Abstract:

SSR markers were used to characterize the genetic variance and relationships among 264 elite genotypes of Japanese Larch (Larix kaempferi), selected from the first-generation trials, which will be used as materials for second-generation breeding. A total 1 620 expressed sequence tags (ESTs) from larch were collected to develop simple sequence repeats (SSRs) by data mining. Totally 58 contigs with 67 SSRs were identified from all these contigs, and accounted for 3.58% of the total number of ESTs. Seven polymorphic simple sequence repeat (SSR) markers were developed and characterized; five of the loci had the advantage of high cross-species transferability to other larch species that naturally occur in China. These polymorphic and cross-taxon markers should be valuable for genetic studies on Larix. Six of these EST-SSR markers and four gSSR markers were used to detect genetic diversity of the elite population selected from the northern subtropical region. The average number of alleles and effective alleles per locus was 4.6 and 3.1, respectively. The means of expected and observed heterozygosities were 0.590 2 and 0.570 2, respectively. The genetic similarity coefficients between all elite tree individuals ranged from 0.172 5 to 0.966 7; Nei's gene diversity and Shannon's information index for this population were 0.569 1 and 1.096 6, respectively. The research suggests that these elite trees have good potential to establish second-generation breeding population with high genetic diversity.

Key words: Larix kaempferi, SSR, EST-SSR, second cycle elite population, genetic diversity