Metabonomics Study On Ethephon And Methyl Jasmonate Synergistically Regulating Peel Coloration Of 'Hongzaosu' Pear

Fruit color is an important appearance factor which could determine fruit quality.Fruit color is mainly determined by lipid-soluble chlorophylls,carotenoids and water-soluble flavonoids.Red pears are favored by consumers because of their unique color.The research on pear fruit coloration is mostly focused on anthocyanin and its regulation mechanism,while the research on other flavonoids and carotenoids is very scarce.In this study,the effects of ethephon,ethylene inhibitor and methyl jasmonate treatments on the peel coloration of red pear were studied and the phenotypes different from apple and other species were obtained,using red pear cultivar'Hongzaosu' as material.We studied the accumulation of flavonoids and carotenoids in the peel of red pear cultivar 'Hongzaosu' at the metabolic level by using metabonomics research strategies,technical means and analytical methods.The main results are as follows:1.Ethephon(ETH)treatment could induce the peel to turn yellow and not red by inhibiting anthocyanin accumulation and increasing the content of other yellow flavonoids in 'Hongzaosu' pear.Ethylene receptor inhibitor 1-methylcyclopropylene(1-MCP)treatment resulted in peel of 'Hongzaosu'pear turning red by promoting anthocyanin accumulation.Methyl jasmonate(MeJA)treatment could promote the accumulation of anthocyanin and other yellow flavonoids to makde the peel yellowing and reddening.MeJA's yellowing effect was stronger than that of ETH treatment and the reddening effect was weaker than that of 1-MCP treatment.MeJA could further promote the accumulation of yellow flavonoids in the peel of'Hongzaosu'pear with ETH to make it more yellow and also could synergize with 1-MCP to accumulate more anthocyanins in the peel to make it redder.2.Through extensively targeted metabonomics,211 flavonoids were identified in the peel of'Hongzaosu' pear.The metabolic profiles of flavonoids accumulation in the peel after different treatments were obtained,and the different metabolites between different treatments and control were screened out.Further analysis showed that:ETH treatment could induce the yellowing of peel by promoting the accumulation of 6 isoflavones and inhibiting the accumulation of 8 anthocyanins;1-MCP treatment could induce the reddening of peel by promoting the accumulation of 8 anthocyanins;MeJA treatment could induce the yellowing and reddening of peel by promoting the accumulation of isoflavones,flavonols,anthocyanins and other flavonoids;The combination treatment of MeJA+ETH and MeJA+1-MCP further induced the accumulation of flavonoids to their respective directions to make coloration more significantly.3.MeJA treatment and 1-MCP treatment could promote the accumulation of carotenoids in the peel of'Hongzaosu'pear,while ETH treatment had no significant effect.According to the results of spectral analysis,it is speculated that 1-MCP treatment has greatly changed the carotenoid composition in the peel.Based on the ultra-high performance liquid chromatography tandem mass spectrometry and the local database containing 17 kinds of carotenoids,nine kinds of carotenoids were detected in the peel of 'Hongzaosu' pear.It was found that MeJA promoted the accumulation of all nine kinds of carotenoids.The effects of 1-MCP treatment on different kinds of carotenoids were different,which mainly promoted the accumulation of lutein,violaxanthin and neoxanthin,while the contents of zeaxanthin and antheraxanthin decreased significantly.