Fruit firmness of raspberry parent forms and its inheritance in posterity

Abstract

The possibility of increasing in raspberry fruit firmness as the limiting indicator of variety aptitude to mechanized harvesting of berries as well as long-term transportation and storage have been considered in the article. The objects of research were 23 raspberry varieties of domestic and foreign breeding, 16 selected forms, as well as their offspring from controlled crossings and populations from free pollination. The evaluation of firmness characteristics was carried out at the hybrid plot and the plot of competitive varietal trials in the period from 2016 to 2018. The berries from each variety and an elite seedling were collected in a state of full maturity in triple frequency. The number of berries in each frequency was 10 pieces. There were took 10 berries in the optimum degree of maturity of the hybrid offspring from each seedling. The effort to crush the berries was determined using torsion weights and transferred to international units –Newton; the separation force was determined with the help of a pistol-dynamometer. The weather conditions of the research period were contrasting, which allowed evaluating more objectively the collection and selection material of raspberries on the fruit firmness. The evaluation of the parent forms of raspberries by the effort of crushing the berries allowed revealing the sources of increasedthe fruit strength – varieties Glen Ample, Cascade Delight, Peresvet, Lazcka, Gusar and the selected form 2-90-2. The “crush effort” indicator of the fruits of these forms over the research period was not lower than 5.0 N and was less affected by weather conditions. The analysis of the hybrid offspring of raspberries from controlled crossings and populations from free pollination showed the polygenic character of inheritance of the trait. The promising parent forms for breeding to increase the berry firmness – varieties Glen Ample and Gusar, as well as the selected form 2-8-3 have been identified. Among the studied hybrid combinations, the families of Tarusa x 2-8-3, Gusar x Vol’nitsa, as well as the populations from free pollination of Glen Ample and Gusar varieties are of the greatest interest. In the offspring of these genotypes the transgressive seedlings with effort of crushing of fruits more than 6.0 Н have been revealed.