Effects of 5-azacytidine and gibberellic acid on flower development of azalea

Abstract

Azalea is one of the most popular ornamental plants in China. On the production of pot azaleas, heating strategy is widely used to force flowering, so the products can meet the needs of Spring Festival market in China. This study was conducted to find another possible way to break flower bud dormancy and promote anthesis through environment friendly ways. Four-year-old azalea ‘Hong Shanhu’ (Chinese azalea cultivar) were sprayed with different combinations of 5-azacytidine (2.5, 10, 40 and 160 mg L-1) and gibberellic acid (300 mg L-1). These were kept in greenhouse during the winter with no extra heating device. Morphological changes, endogenous hormones, and the degree of DNA methylation were recorded. The results showed that the combination of 40 mg L-1 5-azaC and 300 mg L-1 GA3 can highly promote flower bud growth and brought anthesis 17 days earlier than controls. IAA content increased about twofold (control and T1) and fivefold (T4) after growing for four months. A steep decrease of DNA methylation was observed from November to February and followed by an increase until flowering in all treatments. The foliar application of these chemicals was found to be more effective on bud dormancy breaking by DNA demethylation and decrease of ABA levels.