Effects of cytokinin types and their concentrations on shoot proliferation and hyperhydricity in in vitro pear cultivar shoots

This study was made to clarify the effects of cytokinin type and their concentrations on shoot proliferation and hyperhydricity in in vitro Pyrus pyrifolia N. ('Hosui' and 'Kosui') shoots. The shoots were subcultured in a woody plant medium supplemented with 0.5 muM 3-indolyl-butyric acid, 3% (w/v) sorbitol, 0.8% (w/v) agar, and with cytokinins kinetin, 6-benzylaminopurine (BA), N-(2-chloro-4-pyridyl)-N'-phenylurea (CPPU), 1-phenyl-3-(1,2,3- thiadiazol-5-yl) urea (TDZ) added at concentrations 0.44, 4.40, 11.0 and 44.0 muM. The highest number of shoots was induced by adding BA at concentration 11.0 muM, then by 4.4 muM BA, in both cultivars. TDZ and CPPU caused greater hyperhydricity in cultured explants than BA and kinetin. 'Kosui' was more susceptible to hyperhydricity compared with 'Hosui'.