| Pear (Pyrus L.), one of most important fruits in the world, belongs to Pomoideae, Rosaceae family. In this paper, genetic linkage maps of the European pear (Pyrus communis L.) cultivar ’Bayuehong’ and the Chinese pear (Pyrus pyrifolia Nakai) cultivar ’Dangshansuli’were constructed based on SSRs, SRAPs, AFLPs and a S locus by using their F1 progenies. Twelve fruit traits were measured and analysised statistically, of which QTLs were identified by interval mapping (IM).The main results were showed:1. EST-SSRs were searched for in pear EST sequences pubulished in NCBI by using the SSRHunter software. Sixteen EST-SSR primers were designed and synthesized through Primer 5.0 software. Six of them caused polymorphisms in different pear cultivars which can be used in comparative mapping and for carrying out evolutionary studies.2. Genetic structure of 97 F1 progenies of ’Bayuehong’ and ’Dangshansuli’ cross was analyzed by SRAP and AFLP molecular marker.The genetic similarity coefficients between them was 0.36-0.68, except that only one is 0.86. The UPGMA dendrogram of phylogenetic relationship demonstrated that the segregation of the progenies was balanced. These demonstrated that the population was suitable for genetic linkage mapping.3. Two high density genetic map were constructed using Joinmap3.0 based on the SSR, SRAP and AFLP locuses segregated in the F1 populations. The genetic linkage map of paternal parent’Dangshansuli’consists of 216 markers ordered in 17 linkage groups, including 142 AFLPs,70 SRAPs,3 SSRs and S locus, defining 1621.3 cM of total map distance. The length of the linkage groups varied from 32.4 cM to 204.1 cM with an average of 95.4 cM. The number of markers for each linkage group varied from 3 to 47 with an average of 12.7. The average distance between adjacent markers was 7.5 cM.For maternal parent’Bayuehong’,240 markers were placed in 17 linkage groups, including 151 AFLPs,83 SRAPs,5 SSRs and S locus, defining 1703.8 cM of total map distance. The length of the linkage groups varied from 45.8 cM to 152.4 cM with an average of 100.2 cM. The number of markers for each linkage group varied from 6 to 47 with an average of 14.1. One marker was found on average every 7.1 cM.45 QTLs’LOD> 3.5, maybe were major QTLs.4. With MapQTL 5.0,78 QTLs were detected for twelve fruit traits based on IM (Interval Mapping) QTL mapping, and were mapped on genetic linkage maps of ’Dangshansu’and’Bayuehong’. They were distributed on 18 linkage groups of parents. The number of QTLs for fruit stone cell content detected was 10; The QTLs for fruit soluble solid was only one; Ten QTLs for fruit weight were detected; For fruit shap index, five QTLs were found; Fruit core size was associated with 11 QTLs in total; Two QTLs were detected for soluble sugar content; Seven QTLs of titratable acid contend were got; Nine QTLs were detected for crispness; For hardness, six QTLs were detected; QTLs for transverse diameter was 3; For vertical diameter, only one QTL detected; For maturity,12 QTL were identified.5. All 78 QTLs detected for pear fruit traits were located on 18 linkage groups of ’Bayuehong’ and ’Dangshansu’, and 70 of them (89.7%) distributed on 16 linkage groups at least two of which were co-located or closely linked.71 QTLs located on BYH2/DS2, BYH3/DS3、BYH7、BYH8/DS8、DS9、BYH11/DS11、DS12、BYH13/DS13 linkage groups, separately 4/3、6/4、7、6、7/4、5、5/8、6、6/2.Construction of genetic map and QTL mapping will provide an available reference to genetic breeding and molecular marker assisted seleetion in pear. |
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