Polyploidization in Hippeastrum hybrids and H. papilio

Polyploidization is being introduced into our amaryllis (Hippeastrum) breeding project in order to broaden the gene pool, and facilitate the hybrid breeding process. In vitro bulblets of several tetraploid hybrid Hippeastrum (4n=44), Christmas Gift (CG), Orange Sovereign (OS), Red Lion (RL)], and one diploid  H. papilio (2n=22), Papilio Butterfly (PB), were treated with various concentrations of colchicine (0, 0.025, 0.25, 1.25, 2.5 mM) for 23 or 30 days. Colchicine concentrations higher than 0.25 mM greatly reduced plant survival rate and plant growth. No plants in all 4 genotypes showed chromosome doubling at the lower concentration (0.025 mM) treatments either for 23 or 30 days.  Colchicine concentrations between 0.25 and 1.25 mM were suitable for both plant survival and chromosome doubling.  Eight plants of H. papilio out of 33 tested were shown to be tetraploid though flow cytometry analysis. In experiments with hybrid amaryllis, octaploid plants were identified though flow cytometry analysis for OS and RL, but not for CG. Additional plants are to be tested via flow cytometry, with additional confirmation using root tip chromosome counting.