Effect of Induced Polyploidy on Morphology, Antioxidant Activity and Dissolved Sugars in <em>Allium cepa</em>

The role of onion as a second most consumed and cultivated vegetable around the world and its renown qualities that made it to be called as “queen of the kitchen” have positioned it to be very vital to the nutritional and economical contributions around the world. Polyploidy serves the purpose of groundbreaking innovation towards plant breeding by improving plants’ yield and vigor. This study was conducted to determine the effect of different concentrations of colchicine on the seedlings of onion on the morphology, antioxidant activity and dissolved sugars. Three concentrations of colchicine were used; including 0.05, 0.1 and 0.2% (w/v) which were applied to the seeds of Allium cepa for the exposure period of 24 hours. Chromosomal analysis confirmed the induction of polyploidy which led to the successful duplication of the chromosomes number from diploid (2n = 16) to tetraploid (4n = 32). Successful induction of polyploidy was achieved by the application of 0.05% (w/v) concentration of colchicine as it yielded the formation of seedlings which were morphologically and biochemically superior over the remaining concentrations and control at p ≤ 0.05 probability. The 0.05% (w/v) concentration showed the highest survival rate between the treatments by recording 83.33% compared to 33.33% and 0.00% of 0.1 and 0.2% (w/v) concentrations respectively, but topped by the control which recorded 91.57% survival rate. Furthermore, the 0.05% concentration of colchicine showed significant difference in the morphology as it recorded the biggest size of seedlings by height reaching up to 73.6cm tall with the diameter of the bulbs reaching 5.64 cm after 14 weeks. It also showed significant difference in the antioxidant activity by recording the highest DPPH scavenging percentage of up to 72.58%, followed by 0.1% and control. The tetraploids also showed significant difference in the dissolved sugars as they recorded the highest refractive index between the treatments and control. The application of 0.05% (w/v) concentration of colchicine resulted in the formation of the seedlings that have superiority in the morphology, antioxidant activity and amount of dissolved sugars compared to other treatments and control.