Effects Of Storage Preservatives On Quality And Endogenous Hormones Of Chrysanthemum Cutting

Chrysanthemum（Chrysanthemum×morifolium）is a perennial herb of the Compositae with rich varieties,and is one of the traditional famous flowers in China.In the production of chrysanthemum seedlings,the most important production method is the propagation of terminal bud cuttings.The storage and transportation requirement of seedlings and cuttings has gradually increased with the expansion of cross-regional cooperative production.However,there is no specialized research on the preservation method and preservation mechanism of chrysanthemum seedlings at present.In this paper,the chrysanthemum variety’Hong Ri’was used as the main material,and a variety of chemical preservatives were formulated to treat its cuttings.Based on metabolomics and gene expression detection,the internal mechanism of the effect of storage preservatives on chrysanthemum cuttings was explored.The experiment screened out the storage preservative formula which takes a better effect on the fresh-keeping of chrysanthemum cuttings,and provided scientific data for the action mechanism of the storage preservative at the molecular level,which has a production and application significance.The main results of this study are as follows:（1）When the AgNO₃-containing preservative is used to maintain the quality of chrysanthemum cuttings,compared with the cuttings in the control group,the cuttings stored for at least 12 days had a 23.91%lower rate of yellow leaves,a higher reducing sugar content of 0.50 nmol/g,and a 4.76%higher proportion of cuttings with good sensory quality.It is proved that the AgNO₃-containing preservative can inhibit leaf yellowing and internal nutrient loss by killing bacteria.It can also inhibiting ethylene-responsive senescence mechanism,and maintains a high level of sensory quality during long-term storage;however,The MDA content of the cuttings treated with the preservative was 20.59nmol/g,and the POD enzyme activity was 12348.00 U/g FW,which were significantly different from other treatments.,the rooting was slow after cuttings,and the growth and development progress was delayed by about 10 days after planting in the field.It shows the damage in plasma membrane,with the root elongation and the process of growth and development of its cuttings is inhibited,so AgNO₃-containing preservatives are not suitable for the preservation of chrysanthemum cuttings.（2）When the phytic acid-containing preservative is used to maintain the quality of chrysanthemum cuttings,the weight loss rate of cuttings during storage was 15.88%lower than that of the control group,and the MDA content was 4.47 nmol/g lower,which proves that the preservative can maintain the water balance of the cuttings,inhibit the reactive oxygen species metabolism and cell membrane lipid peroxidation in cuttings through anti-oxidation,reducing the impact of environment stress on chrysanthemum cuttings;at the same time,the rooting number and root fresh weight of the cuttings treated with the preservative were significantly increased,which were 12.11%and 28.69%higher than the control,respectively.,and the cuttings treated with the preservative has a earlier flowering and higher number of flower after planting the field.The results show that the preservative can promote the root growth of chrysanthemum cuttings,accelerate the growth and development of chrysanthemum seedlings,increase the number of flowers and prolong the blooming period of chrysanthemum,which makes it a better storage preservative for chrysanthemum cuttings.（3）After metabolomic analysis of chrysanthemum cuttings,the results showed that the hormones of cytokinin（CTK）were the main differential metabolites of cuttings after different preservative treatments.A total of 23 hormones of cytokinin were found with a differential content changes or specific content expression occurred in treatment groups.Different regulatory effects were also found among different specific hormones belonging to the same cytokinin classification.In addition,it was also found that various types of endogenous hormones,such as jasmonic acid,salicylic acid,gibberellin,and ethylene,changed significantly in cuttings treated with different preservatives.（4）On the basis of gene function prediction and RT-qPCR technology verification,based on 4 gene functions related to cutting quality change and the regulation of cutting endogenous hormones（Auxin synthesis,cytokinin synthesis,coding of stress-responsive enzymes and aging process）,4 key functional genes showing significant differences among the groups were screened out.:YUCCA10（Cse＿sc000197.1＿g040.1）,CKX7（Cse＿sc008490.1＿g060.1）,POD（Cse＿sc007626.1＿g030.1）,SAG39（Cse＿sc001654.1＿g030.1）.The phylogenetic tree of the protein-encoding proteins regulated by these 4 key functional genes was constructed.