The Cytological Structure And Gene Expression Of Sweet Cherry Grafted On ’Red Bark’ In Guizhou

Sweet cherry（Prunus avium Linn.）,belonging to the genus Rosaceae,which is a kind of deciduous fruit tree.Because of its,large furit size,as well as colorful and nutritious characters,the fruit has high economic value.In recent years,the plant area of sweet cherry in Southern China has expanded.In the long-term production practice,it has been found that the selection of sweet cherry rootstock is of high importance.Rootstocks have an important effect on the growth,fruit yield and fruit quality of sweet cherry.During the introduction and cultivation of sweet cherry,it was found that the rootstocks used in the northern regions were not suitable for the climatic soil conditions in Guizhou province.However,there has abundant wild cherry germplasm in Guizhou.In our preliminary work,an elite germplasm of‘Red Bark’of wild cherries（Prunus pseudocerasus）was obtained,which demonstrated the advantages of better compatability for grafting with sweet cherry,anti-nodules,early fruit,high yield,and resistance to pods in comparison with another type,‘Cyan Bark’.Currently,the grafted plants of an elite line‘Shuguang’were cultured using‘Red Bark’and‘Cyan Bark’wild cherry as rootstocks,subsequently,the cytological structures of grafting site,the physiological characteristics of scion and the molecular mechanism of function were investigated.The main results are as follows:1.At the 120^th day after being grafted,the cytological structures of grafting site showed no obvious abscission layer,and vascular bundle formed in the grafting site of‘Red Bark’.However,the grafting site of‘Cyan Bark’still exists the abscission layer and few cells,and vascular bundle are rarely connected.Therefore,the‘Red bark’presents well compatibility between the scion and the rootstock on sweet cherry.2.There was no significant difference in the grafting survival rate of the two tupes of rootstocks,which both were more than 70%.However,the growth rate of the shoots grafted on‘Red Bark’was significantly higher than that of‘Cyan Bark’and the new shoots grew well.3.During the light response process,the stomatal conductance and the photosynthetic rate of scion grafted on‘Red Bark’rootstock was significantly higher than that of‘Cyan Bark’by determinating the photosynthesis characteristics of the scion.The scion grafted on the‘Red Bark’demonstrated higher contents of chlorophyll as well as soluble sugar in comparison with that on the‘Cyan Bark’4.RNA-Seq was used to compare the gene expression of scion grafted on different rootstocks at three developmental periods,and a further significant difference in developmental period was selected for further analysis.A total of 4421 different expression genes were obtained.GO-enrichment of DEGs is based on biological processes,molecular functions,and cellular components.Among them,biological processes included biologically regulated,cellular components or biogenesis and cellular processes;cell components enriched in cell components,membrane structures and molecular complexes;molecular functional enrichment include binding,catalytic activity,transport activity and so on.After KEGG metabolic pathway analysis,significant metabolic pathways included photosynthesis,photosynthesis-antenna proteins,porphyrin and chlorophyⅡmetabolism,carbon fixation,and hormone signal transduction.From the transcriptome data,15 genes related to photosynthesis,chlorophyll synthesis and auxin signal transduction pathways were screened out.The transcriptome data were verified by qPCR.The result showed that the results of RNA-Seq were reliable and believable.