Study On Morphologic,hormonal And Molecular Mechnism Of Flowering Time In ‘Chunhua No.1’ Loquat (Eriobotrya Japonica Lindl.× Eriobotrya Bengalensis Hook.f.)

In this study,‘Chunhua NO.1’（Eriobotrya japonica Lindl.×Eriobotrya bengalensis Hook.f.）and‘Dawuxing’（Eriobotrya japonica Lindl）were used as experimental materials,to explore the flowering mechanism of loquat in three aspects---morphological differentiation,endogenous hormones and genes regulation.Firstly,the time of inflorescence bud differentiation of two loquats was confirmed by paraffin section of apical buds in each period.Secondly,apical buds at different stages or flowers were used as the experimental material to carry out the qualitative and quantitative analysis of ZT,ABA,IAA and GA₃ in two loquats by HPLC.Then,the transcriptional levels of 13 flowering genes at different stages,in different tissues were analysised by Real-time quantitative PCR.Finally,cloning and sequencing were performed on AP1,TFL1,SVP,and PIF4,the candidate key genes that caused loquat different flowering time deduced from the significant expression differences.The results of this study were as follows:（1）The morphological observations of apical buds showed that the differences of flowering time between‘Chunhua NO.1’and‘Dawuxing’were primarily related to the starting time of inflorescence bud differentiation and the speed of inflorescence development,rather than the length of the time for differentiation.（2）HPLC analysis showed that though GA₃,ABA,ZT and IAA had slightly different regulatory effects in different variety（line）during inflorescence bud differentiation period,GA₃ significantly inhibited loquat inflorescence bud differentiation.Moreover,GA₃,ABA and ZT promoted the final blooming of loquat,while IAA had little impact on it.In addition,ABA played a dominant role in the regulation of loquat flowering and high ratios of ABA/IAA and ZT/IAA could promote loquat flowering.（3）The results of q RT-PCR showed that multiple flowering genes could synergistically regulate the flowering of loquat.Among them,the expression patterns of AP1,TFL1,SVP and PIF4 between two loquats were significantly different,and speculated to be the key genes of regulating the flowering time of loquat.（4）The CDS of AP1,TFL1,SVP1,SVP2 and full-length c DNA sequence of PIF4were obtained,all containing intact open reading frames.Sequence analysis showed that AP1,TFL1,and SVP2 had no difference in CDS between‘Dawuxing’and‘Chunhua NO.1’,which ruled out the possibility of expression difference caused by CDS mutation.However,there were several base mutations in the coding region of SVP1 and PIF4,whose amino acid sequences also showed some differences,indicating that there was a possibility that base mutations occurred in coding region could lead to different flowering time of two loquats.（5）Integrating the results of this study,it was found that,the time when endogenous hormones and flowering genes expression levels in different periods showed significant differences between two loquats was corresponding to the specific dates of inflorescence bud differentiation and blooming.This indicated that the morphological differentiation of shoot apices of loquat and its final blooming might be comprehensive results of joint regulation of endogenous hormones and flowering genes expression.