Development Of EST-SSR And Their Application In Jackfruit And Construction Of Genetic Maps

For the present number of available molecular markers which can be used in the genetic research of jackfruit is very limited, and the progress of genetic linkage map construction is very slowly. In order to improve the efficiency of jackfruit molecular marker assisted breeding, and promote genetic improvement of jackfruit germplasm, this study will be the first to attempt to develop EST-SSR markers derived from jackfruit and analyze the stability and the ability of revealing polymorphisms,then research genetic diversity of jackfruit germplasm and construct genetic linkage map. The main findings are as follows:(1) Totally, 479 pairs of EST-SSR primers were designed in this paper, and 379 pairs of which could amplify products in jackfruit DNA, and 282 pairs were polymorphic bands,accounting for 58.87%.(2) Then 60 pairs of polymorphic primers were selected to analysis genetic diversity among 64 jackfruit germplasm. Sixty pairs of EST-SSR primers produced 188 bands, and the amplified bands per pair of primers ranged from 2 to 11 with an average of 3.20,showing a polymorphic rate of 89.36%. Polymorphic information content(PIC) of each pair primers was 0.4077- 0.9589 with an average PIC of 0.7922, indicating that the EST-SSR markers had a higher ability of revealing polymorphisms.(3) Cluster analysis showed that 64 jackfruit germplasms were clustered into two groups at the similarity coefficient of 0.6881, the larger group were then divided into four subgroups at the similarity coefficient of 0.7325, which still could not be divided the accessions of soft flesh type and firm flesh type into independent classification.(4) F1 mapping population was built by hybrid of two jackfruilt parents which contained 101 individuals. The results of screening primer polymorphism showed that 93 polymorphic EST-SSR markers were get, accounting for 23.31%. F1 mapping population for genotyping, two linkage genetic maps were constructed by JoinMap4.1 software via two method named "one-step" and "two-step" mapping. The "one-step" map contained67 markers and was distributed in 22 linkage groups, covering a total genetic distance of2232.8cM, linkage group length ranged in 4.2 ~ 390.3cM, with an average interval of33.33cM; while "two-step" pattern contains 59 markers, distributed in 19 linkage groups,(5) covering a total genetic distance 1161.2cM, linkage group length in the range of4.2 ~ 172.6cM with an average interval of 19.68 cM.