When exotic poplars and native Populus balsamifera L. meet on the Canadian Prairies: Spontaneous hybridization and establishment of interspecific hybrids.

Tue, 25 Sep 2012

As the interest in plantations of fast-growing tree species increases, concerns regarding the possibility of gene flow between plantations of exotic trees and their wild relatives are being raised. In Canada, the Prairie ecozone provides a unique opportunity to examine spontaneous hybridization and the spread of exotic genetic material because of the historical introduction of large numbers of exotic poplar species and their hybrids. In this region, poplar shelterbelts bearing exotic components such as Populus laurifolia Ledeb. and Populus nigra L. have been in contact with the native populations of Populus balsamifera L. since the 19th century. Given the ability for poplar species to hybridize, the objective of this study was to estimate the rates of spontaneous hybridization between one common poplar cultivar planted in shelterbelts, ♂‘Assiniboine’ (♀‘Walker’[♀Populus deltoides Marsh. x ♂(P. laurifolia x P. nigra)] x ♂P. deltoides), and its neighbouring native congener, ♀P. balsamifera, on two study sites. To distinguish the genetic contributions of the species under study, a set of 26 diagnostic single nucleotide polymorphisms (SNPs) representative of 23 genes was used. We genotyped 2116 seeds sampled from P. balsamifera and identified paternal alleles specific to P. laurifolia, P. nigra and P. deltoides, which are typical genetic components of poplar shelterbelts. Surprisingly, the highest hybridization rate (2.3%) was observed at the site where 100-year-old Russian poplar shelterbelts (P. laurifolia x P. nigra) were found. A preliminary study of the P. balsamifera stands established in an 8 km radius around the study site confirmed introgression of P. laurifolia and P. nigra alleles at a rate of 4.6%. These results indicate that spontaneous hybridization between shelterbelts of exotic cultivars and native P. balsamifera does occur in the Canadian Prairies and that interspecific hybrids can establish and survive in this landscape. This study suggests that biological factors such as the genetic composition of the native population and the gender of the exotic cultivars should be taken into consideration in the management strategies of this ecozone.

An efficient single nucleotide polymorphism assay to diagnose the genomic identity of poplar species and hybrids on the Canadian prairies.

Wed, 04 May 2011

Hybridization frequently occurs among poplars, both naturally and artificially, hindering identification. Over 32 million clonal poplars, predominantly hybrids, have been planted throughout the Canadian prairies over the past century, making confirmation of genomic identity important. We developed a genotyping assay that rapidly diagnoses four compatible Populus species (Populus balsamifera L. and Populus deltoides Bartr. ex Marsh.: indigenous, Populus laurifolia Ledeb. and Populus nigra L.: exotics) and their hybrids found throughout this ecozone. First, we sequenced 23 genes from representative provenances of the four Populus species to discover single nucleotide polymorphisms (SNPs). Second, we developed and validated a medium-throughput genotyping assay of 26 diagnostic SNPs within these genes. We used this assay to genotype 198 trees from natural populations as well as 30 clones (pure species and hybrids), including those broadly distributed by Agriculture and Agri-Food Canada’s Agroforestry Development Centre since 1910. This suite of SNPs has the resolving power to correctly identify pure species and hybrids of Populus. We confirmed the identity of clones of welldocumented origin, complex hybrids with exotic components, and paternity of open-pollinated progenies from breeding programs. This diagnostic tool should prove useful for efficient molecular fingerprinting of breeding material and for further studies of interspecific gene flow on the Canadian prairies.

Publications by P. Talbot

When exotic poplars and native Populus balsamifera L. meet on the Canadian Prairies: Spontaneous hybridization and establishment of interspecific hybrids.

An efficient single nucleotide polymorphism assay to diagnose the genomic identity of poplar species and hybrids on the Canadian prairies.