Polyploidisation as a tool to introgress compact growth in Escallonia

Escallonia is a genus of flowering shrubs native to South-America. As for most woody ornamentals, current breeding efforts are low. Important breeding goals are, besides flower characteristics, winter hardiness and a compact growth habit. Polyploidization is a method shown to deliver plants with altered morphology and increased stress resistance. Therefore we established an in vitro polyploidization protocol for Escallonia.
In a first step we optimized the in vitro polyploidization method on E. rubra and E. rosea. A short 3 day treatment with 250µM oryzalin or a chronic 10 week treatment of with 5µM trifluralin resulted in the highest efficiency (17% and 43% tetraploids for E. rosea; 60% and 54% tetraploids for E. rubra).
In a second step, the most efficient treatments were applied to 15 other Escallonia species. First results reveal large differences between genotypes, both in polyploidization efficiency and in mortality.
Ploidy doubled plantlets of E. rubra and diploid controls were acclimatized in the greenhouse for further morphological evaluation. Tetraploid E. rubra shows larger leaves, both in width and length, but a smaller length/width ratio (2.5 for diploid plants and 2.0 for tetraploids). Plant morphology and growth of obtained tetraploids of different Escallonia species will be evaluated in future.