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Professional and scientific networks built around the production of sweet cherry (Prunus avium L.) led to the collection of phenology data for a wide range of cultivars grown in experimental sites characterized by highly contrasted climatic conditions. We present a dataset of flowering and maturity dates, recorded each year for one tree when available, or the average of several trees for each cultivar, over a period of 37 years (1978–2015). Such a dataset is extremely valuable for characterizing the phenological response to climate change, and the plasticity of the different cultivars’ behaviour under different environmental conditions. In addition, this dataset will support the development of predictive models for sweet cherry phenology exploitable at the continental scale, and will help anticipate breeding strategies in order to maintain and improve sweet cherry production in Europe.

The research conducted in the present doctoral dissertation looks at the reproduction and main pomological characteristics of the introduced sweet cherry cultivars ‘Karina’, ‘Kordia’, ‘Regina’ and ‘Summit’, grown in agro-environmental conditions of Cacak. The investigations included determining suitable pollenizers for each of the cultivars studied. The analysis of characteristics of pollen tubes growth and fruit setting in 20 combinations of cross-pollination, open pollination and selfpollination was done to investigate the reproduction properties of cultivars serving both as pollenizers and pollen recipients. Quantitative indicators of in vivo pollen tubes growth (number and growth dynamics) and ovule vitality by means of fluorescent microscopy were examined in the study. Morphometric properties of pollen grains were examined using scanning electron microscopy. Characteristics of flowering phenophase and ripening, in vitro pollen germination, morphometric properties and biochemical composition of the fruit, organoleptical assessment of fresh fruits and yield of the cultivars studied were determined using methods considered as standard for this type of investigation. The investigations confirmed that high temperatures had positive effect on some pollenizers (‘Summit’, ‘Regina’), while in some (‘Kordia’, ‘Karina’) high air temperatures produced an adverse effect on number of pollen tubes in the style. Correlation between dynamics of pollen tubes growth and sporophyte of pollen recipient is primarily associated with viability of primary ovules. Tendency to rapid loss of vitality of ovules was most prominent in ‘Kordia’, and least pronounced in ‘Regina’. High temperatures during flowering and flower emasculation had an adverse effect on ovule vitality, while pollination influenced it positively. The correlation between fluorescence of ovules and unusual behaviour of pollen tubes in obturator zone was positive. Fruit setting was positive influenced by styles with pollen tubes terminating their growth in the nucelus on the tenth day after pollination. The influence of fluorescence of ovules and the unusual behaviour of pollen tubes growth were negative. Cultivars with better adaptability to high temperatures during flowering with regard to their effectiveness as pollenizers also showed better adaptability in respect of ovule vitality. ‘Kordia’ has showed better adaptability to somewhat colder climate. The remaining three cultivars studied cannot be recommended as pollenizers for ‘Kordia’ because of inappropriate overlap during flowering and non-lasting viability of its ovules. ‘Kordia’ and ‘Summit’ showed the best performance in terms of pollination efficacy for ‘Karina’. ‘Karina’ and ‘Kordia’ are suitable pollenizers for ‘Summit’, whereas ‘Summit’ and ‘Karina’ can be recommended as pollenizers for ‘Regina’. The cultivars studied ripen in the IV (‘Summit’), V (‘Kordia’ and ‘Karina’) and VI (‘Regina’) week of sweet cherry ripening season. Fruits of ‘Summit’ are very large, whereas those of ‘Karina’, ‘Regina’ and ‘Summit’…

In vitro pollen germination on agarose-sucrose medium, and pollen grain morphology by scanning electron microscopy, were investigated in four sweet cherry (Prunus avium L.) cultivars ('Karina', 'Kordia', 'Regina' and 'Summit'). The highest percentage of in vitro pollen germination over a three-year period was observed in 'Regina' (46.60 +/- 3.58%), and the lowest in 'Kordia' (26.68 +/- 1.59%). The results suggested a major influence of cultivars specificities which induced the different response to experimental conditions among years. The differences in morphological characters of pollen grains - size and shape (length, width and length/width - L/W ratio), germinal furrows (number and shape, length, width, distance between furrows) and exine ornamentation (the number of ridges in 100 mu m(2) of exine, ridges and stria width) were significant enough to separate and identify the investigated cultivars. When all parameters were considered together, the pollen of each cultivar exhibited a unique pattern. The results also suggested a relationship between pollen grains properties and origin of the studied sweet cherry cultivars. The most significant differences were observed among 'Summit' (North American cultivar) and the other three European cultivars investigated. The highest similarity in pollen grain characteristics was observed between 'Karina' and 'Regina', originating from the same parental combination.