In vitro synthetic polyploidization and enhancement of anticancer compounds in Catharanthus Roseus (L.) G. Don important cultivars

Catharanthus roseus (L.) G. Don is a plant belonging to the Apocynaceae family, which is native to Madagascar. The important alkaloids isolated from C. roseus are vinblastine and vincristine, both of which are important early indole-based anticancer drugs. Induction of polyploidy using mutagenic agents serves as an efficient method to improve the genetic potential of cells to synthesize secondary metabolites in medicinal plants. The variety of traits that occur through polyploidy induction, depends on the plant's species and genotypes. In this study, in vitro seedlings of 'Red Really' and 'Polka Dot' cultivars of C. roseus (for the first time) in the cotyledonary stage, were treated with various concentrations of colchicine (0, 0.05, 0.1, 0.2 and 0.5%) at three exposure time (24, 48 and 72 h). To distinguish the ploidy level of seedlings, morphological changes as well as, microscopic examinations, flow cytometry and chromosome counting were performed. In our experiment, the concentration and exposure time of colchicine and their interaction affected the tetraploidy percentage. Karyotype analysis suggested that the number of chromosomes in the diploid species was 2n = 2x = 16 and tetraploid plants contained 2n = 4x = 32. The maximum tetraploidy frequency was observed at 0.2% colchicine for 48 h in 'Red Really' and 0.1% colchicine for 48 h in 'Polka Dot'. The polyploid seedlings produced visible changes in plant height, leaf length and width, plant fresh and dry weight, stem and flower diameter compared to the control. Artificial ploidy manipulation caused significant changes in the chlorophyll and carotenoid content in polyploid seedlings compared to diploids. Also, vincristine, vinblastine, catharanthine and vindoline content increased 82.2, 80.9, 44.3 and 71.2% in Red Really as well as 64.7, 31, 48.2 and 95.3% in Polka Dot, respectively, compared to diploid plants. Increasing the ploidy level as an effective breeding strategy is noticeable for commercially producing these valuable medicinal compounds. The resulting polyploid lines have the potential to be used in breeding programs to develop C. roseus cultivars.