Gamma irradiation of in-vitro proliferated cultures of rose (Rosa hybrida) for induction of novel mutants

In-vitro mutations were induced in two Hybrid Tea rose (Rosa hybrida L.) cultivars Pusa Mohit and Raktima for induction of novel traits. Single node cuttings were used to proliferate cultures under in-vitro and were irradiated with different doses of g-rays (0, 5, 10, 15, 20 or 25 Gy) using a 60Co source. The g-irradiated microshoots were then cultured aseptically on to rooting medium containing 0.5 × MS basal medium supplemented with 2.69 µM a- naphthalene acetic acid (NAA) plus 2.46 µM 6-benzylaminopurine (BAP) plus 40 g/l sucrose and 0.8% (w/v) agar- agar for rooting. Decreased root lengths, numbers of roots per shoot were observed at 25 Gy. In-vitro proliferated cultures and non-irradiated (control) plants were transferred to plastic pots 1 month after acclimatization under laboratory conditions and examined for their morphological traits. Marked vegetative abnormalities with respect to leaf shape, leaf lamina, fused leaves, albinism or leaves with less chlorophyll, variegated leaves with stunted growth etc. were observed between the mutated and control populations. Four new variants with altered or novel flower colour, form, shape and size were isolated and numbered as PM 1, PM 2 (from cv. Pusa Mohit) and RK 1, RK 2 (from cv. Raktima) as compared to the original cultivars. These variants were multiplied on a large-scale through micropropagation and evaluated for their stability. This study developed a mutagenesis protocol that could be used to develop novel flower colour mutants in rose