The Genctic Diversity And Effects Of GA₃ On Bud Dormancy Of Herbaceous Peony

Herbaceous peony,species of herbaceous perennial flowers belonging to the Paeoniaceae,is a popular traditional flower in China,and more than 1 000 varieties of herbaceous peony are cultivated in the world with its abundant variation types.But the lack of corresponding parental information makes it impossible to learn fully about the hereditary information of each species.This paper studied the genetic diversity of different cultivar groups herbaceous peony via the chromosome karyotype analysis and SSR molecular marker technique,it can provide scientific basis for the classification of herbaceous peony,breeding and the utilization of gennplasm resources.While breaking donnancy by GA₃ is widely accepted in the cultivation of penoy,but none of the molecular mechanism for promoting dormancy's breaking of the peony flower buds has been reported.In this study,we studied the effects of different GA₃ treatments on morphological differentiation of peony flower buds,physiological and biochemical metabolism,GID1 and DELLA gene expression pattern to explore the physiological and molecular mechanisms of dormancy's breaking of the peony flower buds and to provide theoretical guidance for flowering regulation and molecular breeding.The results are as follows:1.Chromosome karyotype identification of different cultivar groups of herbaceous peony:the result of the 21 peony cultivars with unknown chromosome ploidy in this study showed that one cultivar of lactiflora group is diploid;five cultivars of itoh group are triploid and the remaining 15 cultivars of hybrid group are diploid,triploid and tetraploid,respectively.2.SSR Molecular marker screening and genetic diversity analysis:86 alleles?76 polymorphic alleles?were obtained by screening 13 pairs of polymorphic primers from the 100 primers,each of them having an average of 6.615 alleles.The ranges of variation of the effective alleles are 2.243-7.800,PIC content is 0.554-0.872 and genetic diversity index is 1.701-3.126.55 herbaceous peonies were divided into 9 groups by UPGMA method.3.Effect of GA₃ treatments on morphological differentiation of 'Da Fu Gui' peony flower buds;herbaceous peony that entering the petal primordia were transferred to the cold storage.The herbaceous peony over which was sprayed 150 mg/L of GA₃ showed that effect of GA₃ on herbaceous peony flower bud's differentiation process is very significant,and greatly shortens the period of flower bud's differentiation and those with 150 mg/L of GA₃ can be quickly differentiated into pistil primordia in only 25 days from petal primordia,40 days earlier than the control group.4.Research on the physiological metabolism of 'Da Fu Gui' flower bud during dormancy release:a certain regular change concerning the content of soluble sugar,starch,soluble protein and other 10 physiological indicators were observed,the content of soluble sugar and starch,the SOD and PDO activity showing a decreasing trend,CAT an increasing trend.The GA₃ and the ratio of GA₃/ABA which could essentially reflect the tendency of peony flower bud's dormancy release.It presented an increasing trend when the flower bud dormancy release.5.Study on the expression pattern of GID1 and DELLA gene:2 GID1 genes?PlGID1a and PlGID1b?and 3 DELLA protein genes?PlDELLA1,PlDELLA2 and PlDELLA3?were screened from the existing transcriptome data of our research group,the result of which showed that peony flower bud dormancy was released with the gradual raise of gene expression of GID1?PlGID1a and PlGID1b?.And its dormancy was released gradually with the gradual decline of gene expression of DELLA?PlDELLA1,PlDELLA2 and PlDELLA3?.We could hypothetically conclude,as a result,that PlGID1a and PlDELLA2 may be the key genes of the GID1 and DELLA owing to the relatively high differences between the gene expression of different group.