Preliminary Study On The Compatibility And Mechanism Of Litchi Grafting

Litchi(Litchi chinensis Sonn.),a specialty fruit tree,is widely cultivated in the subtropical regions of southern China.With the improvement of people’s living standards and post-harvest processing technology,the demand for litchi is expanding continuely.However,the unreasonable variety structure and the large proportion of low-efficiency varieties,which has limited the improvement of the litchi industry.Grafting technology can solve the problems quickly and effectively,but not all varieties are grafting compatibility.,’Feizixiao’,as a scion,is widely compatibility,but it’s still to be tested.On the basis of field experiments,anatomy,physiology and biochemistry,transcriptomics and other technologies are used to verify the preliminary mechanism of grafting with wide compatibility.The main findings are as follows:1.To investigate the grafting compatibility,’Feizixiao’ was grated with premature cultivar’Sanyuehong’,late-maturing cultivar ’Maguili’,normal-seeded cultivar ’Kulin’,aborted-seeded cultivar ’Lingfengnuo’,seedless cultivar ’Wuheli’,as a rootstock,’Zhuangyuanhong’ is difficult to survive and ’Huaizhi’ is reverse,and other 44 litchi varieties from various production areas.Thecontrast was ’Feizixiao’/’Feizixiao’auto-graft.The graft joints healed well,new shoots grew fast,and the new leaves was bright green.It was confirmed that ’Feizixiao’ was wide compatibility as a scion.2.The content of K ion and soluble sugarin functional leaves of scion,,the activity of SOD and POD of scion phloem were measured.It was found that SOD of auto-graft in the graft phloem was lowest,and there was no significant difference at the level of p≤ 0.001,the content of K ion,soluble sugar in the leaves,POD in graft phloem have no obvious varieties.Therefore,’Feizixiao’ was widely compatibilityas a scion,which is related to SOD-in the phloem of the grafting union.The K ion,soluble sugar,and POD may not be the key indicators,and further exploration are needed to investigate whether these three can be used as indicators of wide compatibility.3.After the grafting of 2h,3d and 8d,comparing the graft joint of auto-grafted of’Feizixiao’/’Feizixiao’,traditional grafting difficult to survive rootstock of’Feizixiao’/’Zhuangyuanhong’,intermediate grafting rootstock of ’Feizixiao’/’Fenghua’,and traditional grafting easy to survive rootstock of ’Feizixiao’/’Baila’ by transcriptomics,there were 95786 different genes obtained.Among them,the up-regulated differential genes were 49,209,and the down-regulated were 46,577.it was found that the differential genes are mainly related to carbohydrate metabolism,cell growth anddifferentiation,environmental stress adaptation,photosynthesis and other related pathways through annotating these genes by GO,KEGG,etc..4.Screening differentially expressed genes in the same period of different healing by transcriptomics analysis,it showed that the genes related to the negative regulation of ABA accumulation werehighly expressed.In the ABA anabolic pathway,the abscisic acid 8’-hydroxylase gene may negatively regulate the ABA content accumulation process,reduce the ABA content at the graft union,and improve the compatibility of the graft.5.Transcriptomics analysis indicated that genes related to ascorbic acid synthesis were highly expressed.After analyzing the biological functions of ascorbic acid,it is speculat that ascorbic acid may has connection with the graft compatibility.6.Screening the differentially expressed genes in different grafting combinations found that the genes with common differential expression higher than ’Feizixiao’/’Feizixiao’,It was found that the genes were enriched in the phenylpropane biosynthetic pathway through KEGG analysis.It is speculated ’Feizixiao’ grafted as a scion will accumulated rapidly of lignin in the early stage of graft healing,it will promote the reconnection of the vascular bundles and improve the graft compatibility.7.After comprehensive analysis,it was found that the grafted compatibility combination promoted callus formation,growth,improved plant stress resistance;promoted lignin content accumulation;reduced metabolic activity related to stress factors such as ROS and ABA,and formed a complete vascular bundle bridge to provide the material foundation and increased resistance to adverse external influences.