The influence of putrescine (Put), spermidine (Spd), and spermine (Spm) on somatic embryogenesis (SE) and plant regeneration of three indica rice cultivars (ASD16, IR64, and ADT43) were evaluated since polyamines (PAs) are reported to play vital roles in SE and plant regeneration. Significant increases in the regeneration potential of the rice cultivars upon polyamine treatments were observed. Put (1.0 mM) induced the highest regeneration frequencies, somatic embryos, and shoot numbers. PAs influenced the fresh weights of the suspension cultures. Spd was found to be detrimental to cultivar ADT43 towards embryogeneicity, regeneration, and somatic embryo induction. Among the cultivars, ASD16 was found to respond superiorly to the polyamine treatment. Experiments with long-term cultures of the rice revealed that Put and Spm enhanced the regeneration potential, and the highest frequencies were recorded for ASD16 and IR64. Results indicate that PAs can be effectively used as growth modulators to achieve success in in vitro tissue and genetic manipulation studies with elite recalcitrant indica rice cultivars.
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