| Kiwifruit is sensitive to water and belongs to a typical fruit tree that is not resistant to waterlogging stress.In production and cultivation,the lack of oxygen in rhizosphere of kiwifruit is often hindered by unfavorable seasonal rainfall and improper water and fertilizer management,which seriously restricts the large-scale development of the kiwifruit industry.Therefore,waterlogging stress has become an important limiting factor for the distribution of kiwifruit in southern China.The selection of tolerant rootstock is of great significance to the kiwifruit industry.Tissue culture seedlings from Actinedia polygama were used in the present study.We artificially simulated waterlogging stress to comprehensively evaluate the waterlogging tolerance of Actinedia polygama by external morphology,physiological and biochemical indicators and related gene expression.In addition,the study on the grafting compatibility of 4different scions to Actinedia polygama was analyzed to provide a more powerful basis for the kiwifruit as an alternative tolerant rootstock.The main results are as follows:1.In the process of waterlogging stress,the morphological characteristics,chlorophyll,stomata,and endogenous substances of Actinedia polygama were observed.The results showed that during the entire waterlogging stress process,the phenotypes of early stage damage were obvious,that the chlorophyll content root activity,the stomatal conductance were decreased,and the stomatal density increased;in addition,the increase of endogenous substances malondialdehyde and H2O2 showed that it was damaged by waterlogging;in the middle and later waterlogging treatment,the plants gradually adapted to the waterlogging environment,the aerial roots developed obviously,the number and length increased rapidly,and the endogenous protective enzyme POD activity increased,accompanied by the content of malondialdehyde and H2O2 decreasing,the plants gradually adapted to the waterlogging environment and showed good viability in the late waterlogging period.Actinedia polygama showed long-term tolerance to waterlogging stress,and these results provided a theoretical basis for the selection of kiwifruit rootstocks.2.During the process of waterlogging stress,the expression of stress-related genes under stress conditions was analyzed using real-time PCR.Calcium is an important signal factor in plant stress response,and its members AdCIPK9 and AdCIPK13 showed no obvious change in the early stage of waterlogging stress,and they were significantly up-regulated in the late stage.This indicates that CIPK gene plays an important role in kiwifruit adaptation to long time waterlogging stress.ERF4 and ERF5 are members of ethylene responsive transcription factor ERF family subgroup VII.Members of this group have an important regulatory role against hypoxia stress and waterlogging stress.The expression levels of AdERF4 and AdERF5 met the top at 42 days of treatment,and the up-regulated expressions activate the expression of downstream function genes.The related functional genes AdACP,AdADH,AdHSP17.5,AdLBD,Ad PRT6,AdHB1 were up-regulated in different degrees during the late stage of waterlogging stress,which was of great significance for persistent resistance to waterlogging,further demonstrating the long-term tolerance of Actinedia polygama.3.Actinedia polygama was used as the rootstock.Miliang 1,HWD,Jinkui and 13-4 were used for scions.The results of the different grafting combinations were as follows:the survival rate and preservation rate of Jinkui is higher than others,13-4 grows faster and the stem diameter ratio is also higher;the stem diameter ratio of HWD is the lowest,but its growth rate is also higher;Miliang 1 has a lower survival rate,and it has a fast growth rate in the first 6 months.Together,the graft-compatibility of Jinkui and Actinedia polygama is significantly higher than the other three combinations.Actinedia polygama is suitable as the rootstock with variational graft-compatibility. |
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