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Quercus suber L. is a Mediterranean forest species with ecological, social and economic value. Clonal propagation of Q. suber elite trees has been successfully obtained from in vitro-derived somatic and gametic embryos. These clonal lines play a main role in breeding and genetic studies of Q. suber. To aid in unravelling diverse genetic and biological unknowns, a proteomic approach is proposed. The proteomic analysis of Q. suber somatic and gametic in vitro culture-derived embryos, based on DIGE and MALDI-MS, has produced for the first time proteomic data on this species. Seventeen differentially expressed proteins have been identified which display significantly altered levels between gametic and somatic embryos. These proteins are involved in a variety of cellular processes, most of which had been neither previously associated with embryo development nor identified in the genus Quercus. Some of these proteins are involved in stress and pollen development and others play a role in the metabolism of tannins and phenylpropanoids, which represent two of the major pathways for the synthesis of cork chemical components. Furthermore, the augmented expression levels found for specific proteins are probably related to the homozygous state of a doubled-haploid sample. Proteins involved in synthesis of cork components can be detected at such early stages of development, showing the potential of the method to be useful in searching for biomarkers related to cork quality.

O. 1997. Stress-indueed formation of haploid plants through anther culture in eoik oak (Quercus suber). -Physiol. Plam. 99: 335-341.Induetion of haploid embryos and regeneration of plantlets have been obtained, for the first time, in cork oak (Quercus suber L.) by combining a starvation treatment in anther culture with a mild heat shock at 33°C for 5 days, followed by eulture at 25°C in a simple agar medium without growth regulators. The same conditions had been shown previously to be optimal for embryogenic induction in isolated microspore cultures of' several model species such as tobacco and wheat. These results support the notion that stress, particularly sucrose starvation, a heat shock or a combination of both treatments could be the major and general signal responsible for the inhibition of normal gametophytie development of the mierospores and for the induetion of the alternative embryogenic pathway. A similar approach may be used for the production of haploid and doubled haploids for plant breeding in other species that, like most forest trees, are still recalcitrant in anther culture. lntrod cfadays doubled haploid formation through anther culture is a well established technique, used for the production The potential of mierospores and immature pollen grains of bomozygous lines in many crops (Heberle-Bors et al. to deviate from their normal gametophytic developmen-1996, Morrison and Evans 1988, and references therein), tal pathway, giving rise to haploid plants via embryogen-research in this field has proceeded mostly on a trialesis, has been known for more than 30 years since the and-error basis and until now it has not been possible to original experiments of Guha and Maheshwari (1964, establish a protocol for haploid formation generally ap-1966) who observed the formation of embryos of pollen plicable to different species. A bewildering multitude of origin in anther cultures of Datura innoxia. Due to the treatments and conditions appears to be required for the importance of doubled haploid plants (produced sponta-induction of embryogenesis, depending on the particular neously or by colchicine treatment of the haploids) for experimental system used, and many species or specific plant breeding, much effort has been invested to produce genotypes within a species are still recalcitrant. Howpollen-derived plants from other species. Although now-ever, it seems logical to assume the existence of general.

Cork oak (Quercus suber L.) zygotic embryos, endosperm and ovules were treated with different concentrations of 2,4‐D for induction of somatic embryos. Plant material was collected during the embryo development season, from June to September. Immature embryos proved to be the most reactive initial explant. Callus and somatic embryos developed a few weeks after the beginning of the 2,4‐D treatment. For embryo development experiments, different growth regulators and cold and desiccation treatments were tested. Cold storage of somatic embryos matured in vitro at 5°C was the best treatment for breaking dormancy.

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