In an attempt to

Rose is one of the most important floricultural crops in the world and the production of new cultivars in this plant has been a major issue for many years. Modern roses have been mainly developed through spontaneous or artificially induced bud sport1), but the recent progress of plant biotechnology provides the alternative applications such as tissue culture2, 3) and gene manipulation technologies4) for plant breeding. In our laboratory, we have investigated the use of abundant somaclonal variations induced in tissue cultures and attempted to establish an efficient system for the selection of useful genetic variations for improving important traits such as disease resistance in various crop plants5). Also in rose plants, we have elaborated an effective method for tissue culture and clarified the conditions suitable for plant regeneration from the leaf explant-derived calli6). To further develop our culture system, the present work describes an utilization of petal tissues as a culture material for successful callus induction and subsequent plant regeneration in rose plants.Fully opened flowers were harvested from rose plants (Rosa hybrida cv. Carl Red) grown in a greenhouse for 2-3 months and used in the following culture experiment. The receptacles, sepals, and outermost petals were removed from flowers, and the remaining petals were excised and dipped into 70% ethanol for 30 sec and then into a 1 % sodium hypochlorite solution for 90 sec for surfacesterilization. After rinsing with sterilized distilled water, petals were cut into smaller segments (1X1cm) and then placed on a Murashige-Skoog7) (MS) medium supplemented with 3% sucrose and different concentrations of a-naphthaleneacetic acid (NAA) and 6-benzylaminopurine (BAP) and solidified with 0.3% Gelrite (Merk, NJ., USA). The medium was adjusted to pH 5.7 with 1 N NaOH before autoclaving. Culture bottles were tightly sealed with Parafilm and incubated at 26+ 1C in the dark. After 7-10 days of incubation, pale yellow calli were induced from the decolorized edge portions of red-color petal explants of Carl Red in all the combinations of NAA and BAP concentrations ( Fig. 1-A). These calli proliferated slowly, became brownish, and produced adventitious roots (5-10 roots from each petal explant) 14-16 days after incubation ( Fig. 1-B). The root elongation ceased 30-40 days after incubation, and subsequently the bugle-like structures (BLS), as shown in Fig. 1-C, were produced apart from the adventitious roots in the callus tissues approximately 50 days after incubation. The formation of BLS was frequently observed in calli cultured in the presence of 0.25-1.0 ug/ml of NAA and 0.0025-0.015 cg/ml of BAP (Table 1). Especially, the BLS formation was highest in frequency (62% in average of four separate experiments) and in number (15-20 per explant) in combination of 0.75 cg/ml NAA and 0.01, ag/ml BAP. In a previous

Meristem tissues were excised from axillary buds of rose plants (Rosa hybrida cv. Carl Red) and cultured on media containing various concentrations of BA in order to clarify the condition for micropropagation. The meristem tissues showed rapid and effective shoot formation when cultured with 1. 0 jig/ ml BA. After 1 month of incubation, small leaflets of shoots were harvested and cultured on MS medium 297 cotaining either IAA and BA or NAA and BA for callus induction. Adventitious buds were frequently induced in callus tissues cultured in the presence of 0.25ug/ml NAA and 0.005ug/ml BA, and effectively differentiated into shoots when transferred to MS medim containing 1.0jig/ml BA. Abundant roots were formed when shoots were cultured on 1/4 x strength regeneration medium.