The Fresh-keeping Meachisms Of Plant-derived Products Burdock Fructooligosaccharide(BFO) And Trans-2-hexenal(E2H) On 'Crimson Seedless' Grape(Vitis Vinifera L.)

China is the largest producer of table grape in the world.�Crimson seedless' grape is a widely popular late-maturing grape variety for fresh fruit all over the world,which fills the gap period of market supply from october to december each year.The �crimson seedless' grape has the characteristics of crispness and sweetness,but they are prone to problems such as loss of sweet and crisp taste,lose of luster and pericarp shrinkage in the early storage stage.In the late storage period,serious fungal diseases are prone to occur.Therefore,the technologies with obvious preservation effects should be targeted for short-term and long-term circulation.As table grapes are directly edible fruits,the use of synthetic chemical preservatives after harvest will seriously affect the health of consumers.Therefore,it is of important theoretical significance and great practical value to use plant-derived natural products for the preservation of grapes after harvest.Our research group found that the natural products of plant-derived burdock fructooligosaccharide(BFO)and trans-2-hexenal(E2H)have obvious fresh-keeping effect on grapes,but the mechanism is still unclear.This experiment uses �crimson seedless' grapes as materials and uses plant physiology and biochemical research techniques to reveal the mechanism of BFO and E2H in the preservation of grapes after harvest,in order to provide a theoretical basis for the research and development of fruit and vegetable preservatives of plant-derived natural plant products,and provide technical support for their fresh-keeping applications in the grape industry.The main results are as follows:1.BFO can delay the process of senescence and decrease of sweetness and crispness of grape by inhibiting the transport of sucrose from flesh to peel.In the mesocarp,BFO limits the output of sucrose,which makes more carbohydrate remain in the mesocarp,and increases total soluble sugar and sweetness,and cell osmotic pressure and firmness are indirectly retained.In the exocarp,BFO restricts the input of sucrose,and the sucrose as a signal molecule decreases,and the aging related processes are inhibited.The effect of exogenous sucrose treatment is opposite to BFO,which further verified its mechanism.It was found that BFO inhibited the transport of sucrose from flesh to peel,which may be achieved by down-regulating of SUC12 and SUC27.2.E2H can keep the fresh of grape after harvest by inducing the synthesis of secondary metabolites and related hormones with antibacterial effect.E2H can well inhibit the postharvested fungal diseases in �crimson seedless' grapes,and the optimum concentration is 2.5 u L/L.The inhibition of Penicillium digitatum(P.d),Penicillium expansum(P.e),Botrytis cinerea(B.c)and Alternaria nees(A.n)in vitro experiments further verified the antibacterial effect of E2H.The results of transcriptome analysis showed that the antibacterial mechanism was that the antibacterial properties of grape was enhancing by inducing the synthesis of phenolic compounds such as flavone,flavanone and resveratrol,and flavonoids such as naringenin and isoflavones,and inhibiting the synthesis of ethylene and abscisic acid,which provided an effective reference for the study of the molecular preservation mechanism of E2H.3.Plant-derived natural products BFO and E2H can both keep fresh of grapes after harvest,but there are obvious differences in the mechanism of preservation between the two.BFO solves the physiological problems that exist in the early stage of grape storage,and E2H inhibits the fungal diseases in the late stage of grape storage,which provide a theoretical basis for the promotion and application of BFO and E2H in the preservation of fruits and vegetables.Therefore,in the post-harvest circulation process of grapes,different plant-derived natural products can be selected according to the length of aging.BFO is suitable for short-term circulation and E2H is suitable for long-term circulation.This provides a new idea of �selecting the appropriate preservative according to the circulation period� for grape postharvest preservation.