Effect of green cutting propagation of clonal apple rootstocks using various rooting methods

This paper studies the regenerative capacity of softwood cuttings from 14 clonal apple rootstock genotypes. The research was conducted in 2022–2024 using the facilities of the Federal Horticultural Research Center for Breeding, Agrotechnology and Nursery in Moscow region. The study included dwarf rootstocks (62–396, 57–146, 60–160, R 60), semi-dwarf rootstocks (54–118, 57–545, S–79–1, S-68–3, SK 2, SK 2U, 60–164, M 26), and semi-vigorous rootstocks (57–233, MM 106). A comparative experiment assessing the efficiency of rooting on open ground beds versus cassette cells was conducted with five rootstock genotypes: 57–545, 62–396, 54–118, 57–233, and S–79–1. We found that the rooting rate, subsequent development, and field adaptability of the cuttings depended not only on the genotype capacity for adventitious root regeneration but also on the rooting method. On ground beds, the rooting percentage varied from 64.0 to 88.0 % for dwarf rootstocks and from 65.0 to 81.0 % for semi-dwarf rootstocks, while for semi-vigorous rootstocks (57–233 and MM 106) it exceeded 80 %. When cassettes were used, the rooting rate for genotypes 57–545, 54–118, 57–233, and S–79–1 was over 94 %. Regarding key biometric parameters, such as shoot height, stem diameter, and root length, the cuttings rooted in ground beds outperformed those from cassettes. However, the cuttings rooted in cassettes developed a higher number of roots. Among the genotypes, 57–545, 57–233, and 54–118 exhibited the most developed root and shoot systems, whereas S–79–1 showed the weakest root development. The cassette system proved to be the most effective technique for green cutting propagation of clonal rootstocks. This approach ensured better root system development and minimizing losses during the stages of rooting, storage, and field establishment. The average loss from the initial cutting stage to the survival assessment in the first nursery field was 40 % for ground bed rooting, compared to only 16 % for cassette rooting.