The Use of Wheat Starch as Gelling Agent for In Vitro Proliferation of Blackberry (Rubus fruticosus L.) Cultivars and the Evaluation of Genetic Fidelity after Repeated Subcultures

Micropropagation has an important role in the large-scale production of blackberry plant material, given the high proliferation rates of this species. The aim of the present study was to evaluate the proliferative capacity of blackberry grown in vitro on wheat starch-gelled culture medium compared to classical agar-gelled medium and to assess the genetic fidelity between the proliferated shoots in starch-gelled culture medium and their mother plants. Six blackberry varieties ('C. ac.anska Bestrna', 'Chester Thornless', 'Driscoll's Victoria', 'Loch Ness', 'Polar', and 'Karaka Black') were tested. For the in vitro shoots proliferation, Murashige and Skoog (MS) medium supplemented with 0.5 mg dm 3 6-benzyladenine (BA) was used. The conventional medium was gelled with 0.5% plant agar, and wheat starch was used as an alternative gelling agent in a concentration of 5%. The results showed that for all blackberry cultivars, the highest number of shoots/inoculum was obtained in wheat starch-gelled culture medium, with a maximum value of 54.42 +/- 4.18 presented by 'Karaka Black'. Considering the length of the proliferated shoots, all tested cultivars presented outstanding results on the culture medium gelled with 5% wheat starch. The highest values regarding shoots length were observed on the 'Chester Thornless' followed by 'C. ac. anska Bestrna', and 'Loch Ness' with values of 5.55 +/- 0.04 cm, 5.46 +/- 0.06 cm, and 5.37 +/- 0.09 cm, respectively. The genetic uniformity of the micropropagated shoots in relation to their mother plants was confirmed by sequence-related amplified polymorphism (SRAP) and start codon targeted (SCoT) molecular markers.