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 (

Abiotic stresses have considerable negative impact on Mediterranean plant ecosystems and better comprehension of the genetic control of response and adaptation of trees to global changes is urgently needed. The single cell gel electrophoresis (SCGE) assay could be considered a good estimator of DNA damage in an individual eukaryotic cell. This method has been mainly employed in animal tissues, because the plant cell wall represents an obstacle for the extraction of nuclei; moreover, in Mediterranean woody species, especially in the sclerophyll plants, this procedure can be quite difficult because of the presence of sclerenchyma and hardened cells. On the other hand, these plants represent an interesting material to be studied because of the ability of these plants to tolerate abiotic stress. For instance, holm oak (Quercus ilex L.) has been selected as the model plant to identify critical levels of O3 for Southern European forests. Consequently, a quantitative method for the evaluation of cell injury of leaf tissues of this species is required. Optimal conditions for high-yield nuclei isolation were obtained by using protoplast technology and a detailed description of the method is provided and discussed. White poplar (Populus alba L.) was used as an internal control for protoplast isolation. Such a method has not been previously reported in newly fully developed leaves of holm oak. This method combined with SCGE assay represents a new tool for testing the DNA integrity of leaf tissues in higher plants under stress conditions.

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Amplification products of these 13 loci were also generated for T. gallica. These new EST-SSR markers will be useful in genetic characterization of Tamarix, as additional tools for taxonomic clarification, and for studying invasive populations where they are a threat.

Both the negative and positive ecological impact of Tamarix plants is controversial, and thus a more comprehensive understanding is necessary. Tamarisks are invasive in many countries but the inter-specific transferability that characterizes simple sequence repeats (SSRs) could be harnessed to track the spread of specific genotypes or to study invasive populations. Thirteen polymorphic SSR markers, derived from expressed sequence tag (EST), were identified by first screening 26 samples of T. aphylla, T. jordanis, T. nilotica, and T. tetragyna and then 33 unidentified tamarisks from Yotvata, Israel. The mean number of alleles per locus ranged from two to 14 and the mean expected heterozygosity was 0.415. These EST-SSR markers will undoubtedly be useful in the genetic characterization of the genus Tamarix due to their high cross-species transferability which enables the estimation of the genetic diversity among and within different species, that are adapted to the same desert habitat under severe environmental constraints.