| Genetic linkage map provides plant genetists with a powerful tool for the analysis of plant genome structure and function. Soybean, a widely studied and economically important species, is derived from ancient tetraploid and strictly self-pollinated. Its genome contains a large amount of duplication areas and repetitive sequences. The homology within the species is very high. For these reasons, the research of genetic mapping in soybean is dropped behind other crops. SSR markers play a critical role in integrating maps from different populations. One of the most important attempts in soybean genome research is to construct populations with large contents and facilities to locate special important agronomic traits.Jinbean23 is a releasing cultivar in Shanxi province. It has properties of high yield but it is sensitive to soybean cyst nematode. Huibuzhi, a local germplasm of Shanxi province with black seed coat, is high resistant to soybean cyst nematode. A cross of Jinbean23 x Huibuzhi was made, then selfed for 8 generation by single seed multiple descent method to construct RIL populations. SSR markers-based genetic map of this population were constructed and QTL analysis of some important agronomic traits were also carried out. Results of these studies are as follows:A genetic map based on SSR markers were constructed with this population. It covers 30 linkage groups and contains 258 SSR loci. The total length of the map is 1900.8 cM and the average distance is 8.3 cM. The number of markers on each group ranges from 2 to 18, and the length of eachgroup ranges from 3.3 to 171.6 cM. The longest average distance is 15.77 cM, on group B1. The nearest average distance is 1.65 cM, on group J3. There are 25 intervals longer than 20cM. In general, SSR markers spread evenly on the map except for several clusters, such as, A21, B2, D2, E, F1, G, H1, I, K2, O. There exist 9 gaps. Group A1, A2, H, L are devided into two small linkage groups and F, J, K are devided into three small linkage groups. It is easy to compare this map to soybean public integrated genetic map for most markers in this map are SSRs. It fits the public integrated genetic map well both in the sequences and the distances of markers.Windows QTL Cartographer V2.0 were used to detect QTL concern to oil and protein content, the traits associated to yield, SCN resistance, pod and seed traits, plant grownth traits and leaf traits, etc..When LOD>2.0, a total number of 154 QTL are found and they are mapped on 18 groups. Most of the QTL are clustered, especially on group A2, Bl, B2, C1, C2, M. Some QTL are mapped to the same loci. Among the QTL we get, there are 66 QTL which can explain the total variation more than 10%, 9 QTL which can explain the total variation more than 20%. Of the QTL associated to oil content, qOIL-a2l-2 and qOIL-a2l-3 can explain 32.54% and 52.13% total variation, respectively; of the QTL associated to flowering date, qFD-c2-3 and q-c2-4 can explain 31.97% and 40.58% total variation, respectively. These QTL are proposed as main effective genes and further fine mapping will be carried out. It's the basic for map-based cloning. At the same time, marker assistant breeding will be done. |
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