Development Of SSR Markers In Litchi Chinensis And Application For Analysis Of Genetic Diversity Within Litchi Varieties

As a native of Litchi chinensis, China is abundant in germplasm resources in the tropical and south sub-tropical zone. In Hainan province, Some big wild litchi trees and batches of wild litchi have been found in the tropical origenate forestry of Bawang, Wuzhi, Jianfeng, Diaoluo, and Jingu Mountains. In addition, there are 4,000hm2 of litchi seedlings scattered on Hainan island. They comprise a huge gene pool of litchi's germplasm resources,Which is both bases of seedling selection at present and source of genetic breeding in the future.As far as breeding of litchi, the methods of seedling selection and bud breeding are often used, but genetic breeding hasn't been done all the time. Because it is not clear for the genetic background of all litchi's germplasm resources we have owned. So it is necessary to look for a powerful genetic tool for analysis of germplasm in litchi so as to make full use of those precious deposits.Consequently, the development of SSR markers in litchi was conducted in order to offer a powerful and efficient testing means for studies of population genetic structure in litchi. Meanwhile, Those locus-specific SSR markers isolated and characterized by ourselves were used to analyze the genetic diversity within 37 litchi varieties and 2 longan ones.The major results are as follows:(1) This research successfully developed 22 SSR markers in litchi for the first time. 100 SSR sequences were isolated and cloned by adaptation of SAM techniques and another one was obtained by searching the NCBI and EMBL databases. There were 101 SSR sequences together used for design of special primers. As a result, they were designed at 82 loci from 71 fragments. 52 special primers were synthesized, pairing with 5'-anchored degenerate SSR primer, to detect41 SSR loci. 19 of them amplified the corresponding SSR sequences and Other 15 SSR primer pairs amplified non-expected fragments. In the end, 28 polymorphic primer pairs were selected from 34 primer pairs which amplified clear and robust DNA fragment and 22 locus-specific SSR markers were obtained. The efficiency of SSR marker development was 44% from sequencing data to operationally useful loci.(2) The use of 34 SSR primer pairs developed from litchi across two varieties of langan (Dimocarpus longan) was performed. 22 of them amplified SSRs at 26 loci within longan. The transferability was 64.7%. It showed that a large number of SSR primers from litchi had applicability to Longan.(3) 17 SSR primer pairs developed for litchi were used to analyze the genetic diversity within 37 litchi varieties and 2 longan varieties. Genetic similarity matrix was obtained. Similarity coefficient ranged from 0 to 1, with a mean value of 0.556. Of them, the similarity between sanyuehong and haiken!4, haikenll were smallest, while ones between baitangyin and haiken8 was biggest. In addtion, it was identified that chanchuhong and haikenl8 were the same variety.(4) 39 varieties were divided into 5 groups at Similarity coefficient being 0.556 by applying UPGMA for clustering analysis of them.(5) Genetic Similarity coefficient between seedless litchi A4 and An was 0.762 which was bigger than that of between the former and two heiye seedlings. It was considered that the effect of using Haiken 4 and Haiken 13 as seedling stock wound probably be better than that of using A13.