| Construction of molecular genetic map and agronomic trait would be useful for spreading peat genus resources and marker-assisted selection for genetic improvement in pear. In this study, SSR primers were developed based on the selected SSR sequences from the EST sequences of pear in GenBank and GDR database of NCBI, and used for analysing genetic diversity within F1 progeny of Pyrys pyrifolia Nakai 'Xizilv×Kisui'. SSR, EST-SSR, RAPD technology which were used to analyze pear genome DNA were established firstly. The molecular genetic map of Pyrys pyrifolia Nakai was constructed by adopting "double-pseudo-testcross"strategy and F1 population ('Xizilv×Kisui'). We used BSA to screen related to skin color marker. The molecular marker linked to agronomic trait was analyzed.The main results were as follows:1. EST sequences of pear from GenBank of NCBI and GDR database, screened 60 SSRs distributed in the 54 EST sequences, in which dinucleotide repeats was dominant, the next were trinucleotide repeats and hexanucleotide repeats, accounting for 51.7%,25% and 1.7%, respectively. Of the dinucleotide repeats in 23 motif types, AT dinucleotide repeats had the highest occurrence frequence.25 pairs of SSR primers from 54 EST sequences were used for PCR amplification in F1 progeny of Pyrys pyrifolia Nakai 'Xizilv×Kisui', of which 14 pairs were available,9 pairs of primers amplification results showed polymorphism, with the ratio of 36% in the desigend SSR primers. According to the amplification bands by the 9 pairs of primers, the average number of alleles (No) and the effective number of alleles (Ne), were 2 and 1.9324, and the mean observed heterozygosity (Ho) and the mean expected heterozygosity (He) were 1 and 0.4809, respectively.2. The segregation patterns and ratio of SSR, EST-SSR and RAPD markers in 'Xizilv×Kisui' F1 population were studied according to "double-pseudo-testcross". For SSR marker, frequency of Mendelian segregation and deviation from Mendelian segregation in F1 population were 91.8% and 8.2% respectively (p=0.01). For EST-SSR markers, frequency of Mendelian segregation, deviation from Mendelian segregation and abnormal segregation in F1 population were 66.7%,22.2% and 11.1% respectively (P=0.01). For RAPD markers, frequency of Mendelian segregation and deviation from Mendelian segregation in F1 progenies were 94.5% and 5.5%(p=0.01) in this research. After a high density genetic map was constructed using JoinMap3.0 software based on 120 SSR,9 EST-SSR and 45 RAPD markers, including 162 markers. Respectively,53 SSR,2 EST-SSR and 107 RAPD markers were located on 19 linkage groups, covering a total distance of 901 cM of pear genome, with an average distance of 5.63 cM between adjacent markers, map with 56.8% genome coverage. The LOD value of linkage group was between 2.0-8.0.3. We used SSR marker to screen related to skin color marker. Result:Screened CH05g02 and NH015b primers, polymorphic bands was amplied in gene pools from 120 pair of primers. CH05g02 were verified in progeny and genetic linkage analysis, CH05g02 was linked to russet skin of Pyrys pyrifolia Nakai. This SSR marker band size was 114 bp, named CH05g02114. This molecular marker linked to agronomic trait was analyzed and located in the genetic linkage map. The marker with distance from the nearest SSR marker was 4.6 cM and russet skin was linked on LG5. |
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