| In this study, a tetraploid F1 segregated population for plant maturity was constructed and used to explore genetic block related to maturity via reduced-representati on sequencing and bulked segregant analysis method. Some molecular markers related to maturity were developed in this genetic block and verified in the same population. Among those, one molecular marker tightly linked to maturity was identified, which can be applied to the potato marker-assisted breeding via molecular detection in tetraploid clones. A genetic linkage map of chromosome 5 was further constructed which can be used to determine the maturity candidate gene loci. The main results are as follows:1. A F1 segregating population consisting of 221 individuals derived from early maturity parent ‘Zhongshu 3’ and late maturity parent ‘Zhongshu 19’ was used in this study. The growth period of each plant has been investigated within two consecutive years. Eventually, 53 early maturity individuals with less than 80 days of growth period, 105 medium maturity individuals within 80 to100 days and 63 late maturity individuals with more than 100 days were obtained, respectively.2. Two DNA pools were constructed with 35 extreme early maturity individuals and 33 extreme late maturity individuals from above mentioned segregating population, respectively. The two DNA pools and two parents genomic DNAs were then sequenced via 2b-RAD technique for SNP screening in the whole genome. And over 90 percent of high quality reads including the BsaXI restriction enzyme cutting site, indicated that the quality of the sequence data is very high. An average of 125,556 unique tags with an average depth of 42× were further obtained via mapping the high quality reads to the reference genome DM sequence by the software of SOAP. According to the density distribution of unique tags in different chromosomes, The density distribution map of specific unique tags in 12 Chrs was obtained, and the result showed that the big difference block of specific unique tags mainly located in IV, V and IX Chrs, and the most extreme difference block was mapped in 4.0~4.2Mb of the V Chrs, and this chromosome block was related to potato early maturity.3. A total of 52 pairs of primers were designed based on the sequence of unique tags in the maturity-related genetic block combining with the reference genome DM sequence, and used for assessment of amplification and polymorphism in the female parent Zhongshu 3, male parent Zhongshu 19, and the DNA pools, out of which 8 polymorphic markers were detected including 5 markers tightly linked to maturity. A further testing of these 8 polymorphic markers were performed using 53 early-maturity individuals, 63 late-maturity individuals and 70 tetraploid varieties, and the result showed that the 5 markers SCAR5-5, SCAR5-8, CAPS5-3-2, CAPS5-21-2, CAPS5-24 were tightly linked to early maturity, and could be used for marker-assisted selection in potato breeding.4. One hundred and fifty one SSR markers on chromosome V were used to screen the segeragating population, and finally 32 polymorphic SSR markers were obtained. With these 32 polymorphic markers and 8 polymorphic markers developed above in this study, a linkage genetic map of V Chrs was constructed using the Tetraploid Map software. This genetic map spans 223 cM with an average genetic distance of 4.46 c M. The QTL for early maturity was mapped at the position of 140 cM, and the 5 markers developed above were tightly linked to this QTL, and this QTL could explain 31.96 percent of variance with the maximum LOD of 16.492. The QTL for early maturity was mapped in the physical interval of 230 Kb based on the results of maturity QTL mapping and high-throughput simplified genome sequencing data, which laid a solid foundation for further cloning and functional verification of maturity genes.In this study, 53 early maturity individuals, 105 medium maturity individuals and 63 late maturity individuals were obtained from a F1 segregating population consisting of 221 individuals, respectively. The genetic block for maturity was mapped on the V Chrs based on the density distribution map of specific unique tags in 12 Chrs. 8 polymorphic markers were developed, in which 5 markers tightly linked to maturity could be used for marker-assisted selection in potato breeding. A linkage genetic map of V Chrs was constructed including 50 molecular markers with the genetic map spans of 223 cM. And the QTL for early maturity was mapped at the genetic position of 140 c M near SCAR5-8 with the physical interval of 230 Kb, explaining 31.96 percent of variance. |
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