Brassica carinata (A. Braun) is an amphi-diploid species that originated from interspecific hybridization between Brassica nigra and Brassica oleracea in the highlands of Ethiopia. The crop has many desirable agronomic traits but with oil quality constraints like high erucic acid and glucosinolate contents. In this study, two genotypes and two types of explants were tested for callus induction, shoot and root regeneration in Murashige and Skoog (MS) medium under different concentrations of naphthalene acetic acid (NAA), 2,4-dichlorophenoxy acetic acid (2,4-D), and 6-benzyl amino purine (BAP). Cotyledon proved to be most responsive for callus induction at a higher rate in a short period of time. Growth regulator type and concentration had a significant effect on the callus induction and physical appearance. The highest frequencies of callus growth (80.7 and 95%) were observed on hypocotyl and cotyledon explants, respectively, cultured on MS basal medium supplemented with 0.5 mg/L 2,4-D in Yellow Dodola. Two types of calli were obtained: white and friable callus with large cells; green and compact callus with smaller cells. For shoot induction, successful shoot regeneration from white/friable callus was achieved when MS medium was supplemented with 6-benzyl amino purine (2 mg/L). Significant genotypic difference was observed between the genotypes, Yellow Dodola giving the highest response. Maximum shoot induction was recorded in the hypocotyls of Yellow Dodola (90%) when MS medium with 2 mg/L BAP was used. Highest percentage of shoots with roots (98.7%) and highest mean number of roots per shoot (9) occurred on medium with 0.3 mg IBA, while the maximum root length (4.7 cm) was attained on MS medium without plant growth regulator (MSO) in Yellow Dodola. Plantlets were successfully acclimatized in potting medium containing a mixture of 25% sand, 50% red soil and 25% compost on acclimatization pots (1:2:1). The in vitro regeneration protocol developed can be used for further undertaking of other tissue culture and genetic engineering work on B. carinata.
Key words: Auxin, callus, cotyledon, cultivars, cytokinin, in vitro regeneration, hypocotyls.