STUDIES ON IN VITRO INDUCTION OF MUTATIONS IN ROSA SPECIES THROUGH DIFFERENT TECHNIQUES

Abstract

Among the highly fragrant rose species, R. centifolia, R. gruss an teplitz and R. borboniana have high commercial importance and value added potential. However, their large plant size, small flower size and lack of diversification in color detracts these species from recent trends of floriculture market. Therefore, this study aimed to produce reduced-stature plants and to improve flower color and size through in vitro mutagenesis using gamma irradiation, colchicine and somaclonal variation techniques. For this purpose cultures of R. gruss an teplitz, R. centifolia and R. borboniana were established by disinfestation of shoot tips with 0.1% HgCl2. It gave maximum survival percentage with limited occurrence of bacterial and fungal contamination. BAP @ 1.0 mgl-1 and IBA @ 0.50 mgl-1 found to be the optimum concentrations for shoot proliferation and in vitro rooting respectively. Micropropagated shoot tips of R. gruss an teplitz, R. centifolia and R. borboniana were irradiated with gamma rays upto 120 Gy. Minimum survival percentage was recorded at 60, 30 and 50 Gy respectively. Above these doses of gamma rays there was a complete mortality. Moreover, plant height was decreased with reduction in color and size of flowers. During selection variegated, pink color and abnormal shape flowers were also found in R. gruss an teplitz. Influence of colchicine was found to be species specific and its response showed significant results. Shoot tips treated with colchicine solutions for three hours resulted in minimum survival percentage at the maximum level of colchicine (1100 mgl-1). However, plant height was maximum in the plants of R. gruss an teplitz, R.centifolia and R. borboniana treated with colchicine solution at 900 and 1100 mgl-1. Moreover, treated R. gruss an teplitz and R. centifolia produced large size flowers with more intensification of color. This technique resulted in generation of variegated, serated petals and abnormal shape flowers in R. gruss an teplitz. In another set of trial micropropagated shoot tip explants were incubated for 5, 7 and 11 days in MS media fortified with different concentrations of colchicine. It resulted minimum survival percentage with the increase in the colchicine concentration and incubation period. However, plant height, flower size and intensification of flower color were increased with increase in the concentration of colchicine upto 450 mgl-1 with incubation period of 11 days. Use of colchicine in medium also yielded variegated flowers in R. gruss an teplitz species. Plants of R. gruss an teplitz obtained through regeneration via callus exhibited significant somaclonal variation than other regeneration methods. Genetic variation found in rose species was confirmed through RAPD analysis. Now these mutants need to be screened over the next few years for floral and vegetative characteristics. This study adds to the ongoing efforts to increase diversification in plant height, flower color and size of rose flowers. The outcome of the study will be helpful for future studies regarding induction of mutations in rose species.