Abstract:

【Objective】 Polyploid breeding is an important approach to generate elite varieties of forest trees. In this study, we assessed ploidy levels in germplasm collections of Populus deltoides Marsh. to identify candidate polyploids for breeding.【Method】 In total, 448 P. deltoides stands were examined with 9 SSR primer pairs, and the ploidy levels of these stands were assessed based on the number of alleles detected per locus. Subsequently, the polyploid candidates based on the preliminary identification results were examined by flow cytometry.【Result】 By SSR genotyping, 129 polymorphic bands were generated at 9 SSR loci, ranging from 5 (Ploidp-10) to 25 (Ploidp-07) alleles per locus, with a mean of 14.33. The polymorphic information content (PIC) of the 9 microsatellite markers ranged from 0.46 to 0.93, with an average value of 0.76. Among the 448 stands evaluated, no more than two alleles were amplified at each of the 9 microsatellite loci in 440 stands. However, for eight stands, three alleles were obtained at two of the microsatellite loci. In particular, for clones 1346, 16-42, 17-49 and 18-25, three alleles were obtained using the Ploidp-02 primer, and for clones 5-43, 5-45, 15-14 and 19-37, three alleles were obtained using the Ploidp-04 primer. An additional chromosomal segment was detected at the corresponding genetic loci in these eight stands. Therefore, these stands were candidate triploids. A flow cytometry analysis confirmed that clone 1346 was triploid and the remaining seven stands were suspected aneuploid candidates with additional local chromosome segments.【Conclusion】 The nine microsatellite markers employed in this study have high polymorphic information content and are suitable for screening polyploid candidates fromP. deltoides germplasms, and, combined with flow cytometry, we can rapidly identify polyploids from a large number of individuals.

Key words: Populus deltoides Marsh., microsatellite marker, flow cytometry, ploidy level, polyploid