Genetic linkage maps of Populus alba L. and comparative mapping analysis of sex determination across Populus species

White poplar (Populus alba L.) is native to Eurasia and is unexploited for its growth potential and stress-adaptive mechanisms. A better knowledge of its genome will allow for more effective protection and use of critical genetic resources. The main objective of this study was the construction of highly informative P. alba genetic maps. Two genotypes were selected from contrasting natural Italian populations and crossed to generate an F-1 mapping pedigree. Amplified fragment length polymorphism and simple sequence repeat markers were used to genotype 141 F-1 individuals. The pseudo-testcross strategy was applied for linkage analysis. The generated maps showed good overall colinearity to each other and allowed for a complete alignment with the 19 haploid chromosomes of the Populus genome sequence. The locus that determines sex as a morphological trait was positioned on a non-terminal position of LG XIX of the female parent map. Comparison among Populus species revealed differences in the location of the sex locus on LG XIX as well as inconsistencies in the heterogametic sex. The genetic analysis of the sex locus in P. alba provides insights into sex determination in the genus and is useful for the identification of sex-linked markers and the early assessment of plant gender. Furthermore, these genetic maps will greatly facilitate the study of the genomics of Populus and how it can be exploited in applied breeding programs.