| Peach belongs to Prunus of Rosaceae,has richness in nutrients of fruit and important ornamental value.Perfecting of tree architecture is always an important direction of peach research due to excessive sprout and tree vigor which caused a lot of waste of manpower and material resources.Due to the long breeding cycle and low selection efficiency,the process of traditional breeding is slow.The exploring key genes for controlling peach traits is difficult because the construction of advanced generation groups is difficult,the generation cycle is long and the area is large,and the management cost is high.Markers which associated with traits can be gained by construction of high-density genetic map and QTL analyses using SNP markers.Marker-assisted selection(MAS)breeding can greatly reduce the proceed of breeding and improve the breeding efficiency.In this research,the genome of both parents and progeny generated by the female ‘Huangshuimi'(standard,showy flower,very large flower diameter)and the male ‘Zhongyoutao14'(temperature-sensitive brachytic dwarfism,non-showy flower,very small flower diameter)were sequenced and a high-density genetic map was constructed.QTL loci for peach temperature-sensitive short internodes,flower type(Showy/Non-showy)and flower diameter traits were obtained.The molecular mechanisms of temperature-sensitive brachytic dwarfism(Tsbd)were studied.The results provide a theoretical basis for the subsequent screening of candidate genes for several traits such as temperature-sensitive brachytic dwarfism.Meanwhile,the molecular markers related to traits lays a foundation for improving selection efficiency and shortening the breeding cycle.The main results are as follows:1.Constructed a hybrid population and a high-density genetic linkage mapThe hybrids population was constructed by using ‘Huangshuimi' as the female parent and ‘Zhongyoutao14' as the male parent.86 well-grown hybrid progeny plants were obtained combined with the embryo culture technology.The genome of two parents and 86 individuals were re-sequencing.The average sequencing depth of‘Huangshuimi',‘Zhongyoutao14' and 86 individuals were 28 X,31X and 3X,respectively.Meanwhile,54793 and 65214 In Dels were detected in ‘Huangshuimi'and ‘Zhongyoutao14',respectively.69483 SNPs were used for the genetic map construction by filtering of differential SNPs in the parent and genotyping statistics for the corresponding sites in the offspring,and 948 bin markers were mapped on eight linkage groups after linkage analyses,with a total genetic length of 1354.62 c M and an average of 1.43 c M between adjacent loci.The collinear analysis of genetic position of markers and physical position showed good linear agreement,which indicated that this genetic map is reliable and could be used for the QTL analysis of traits in peach.2.The Tsbd was located within 0.24 Mb on chromosome 3(Chr3),a In Del marker linked to Tsdb was developed,and a transcriptional regulatory network during thermomorphogenesis in Tsdb was summarized.Temperature-sensitive brachytic dwarfism is controlled by one dominate gene.The temperature-sensitive short internode trait was located to Chr03: 4.74 Mb-4.98 Mb on chromosome 3,with a total range of 0.24 Mb.A In Del marker linked to Tsdb was developed by developing In Del marker.It was used to identify the phenotype of offsprings in ‘Bairuyu' בSD9238' segregation populations with correct distinction,100%.Prupe.3G098100(WRKY),Prupe.3G043600(polygalacturonase)and Prupe.3G050500 were considered as candidates.Terminal internode length was temperature dependent,which was called called thermomorphogenesis.There was a significantly positive correlation between the length of the terminal internode(TIL)and the maximum temperature three days prior to the measuring day(DPM).At lower temperatures,the dwarf phenotype was due to inhibition of cell elongation in the internode.IAA,GA1,3 might be associated with thermomorphogenesis in peach.HSFs(heat shock factors)were up-regulated in response to the elevated temperature.Expression of HSPs was also up-regulated,which might influence hormone signaling pathways.The expression levels of DEGs involved in auxin were lower in temperature-sensitive peach at 3 WABB.While he expression levels of DEGs involved in CTK and BR were higher at 3 WABB.Genes related to circadian rhythm were also differentially expressed(up-or down-regulated)during temperature-sensitive peach shoot development.Genes related to aquaporins,expansins,pectinesterases and endoglucanase were up-regulated,which would promote cell elongation.Based on the above results,a hypothetical co-regulation network during the thermomorphogeneic response in temperature-sensitive peach was proposed.3.QTL of flower shape and flower diameter traits and a SNP marker linked to flower shape was exploitedThe trait of flower type is controlled by one gene.This trait was located at Chr08:14.46 Mb-14.83 Mb on chromosome 8,for a total of 0.37 Mb.The SNP locus at the position of Chr08: 14,484,624 bp was used to identify the phenotype of offsprings in natural populations with 100% accuracy,which laid a foundation for molecular marker-assisted breeding.Three candidate genes,Prupe.8G122600,Prupe.8G122700 and Prupe.8G122800,encoding B3 transcription factor,were selected for flower type trait.The flower diameter of the offspring of the hybrid population ranged from 2.11 cm to 5.38 cm.After testing,the flower diameter traits were consistent with the genetic traits of quantitative traits.Based on the constructed high-density genetic map of peach,four QTLs(q-FD-2-1,q-FD-6-1,q-FD-7-1 and q-FD-8-1)were firstly detected for this trait.q-FD-2-1 was located within 0.01 Mb(Chr02:20.15 Mb-20.16Mb)on Chr2,with explanation 4.60%.q-FD-6-1 was located within 1.28 Mb(Chr06:20.38 Mb-21.66 Mb)on Chr6 with explanation 17.85%.q-FD-7-1 was located within 0.01 Mb(Chr07:19.73 Mb-19.74 Mb)on Chr7 with explanation 5.92%.The major QTL(q-FD-8-1)was located within 0.28 Mb(Chr08:15.53 Mb-15.81 Mb)on Chr8,with explanation 47.79%.Prupe.6G203000(ANT),Prupe.8G134900(MYB)and Prupe.8G136800(b HLH123)were selected as candidate genes on Chr6 and on Chr8. |
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