Screening Of Suitable Rootstocks Of Green Crisp Plum And Primary Study On Regulation Mechanism Of Drought Tolerance

Plum(Prunus salicina Lindl.)is a plant of the genus Rosaceae.It is a temperate deciduous fruit tree suitable for planting in the north and south of my country.In recent years,the planting area and output of crisp plum,one of the three major fruits in Chongqing,have continued to grow.As of 2021 In June of this year,the city’s plum planting area reached 1.4385 million mu,becoming the second largest fruit after citrus.Among them,the crispy plums represented by Wushan crispy plums have a dignified fruit shape,crisp and tender meat,sweet and juicy,etc.It accounts for about 80% of the city’s plum planting area,and is deeply loved by consumers.At present,the rootstocks used for the propagation of green crisp plum seedlings are mainly peach,and there are problems in production such as susceptible root nodules,serious harm of longhorn beetle,easy flow of glue,and easy premature aging.Therefore,the selection of alternative plum rootstocks is of great significance for promoting the sustainable development of the crisp plum industry.In this study,the annual branches of the representative cultivar ’Wushan Cui Li’in Chongqing were used as scions,and were grafted on four different rootstocks.The mechanism of drought tolerance regulation of grafted seedlings has been preliminarily discussed,and the main results are as follows:1.In this study,the results of the analysis of the survival rate,enzyme activity and other indicators of 4 rootstocks grafted with ’Wushan Crispy Plum’,which were cherries,peach,wild plum and apricot,showed that the survival rate,growth rate,chlorophyll content of grafted seedlings of peach and wild plum rootstocks were improved.The content,SOD,POD enzyme activity and affinity-related gene expression in the callus of the grafted interface were significantly higher than those in the grafted seedlings of the two rootstocks,the mountain cherry and the mountain apricot.The leaf ratio,dry weight and relative expression of incompatible genes in callus between rootstocks and rootstocks of peach and wild plum rootstocks were lower than those of peach and prunus rootstocks;The wild plums were in good healing condition,and there was no obvious bad growth phenomenon.Therefore,Wushan brittle plum had higher compatibility with wild plum and peach rootstock,and relatively speaking,the grafting compatibility of wild plum was higher.2.The physiological performance of the grafted seedlings of peach and wild plum rootstocks under drought stress was analyzed.The results showed that under severe drought stress,the grafted seedlings of peach rootstocks were more phenotypically tolerant to drought than those of wild plum rootstocks.Leaf relative water content(RWC)was lower,net photosynthetic rate was higher,leaf stomatal density was smaller,long and short axes and area of stomata were larger,and there was no difference in stomatal opening.In terms of leaf drought tolerance-related enzymes and osmotic substances,the enzyme activities of SOD and POD were 607.59±26.11 μ/g FW and 89.42±9.42 μ/g FW,respectively,the higher Pro content was 0.08 μmol/g,and the MDA content was higher.The low was 42.51±5.18 μmol/g.Both wild plum and peach have strong drought tolerance,and the grafted seedlings of peach rootstock are more drought tolerant than the wild plum rootstock grafted seedlings.3.Analyze the transcriptome and metabolome of the rootstock grafted seedlings of peach and wild plum under drought stress,screen out 17470 and 17603 differentially expressed genes,862 and 861 differential metabolites,and analyze the differential genes and differential metabolites It was found that there are 507 co-expressed genes and 54 coexpressed metabolites in peach and wild plum.The GO pathway enrichment analysis of the differential genes found that both peach and wild plum were enriched in signal transduction,kinase activity,and metabolic processes under drought stress;KEGG pathway enrichment found that both were enriched in photosynthesis,phytohormone signaling Transduction and hormone metabolism pathways.The combined analysis of these differential genes and differential metabolites found that they were all significantly enriched in the upstream material synthesis and downstream signal transduction pathways of plant hormones.It plays an important role in plant leaves.Therefore,the combined metabolite analysis of genes related to ABA signal transduction pathway found that ABA controls leaf stomatal closure and regulates leaf photosynthesis by down-regulating the abscisic acid receptor PYL4.The ABA content was increased by up-regulating the expressions of ZEP,NCED1,2,and AAO3 in the leaves of grafted seedlings of peach and wild plum rootstocks,and the ABA concentration in leaves was regulated by oxidative inactivation of ABA by 8’ hydroxylase CYP707 As.The ABA signal transduction pathway also has crosstalk with other plant hormones.It is mainly found that ETH and JA act as positive regulators of ABA,and indirectly increase the concentration of ABA to close plant stomata to improve plant drought tolerance.IAA and GA are negative regulators of drought stress.The factor antagonizes ABA.