Breeding prospects for increasing fruit firmness in remontant raspberries

Abstract

The majority of raspberry breeding programs focus on the creation of varieties with firm and transportable fruits that can be stored for a long time without losing their quality. Our research aimed to establish the possibility of creating remontant raspberry forms with the fruit firmness exceeding that of the best modern varieties in order to identify promising parental pairs. The physical and mechanical properties of raspberry fruits harvested in 2020 were studied. The research material included 19 remontant raspberry varieties, eight selected forms and 10 combinations of crosses with the total seedling number of 627 pcs. The original parental forms and hybrid offspring were evaluated in terms of berry crushing force and detachment from the peduncle using conventional horticultural methods. During the study period, no genotypes with very soft berries were identified among the studied varieties. Only two varieties (Oranjevoye Chudo and Elegantnaya) produced soft fruits (up to 5.0 N) unsuitable for transportation. More than 65 % of the samples exhibited a medium level of firmness, thus allowing the high quality of fruits to be preserved during manual harvesting and transportation over limited distances. The Sugana, Salut, and Atlant varieties, as well as 3-59-30, 2-53-1, 44-154-2, 1-60-1, and 9-113-1 selected forms produced firm berries withstanding a crushing force of 7.2–8.3 N. In the hybrid progeny of raspberry remontant type, large variations in fruit firmness were observed, depending on the combination of crosses. The calculation of dominance degree (D = -19-0) confirmed the difficulty in transmitting the trait of high fruit firmness to progeny. Among the studied hybrid families, the yield of transgressive seedlings ranged from 1.7 to 15.6 %. Only in the 9-113-1×Salut combination, no hybrids exceeding the best parental form in terms of fruit firmness were identified. Promising combinations of crosses in breeding for obtaining remontant raspberry varieties with increased fruit firmness include the following: 9-163-1×44-154-2, Podarok Kashinu×Atlant, 9-113-1×Podarok Kashinu, 9-155-1×Atlant, as well as populations from free pollination of Zolotaya Osen, Pokusa, and the 7-42-3 selected form. In the offspring of these parental forms, the 21-166-11, 21-166-10, 8-163-10, 1-188-2, 8-163-11, 15-132-1, 6-124-21, 2-159-10, and 1-135-31 selected forms withstanding a crushing force of 8.5–10.4 N were identified.