Abstract
The growth of lateral bud can greatly affect the development of apical bud and reduce the quality of single-flower cut chrysanthemum. However, the wide use of artificial bud removal in production leads to the increase on production cost. Therefore, it is important to study the lateral bud development mechanism in chrysanthemum for plant type regulation and genetic improvement. Auxin (IAA), cytokinins (CKs) and strigolactones (SLs) have direct or indirect effects on the formation of lateral buds. D14, BRC1 and LsL are key factors regulating the signal pathways of hormones, but their regulation mechanisms on the development of lateral buds in chrysanthemum are still unclear. In this study, single-flower cut chrysanthemum ‘Jinba’ and spray cut chrysanthemum ‘Fenyan’ were used as experimental materials. Quantitative real-time PCR was used to observe the effects of apical bud removal and exogenous hormones on the growth of lateral buds and the expression levels of DgD14, DgBRC1 and DgLsL, so as to clarify the expression characteristics of three genes in the process of lateral bud formation. The results showed that GA was effective in promoting the growth of lateral buds, whereas IAA and ABA had little effects on lateral bud growth or even inhibited. Removing apical dominance can significantly affect the expression levels of three genes, which regulated the formation and elongation of lateral buds. Additionally, the three genes showed different responses to different hormone treatments. DgD14 had a significant response to GA, but a gentle response to ABA. The expression levels of DgBRC1 varied in different trends, and it responded to IAA in a more dramatic way. The levels of DgLsL reached the peaks quickly before decreased in most experimental groups, and its response to GA was extraordinary severe.
Highlights
Chrysanthemum is one of the top ten famous flowers in China and top four cut flowers in the world
Comparing the measured data, it could be found that the average lengths of lateral buds at day 6 that were sprayed with GA were significantly greater than those sprayed with other exogenous hormones, but the average lengths of lateral buds in IAA and ABA groups were lower than those in the control groups
The data are expressed as mean ± standard deviation (SD)
Summary
Chrysanthemum is one of the top ten famous flowers in China and top four cut flowers in the world. Single-flower chrysanthemum and spray chrysanthemum are two cultivars in cut chrysanthemum [2]. Single-flower chrysanthemums require artificial bud removing whereas spray chrysanthemum requires pinching to improve branching in the production, which results in a significant increase in the production costs of cut chrysanthemum [5]. Previous studies have found that after the apical bud of ‘Jinba’ was removed, the elongation of upper lateral buds was obvious, whereas that of lower lateral buds was inconspicuous. It indicated that apical dominance had an inhibitory effect on the lateral bud of chrysanthemum [7,8]
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