2018 ASHS Annual Conference

Poinsettia is one of important pot flower crops in the world. In recent years, interspecific hybridization is adopted to introduce new plant character of Poinsettia. In 2003 US company Ecke created ‘Dulce Rosa’, novel interspecific hybrid conducted by the pollination between Euphorbia pulcherrima and E. cornastra. However the pollen sterility of ‘Dulce Rosa’ prevents it from being material for continuous breeding work. The main purpose of present research was to restore its fertility by polyploid mutagenesis. The in-vitro internode explants of ‘Dulce Rosa’ were cultured on artificial medium which contains colchicine for mutation treatment. The survival mutants evaluated the plant characteristics and pollen fertility, as well as the relative DNA content also confirmed by flow cytometry to compare the differences. The results indicated that ‘Dulce Rosa’ bract color being RHS-57D, the bract color of mutant significantly darkened (RHS-57B&57C). In addition, the blade aspect ratio of ‘Dulce Rosa’ being 2.37, but the mutant’s blade is widened (aspect ratio 1.71), as well as thickened leaf and increased hair villus amount. The width and length of mutant’s guard cell is increased 1.3 times. In addition, the lack of stamen due to ‘Dulce Rosa’ flower abnormality, the mutant with functional reproductive organs, and the anther stretches from involucrum and releases fertility pollen after colchicine induction treatment. Under optical microscope, mutant’s pollen characteristic turns normal without wrinkling. The M2 mutant has highest pollen germination rate and its pollen tube germinates well in BK medium (20% sucrose). The DNA content of mutant is twice as many as those of ‘Dulce Rosa’, proving the evidence of colchicine mutant being polyploidy.