Induction of tetraploid hardy rubber tree, Eucommia ulmoides, and phenotypic differences from diploid

Polyploid plants tend to have larger organs than diploids due to the doubling of their chromosome number. However, the enlarged regions, whether cells, tissues, or individuals differ depending on the plant species or taxon, as have metabolic changes. Eucommia ulmoides is a deciduous dioecious plant natively distributed in China that accumulates trans-1,4-polyisoprene (TPI) in laticifers throughout its tissues. To induce tetraploids of E. ulmoides, colchicine treatment time and concentration were assessed for ability to obtain tetraploids, and the resulting plants were analyzed for phenotypic differences from diploids with respect to individual size, 16 leaf attributes, sizes of three cell types (epidermis, laticifer, and parenchyma), and TPI content and molecular weight. Effective conditions for obtaining tetraploids were 0.05% colchicine for 48 h, which led to obtaining a total of 9 tetraploids. The tetraploids showed larger stomata size but lower stomata density than diploids. Significant differences in the mean values of other attributes including leaf size, cell size, and TPI content of tetraploids could not be detected between tetraploids and diploids, suggesting that E. ulmoides is less affected by gene doubling than other plant species, and that tetraploid individuals might not have a tendency to increase their biomass.