| Brassinosteroid can promote plant growth,increase the fruit-setting rate of plants,but there are few studies on the application of brassinosteroid to the prevention and control of postharvest diseases of fruits.At present,strawberry and peach postharvest disease prevention and control mainly rely on chemical fungicides,but continuous use of chemical fungicides will bring food safety and other issues.Therefore,it is necessary to find natural,safe and effective postharvest disease control methods.In order to explore the application of brassinosteroid in the prevention and control of postharvest diseases of fruits,berry fruit strawberry and drupe fruit peach,which are common berry fruits on the market,are selected as the research objects.Strawberry and peach are easy to rot after harvest because of their delicate tissues and high water content.Strawberry gray mold caused by Botrytis cinerea and peach soft rot caused by Rhizopus stolonifer are the main diseases of these two fruits during postharvest transportation and storage.This article studies the effect of brassinosteroid treatment on the postharvest quality and disease resistance of strawberry and peach fruit.The mechanism of disease resistance induced by brassinosteroid treatment in strawberry and peach fruits was discussed.The results were as follows:1.Screening the optimal concentration of brassinosteroid treatment to control postharvest gray mold of strawberry and soft rot of peach,among them,the decay rate and decay index of strawberry treated with 10 mmol·L-1 brassinosteroid were lower than the control group by 19.68%and 30.00%,the lesion diameter and disease incidence of lesions on peach fruits were 2.60 cm and 10.00%lower than those of the control group.Therefore,10 mmol·L-1 of brassinosteroid is the best concentration for the control of Botrytis cinerea of strawberry and Rhizopus stolonifer of peach.2.Strawberries treated with 10 mmol·L-1 brassinosteroid can effectively prevent and control gray mold caused by B.cinerea,inhibit the rot rate and rot index of strawberry,the decay rate and decay index of the treatment group were19.00%and 39.08%lower than those of the control group.Brassinosteroid treatment can maintain the quality of fruits after harvest,the sugar-acid ratio of the treatment group was 28.23%higher than that of the control group.Treatment group induced chitinase,?-1,3-glucanase,phenylalanine ammonia lyase(PAL),and peroxidase(POD)enzyme activities,promote the synthesis of total phenols and other anti-disease-related substances,increase superoxide dismutase(SOD),catalase(CAT),ascorbate peroxidase(APX)active oxygen metabolism related enzymes and polyphenol oxidase(PPO)enzymes active.In addition,brassinosteroid treatment also inhibited the accumulation of malondialdehyde and increased the content of DPPH free radical.The results of gene expression showed that brassinosteroid induced the transcription of MPK3/6 in strawberry MAPK signaling pathway,and further activated the expression of downstream disease resistance gene PR1,the expression level of these genes at BR?6 d is twice that of CK?6 d.In addition,the expression levels of POD,WRKY transcription factors and genes related antifungal effects were significantly increased.These results indicated that brassinosteroid treatment was mainly responsible for the prevention and control of postharvest gray mold in strawberry by inducing fruit disease resistance.3.10 mmol·L-1 brassinosteroid treatment of peach can effectively prevent and control soft rot caused by R.stolonifer,and inhibit the lesion diameter and disease incidence of postharvest disease spots.The lesion diameter and incidence incidwnce in the treatment group were lower than those in the control group by1.76 cm and 10.25%.At the same time,brassinosteroid treatment could significantly improve the fruit quality post harvest,the sugar-acid ratio of the treatment group was 2.77%higher than that of the control group.Chitinase and?-1,3-glucanase in the brassinosteroid treatment group were higher than those in the control group by 13.88%and 7.20%.The brassinosteroid treatment group also induced phenylalanine ammonia solution(PAL)and polyphenol oxidase enzyme(POD)activity and total phenol content rise,maintained the superoxide dismutase(SOD),catalase(CAT)and ascorbic acid peroxidase(APX),and other active oxygen metabolism and related enzyme activity of polyphenol oxidase(PPO).In addition,brassinosteroid treatment inhibited the accumulation of malondialdehyde and increased the content of DPPH free radical.The gene expression results showed that the expression levels of WRKY,chitinase and other disease-resistance related genes were also up-regulated by brassinosteroid treatment. |
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