Impact Mechanisms Of Chilling Requirement On Spring Flowering Of Blueberry Berkely ×(Lowbush×Pioneer)

In this study,we use perennial blueberries(Vaccinium corymbosum Berkeley×(Lowbush×Pioneer))as material,set up different treatments to satisfying the chilling requirement and not satisfying the chilling requirement,by analyzing the difference of external morphology and the content of hormones,sugars and flavonoids,and transcriptome sequencing of flower buds at different stages of development,To study the effect of chilling requirement on the development of flower buds and branches and leaves of blueberry,and to screen key regulatory genes through distinct metabolic pathways.To elucidate the effect of chilling requirement on flower bud development and the mechanism of molecular regulation.The results indicate:Morphological aspects:(1)Not satisfying the chilling requirement will make blueberry plant flower bud can not carry on normal reproductive growth,so that the plant can not blossom and bear fruits;and the time of vegetative growth will be obviously delayed.The physiological characteristics of response to chilling requirement are as follows:(2)During the flower bud sprouting and flowering process,the content of IAA and GA3 was lower,but ABA was higher in the bud that not satisfying the chilling requirement,and the content of flavonoids in flower bud was higher in all stages of not satisfying the chilling requirement except that there was no significant difference between flavonol in dormancy with the bud that satisfying the chilling requirement.There was a significant positive correlation between IAA and GA3,proanthocyanidins and IAA,flavonoids and GA3.(3)Compared with the leaves that satisfying the chilling requirement,except for the difference of insoluble proanthocyanidins content in the mature stage of leaves,the flavonoid content in the leaves not satisfying the chilling requirement is higher in other stages;compared with the total sugar,sucrose,fructose and glucose content in the leaves not satisfying the chilling requirement,the total soluble sugar content in the leaves not satisfying the chilling requirement is lower.(4)The content of total sugar and sucrose in the branches that did not satisfy the chilling requirement was always higher than that in the branches that satisfy the chilling requirement,while the content of fructose and glucose in the branches that did not satisfy the chilling requirement was higher in the period of flower bud development(dormancy-elongation period).The results of principal components analyse showed that the main factors affecting flower bud germination were hormones in flower bud and soluble sugar content in branch.(5)In different periods,the genes that satisfy and do not satisfy the chilling requirement were significantly enriched in carbohydrate metabolism,plant hormone signal transduction,flavonoid metabolism,photosynthesis,cold and floral pathways.Transcriptome analysis results:(6)Through the correlation analysis of hormone and flavonoid content in flower bud and related regulatory genes,it was found that ABA was significantly or significantly positively correlated with AUX1/LAX and SAUR,GA3 significantly or significantly negatively correlated with DELLA、GID1.Proanthocyanidins and flavonols were significantly or significantly positively correlated with their CYP75A、CHS.(7)Through analysis and test,the results showed that the chilling requirement affected FRI,DA,FUL and LFY in the vernalization pathway,and the expressiong of not satisfying the chilling requirement of flower bud in each period was significantly up-regulated;In the model of flower development,AP3,PI of class B,AG of class C and SEP of class E all of them were significantly up-regulated with the development of bud in the flower that satisfy the chilling requirement,but significantly down-regulated with the elongation of the flower buds that did not satisfy the chilling requirement,that is significantly down-regulated with not satisfying the chilling requirement.According to the above results,the chilling requirement affects the expression of regulatory factors(AP1/Ful1,AP3/PI,AG,SEP2)and physiology of flower development model by affecting the expression of vernalization pathway(FRI,DAM,LYF),gibberellin pathway(GI,DELLA)and photoperiod pathway(PHYB,CO,GI,LHY),to regulate flowering pathway,plant hormone signal transduction and carbohydrate metabolism of blueberry,thus affecting the expression of hormones,sugars and other substances,and then affecting normal growth and development and flowering.To lay the foundation for further solving the limitation of the region and condition of blueberry cultivation.