Effects Of Cooling Methods On Postharvest Quality And Expression Of Flesh Browning-related Genes In Yali Pear

Yali（Pyrus bretschneideri Rehd cv.Yali）has the advantages of rich nutrients,fresh sweet and juiciness.However,the browning of yali pear fruit is easy to occur due to the imperfect postharvest storage and transportation conditions after harvest,which affects the storage quality of Yali pear.In recent years,researchers have obtained some genes related to core browning of Yali pear,but the key genes leading to flesh browning have not been discovered.Therefore,in this experiment,we used Yali Pear with different harvest maturity as the test material,and the genes related to flesh browning of Yali pear were screened out by transcriptome sequencing technique to study the effects of different cooling methods on postharvest storage quality,relative expression and enzyme activity of genes related to flesh browning of Yali pear.The conclusion is as follows:1.Compared with rapid cooling,slow cooling maintained good fruit rate,firmness and soluble solid content of early and middle harvest Yali pear,inhibited fruit respiration,reduced weight loss rate and flesh browning index,better maintained fruit aroma,delayed flesh browning.At the end of storage（210 days）,the rate of good fruit was kept high.The percentage of good fruit was 89.17% and 91.7% in early harvest and middle harvest.Among them,the flesh browning index of slow falling fruit was only 0.0083.Because of the high maturity of late-harvested Yali pear,compared with rapid cooling,slow cooling not only accelerates fruit senescence,browning occurs early,but also the good fruit rate of slow fruit at the end of storage is only 63.1%,and the browning index reaches 0.1583.Therefore,late fruit picking is not suitable for slow cooling.2.A total of 71.82 G Clean Data was obtained from Yali pear flesh transcriptional group.In the results of GO enrichment,the functions of browning genes are mainly concentrated in biological processes and molecular functions.KEGG pathway enrichment is mainly concentrated in steroid biosynthesis,amino acid biosynthesis,plant hormone signal transduction,MAPK signal pathway-plant,glycolysis/gluconeogenesis,α-linolenic acid metabolism and other process.According to the results of differential genes,six genes related to flesh browning were analyzed,which were SAMDC,ADH4,WRKY33,b ZIP60,GST related to chilling injury and LOX6 related to ripening and senescence.3.Quantitative analysis of genes by q RT-PCR showed that slow cooling promotedthe up-regulated expression of SAMDC and transcription factor WRKY33,down-regulated expression of LOX6 in flesh,increased low temperature resistance and delayed flesh browning of Yali pear.Rapid cooling promoted the up-regulation of GST and ADH4 expression and the increase of GST enzyme activity,stimulated the expression of b ZIP60 transcription factors,increased respiratory intensity,increased weight loss rate and accelerated flesh browning.The expression of SAMDC,ADH4 and GST genes in late fruit harvest was low,and the stress resistance was poor.In short,slow cooling promoted the expression and activity of SAMDC gene,upregulated the expression of transcription factors WRKY33 and b ZIP60,inhibited the increase of expression and activity of LOX6,decreased respiratory intensity,increased fruit firmness,maintained fruit flavor,delayed ripening and senescence,reduced low temperature injury and reduced flesh browning index.Due to the high maturity of late-harvested Yali pear,slow cooling inhibited the up-regulated expression of SAMDC and transcription factor WRKY33,promoted the expression of ADH4 and transcription factor b ZIP60,and led to flesh browning.Therefore,mid-harvest combined with slow cooling can effectively inhibit flesh browning and maintain fruit quality.