Abstract:

Species-specific simple sequence repeat (SSR) markers are desirable for genetic studies and to harness the potential of MAS-based breeding for genetic improvement of wood fiber traits in trees. In this study, we report that a set of new polymorphic nuclear SSR markers were developed and characterized in Populus tomentosa by means of direct sequencing of functional genes involved in wood formation. A total of 20 polymorphic SSR loci were identified within 16 genes from 40 unrelated individuals in P. tomentosa. The SSR types of di-, tri-, penta-, hexa-, and hepta- nucleotide repeats and motifs repeats varied from 2 to 34 were displayed, with dinucleotide SSRs being the most frequent, accounting for 55.0% of the total loci in the natural population of P. tomentosa. Twenty primer pairs for PCR amplification SSR loci were designed based on the conservative flanking sequences of SSR loci. The efficiency and conservation of SSR loci were tested among 15 individuals under genus Populus. The PCR amplification exhibited an average of 90.0% conservation in at least two groups under genus Populus, and the number of alleles produced ranged from 3 to 9, with an average of 5.3 alleles per locus. Furthermore, the SSR loci were non-randomly distributed within different regions of functional genes. The gene-based SSR markers developed here would provide a powerful tool for MAS breeding of new germplasms with desirable wood fiber traits in P.tomentosa, and have theoretical and practical significance in tree breeding.

Key words: Populus tomentosa, wood formation, gene-based SSR marker