In order to induce of autotetraploidy and to evaluate changes in morphological and phenology characters of Madagascar (Catharanthus roseus cv. Rosea) an experiment was implemented in a randomized complete blocks design with four concentrations of colchicine (0, 0.1, 0.2 and 0.4%) Spraying was carried out in six replicates in the two true leaf stages. The results of the analysis by using flow cytometry, cytogenetic and morphological indicated that treatments of 0.2 and 0.4% had significant effect (p<0/01) on all traits and also on the percentage of tetraploid and death. The highest percentage of tetraploid showed in 0.4 percent treatment (42 percent).The results of this study suggested a significant increase (p<0/01) in growth duration, number of branch, leaf area, leaf number, flower diameter, duration of flowering, durability of flowers on the plant, chlorophyll content, weight of seed 1000 and shoot fresh and dry weight of tetraploid plants compared to the diploid plants. Flowers diameter was 42 and 52 mm on average, respectively for diploid and tetraploid. Also durability of flowers and flowering period in diploid plants was 3.2 and 150.4 days respectively, and in tetraploid plants 6.8 and 178 days respectively. Some traits such as number of fruits and seeds per plant were significantly higher in diploid than tetraploid plants. Samples treated with 0.2 % colchicine due to a lower percentage of death compared to treatment with 0.4 % was known as the best concentration for polyploidy stimulating in Madagascar periwinkle plant.

Keywords: Catharanthus, Ploidy level, Flow cytometry, Phenology, Colchicine

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