Olive (Olea europaea L.) is one of the oldest agricultural tree crops worldwide and is an important source of oil with beneficial properties for human health. This emblematic tree crop of the Mediterranean Basin, which has conserved a very wide germplasm estimated in more than 1,200 cultivars, is a diploid species (2n = 2x = 46) that is present in two forms, namely wild (Olea europaea subsp. europaea var. sylvestris) and cultivated (Olea europaea subsp. europaea var. europaea). In spite of its economic and nutritional importance, there are few data about the genetic of olive if compared with other fruit crops. Available molecular data are especially related to the application of molecular markers to the analysis of genetic variability in Olea europaea complex and to develop efficient molecular tools for the olive oil origin traceability. With regard to genomic research, in the last years efforts are made for the identification of expressed sequence tag, with particular interest in those sequences expressed during fruit development and in pollen allergens. Very recently the sequencing of chloroplast genome provided new information on the olive nucleotide sequence, opening the olive genomic era. In this article, we provide an overview of the most relevant results in olive molecular studies. A particular attention was given to DNA markers and their application that constitute the most part of published researches. The first important results in genome analysis were reported.

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Zinc (Zn) is an essential element for plant growth and development, but at high levels this metal can become toxic. Hyperaccumulator species are often not suitable for phytoremediation technologies because they need to be fast growing and have high biomass production, such as those of the Populus genus. Comparative genomics studies of poplars subjected to stress conditions such as heavy metal contamination have generated resources useful for improving the annotation of genes and have provided novel insights in the defense/tolerance mechanisms governing adaptation in non-hyperaccumulator plants. Using a microarray-based comparative analysis, we identified functional gene sets that are differentially regulated in the leaves of Populus × euramericana clone I-214 subjected to an excess but sub-lethal dose of Zn (1 mM). Eco-physiological and chemical analyses confirmed the results obtained in previous similar experiments. A total of 3861 expressed sequence tags (ESTs) were differentially expressed and grouped into two distinct libraries of up-regulated (40%) and down-regulated (60%) putative genes. The annotation of genes and gene products according to the Gene Ontology vocabularies was performed using Blast2GO software. The two transcriptome data sets were used to query all known Kyoto Encyclopedia of Genes and Genomes (KEGG) biosynthetic pathways of the genes identified in this study. The most represented molecular functions and biological processes were nucleotide binding and transcription, transport and response to stress and abiotic and biotic stimuli. The chloroplast, mitochondrion and their membrane systems were the cellular components most affected by excess Zn, as well as the photosynthetic, defense, sulfur and glutathione (GSH) metabolic pathways. The most up-regulated genes encoded electron carriers associated with ferrodoxin, the small subunit of ribulose-bisphosphate carboxylase oxygenase, and enzymes involved in GSH metabolism. This study is the most in-depth transcriptome and gene-annotation analysis of a hybrid poplar to date. The results are presented and critically discussed in terms of poplar response/tolerance to Zn stress for the characterization of non-hyperaccumulator phenotypes and the identification of candidate genes in perennial plants. These genetic findings provide useful information on tree species' adaptation to metal stress and provide powerful tools for the selection and/or genetic manipulation of stress-tolerant poplar clones.

Summary• Transformed aubergine plants constitutively expressing the Dm-AMP1 antimicrobial defensin (from Dahlia merckii ) were generated and characterized.• Transgenic plants were selected on kanamycin and screened by polymerase chain reaction analysis. The expression of Dm-AMP1 in plant tissues and its release in root exudates were detected by Western blot analyses. Dm-AMP1 localization was performed by immunohistochemical experiments.• Dm-AMP1 expression ranged from 0.2% to 0.48% of total soluble proteins in primary transformants and from 0.16% to 0.66% in F 2 plants. Transformed clones showed resistance to the pathogenic fungus Botrytis cinerea , whose development on leaves was reduced by 36-100%, with respect to controls. The protein was released in root exudates of the transformed plants and was active in reducing the growth of the co-cultured pathogenic fungus Verticillium albo-atrum , whereas it did not interfere with recognition responses and symbiosis establishment by the arbuscular mycorrhizal fungus Glomus mosseae .• Dm-AMP1 transformants may represent a useful model to study the interactions between genetically modified plants and pathogenic fungi or beneficial nontarget microorganisms.

In vitro culture of rooted and unrooted olive microshoots, established from seed lines of free-pollinated ''Frantoio'' and ''Moraiolo'' cultivars, were evaluated for NaCl tolerance. The aim was to use growth and physiological parameters in order to identify salt-adapted genotypes. Leaf tissue elemental distribution of Na, Cl and K was also investigated in unrooted plantlets by cryo-scanning electron microscopy and energy-dispersive X-ray microanalysis. Both in unrooted and rooted plantlets, increased concentrations of NaCl reduced shoot growth, whereas plant survival was not affected. However, no significant interactions between line and NaCl concentration were found. Elemental distribution showed that Moraiolo J and Frantoio Z accumulated more Na and Cl inside leaves, and that these elements followed a tissue-dependent pattern. Rooting capacity was reduced at the higher levels of NaCl. Significant interactions between seed line and salt treatment were found. Seed lines showed different abilities to develop roots at different salt levels. In particular, Frantoio Z showed a significant and different behaviour relative to the other seed lines at 50 mM NaCl with regard to both length and dry weight of roots. The results obtained suggest that rooting parameters are the most useful tools in the evaluation and screening of salt-tolerant olive genotypes through in vitro shoot culture.