| Apple dwarf and high density cultivation is the trend of the world’s apple production.Spur type varieties are an important way to realize dwarf and high density cultivation.In the recent years,a large number of spur type varieties of Fuji have emerged and have been identified and popularized.The research on the physiological morphology evaluation and regulation technology of spur type varieties is not deep enough,which restricts the application and promotion of spur type varieties.Among them,the growth and development process of branches plays an important role in it.In this study,4 spur type varieties(’Yanfu No.6’、’Liquan spur’、’Miyazaki’、’Jinfu 18’)and 4 standard type varieties(’Yanfu No.3’、’Aomorifu’、’Shou Fuji’、’Yanfu No.10’)as the materials to investigate the growth and development of the tree and the result characteristics.and carry out exogenous gibberellin(GA3)and its synthesis Inhibitor PAC spraying treatment,through the effect investigation of the treatment and transcriptome sequencing analysis,in order to reveal the morphological and physiological development mechanism of apple spur bud varieties,and to select and match the stub varieties and tree shape in the practice of apple dwarf and hight density cultivation regulation provides theoretical guidance.1.Evaluation and analysis of physiological and morphological development characteristics of Fuji apple spur-type bud mutation varieties.During the period when the tree body completely stops growing,systematically analyze the tree growth indicators,leaf physiological morphology,fruit quality,photosynthesis parameters,and endogenous hormone levels of the apical meristem of Fuji apple spur type varieties and standard varieties.Small differences in plant height,between spur type varieties and standard varieties,with plant heights ranging from 2.86 m to 3.3 m.The crown diameter and branching ability of short-branched varieties are significantly lower than those of standard varieties.In the terms of branch composition,the short branches proportion of spur-type variety ’Miyazaki’ is highest,reaching to 88.08%,and the standard variety ’Yanfu No.10’has the lowest proportion of short branches,only 32.19%.The short rate and the germination rate of spur-type varieties are significantly higher than those of standard varieties.The leaf area of The leaf area of ’Jinfu 18’ is the largest,and the leaf area is about 1.53 times that of ’Shou Fuji’;The maximum dry weight per unit area of ’Yanfu No.6’ is 51.5 mg/cm2.’Jinfu 18’ is the largest,and the leaf area is about 1.53 times that of‘Shou Fuji’;The maximum dry weight per unit area of ’Yanfu No.6’ is 51.5 mg/cm2.The bark rate of spur-type varieties was significantly higher than that of standard varieties,and the bark rate of ’Jin-18’ was the highest,as high as 0.38.In terms of leaf physiological morphology,the leaf area and leaf dry weight per unit area of the spur-type varieties were significantly larger than those of the standard type.spur-type varieties have a higher branch bark rate than standard varieties.The contents of zeatin(ZT),gibberellin(GA),auxin(IAA)and abscisic acid(ABA)are quite different in spur-type and standard type.The contents of ZT,ABA and GA in standard varieties were significantly higher than those in spur-type varieties.Among them,the zeatin content of ’Yanfu No.6’ is only the standard-type variety’Aomorifu’ 60%of the gibberellin content of ’Jinfu 18’,the lowest content of gibberellin is 3.59 ng.g-1.2.Analysis of the effect of exogenous gibberellin on the physiological development of Fuji apple spur-type bud mutation varieties.Spray 500mg.L-1 on the new shoots of 6-year-old spur and standard varieties respectively.7 days after treatment of Gibberellin(GA3)and gibberellin synthesis inhibitor PAC,we measured the branch length,average internode length,endogenous hormone content,photosynthesis parameters,and leaf physiological morphology of different treatments.According to the investigation,it was found that GA3 can promote the internode length of spur-type varieties.The exogenous gibberellin promoted the internode length of the spur-type varieties,GA3 have the most influence on ’Yanfu No.6’,internode length increased by 19.05%.In terms of photosynthesis parameters,exogenous gibberellin increased the stomatal conductance of spur-type cultivars,and at the same time significantly reduced the transpiration