| Dendranthema morifolium is a traditional Chinese flower.It is widely grown throughout China and plays an essential role in current cut and potted flower market,with numerical color variations.Flower color,a crucial ornamental characteristic of chrysanthemums,is vital to their commercial value.However,the color of chrysanthemum is susceptible to the the external environment,especially for instance,the heat,i.g.it is easy to loss color under high temperature.In this study,a heat-tolerant cultivar ’Zi Feng Che’ with stable flower color under high-temperature and a heat-sensitive cultivar ’Zi Hong Tuo Gui’ with easily degradable flower color were adopted as materials.A comparative metabolomic study of these two cultivars was carried out via physiological parameters and metabolite changes under high-temperature stress.This study aims to demonstrate the mechanism of color stability and fading in chrysanthemum flowers under high temperature,furthermore to provide a theoretical basis for practical applications in novel chrysanthemum breeding in the future.Additionally,it can give some valuable data reference for fully understanding the molecular mechanism of anthocyanin degradation in plants.The main results of this study are as follows.1.Through measuring the total anthocyanin content of ’Zi Feng Che’ and ’Zi Hong Tuo Gui’ under normal and high-temperature stress,we found,in general the anthocyanin content was positively correlated with capitulum developmental stages,hitting its peak at stage 8(S8),and then decreased at S9 for flower senescence.’Zi Feng Che’ and’Zi Hong Tuo Gui’ had the highest anthocyanin content at S8 stage with 19.055 OD/g(FW)and 3.937 OD/g(FW),respectively.After heat treatment,flower fading occurred during the flower bud period in Dendranthema morifolium.At S2,the anthocyanin content of ’Zi Feng Che’ and’Zi Hong Tuo Gui’ decreased by 0.242 OD/g FW and 1.184 OD/g(FW),respectively.Our results showed that the total anthocyanin content of ’Zi Hong Tuo Gui’ reduced dramatically at S7,with a 6.3-fold decrease from 2.931 OD/g(FW)in control to 0.464 OD/g(FW).However,at the same stage,’Zi Feng Che’ just performed a 1.86-fold decrease.These results illustrated that ’Zi Feng Che’ is significantly more stable in flower color at high temperature compared to ’Zi Hong Tuo Gui’2.After pH measurement of’ ’Zi Feng Che’ and ’Zi Hong Tuo Gui’,their pH values were both around 5.6-6.3(weak acidic).Anthocyanins in this range were purplish-red,with no significant differences between cultivars.It is tentatively assumed that the decrease in anthocyanin content of ’Zi Feng Che’ and ’Zi Hong Tuo Gui’ is not necessarily related to the pH value.3.A total of 172 flavonoid compounds,including 15 anthocyanins,were detected by comparative metabolomic analysis of the two cultivars.After heat treatment,66 flavonoid metabolites were altered in ’Zi Feng Che’,and 52 flavonoid metabolites were altered in’Zi Hong Tuo Gui’.For the first time,Delphinidin and Pelargonidin were detected in ’Zi Feng Che’ and ’Zi Hong Tuo Gui’.And Pelargonidin-3-O-glucoside was specifically detected and accumulated in heat-treated ’Zi Feng Che’ at S2,which might be associated with the stabilization of ’Zi Feng Che’ flower color.4.In ’ZiFengChe’,8 flavonoid metabolites showed consistently up-regulated levels.Four different flavonoid metabolites,5,7,4’-trihydroxy-8-C-β-D-glucose flavonoid carbides,Naringenin,Apigenin and Apigenin 6-8-C-glucoside,were selected for in vitro anthocyanin stability testing to verify the effect of flavonoid copigment on the rate of anthocyanin degradation.The results showed that the half-life of anthocyanin was 95 h and 105 h comapring to 84 h in the control,which slowed down the degradation of anthocyanin glycosides with the participation of 1× Naringin and,1× Apigenin 6-8-C-glucoside.However,2× and 5× did not have any obvious effect on the stability indicating high concentrations of flavonoid metabolites have no considerable effect on anthocyanin stabilization. |
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