Oryzalin-induced chromosome doubling in triploid Populus and its effect on plant morphology and anatomy

Populus is an important economical woody species due to its fast growth. In vitro induction of hexaploidy and investigation of morphological and anatomical characteristics in ((Populus alba × P. glandulosa) × P. tomentosa) were conducted in this study. Chromosome doubling was induced in vitro in a triploid clone ((Populus alba × P. glandulosa) × P. tomentosa) with oryzalin as a tubulin inhibitor. Nodal sections of 5 and 10 mm were exposed to 2.5 and 5.0 mg l oryzalin for 24, 48 and 72 h. No significant differences in survival rates were observed between the different oryzalin dose, exposure time or nodal length; however, all rates were significantly lower than those in the no-oryzalin controls. The highest frequency of hexaploidy was 100% for the treatment of 5-mm nodes with 5 mg l oryzalin for 72 h and the treatment of 10-mm nodes with 5 mg l oryzalin for 24 h. The hexaploid plants were distinguishable from the triploid plants by morphological and anatomical characteristics. Chromosome doubling was accompanied by increases in the thickness and chlorophyll content of leaves. The stomata of hexaploids were larger and had a lower density than those of the original triploids. In particular, in triploid-to-hexaploid conversion, roots were less abundant, were shorter and had larger diameters. Root characteristics were determined to be suitable parameters for identifying putative hexaploids because they can be easily and quickly assessed.