genitors, crossed with several cultivars and selections. The seedling vigour was noted when hybrids were four to seven years old, in accordance with UPOV guideline standard: 3 - weak; 5 - medium; 7 - strong. The mean of marks for tree vigour of F1 hybrids in the 25 combinations ranged between 4.00 and 6.13. Compared with the mean of experiment as control (5.20), the most vigorous seedlings were obtained in the families 'Cluj 218/2' x M. niedzwetzkyana and 'Reinette Baumann' x M. prunifolia, both with significant differences of growth versus the mean growth of all combinations. The weakest growth was noted in progenies belonging to 'Rosu de Cluj' x M. coronaria, 'Starkrimson' x M. prunifolia, 'Frumos de Voinesti' x M. floribunda, 'Cluj II-1-2' x M. floribunda, M. zumi x 'Reinette Baumann', M. coronaria x 'Reinette Baumann'. No significant differences were found between the mean of marks for tree vigour in the group of combinations in which the Malus species were used as maternal genitors (5.18) and paternal genitors (5.20). The coefficient of variability ranged in the experiment between 2.6% and 27.4%; in ten families a lower variability for seedlings vigour (under 10%) was identified, in 13 a medium one (between 10-20%) and in two a large one (more than 20%). Even if in some combinations the variability of tree vigour was not very large, there seems to be fair possibilities to identify by selection the seedlings with a desired vigour in each family.