rate of stub-type cultivars.In terms of net photosynthetic rate,exogenous gibberellin promoted different degrees.The net photosynthetic rate of spur-type varieties.In terms of leaf physiological indicators,exogenous gibberellin significantly increased the leaf area of spur-type varieties.Among them,gibberellin made most significant influence of the spur-type variety’Miyazaki’ and the stomatal conductance is about 1.33 times that of the control.At the same time,it significantly reduced the transpiration rate of the spur-type varieties ’Liquan spur’ and ’Jinfu 18’,and the Evaporation rate were 88.14%and 90.99%of the control,respectively.In terms of specific leaf weight,exogenous gibberellin significantly increased the specific leaf weight of spur-type varieties ’Miyazaki’ and ’Jinfu 18’.which were 107.16%and 101.58%of the control respectively.In terms of specific leaf weight,exogenous gibberellic acid significantly increased the specific leaf weight of’Miyazaki’ and ’Jinfu 18’,which increased by 24.69%and 27.58%respectively compared with the control.3.Transcriptome analysis of exogenous gibberellin regulating the physiological development of Fuji apple spur type mutation.The KEGG pathway enrichment analysis of the differentially expressed genes obtained by transcriptome sequencing revealed that the different expression genes were mainly enriched in the hormone pathway.The analysis of the different expression genes in the relevant hormone signal transduction and synthesis pathways respectively led to the following conclusions:The expression of key genes in the auxin synthesis and signal transduction pathway,YUCCA,PIN,ARF and most SAUR in Y3-CON was significantly higher than that in Y6-CON,and the expression of GH3,which is involved in auxin signal transduction,was significantly higher in Y6-CON.Compared with the standard variety Y3-CON,PAC inhibited the expression of GH3 in ’Yanfu 3’compared with the control.Compared with standard varieties,the expression of IAA in short-branched varieties showed an upward trend.PAC promoted the expression of IAA,and gibberellin inhibited the expression of IAA.In the ethylene signal transduction pathway,the expression of most ERF transcription factors in Y6-CON is higher than that in Y3-CON,and exogenous PAC promotes the expression of ERF.The expression of CYP707A4,a key gene that regulates ABA catabolism and the key gene of abscisic acid synthesis pathway.NCED1,was significantly higher in standard cultivar Y3-CON than in Y6-CON,and the expression levels of the two genes in response to exogenous PAC and gibberellin big different.Most PP2C has a higher expression level in Y6-CON,and exogenous gibberellin significantly up-regulates the expression of PP2C.In the gibberellin biosynthesis pathway,GA20ox was down-regulated by PAC and up-regulated by gibberellin.At the same time,the expression in Y6-CON was significantly lower than that in Y3-CON;the expression of GA2ox and GID1 was induced by gibberellin and PAC.Gibberellin promotes the expression of two genes,and PAC inhibits the expression of two genes.The receptor BRI1 and related kinase BAK1 of the brassinolide signal transduction pathway showed a trend that the expression level of Y6-CON was significantly lower than that of Y3-CON.Through the GO enrichment analysis of the different expression genes in the two comparison groups Y3-CON vs Y3-PAC and Y6-CON vs Y6-GA,it was found that pathways related to the promotion of cell elongation and growth,such as cell wall biogenesis,gibberellin-mediated Pathways such as guided signaling pathways and tissue regeneration have been significantly enriched,and the expression of related genes in short-branched varieties has a downward trend compared with standard varieties.In summary,the morphological and physiological characteristics of spur-type cultivars are characterized by high germination rate,weak branching ability,spur rate,high branch bark rate,large leaf area,and low content of endogenous hormones such as ZT and GA;exogenous GA3 promotes the growth of internodes and shoots of spur-type varieties,exogenous GA3 promotes the net photosynthetic rate of spur-type varieties,inhibits transpiration,and regulates the transcription of genes related to gibberellin,auxin,cell wall biogenesis and tissue regeneration to influence internode elongation. |
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