Breeding columnar apple-tree cultivars for supercompact growth habit

Abstract

This work was based on the combinatorial breeding technique using donors of the columnar growth type (Co gene), sources of winter hardiness and high consumer qualities, and scab immunity donors (Rvi6 gene). The selection in the columnar apple-tree hybrid progeny was accompanied by the assessment of growth vigor, compactness degree, and seedling cultivability in accordance with the guidelines.Due to the increasing popularity of apple trees with the columnar crown type, the volume of breeding work for columnar growth habit at the Russian Research Institute of Fruit Crop Breeding (VNIISPK) over the past 9 years amounted to 133,582 flowers, or one third of the entire hybridization envisaged by the apple-tree breeding program. Meticulous selection of parent forms is carried out in order to incorporate a set of useful traits in the columnar growth habit genotype. Both cultivars and hybrid forms serve as sources and donors of the traits interesting for breeders. All the studied cultivars released by VNIISPK are dwarf: their height is within the range from 287 cm (cv. ‘Priokskoe’) to 198 cm (cv. ‘Orlovskaya Yesenia’), and they can be recommended for both commercial plantations and amateur gardens. The columnar form 34-34-98 is characterized by a unique degree of compactness (the ratio of the internode length to the shoot diameter) equal to 0.4 versus the average value of 1.6 for this indicator in the studied columnar cultivars. This form was involved in the release of 78 promising hybrid seedlings, the best of which (38.5%) were transferred to the garden for primary variety trials. A large yield of seedlings characterized by high compactness in the progeny of the columnar apple tree 34-34-98 makes it possible to recommend it for the development of new apple-tree genotypes for highly cost-effective orchards with high tree planting density.