The colored calla lily (Zantedeschia hybrida), as the“flower star of the 21st century”, is becoming more and more popular for its special morphology and high ornamental value. But at present, the varieties of colored calla lily in the market are imported from foreign countries like the Netherlands, New Zealand, Japan, etc. Without independent intellectual property rights, the industry of colored calla lily has been seriously restricted in China; therefore, breeding new varietyies of colored calla lily with excellent ornamental traits, resistance to disease and strong growth vigor is of great significance to our country. Polyploids of ornamental plants are usually characterized by their superior growth vigor, flower size, stem sturdiness, and better resistance as compared with diploids. Two tetraploid variations of colored calla lily varieties “Tanswan” and “Liberty” were successfully established in the previous study; however, whether the tetraploid varaitions have more advantages in growth performance, morphological characteristics and resistance to stress than the diploids are still unclear.
In this study, the tissue culture plantlets of the diploid and tetraploid of colored calla lily were transplanted and managed at the same environmental condition and cultivation measure. Their ploidy level, survival rate, morphological characteristics (including plant height, stem diameter, maximum leaf length, maximum leaf width, leaf-shape index, leaf color, and uniformity), dry matter in bulb, resistance to stress and dormancy were investigated and analyzed.
The results showed that the chromosome number of two tetraploid variations was 64 after two months of transplanted into the field, suggesting the ploidy of the tetraploid variations are stable. The survival rate of colored calla lily cultured in the medium with more peat moss [V(peat moss)：V(pelite)=6：4] was higher than that in the medium of V(peat moss)：V(pelite)=7：3, which suggests the permeability of the medium is important to the growth of the colored calla lily. Compared with the diploid plants, the tetraploid plants of colored calla lily grew faster and stronger, had higher survival rate, thicker/darker green leaves, earlier germination time and shorter dormant period. Furthermore, the tetraploid plants had higher survival rate with an increase of 23.59% and 26.74% respectively in “Tanswan” and “Liberty” than the diploids under the low temperature stress, indicating the tetraploids of colored calla lily have higher resistance to low temperature. Under the same environmental condition, the difference in fresh mass and dry mass of the bulbs was quite significant at different ploidy levels. The tetraploids had higher ratio of dry to fresh mass than diploids, which suggests that the tetraploids have stronger ability to accumulate dry matter than the diploids. By comparing and analyzing the content of free proline, activities of superoxide dismutase (SOD) and peroxidase (POD), we found the tetraploids of colored calla lily had higher resistance to low temperature than the diploids; meanwhile, the resistance to low temperature stress of colored calla lily was negative correlation with the changes of free proline content, and the varieties with higher resistance to low temperature stress had a stronger antioxidation system.
In conclusion, the tetraploids of colored calla lily have significant advantages in morphological characteristics, dry matter accumulation in bulb, resistance to stress and dormancy characteristics; therefore, the tetraploid of colored calla lily has great potential to be applied the production in the future.