Autopolyploidy in Chrysanthemum cv. ‘Gongju’ Improved Cold Tolerance

Abstract

A total of 120 nodal segments of Chrysanthemum ‘Gongju’ plantlets were treated with colchicine to obtain autopolyploidy. Flow cytometry showed that 1 of the 12 surviving seedlings had DNA contents that were twice that of tetraploid plants. Microscopy revealed that the epidermal cell and stomatal area of octoploid plant leaves were larger than those of tetraploid plant leaves. Morphological characteristics showed that the plant height of octoploid plants did not differ from that of tetraploid plants, but their leaves and flowers remarkably varied. The leaves and flowers of octoploid plants were larger than those of tetraploid plants. The diameters of the inflorescence and disc flower of octoploid plants increased by 7.2% and 28.4% compared with those of tetraploid plants, respectively. Similarly, the numbers of their ligulate and tubular flowers increased by 22.6% and 34.0% compared with those of tetraploid plants, respectively. Semi-lethal temperature (LT₅₀) of tetraploid plants was − 8.58 °C, while LT₅₀ of octoploid plants decreased by 3.4 °C. At low temperatures, the relative expression levels of CmICE, CmDREB, CmCOR, CmPYR1, CmFAD, CmWRI, CmBAM, and CmPSP genes related to cold resistance in octoploid plants were higher than those in tetraploid plants. Conversely, the expression levels of CmAPX and CmGSH in octoploid plants were lower than those in tetraploid plants. The relative expression levels of CmOST, CmPDH, and CmOAT did not differ between octoploid and tetraploid plants.