Micropropagation of dahlia plants Dahlia variabilis Wild (Desf.). Effect of explant and plant growth regulators on shoot regeneration and growth

The present study was conducted to determine the effect of explant, BA (6-benzyl amino purine) and NAA (a- naphthalene acetic acid) in the shoots regeneration and growth. The results showed the superiority of the shoot tip on hypocotyl in response to shoot formation reached 86.67% and 43.33% respectively. While the cotyledon, nodal segment and root segment did not respond for it. Also the results indicate that MS medium (Murashige & Skoog medium) supplemented with BA and NAA at 2.0 + 2.0 mg L-1 concentration gave the highest significantly response to shoot formation reaching 86.67%. While the MS medium supplemented with 2.5 + 2.5 mg L-1 BA and NAA combination was less responsive to form shoots, reaching 46.67%. But the two combinations of BA and NAA (1.5 + 1.5 and 3.0 + 3.0 mg L-1) did not give any response for shoot regeneration. The 2.0 + 2.0 mg L-1 combination was significantly superior on 2.5 + 2.5 mg L-1 in number of formation shoots reaching 5.0 and 2.0 shoots/shoot tip respectively. The regenerated shoots cultured on half strength of MS supplemented with 0.6 mg L-1 IBA (Indole^ butyric acid) proved to be significantly superior beside other concentrations of IBA in the response of root formation which reached 96.67%, when compared with the concentration of 1.0 mg L-1 of IBA which gave the lowest response for root formation (56.67%). As well as the 0.6 mg L-1 IBA concentration gave the highest rates in number of main and secondary roots and root length compared with other concentrations of IBA. The plants produced by micropropagation have been acclimatized at high success rate of 100%.