Effect Of Hydrogen Cyanamide Treatment On Winter Buds Germination Of Grapevine And The Study Of Its Regulation Mechanism

In recent years,with the rapid development of China's grape industry,the southern high-temperature region has become an important production area.However,due to insufficient accumulation of low temperature in winter,winter buds can not complete natural dormancy resulting in low germination rate and irregular germination in spring,which affects grape yield.Hydrogen cyanamide is a commonly used reagent to break dormancy,which is often used in warm winter to break dormancy and promote germination.However,the mechanism of hydrogen cyanamide breaking dormancy is still unclear.In this study,‘Summer Black'grape was used as the material to study the effect of different concentrations?2%,2.5%and 3%?and different times?10d,25d,40d and 55d before natural germination?of hydrogen cyanamide on the growth characteristics of grape,such as phenological period and germination rate.On basis,hydrogen cyanamide breaking dormancy of vitro was carried out and analyzed the changes of antioxidation,carbohydrates and hormones levels of buds and the expression level of related genes.The physiological and molecular mechanism of hydrogen cyanamide to break winter buds dormancy was preliminarily explored,which provided a theoretical basis for grape industry in the area of high temperature and humidity in the south of China.The main findings are as follows:?1?Under the conditions of rain shelter cultivation in high temperature,humidity and low solar radiation areas in Chengdu city,with 2%³%hydrogen cyanamide treatment at10⁵5d?mid-December?before natural germination led to the phenological period of‘Summer Black'grape advanced to different degrees.About 40 days before Summer Black grape sprouting?mid-January?,2.5%hydrogen cyanamide solution had the best effect on breaking dormancy.?2?In vitro,2.5% hydrogen cyanamide treatment group and control group at 8 d and12 d was observed germination,respectively,was the germination stage at 8-12 d and 16 d,respectively,and the sprouting rate reached 97.85%and 57%at 16 d,respectively.?3?At the level of antioxidant metabolism,compared with the control group,both the content of H₂O₂ and the activity of POD in the hydrogen cyanamide treatment group increased significantly at germination stage?8-16 d?,and the activity of SOD increased rapidly from 0 to 12 days,and then maintained a high level,but the activity of CAT decreased rapidly from 0 d to 16 d.The expressions of the enzymes VvSOD-Fe,VvPAO and VvPAOX related H₂O₂-generating and the enzymes VvPOD and VvGSH-Px related to H₂O₂-scavening did not changes before germination,but were significantly up-regulated during germination.?4?In carbohydrate metabolism,after treatment of hydrogen cyanamide,the soluble sugar content increased significantly while the starch content decreased significantly at germination stage.Sucrose synthesis related enzymes VvSUS,VvSPS and VvHK were up-regulated and decomposition related enzymes VvINV and VvFK were down-regulated in the germination.During the germination stage,starch synthesis related enzymes VvGBSS and VvSS were down-regulated,and starch lyase VvAM and VvBM were up-regulated.?5?At the hormone level,with the process of hydrogen cyanamide treatment,the concentration of IAA,ZT and BR in grape buds increased,significantly.The concentration of GA₃ decreased before germination and had no change after germination.The content of ABA decreased significantly in the germination stage.In the plants endogenous hormones signaling pathway,key signaling factors AUX/IAA,ARF and CYCD were up-regulated and DELLA and ABFdown-regulated.It was speculated that oxidative stress was generated in cells after hydrogen cyanamide treatment.The accumulation of H₂O₂ may cause the ABA content to decrease.In order to maintain the homeostasis of plant endogenous hormones,IAA,ZT and BR content increase,GA₃ content decreases,and corresponding hormone signaling Pathway transcription factor up-/down-regulates expression,promotes cell differentiation,and bud dormancy was relieved;while ABA inhibits?-amylase activity,starch hydrolysis converts to sucrose to provide energy for germination and promote bud germination.