To evaluate the phytoremediation capability of some poplar and willow clones a hydroponic screening for cadmium tolerance, accumulation and translocation was performed. Rooted cuttings were exposed for 3 weeks to 50 μM cadmium sulphate in a growth chamber and morpho-physiological parameters and cadmium content distribution in various parts of the plant were evaluated. Total leaf area and root characteristics in clones and species were affected by cadmium treatment in different ways. Poplar clones showed a remarkable variability whereas willow clones were observed to be more homogeneous in cadmium accumulation and distribution. This behaviour was further confirmed by the calculation of the bio-concentration factor (BCF) and the translocation factor (Tf). Mean values of all the clones of the two Salicaceae species showed that willows had a far greater ability to tolerate cadmium than poplars, as indicated by the tolerance index (Ti), calculated on the dry weight of roots and shoots of plants. As far as the mean values of Tf was concerned, the capacity of willows to translocate was double that of poplars. On the contrary, the mean values of total BCF in poplar clones was far higher with respect to those in willows. The implications of these results in the selection of Salicaceae clones for phytoremediation purposes were discussed.

Black poplar (Populus nigra L.) is a tree of ecological and economic interest. A better knowledge of P. nigra genome is needed for an effective protection and use of its genetic resources. The main objective of this study is the construction of a highly informative genetic map of P. nigra species including genes of adaptive and economic interest. Two genotypes originated from contrasted natural Italian populations were crossed to generate a F 1 mapping pedigree of 165 individuals. Amplification fragment length polymorphism (AFLP), simple sequence repeat (SSR), and single nucleotide polymorphism (SNP) markers were used to genotype 92 F 1 individuals, and the pseudo-test-cross strategy was applied for linkage analysis. The female parent map included 368 markers (274 AFLPs, 91 SSRs, and 3 SNPs) and spanned 2,104 cM with 20 linkage groups, and the male parent map, including 317 markers (205 AFLPs, 106 SSRs, 5 SNPs, and sex trait), spanned 2,453 cM with 23 main linkage groups. The sex, as morphological trait, was mapped on the linkage group XIX of the male parent map. The generated maps are among the most informative in SSRs when compared to the Populus maps published so far and allow a complete alignment with the 19 haploid chromosomes of Populus sequence genome. These genetic maps provide informative tools for a better understanding of P. nigra genome structure and genetic improvement of this ecologically and economically important European tree species.

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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 nonterminal 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. Communicated by S. González-Martínez Isabella Paolucci and Muriel Gaudet contributed equally to this research. Electronic supplementary material The online version of this article (