EST-SSR Genetic Diversity and Population Structure of Tea Landraces and Developed Cultivars (Lines) in Zhejiang Province, China

Abstract

Tea (Camellia sinensis (L.) O. Kuntze) has a long history in production and consumption in Zhejiang province, China. Improvement of tea variety, therefore, is of great importance and a good understanding of the genetic diversity and population structure of tea germplasm is a prerequisite to the improvement. In spite of great advances on the use of molecular markers in tea plant, achievement is still gotton very slowly compared with in other cereal crops and woody species. Expressed sequence tag derived simple sequence repeat (EST-SSR) is a less costly alternative way of developing new markers for genetic diversity analy- sis, functional markers development, and marker-assisted breeding of tea plant. A total of 4 833 ESTs generated from a cDNA library of tea young root were subjected to SSR mining using DNAstar 5.0 software, 577 EST-SSRs were identified and 416 primer pairs were designed by Primer premier 5.0. After the determination of annealing temperatures and polymorphism of all the primers, 64 core primers were selected and used for genetic diversity and population structure analyses of tea landraces and im- proved cultivars in Zhejiang province. All selected primers were polymorphic and 232 alleles were amplified with 3.6 alleles per primer pair on an average. Each primer pair identified 2 to 13 genotypes, with an average of 4.3. The mean of polymorphism in- formation content (PIC) was 0.44, ranging from 0.02 to 0.84. Observed heterozygosity (Ho) was 0.44, while expected heterozy- gosity (He) was 0.48. The level of genetic diversity among landraces was slightly higher than that among improved cultivars and breeding lines. There were 226 alleles amplified in 22 landraces with 14 of them that were special. In the thirty-seven improved cultivars, however, two hundred and eighteen alleles were amplified but only six were special. The PIC of the landrace groups