| As the model legume, Medicago truncatula is the third genome completely sequenced plant after Arabidopsis and rice. M. truncatula have the genetic comparability with the mostly crop legume species, especially M. truncatula and alfalfa are the closely relative crop species and their genome have highly homology. So the information from M. truncatula can be used for the other legume species, this is very important to excavate genetic resources of leguminous plant our country and improve the breeding of the crop legume species and alfalfa. In this study, the morphological characteristics about the seed yield of M. truncatula and its components are investigated. The germplasm resources of M. truncatula are identificated and screened combining with molecular markers. And the genetic linkage map of M. truncatula is constracted. The traits of the RILs populations from A17×A20 are analysed by major genes + polygene segregation analysis method from quantitative traits of plants.The traits included the length of lateral branches, florets number, pod number, 100-pod weight, 1000-seed weight and seed yield. Lastly, 100-pod weight and 1000-seed weight are QTL analysed. The main results are as follows:1. There were relation in the seed yield of M. truncatula and constituent elements.The seed yield and the length of latral branches were positively related, the correlation coefficients were 0.720 and 0.358. The seed yield and 100-pod weight and 1000-seed weight were positively related, the correlation coefficients were 0.417 and 0.372. The number of florets and pods was positively related, the correlation coefficient was 0.516. The length of lateral brangches and pods number was positive related, the correlation coefficient was 0.596. There is the lowest correlation about the seeds number per pod and seed yield.2. The seed yield and 100-pod weight of 38 M. truncatula germplasm were analysed by cluster method, at an average of between-class distance of 10.0, M. truncatula germplasm can be divided into 3 groups.3. Six major germplasm be divided into 4 types at 0.68 by 22 pairs of EST-SSR, 4 pairs of SSR and 4 pairs of SRAP primers. A17, J1.12 and WM51 were clustered into the same category, similarity coefficient is 0.40, their genetic relationship is closer. The seed yield of Caliph was lowest, and relationship with other materials away.4. 52 EST-SSR markers from 133 pairs of EST-SSR primers were analysed. The linkage map was obtained with 29 markers. The length of gene coveraged was 493.2cM in this linkage map, the average genetic distance is 14.3cM between markers. Markers are largest in LG3, including 8 EST-SSR markers.5. The traits of P1, P2 and RILs populations from A17×A20 of M. truncatula were analysed by major genes + polygene segregation analysis method. The results showed that the optimal model of the length of lateral branches was 2 pairs of dominant-epistatic effect major genes plus polygenes model. Florets number genetic model was 2 pairs of dominant epistatic effect major genes plus polygenes model. Pods number of genetic model was 3 pairs of additive-epistatic effect major gene model.100-pod weight genetic model was 2 pairs of dominant epistatic effect main gene model and 2 pairs of recessive epistatic effect major gene model.1000-seed weight of the genetic model was 2 pairs of additive effect major genes model. Seed yield optimal model was 2 pairs of additive-epistatic major gene model.6. 100-pod weight and 1000-seed weight were QTLs analysed by composite interval mapping. Two traits have been positioned on LG3, between mt67～mt59 primers. LOD value of 100-pod weight is 3.51, LR value corresponding is 16.18, additive effect value is -2.28, the contribution rate is 23.23%. LOD value of 1000-seed weight is 3.33, LR value corresponding is 15.34, additive effect value is 0.33, the contribution rate is 22.72%. |
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