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

The role of onion as the second most-consumed and cultivated vegetable around the world and its renowned qualities that lead it to be called the “queen of the kitchen” have positioned it as a vital source of nutritional and economic contributions around the world. Polyploidy serves as a groundbreaking innovation in plant breeding, improving the yield and vigor of plants. This study was conducted to determine the effects of applying different concentrations of colchicine to onion seedlings on their morphology, antioxidant activity, and dissolved sugars. The mutagen was applied to the onion seeds at three different concentrations (0.05, 0.1, and 0.2% <i>w</i>/<i>v</i>) for an exposure period of 24 h. A chromosomal analysis confirmed the induction of polyploidy, which led to the successful duplication of the chromosome number from diploid (2n = 16) to tetraploid (4n = 32). The control recorded a survival rate of 91.57%, while 83.33%, 3.33%, and 0.00% survival rates were recorded for seedlings treated with 0.05%, 0.1%, and 0.2% (<i>w</i>/<i>v</i>) concentrations of colchicine, respectively. Furthermore, the tetraploids showed significant differences in morphology, producing the tallest seedlings (reaching up to 73.6 cm tall) and the greatest average bulb diameter (of 5.64 cm) after 14 weeks. The tetraploids also showed significant differences in antioxidant activity and the amount of dissolved sugars, recording the highest DPPH scavenging percentage of 72.58% and refractive index of 1.369. Successful induction of polyploidy was achieved with the application of 0.05% (<i>w</i>/<i>v</i>) colchicine, which produced tetraploids that are morphologically and biochemically superior to other treated and control plants at a significance level of <i>p</i> < 0.05.