| Chrysanthemum ranks one of the top four cut flowers in the world in terms of consumption. Production of standard cut chrysanthemum characterized by one flower per stem has to remove all lateral branches, which is time-consuming and an intensive labor work. In many cultivars of cut chrysanthemum, lateral buds grow out rapidly when the apical buds stop growth and turn into inflorescence differentiation. Growth of lateral buds will consume many nutrition, and effect development of apical buds, reduce the quality of cut flowers. So, lateral buds must be removed timely. Growth of lateral buds inhibited by the apical buds in chrysanthemum plant. This is the ubiquitous phenomenon in plants, named apical dominance. The hormones believed to be involved in this phenomenon. The relationship of lateral buds outgrowth, apical dominance and endogenous hormones has never been reported. Removing lateral buds can harvest cut flowers which have higher quality, however requires much effort and time. Molecular breeding was introduced as an alternative approach to introduce specific characteristics. In this study, changes of endogenous hormones in apical buds and lateral buds during plant growth and development were investigated of different cultivars 'Jinghai' and 'Jingyun', and the relationship of lateral buds outgrowth, apical dominance and endogenous hormones were discussed; sense and antisense transformants of DgLsL were generated, resulting gene expression profiles, branching characteristics and endogenous contents of IAA, GA3 and ZR were investigated. Results showed as below:(1) The character of branching for different cultivars 'Jinghai' and 'Jingyun' were observed, and the change of endogenous hormones in apical buds and lateral buds during plant growth and development were investigated. The results showed that growth speed of lateral buds of'Jinghai'faster than'Jingyun'. In vegetative growth stage, IAA level in apical buds of 'Jingyun' higher than'Jinghai'significantly. After flower induction, IAA level in apical buds of two cultivars all decreased significantly, but the speed of IAA level decreasing in 'Jingyun' faster than'Jinghai'. IAA level in apical buds was higher, inhibition to lateral bud outgrowth was stronger. The growth speed of lateral buds of'Jinghai' is lOLb> 20Lb> 5Lb in vegetative growth stage,20Lb> 10Lb>5Lb in flower bud development. The growth speed of lateral buds of 'Jingyun' is 20Lb>10Lb> 5Lb all time. The ratio of IAA/ABA and iPAs/ABA was correlated with the speed of lateral buds outgrowth, it indicated that the high level of IAA/ABA and iPAs/ABA promote lateral buds outgrowth in chrysanthemum.(2) In order to establish a high frequency regeneration system of cut chrysanthemum, effects of 6-BA and NAA on bud differentiation of leaf explants of'Jinghai','Jingyun' and 'Jinba' were studied. Effects of Hygromycin (Hyg), Carbenicillin (Carb) and Cefotaxime (Cef) on callus induction and shoot regeneration from the leaves of'Jinghai'were studied. Results indicated that the genotype is an important factor in shoot regeneration. The regeneration frequency were:'Jinghai'92.18%,'Jingyun' 65.08%,'Jinba' 81.94%, and the optimized differentiation medium were:'Jinghai'MS+6-BA 3.0mg/L+NAA 1.0mg/L, 'Jingyun' MS+6-BA 3.0mg/L+NAA 0.5mg/L,'Jinba' MS+6-BA 2.0mg/L+NAA 0.5mg/L The suitable concentration of Hyg for selecting was 10mg/L in'Jinghai'genetic transformation. The optimum antibiotics of bacterium inhibition is Carb and the concentration decreased from 500mg/L to 300mg/L and to 200mg/L gradualy during selected culture.(3) The DgLsL gene was transformed by agroinfection into chrysanthemum in both the sense and antisense directions. Sense transformants branched more profusely than the wild type non-transformant, while branching in the antisense transformants was significantly suppressed. An analysis of DgLsL transcript abundance in the shoot tips revealed that expression was enhanced in the sense transformants and suppressed in the antisense ones. Indole acetic acid (IAA) content of shoot tip was reduced in the sense transformants but enhanced in the antisense ones. Gibberellic acid (GA3) content of the sense transformants was lower, and the antisense transformants was higher. ZR content was not affected by the variation in DgLsL expression. We conclude that DgLsL controls shoot branching through its effect on IAA and GA3 levels.
|
PDF Full Text Request