Study On Growth Characteristics And Fruit Quality Of Grafted 'Shatangju' Mandarin Plant

'Shatangju' is the largest cultivated citrus variety in Guangdong and even southern China,it is mainly propagated by grafting.Rootstocks have important influence on the growth and fruit quality of the scion.At present,the research on the dwarfing mechanism of fruit trees mainly focuses on the rootstocks,but dwarfing of dwarfing stocks does not mean that the grafted plants also have dwarfness.The 3-year-old‘Shatangju'plants were used as experimental materials to study the effects of different rootstocks on the growth and development,anatomical structure,physiological and biochemical indicators and fruit quality of the scion,and nine kinds of rootstocks include‘Goutou'orange,Carrizo citrange,Fragrant orange,Sunki mandarin,Red tangerine,Trifoliate orange,Rough lemon,Canton lemon and‘Shatangju'mandarin.The main results are as follows:?1?By investigating the flowering stage of different stock-scion combinations,compared with the grafted plants of the‘Shatangju'/‘Shatangju',except for the Red tangerine delayed the flowering stage of the scions,other rootstocks were early flowering in different degrees,and the most significan was the Sunki mandarin that about 8 days earlier in each stage.The rootstock has a significant effect on the number of flowers in the scions.Trees grafted on‘Goutou'orange,Trifoliate orange and Canton lemon had higher levels of the number of flowers,and the number of flowers in‘Shatangju'/‘Goutou'orange was 3.46times that of‘Shatangju'/‘Shatangju'.?2?There is a significant difference in the growth potential of‘Shatangju'mandarin plants with different stock-scion combinations.The plant height,crown volume,scion and rootstock stem diameter of‘Shatangju'/Trifoliate orange were significantly higher than trees grafted on Sunki mandarin,Carrizo citrang,Fragrant orange and‘Shatangju'.The scion and rootstock stem diameter ratio of‘Shatangju'/Sunki mandarin and‘Shatangju'/Red tangerine were 0.74 and 0.73,respectively,which was closer to the‘Shatangju'/‘Shatangju'?0.74?,indicating that the Sunki mandarin and Red tangerine had good affinity with the‘Shatangju'.?3?By analyzing the anatomical structures of leaves and shoots of grafted plants,it was found that rootstock had no significant effect on the stomatal density of leaves.The thickness of spongy tissue and its percentage of the leaves and the vessel density of shoots were significantly negatively correlated with the growth potential of grafted plants;The ratio of palisade/spongy and upper and lower epidermis thickness of leaves,the cross-sectional area,xylem area,single vessel area and total area of shoots were significantly positive correlation with the growth potential of grafted plants.There was no significant correlation between other anatomical indexes and plant growth potential.?4?There is a significant negative correction between carbohydrate?sucrose,soluble sugar and starch?content and tree vigor.The content of sucrose in‘Shatangju'/‘Goutou'orange was the highest,which was significantly higher than that of other stock-scion combinations,‘Shatangju'/Fragrantorange,‘Shatangju'/Sunkimandarin,and‘Shatangju'/Red tangerine were lower,accounting for only 57.74%,57.33%and 56.17%of‘Shatangju'/‘Goutou'orange;The content of soluble sugar and starch was the highest in‘Shatangju'/Fragrant orange and the lowest in‘Shatangju'/‘Shatangju'.?5?The levels of IAA,GA₃ and the ratios of IAA/ABA,GA₃/ABA,?IAA+GA₃?/ABA were the highest in the leaves of the trees grafted on‘Goutou'orange,which was significantly higher than that of the trees grafted on Fragrant orange;The ratios of?IAA+GA₃?/ABA showed a significant positive correlation with the tree vigor,and there was no significant correlation among the others;The rootstock had no significant effect on ABA content of grafted plants.?6?Although the activities of SOD and CAT enzymes in different stock-scion combinations were different,they were not significantly related to tree growth indexes;POD activitie in the leaves of grafed tree was negatively correlated with the growth vigor,the tree grafted on‘Shatangju'had the highest POD activity;while the lower on Carrizo citrange and‘Goutou'orange,only 58.95%and 61.89%of‘Shatangju'/‘Shatangju';IOD activity was negatively correlated with autumn shoots length,the‘Shatangju'/‘Goutou'orange had the highest IOD activity,the‘Shatangju'/Fragrant orange,‘Shatangju'/Trifoliate orange and‘Shatangju'/Rough lemon were less active,accounting for 88.65%,88.31%and87.95%of‘Shatangju'/‘Goutou'orange,respectively.?7?It shows a significant effect on fruit yield and fruit quality while‘Shatangju'grafted on different rootstocks.The results of this study revealed that fruit yield and contents of titratable acid on Rough lemon were the smallest,the highest fruit size,fruit shape and acid-sugar ratio and the fruit peel was the thickest and the brightest,and the poor mastication of fruit.But the‘Shatangju'grafted on Canton lemon and‘Goutou'orange rootstocks had the higher fruit yield,the brighter fruit peels and the medium size fruits,among them,the shape of fruit and the content of soluble solid,total soluble sugar and reducing sugar from‘Goutou'orange rootsotck were the lowest,the content of soluble solid,sugar and ascorbic acid from Canton lemon rootsotck was the highest.Although the yield of fruits from Trifoliate orange rootstock was higher,but the fruit size was smallest,the content of soluble solid and titratable acid was highest,the content of ascorbic acid and acid-sugar ratio was lowest.The Canton lemon had a better effect on the quality of ‘Shatangju' fruit.