Study On Regulation Of Postharvest Antioxidant Systems In Winter Jujube By Exogenous Salicylic Acid And Abscisic Acid

Winter jujube（Ziziphus jujuba Mill.Cv Dongzao）tastes sweet and enriches in nutrition,which is favored by consumers.However,postharvest winter jujube is prone to rapid senescence and oxidative corruption,which seriously affects its commercialization.Therefore,it is urgent to improve its postharvest storage and preservation methods.The antioxidant systems in plants are responsible for scavenging reactive oxygen species and maintaining fruit quality and resistance.Plant hormones,such as ethylene,salicylic acid（SA）,abscisic acid（ABA）and jasmonic acid,play important roles in stress response,defense response and secondary metabolism.As natural preservatives,they are widely used in plant resistance induction and growth and development regulation.In this study,winter jujube were treated with 0.5 m M L^-1 SA and 0.2m M L^-1 ABA after harvest,then stored at 0±1℃and 85-90%relative humidity.By evaluating the effects of exogenous hormones on the storage quality and antioxidant systems of winter jujube,combined with transcriptome sequencing technology,the changes of transcription level of winter jujube were analyzed to reveal the regulation mechanism of exogenous hormones on the maturity and senescence of winter jujube.This study aimed to provide theoretical guidance for extending the storage and preservation period of winter jujube and improving the development of jujube resources in Xinjiang in production practice.The results are as follows:1.Exogenous SA and ABA treatments were beneficial to maintain the storage quality of winter jujube,and delay the reddening rate,ripening and senescence of fruit.Most quality indexes peaked at 30 d.SA significantly delayed the decline of fruit firmness and maintained the level of sugar and acid.At the end of storage,the firmness,total soluble solids and titratable acid contents of SA-treated fruit were 22.21%,2.56%and 10.53%higher than those of CK fruit,respectively.In addition,SA inhibited respiratory intensity,ethylene production,weight loss and decay rate.At 30 d of the storage,these indexes in SA fruit were 49.76%,79.15%,70.01%and 57.38%of CK fruit,respectively.ABA had the second effect on maintaining postharvest quality,and had no significant inhibitory effect on weight loss,decay rate and respiratory intensity.2.Exogenous SA and ABA treatments induced postharvest antioxidant activity and phenylpropane metabolism of winter jujube,so as to improve antioxidant capacity.SA was more conducive to maintain the contents of ascorbic acid,glutathione and antioxidant enzyme activities.At 30 d of the storage,the activities of SOD,APX and GR in SA fruit were 89.91,115.21 and 74.25 U g^-1,respectively.ABA played a greater advantage in increasing the contents of total phenols and flavonoids and the activities of phenylpropane metabolic enzyme.By the end of storage,the contents of total phenols and flavonoids in ABA fruit was 7.99and 1.91 g kg^-1,and the activities of C4H,4CL and CHS were 218.62,91.62 and 93.46μL^-1 respectively.3.The peak of most physiological indexes of winter jujube appeared at 30 d,indicating 30 d to be the critical storage time point.Thus,the samples stored at 30 d were selected for transcriptome sequencing.The results showed that the differentially expressed genes in SA and ABA treated jujube fruits were mainly involved in metabolic pathway,secondary metabolic biosynthesis,plant hormone signal transduction and so on.Transcriptome data showed that the differentially expressed genes in SA and ABA treated jujube fruit were mainly involved in metabolic pathway,secondary metabolic biosynthesis,plant hormone signal transduction and so on.Exogenous hormones regulate redox homeostasis and mature aging of winter jujube by inducing the expressions of reactive oxygen species metabolism（Cu/Zn-SOD,GR2,GRXC9 and APX3）,plant hormone signal transduction（ABF4,Sn RK2,PYL2,PP2C,MKK4,ERF,EBF2 and JAZ）,phenylpropane metabolism（CLH,PPH,PAO and RCCR）,aging related proteins（PME15,CTL2,INVE,ADH2,SAG21,SRK2H and ATG4）and transcription factors（MYB,ERF,C2H2,MTB3,WRKY,and FAR1）.In conclusion,exogenous SA and ABA may regulate the expressions of related genes and key metabolic pathways in winter jujube,so as to inhibit the physiological metabolic such as respiration,reduce the consumption of nutrition,enhance the antioxidant capacity,and finally delay the ripening and senescence and improve quality of winter jujube.SA was better than ABA in quality maintenance of winter jujube.