Colchicine-induced polyploidy has the potential to improve rubber yield in Taraxacum kok-saghyz

Abstract

Taraxacum kok-saghyz (TK), also known as rubber dandelion, is under development as a source of natural rubber but has not been fully domesticated. Rubber yield is highly variable and biomass is low compared with most crops. Therefore, it is imperative to apply breeding methods to improve rubber yield and accelerate the domestication process. One strategy to accelerate breeding is polyploid induction, which could improve rubber concentration and plant size. A gradient of colchicine concentrations ranging from 0% to 0.5% was used to treat approximately 5000 seeds for different periods of time (12h to 96h), followed by use of flow cytometry to confirm induced tetraploids. The optimal treatment of 0.1% colchicine for 48h resulted in an induction efficiency of 56.6%. An early-screening strategy successfully identified 2-month old tetraploid seedlings based on atypical leaf morphology. Comparisons of leaf, stomata, root morphological traits as well as biochemical traits including rubber, resin and inulin/sugars concentration were made between tetraploids and diploids. A 47.7% increase in rubber concentration but a decrease in inulin/sugars concentration was observed in tetraploid plants. However, there was no significant difference in the amount of rubber per root system among the greenhouse-grown plants in this research, likely due to root stunting observed in tetraploids and treated diploids. Evaluation of progeny is needed to circumvent the confounding physiological impact of colchicine treatment. However, the increase of rubber concentration observed in tetraploids suggests that polyploid breeding has the potential to improve rubber yield in TK.