Evaluation of Multiplication Potential of Cold Stored Shoot Cultures of Selected Fruit Genotypes

We presented the results about preserving in vitro selected fruit genotypes by cold storage strategy and the capacity for following shoot multiplication. The investigation included five fruit genotypes: plum ‘Po`ega~a’, cherry rootstocks (‘Gisela 5’ and ‘Tabel Edabriz’), raspberry ‘Meeker’, and blackberry ‘^a~anska Bestrna’. The best results were achieved with shoots of the plum cultivar ‘Po`ega~a’ which can be successfully stored at 5°C up to 10 months, without subculturing producing viable shoots. Furthermore, a significant increase in the multiplication index (13.0) of this genotype was noticed especially in shoots cultivated for 21 days under standard growing conditions, followed by storage at 5°C in total darkness for six months. ‘Gisela 5’ and ‘Tabel Edabriz’ cherry rootstocks were successfully preserved for three months in the same manner, and the plants (100%) well recovered. After being stored in cold conditions, the multiplication index of shoots in both rootstocks exhibited an increase ranging from 1.7 to 4.8 times compared to those grown under standard conditions. The viability rate of in vitro shoots of the raspberry cultivar ‘Meeker’ in cold conditions was also high (>67%). In this genotype, as well as in both cherry rootstocks, slow growth storage was accompanied by slow nitrogen uptake from the medium. In addition, the multiplication potential of encapsulated raspberry ‘Meeker’ and blackberry ‘^a~anska Bestrna’ and cold stored (5°C, darkness) shoot tips was evaluated. Encapsulated shoot tips of ‘^a~anska Bestrna’ (18.8%) and ‘Meeker’ (6.3%) survived the monthly cold storage period and exhibited regrowth. Shoots of selected genotypes were capable of multiplication in successive subcultures after cold storage, and often the multiplication indexes were higher compared to the control shoots that were consistently grown under standard conditions in the growth chamber. These results represent a significant contribution to the revitalization and further development of the national fruit gene bank.