Effects Of Grafting Regulation On Physiological Properties And Related Genes Expression Pattern Of Fruit Enlargement In The Oriental Melon

Oriental melon is an important protected horticultural crop with high nutritional value.Grafted plants have strong growth potential,thick green leaves,strong photosynthesis,fast fruit enlargement and increased yield.Fruit enlargement processes includes cell division,mutual transformation of cell division and cell enlargement,cell enlargement accounted for three stages of dominance.There are few reports on how grafting can accelerate and promote fruit enlargement.Therefore,in this experiment,the grafted fruit was treated,the self-footed fruit(CK)was used as the control,the oriental melon 'Yinquan No.1' was used as a scion,and the white-seed pumpkin ' Shengzhen No.1' was used as a rootstock.First,the four key periods of fruit enlargement(fruit setting stage,pre-enlargement,mid-enlargement stage and post-enlargement)were screened using morphological determination,cytological observation and cell number statistics.Secondly,the expression patterns of related genes families(CYC,CDK,EXP XTH)were measured by real-time quantitative quantification(q RT-PCR)technology and the endogenous hormone contents in fruit was determined.To clarify the effect of grafting on fruit enlargement of oriental melon and provide a theoretical reference for further analysis of the mechanism of grafting effect on fruit enlargement.The main findings are as follows:1.Screening of key periods of fruit enlargement process of oriental melon:Observed from paraffin section: The grafted fruit had fewer vascular bundles than CK,indicating that the grafted fruit cells develop faster than CK,and some cells start to enlarge in advance.There was no significant difference in single fruit weight between grafted fruit and CK,So the fruit setting period is called the enlargement start period.From 5 to 25 days after anthesis,the single fruit weight of the grafted fruit was significantly higher than that of the CK,indicating that this is the stage of enlargement of the oriental melon fruit.Observed from the paraffin section,the cells of the grafted fruit were significantly larger than the CK.Observed from the number of cells: from the fruit setting stage to the early stage of enlargement,it is the first stage of rapid enlargement of cells.Under the same visual field,the number of grafted fruit cells decreased sharply due to the fact that the enlargement of grafted fruit cells started faster than CK.From pre-enlargement stage,it is the stage of rapid enlargement of single cells.For single cells,the volume of grafted pulp cells grows fast,and the number of cells in grafted fruits decreases faster than that CK,forming a larger cell population.The reason why grafting promotes fruit enlargement is due to accelerated cell enlargement and rapid increase in cell volume.Grafted fruits are larger than CK cells because grafted fruits are larger than CK.2.Effects of grafting on the changes of the contents of IAA,GA3,GA4,ZR,dh ZR,i PA,ABA and BR during the oriental melon fruit enlargement:During the whole fruit enlargement process,the contents of IAA and GA3 in the grafted fruit were significantly lower than CK.The content of GA4 in the grafted fruit was significantly higher than that CK at the fruit setting stage and the pre-enlargement.The content of dh ZR and i PA was significantly higher than that CK in the post-enlargement.The ZR content of grafted fruit did not change significantly during this process,indicating that ZR did not participate in the process of grafted fruit enlargement.BR is higher than CK in the pre-enlargement,while ABA has the opposite trend.ABA is lower significantly than CK during the stage,which may be due to the mutual transformation of ABA and BR.Grafting changed the types of endogenous hormone accumulation,making it promote fruit enlargement.3.Effects of grafting on the expression of related genes in key periods of fruit enlargement:In the fruit setting stage:grafting up-regulated the expression of 7 Cm CYCs,Cm CDKD,7 Cm EXPs and 7 Cm XTHs in the fruit.Grafting down-regulated 2 Cm CYCs,2 Cm CDKs,3 Cm EXPs are expressed in fruits.The expression of CYCs genes and CDKs in the grafted fruit changes significantly,which may control the stop of cell division in the grafted fruit.The expression levels of EXPs and XTHs in grafted fruits may be up-regulated or down-regulated,which may promote the start of cell enlargement.In the pre-enlargement:grafting down-regulated 11 Cm CYCs,4 Cm CDKs,6 Cm EXPs and 7 Cm XTHs are expressed in fruits,and grafting up-regulates the expression of Cm EXPB2 and Cm EXPLA3 in fruits.During this period,grafting caused the expression of most genes to decrease significantly during this period,which promoted rapid cell enlargement and a rapid increase in cell volume.The decrease in the expression of CYCs and CDKs in grafted fruit may be caused by the cessation of cell division and the start of nuclear replication,thus promoting cell enlargement.The significant change in the expression of EXPs and XTHs in the grafted fruit is caused by cell enlargement.This difference can make the cell wall of the grafted fruit have a better ability to enlarge and extend.In the mid-enlargement: grafting reduced the expression of 7 Cm CYCs,2 Cm CDKs,6 Cm EXPs in fruits;grafting up-regulated the expression of 4 Cm EXPs and 8 Cm XTHs in fruits.The decrease of CYCs and CDKs gene expression in grafted fruits may indicate that the ability of cell division is reduced,and cell enlargement is dominant.CYCs and CDKs control the cell cycle and provide a material basis for the expansion of grafted fruit cells.The up-regulation of EXPs and XTHs expression in grafted fruits promoted the enlargement.In the post-enlargement: grafting promoted the expression of 10 Cm CYCs,Cm CDKF2,8 Cm EXPs and Cm XTH13 in fruits,grafting down-regulated the expression of 2 Cm CYCs,2 Cm CDKs and 4 Cm XTHs in fruits.During this period,the enlargement of the grafted fruit cells was basically stable;compared with the CK,there was a significant difference in the expression levels of CYCs and CDKs in the grafted fruits,indicating that the grafted fruit cells still had the ability to divide at this time to complete cell proliferation.The expression of EXPs and XTHs in grafted fruits increased,resulting in the grafted fruit cells eventually being larger than the CK cells,but the expression of XTHs decreased,the elongation of the cells stopped,and they did not participate in the maturation and softening of the fruits,indicating that it are involved in the process of cell enlargement.