| Iron(Fe)is a necessary nutrient element for plants,and iron deficiency can affect on the growth and development of plants and the quality of fruits.Northwest China is a premium production region for wine grape,but iron deficiency,due to alkaline soil limits its production and quality.Wine grape flavor substances such as sugar,acid,phenolic substances and aroma are the main components to determine the quality of grape and wine,but iron deficiency has a certain degree of impact on these ingredients.Most of the current researchs were focused on the impact of iron on grapevine growth and the basic physical and chemical indexes of grape berries.There are few studies about the effects of iron on grape phenols and aromatic substances.In this study,the effects of iron on the main flavor compositions of grapes growing on the alkaline soil were investigated by four foliar spraying treatments,50 ?mol/L and 75 ?mol/L Fe-EDDHA,sprayed at 2 weeks + 4 weeks and 4 weeks + 6 weeks after flowering,water was used as a control.After that,the five treatments: 0 ?mol/L,23 ?mol/L,46 ?mol/L,92 ?mol/L and 184 ?mol/L Fe-EDDHA,were carried out under the condition of sand culture in the greenhouse.Then transcriptome sequencing(RNA-Seq)technique was used to analyze the differences in the transcript level of grape skin treated with low,medium and high levels of iron.The bioinformatics analysis was used to explore the effects of iron on metabolic pathway of grape phenolics.Finally,the q RT-PCR were used to analyze the expression of flavonoid compounds related genes in grape skins.The main findings are as follows:(1)Iron treatments with foliar spraying in field condition did not significantly affect berry weight,berry skin weight and the ratio of berry skin/berry weight,but had a significant effect on fruit flavor.The soluble solids and p H of grapes increased,and the titratable acid content decreased by foliar spraying Fe treatments.There were differences in the effects of different Fe treatments on anthocyanins,flavan-3-ols and flavonols in grape skins.The total content of anthocyanins in mature fruit skins increased by 52.5% and 37.0% with foliar spraying 50 ?mol/L Fe at 2 weeks + 4 weeks after flowering in 2014 and 75 ?mol/L Fe at 2weeks + 4 weeks after flowering in 2015 respectively.The content of flavan-3-ols increased by 45.0% and 84.7% in the treatments of 50 ?mol/L and 75 ?mol/L Fe sprayed at 2 weeks + 4weeks after flowering,and the flavonol content was significantly increased by 112.9% and45.4% in the two treatments in 2014.While,in 2015,the treatments of 50 ?mol/L and 75?mol/L Fe sprayed at 4 weeks + 6 weeks after flowering increased the content of flavan-3-ols by 19.7% and 62.6%,and flavonol content were increased significantly by 58.3% and 89.7%in the two treatments,respectively.The total content of fruit aromas was increased by 26.5%to 279.4% in 2014 and 2.2% to 62.1% in 2015 in Fe treatments.(2)Under the condition of sand culture in greenhouse,the effects of different Fe concentration on fruit flavor were different.The treatments of 23?mol/L,46?mol/L and92?mol/L Fe increased the sugar content,p H value and sugar and acid ratio of grape fruit,decreased the content of titratable acids compared to the treatment of 0 ?mol/L Fe,but the effect of 184 ?mol/L Fe treatment was opposite.Compared to 0 ?mol/L Fe,other treatments increased the contents of anthocyanins and flavan-3-ols in mature fruit skins,among which the highest increase of anthocyanins content was 143.1% by 46 ?mol/L Fe,while the highest increase of flavan-3-ols content was 170.7% by 184 ?mol/L Fe.The 0 ?mol/L Fe and 184?mol/L Fe treatments were beneficial to the accumulation of terpenoids,norisoprenoids,linear fatty aldehydes,linear fatty alcohols,linear fatty acids and branched fatty acids,but not to linear fatty esters,aromatics and linear aliphatic ketones in mature grape berries.(3)The RNA-Seq technique was used to analyze the differences between the veraison grape skins of different iron concentration treatments.There were 418 differentially expressed genes(DEGs)between 0 ?mol/L Fe and 46 ?mol/L Fe treatments,and the number of up-regulated genes was higher than that of down-regulated genes,the ten major enrichment metabolic pathways of DEGs were related to the basic material metabolism and secondary metabolism.There were 3463 DEGs between 184 ?mol/L Fe and 46 ?mol/L Fe treatments,and the number of up-regulated genes was also higher than that of down-regulated genes,the ten major metabolic pathways of DEGs enrichment mainly involve basic metabolic,secondary metabolism,energy metabolism,hormone metabolism and signal transduction.Compared to 46 ?mol/L Fe treatment,the expression of genes related to biosynthesis shikimic acid in the phenylalanine synthesis pathway were up-regulated by 0 ?mol/L Fe treatment,and the expression of genes in the biosynthetic pathway of phenylpropane and flavonoids were also up-regulated,while the expression of genes in the photosynthetic pathway was down-regulated and genes control stomatal closure were up-regulated by 0?mol/L Fe treatment.The expression of tryptophan-related genes in the phenylalanine pathway was up-regulated by 184 ?mol/L Fe treatment.The majority of genes were upregulated in the phenylpropane synthesis pathway,but the expression of most genes in the flavonoid synthesis pathway were down-regulated by 184 ?mol/L Fe treatment.(4)The effects of different concentrations of Fe on the expression levels of selected genes were different.The expression of VvPAL,VvCHI and VvDFR genes in veraison grape skins were increased significantly in 0 ?mol/L Fe treatment compared with other treatments,which was consistent with the results of RNA-Seq and total monomeric anthocyanins and total monomeric flavonols content in this treatment.The expression levels of VvCHI,VvF3H,VvDFR,VvLDOX,VvUFGT and VvOMT were significantly higher in the premature and mature grape skins treated by 46 ?mol/L Fe,which was conducive to the accumulation of phenolic compounds and to the formation of more stable anthocyanins. |
PDF Full Text Request