Evaluation of raspberry varieties by berry density in connection with mechanized harvesting

The article considers the possibility of combining the large-fruiting and density of raspberry fruits as one of the main and decisive limiting indicators of the suitability of raspberry varieties for mechanized cultivation and further harvesting, as well as for long-term transportation to the consumer. The objects of research were 20 varieties of raspberries of domestic and foreign breeding and 15 elite forms from the controlled crosses and populations from open pollination. An annual assessment of the density of raspberry fruits was carried out at the collection and selection breeding site during the period of active fruiting (June-July-August) 2019-2020. 10 berries in full maturity were selected from each variety and sample. The crushing force of the berries was determined using the fruit test device and converted into international units - Newtons (1 kg - 9.8 N). The climatic conditions of the study periods were characterized by high contrast, which indicates the instability of climatic factors of the summer growing season. However, this circumstance made it possible to evaluate objectively the collection and breeding material by the size and density of berries. The evaluation of housing and elite forms of raspberries for the crushing force of berries allowed us to identify varieties - sources of increased fruit density: Early Dawn, Lyachka and Lazarevskaya, having a relatively large (3.5-4.5 g) and dense berry with a crushing force of 7.6-8.4 N, and the following elite forms: 9-58; 9-27; 9-20 with a berry weight of 3.8-4.0 g and with a crushing force of 7.3- 9.7-N. The index of the crushing force of the fruit of these elite forms during the research period was not lower than 5.0 N, but occasionally it was heavily influenced by soil and air humidity, which negatively affected the commercial qualities of the berries.