FACTORS AFFECTING IN-VITRO ESTABLISHMENT AND SHOOT PROLIFERATION OF ROSA-HYBRIDA L AND ROSA-CHINENSIS MINIMA

The effects of nodal explants collected at different plastochrones, us e of various benzyladenine (BA) concentrations, sources of carbohydrat es, and phases of the culture medium on shoot establishment and prolif eration of Rosa hybrida L. and R. chinensis minima were evaluated. Hig her numbers of shoots per explant were obtained from R. hybrida cv. Ca refree Beauty explants proximal to the apical meristem than those from distal nodes. However, proliferating shoots derived from plastochrone s proximal to the apical meristem had a lower number of leaves/explant and were shorter than those derived from other distal plastochrones. Although shoot proliferation increased with higher BA concentration in the medium, a concentration of 4.4 mu M BA was found optimum for axil lary bud-break and shoot development for R. hybrida cvs. Adelaide Hood less and Cuthert Grant. A higher shoot proliferation rate was observed for R. hybrida cv. Carefree Beauty explants grown on a medium contain ing 55.5 mM fructose than 58.4 mM sucrose. However, no differences wer e observed for R. hybrida cv. Cuthert Grant gown on a medium containin g either fructose or sucrose. The mean number of shoots/explant was hi gher for R. chinensis minima cv. Red Sunblaze explants grown on a liqu id (4.5) than on a solid medium (1.7) for the first reculture; while n o significant differences between the two phases of the medium were ob served for the second reculture. However, a higher mean number of shoo ts/explant was observed on solid-phase (4.0) than liquid-phase medium (3.4) for the third reculture. A higher mean number of leaves/shoot wa s obtained on a solidified medium rather than liquid medium in the fir st two consecutive recultures, while no differences were observed for the third reculture. Although a significant effect of BA concentration on mean number of shoots/explant was observed for Red Sunblaze nodal explants, the influence of BA concentration decreased in the two conse cutive cultures for both phases of the medium. Hyperhydricity was obse rved on Red Sunblaze shoots grown on the liquid-phase medium.