Development of EST-SSR marker and genetic diversity analysis of Korla Fragrant Pear

The SSR primers were developed by reference to the public 2 398 strips of EST sequence in pear， and by analyzing their distribution and characteristics of SSR markers，then the suitable primers specific to Kuerle Pear were sorted out，to clarify the genetic diversity of 18 pear trees which showed great variation in damage level by disoperation of Euzophera pyriella. The results showed that there were 1 813 strips of the non-redundant sequence in total of 2 398 EST sequence，of which 141 strips contained 162 SSR，amounting to 7.78% of the whole EST sequence. Their appearance rate was 8.94%，and the average distribution distance was 4.93 kb which showed extensively difference among microsatellite sequences（from 9.51 to 79.87 kb）. The most common sequence was the dinucleotide repeat，which accounted for 51.85% of the whole. Choosing 41 pairs from the devised 123 pairs of primers to conduct primer screening，it was found that there were 111 strips of sequence with polymorphism bands，among which 17 strips showed favorable amplifying results and polymorphism. The allele Na was 5.53， and the number of valid allele gene Ne was 3.74，the H value of Nei’sgene diversity（H）was 0.69，and I value of Shannon’s information index（I）was 40. The individuals suffering serious damage were concentrated on the branch of 0.78 in the cluster of UPGMA.