Development, Chromosome Location And Genetic Mapping Of EST-SSRs In Wheat

EST-SSR is a new type of molecular marker developed from the databank of sequence of expression sequence tags (EST) and/or cDNAs. As a new kind of molecular marker, EST-SSR markers have more advantages than the traditional genomic-derived SSRs because they are part of expressed genes. Therefore, EST-SSRs might be involved in gene functioning directly or indirectly. The ability of SSR markers will be greatly enhanced. In this study, we design primer pairs based on the searching the EST database of NCBI. And we locate these EST-SSRs on specific chromosome utilizing Chinese Spring Nulli-tetrasome. Then we map these EST-SSR markers on the genetic linkage map using a recombinant inbred population of wheat, RIL-8. Using BLAST, partial EST sequences will be related to specific biological functions. The main results are as follows: 1. From 151695 ESTs of Triticum aesticum (2003.7.14-2004.8.24), we have identified 2038 ESTs containing perfect simple sequence repeats (EST-SSR) of di-, tri-, tetra-or pentanucleotides (1.34%). The frequency of EST-SSRs was one in 57.44kb kb in wheat. The most abundant SSR types are Trinucleotide 1042(51.13%) and dinucleotide 417(20.46%) repeats .Among dinucleotide repeat, the motifs of AG, GA, CT and TC occur more frequently. The most abundant motif of Trinucleotide repeats is CAA.The frequency of CCG, CGG, CGC is also higher than others. 2. 249 EST-SSR primer pairs were designed for wheat based on the searching results.Through PCR amplifications and silver detection, 166 primer pairs had successful and distinctive bands in different varieties of cultivar wheat. These EST-SSR markers can as a new molecular marker of wheat and related species. 3. Chromosome location of EST-SSRs is a foundational work of the utilization of the makers. Using Chinese Spring Nulli-tetrasome, 93 EST-SSR primer pairs and 193 EST-SSR loci of 166 primer pairs were...