Variations in Sweetpotato Regenerates from Gamma-ray Irradiated Embryogenic Callus

Radiation induced and somaclonal variations were investigated in the regenerates from gamma irradiated and controlled embryogenic callus (EC) of sweetpotato cvs., Yulmi and White Star by morphological, RAPD and AFLP analysis. Most (approx. 90%) of the EC produced somatic embryos developed into plantlets after being transferred to the auxin-free medium. The frequency of morphological variants derived from the irradiated callus ranged from 3 to 7.8% compared to 0.1-1.1% of that derived from the non-irradiated. Morphological variants were selected from the regenerates and analyzed by RAPD and AFLP procedures. RAPD polymorphisms of Yulmi and White Star regenerates from irradiated calli were 8.8% and 6.1%, respectively. However, the polymerphisms among regenerates from the non-irradiation treatment in these two cultivars were non-detectable and 3%, respectively. AFLP polymorphisms of Yulmi and White Star regenerates from irradiated calli were 29.9% and 28.6%, respectively. while the frequencies for those form non-irradiated calli were 8.5% and 5.6%, respectively. Both the control plants and variants from the nonirradiated were clustered together, while variants from irradiated were separated from the group by Nearest-Neighbor-Interchange Branch Swapping Abbreviation: EC (Embryogenic callus), AFLP (Amplified Fragment Length Polymorphism), RAPD (Random amplified polymorphic DNA)