IN VITRO PROLIFERATION OF NEWLY BRED CZECH PEAR CULTIVARS

Abstract

The objective of this study was to develop a method for rapid in vitro shoot multiplication of four newly bred Czech pear cultivars (‘Bohemica’, 'Dicolor', 'Elektra' and 'Erika'). Six proliferation MS media containing different concentrations of cytokinins BAP (6-benzylaminopurine), TDZ (thidiazuron) or 2iP (6-(g,g-dimethylallylamino) purine) were tested. For the four cultivars, the effect of three growth regulators on proliferation, callus formation and shoot morphology is shown. Selected pear cultivars were successfully established in vitro using mercuric chloride in a concentration of 0.15% as a sterilization solution. Of the 80 shoot tips taken only 3 explants of 'Bohemica', 2 explants of 'Erika' and 1 explant of 'Dicolor' were visibly contaminated with micro-organisms. Proliferation rates varied depending on the genotype and medium used. The highest proliferation rate was obtained for pear cultivar 'Elektra' that produced 4.1 ± 0.1 shoots (longer than 10 mm) on MS medium containing 1 mg L -1 TDZ. The lowest proliferation rate was obtained for cultivar 'Dicolor', which did not multiply at all on MS medium containing the lowest concentration of BAP 1 mg L -1 . Abundant callus formation at the base of explants and abnormally narrow undeveloped leaves were observed on the media containing TDZ. All in vitro plants of pear cultivars on MS medium with 10 mg L -1 2iP developed good foliage. However cytokinin 2iP at the used concentration did not promote satisfactory proliferation.