Effects of light and different plant growth regulators on induction of callus growth in rapeseed (Brassica napus L.) genotypes

The present work describes the effects of winter and spring genotypes of rapeseed (PF7045/91, Okapi and Opera), explants (cotyledons and hypocotyls), light, different kinds and concentrations of auxins [Naphthylacetic acid (NAA) and 2, 4dichlorophenoxyacetic acid (2, 4-D)], presence of cytokinin [benzyladenine (BA)] and different concentrations of micro and macro elements (MS and 1/2MS) on callogenesis in rapeseed (Brassica napus L.). First of all, explant sections were cultured in different combinations of media and plant growth regulators, in dark or light for 10 days. After 10 days, calli fresh weight and root formation were evaluated. When the effects of plant growth regulators on callus color were investigated, it was revealed that auxins had an inhibitory effect on chlorophyll formation, whereas cytokinin tended to promote it. The results also showed that 2, 4-D when combined with cytokinin (BA), callogenesis and cell division were stimulated faster and better in rapeseed cultivars whereas NAA (with BA or without it) stimulated root formation and rhizogenesis. Also, in most cases, calli fresh weight in winter genotypes of Opera and Okapi was higher than spring genotype of PF7045/91. Likewise, MS medium was more effective on callogenesis than 1/2MS medium. In all cultivars and explants (especially hypocotyl sections) light stimulated callus growth, inhibits root growth and in cotyledon derived calli increased browning. The results of this study suggested that using cotyledon sections as explants under dark conditions would be more beneficial for callogenesis, but for hypocotyl sections light conditions is preferred.