In vitro culture to improve breeding activities in Rosa hybrida

In vitro culture techniques may be valuable tools to increase breeding efficiency, introduce genotypes with interesting ornamental traits and shorten the time needed to obtain new cultivars. Hips resulting from a specific tetraploid Rosa hybrida cross were weekly harvested from 21 to 35 days after pollination (DAP). The obtained in vitro seedlings were multiplied using two media: M1) MS and M2) MS added with BAP (1 mg L^-1) and GA₃ (0.5 mg L^-1). The highest multiplication rate was obtained from embryos collected at 35 DAP on MS medium added with hormones. The shoot sprouting and the abnormal rate were generally not affected by the presence of hormones in the medium. For rooting, two media were also tested: R1) MS and R2) ½ MS supplemented with IBA (0.1 mg L^-1). The highest percentage of rooted explants was obtained from embryos collected at 28 DAP on R1 medium. The same conditions induced also the highest number of roots. The addition of IBA to rooting medium induced the development of longer roots in explants obtained from embryos collected at 35 DAP. The rooted plantlets were successfully acclimatized to ex vitro conditions. At flowering, the morphological traits of eight clone groups were compared to those of the seedlings obtained under common practices. Ex vitro plantlets showed more variability in flower colours, presence/absence of prickles, and number of petals flower^-1.