Exogenous gibberellins alter morphology and nutritional traits of garlic (Allium sativum L.) bulb

Gibberellins are important phytohormones that regulate many developmental processes in plants. Garlic bulbs are not only the reproductive organs of garlic but also a popular condiment and vegetable with high nutritional and medicinal value. However, the roles of gibberellins in garlic bulb development are unknown. In this study, we investigated the effects of injecting garlic plants with 1 mM L-1 gibberellic acid 3 (GA(3)) on the bulb development of ten garlic cultivars and determined the effects of treatment with different concentrations of GA(3) on the bulb development of cv. G064. The results showed that GA(3) treatment dramatically stimulated lateral bud formation but inhibited the growth of plants and bulbs in ten garlic cultivars, and lateral buds formation occurred twice in garlic plant treated with 1 mM L-1 GA(3). Bulb nutritional traits were improved by applying 1 mM L-1 GA(3) in five cultivars (cv. G024, G064, G096, G2011-2-1 and G2011-4) and were worsened by applying 1 mM L-1 GA(3) in cv. G2012-3. Meanwhile, the number of cloves and whorls per bulb increased with increased concentration of GA(3). Compared to the control and low concentration of GA(3) treatment (0.1, 0.5, 1, 2 and 5 mM L-1), the number of cloves per bulb and the soluble sugar content were significantly increased, but the mean bulb weight significantly decreased for plants treated with a high concentration of GA(3) (10 mM L-1). To our knowledge, this is the first report that injecting plants with 1 mM L-1 GA(3) led to a sharp increase in the number of cloves and whorls per bulb in garlic. Meanwhile, GA(3) treatment improved bulb nutritional traits for the majority of garlic cultivars. This provided new insights into the induction of plant lateral buds by GA(3) treatment and improving the reproduction efficiency of garlic via exogenous GA(3).