Comparative study of different surface sterilization treatments and optimal month for establishment of aseptic cultures of raspberry cultivars

Removing contaminants from plant material with minimal damage to plant cells using different chemical solutions represents very important and one of the most critical steps in establishing plant tissue culture in vitro. Our study deals with the optimisation of the protocol for successful surface sterilization of initial explants in two raspberry cultivars, 'Meeker' and 'Willamette' in two experimental years. The main objective during the first experimental year was to examine the protocols for surface sterilization which included different combinations of disinfectants (mercuric chloride or commercial bleach solution each in combination with 70% ethanol). In the following year, the impact of the two most effective sterilization treatments on the establishment of aseptic cultures over the four-month period (May, June, July, and August) was investigated in both raspberry cultivars. Aseptic cultures were established on Murashige and Skoog medium (MS) containing 2.0 mg/l N6-Benzyladenine (BA), 0.5 mg/l indole-3-butyric acid (IBA) and 0.1 mg/l gibberellic acid (GA3). The highest percentage of explants initiation in 'Meeker' (79.3%) was achieved with surface sterilization in 70% ethanol (1 min) combined with 10% (v/v) commercial bleach solution (20 min), whereas sterilization in 70% ethanol (1 min) followed by HgCl2 (3 min) gave the best results (38.3%) in 'Willamette'. The most optimal month for the establishment of aseptic culture was May for 'Meeker', while June was the most suitable month for the 'Willamette' cultivar.