Colchicine-induced polyploidy as a strategy for genetic enhancement of Brassica rapa var. chinensis

Polyploidy is also important in evolution of plants, and improvement of crops through increase in morphological, physiological, and biochemical characteristics. The objective of the current investigation was to induce polyploidy in one of the varieties of Brassica rapa namely chinensis with colchicine and to determine its effect on germination, growth, cytological behavior, minerals composition and nuclear DNA content. In vitro results were performed on the mature seeds of five diverse genotypes to be treated with 0.05, 0.08, 0.1, and 0.2 percent colchicine after 0, 24 and 48 h treatment. Parameters of germination such as days to germination and germination percentage were recorded daily. The colchicine level and duration of the treatment had a significant effect on all parameters (p < 0.05). The best responses were realized with optimal treatment (0.08% 24 h) which included early germination (2.33 days), maximum seedling height (5.75 cm), increased root length (6.06 cm), improved biomass accumulation, and stomatal enlargement to a maximum of 31.76 µm. The maximum efficiency of polyploid induction was at 0.2% with a 24 h time yielding 58.67% with lower survival rates and greater cytological anomalies. Mitotic index decreased to 21.2 to 8.0 at 0.2% and 48 h and abnormal frequency of mitosis was raised to 75.0. The nutrient accumulation was better with the optimum treatment as mineral analysis indicated with potassium (38,000 mg/kg), calcium (22,000 mg/kg), and phosphorus (2,600 mg/kg). The successful polyploid induction was supported by the fact that flow cytometric analysis of 30,270 nuclei showed that two groups of cells were present, which are diploid (46.4%) and endoreduplicated (53.6%), with an endoreduplication index of 53.6%. Colchicine (0.08% in 24 h) usage optimally produces polyploidy in Brassica rapa var. chinensis, which increases germination, growth, and mineral composition. Five different genotypes have been used, which makes sure that there will be no genotype-specific findings. Flow cytometry had verified a successful chromosome doubling with definite results of both diploid and endoreduced populations. The results give a basis through which better polyploid lines can be developed, and further field tests should be conducted to determine agronomic potential.