Release of bud dormancy in perennial woody plants is a temperature-dependent process and thus flowering in these species is heavily affected by climate change. The lack of cold winters in temperate growing regions often results in reduced flowering and low fruit yields. This is likely to decrease the availability of fruits and nuts of the Prunus spp. in the near future. In order to maintain high yields, it is crucial to gain detailed knowledge on the molecular mechanisms controlling the release of bud dormancy. Here, we studied these mechanisms using sweet cherry (Prunus avium L.), a crop where the agrochemical hydrogen cyanamide (HC) is routinely used to compensate for the lack of cold winter temperatures and to induce flower opening. In this work, dormant flower buds were sprayed with hydrogen cyanamide followed by deep RNA sequencing, identifying three main expression patterns in response to HC. These transcript level results were validated by quantitative real time polymerase chain reaction and supported further by phytohormone profiling (ABA, SA, IAA, CK, ethylene, JA). Using these approaches, we identified the most up-regulated pathways: the cytokinin pathway, as well as the jasmonate and the hydrogen cyanide pathway. Our results strongly suggest an inductive effect of these metabolites in bud dormancy release and provide a stepping stone for the characterization of key genes in bud dormancy release.

This chapter focuses on the breeding of new sweet cherry cultivars. Information on the origin, parentage, tree growth, productivity, phenology, fruit characteristics and resistance to various biotic and abiotic factors of these sweet cherry cultivars are also presented.

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High CO is able to ameliorate some negative effects due to climate change and intensify others. This study involves the sweet cherry (Prunus avium) cultivar 'Burlat' grafted on the 'Mariana 2624', 'Adara' and 'LC 52' rootstocks. In a climate chamber at two CO concentrations, ambient (400 µmol mol ) and elevated (800 µmol mol ), the plants were submitted to waterlogging for 7 d, followed by 7 d of recovery after drainage. Waterlogging drastically decreased the rate of photosynthesis, significantly endangering plant survival, particularly for the 'LC 52' and 'Adara' rootstocks. 'Mariana 2624' was also clearly affected by waterlogging that increased lipid peroxidation and the Cl and SO concentrations in all the studied plants. Nevertheless, CO was able to overcome this reduction in photosynthesis, augmenting growth, increasing soluble sugars and starch, raising turgor and regulating the concentrations of Cl and SO , while lowering the NO concentration in leaves of all the studied rootstocks. In concordance with these results, the proline levels indicated a more intense stress at control CO than at high CO for waterlogged plants. 'Mariana 2624' was more resistant to waterlogging than 'Adara', and both were more resistant than 'LC 52' in control CO conditions; this clearly enhanced the chance of survival under hypoxia.

The characterization and evaluation of walnut (Juglans regia) germplasm constitute important aspects of taxonomic analysis and are valuable tools for breeding programs. In this work, a collection of 57 common walnut cultivars, mainly coming from Spain and the USA, has been studied with microsatellite markers. To carry out this work, 32 primer pairs flanking simple sequence repeats previously developed in Juglans nigra were screened to select the loci that presented high polymorphism and that were easier to score. The 19 selected microsatellite markers allowed the discrimination of the studied cultivars, with a total of 97 alleles detected and an average of 5 alleles per locus, confirming that these markers are more suitable tools for walnut identification than other molecular markers studied previously. The genetic similarity estimated from the molecular data clearly separated the Spanish walnuts from the Californian genotypes. Allelic data are presented for use as size standards to assist in correcting laboratory-tolaboratory variation of allele size calling. Some of them are compared with previous results published and the discrepancies found are discussed.Additional key words: cultivar discrimination; genetic relationships; molecular characterization; plant breeding; polymorphism. Resumen Identificación de cultivares de nogal (Juglans regia L.) y evaluación de su variabilidad genética mediante marcadores microsatélitesLa caracterización y la evaluación de germoplasma de nogal (Juglans regia) constituyen aspectos importantes del análisis taxonómico y son herramientas eficaces para los programas de mejora. En este trabajo se han estudiado 57 cultivares de nogal común, procedentes principalmente de España y EEUU, mediante marcadores microsatélite. Para llevar a cabo este trabajo se examinaron 32 pares de cebadores, desarrollados previamente en Juglans nigra, para seleccionar los loci que presentaran un polimorfismo elevado y que fueran fácil de detectar. Los 19 marcadores microsatélite seleccionados permitieron discriminar entre los cultivares estudiados, detectando un total de 97 alelos y una media de 5 alelos por locus, confirmando que este tipo de marcadores son más adecuados para la identificación de nogal que otros marcadores moleculares previamente estudiados. La similitud genética estimada a partir de los datos moleculares, permitió separar claramente los genotipos españoles de los californianos. Se presentan los datos aléli-cos para su uso como tamaños estándar de utilidad en la corrección de los tamaños alélicos encontrados entre laboratorios. Algunos de ellos son comparados con los resultados previos publicados, discutiéndose las discrepancias encontradas.