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14In recent years a growing interest to widen the cherry (Prunus avium L.) 15 production calendar results in cultivation out of the traditional cultivation areas. Since 16 cherry has high chilling requirements, this often causes erratic cropping related to 17 phenological alterations. However, appropriate phenological characterisation and 18comparison is hampered, due to the lack of a consensus phenological scale for this 19 species. In this work we have characterised flower development in sweet cherry, 20 framing it in the BBCH scale. For this purpose, the phenology of two cherry cultivars 21 has been characterized over two consecutive years and adapted to the BBCH code, and 22 flower development has been framed within the principal growth stages of this code. 23This provides a unified standardised approach for phenological comparative studies. 24 25

Dormancy appears to mark a boundary between the development of the sporogenous tissue and the occurrence of meiosis for further microspore development. Breaking of dormancy occurs following a clear sequence of events, providing a developmental context in which to study winter dormancy and to evaluate differences in chilling requirements among genotypes.

Most Japanese plum-type cultivars are self-incompatible and cross pollination is necessary to ensure fruit set. In this study, the S-RNase genotype and the incompatibility group of 68 Japanese plum-type cultivars were determined by PCR amplification of the S-RNase gene. The S-RNase genotype of 50 cultivars is first reported here and five new Japanese plum S-RNase alleles (So, Sp, Sq, Sr, Ss) were identified. The results obtained, together with information compiled from previous studies, allowed describing 12 new incompatibility groups (VIII-XIX). The self-incompatibility of several cultivars and the crosscompatibility among different incompatibility groups were verified by self-and cross-pollination experiments followed by observation of pollen tube growth. Five cultivars behaved as self-compatible, but two of them do not have the Se allele, which has been correlated with selfcompatibility. Thus, additional sources of self-compatibility different from Se appear to be involved in Japanese plum self-compatibility.

In many plant species with multiovulate ovaries, a considerable reduction in the number of ovules takes place. However, the underlying physiological causes are not clear. In Prunus spp., although flowers present two ovules, usually only one seed is produced. We have followed the development and degeneration of the two ovules in apricot (Prunus armeniaca L.) and examined the extent to which carbohydrates within the ovule might be involved in determining the fate of the ovule. While the primary ovule grows in the days following anthesis, growth of the secondary ovule is arrested. Starch distribution along the different ovular tissues exhibits several changes that are different in the two ovules. Primary ovule growth is inversely related to starch content and this growth takes place independently of pollination since it occurs in the same way in pollinated and unpollinated flowers. In the secondary ovule, starch disappears simultaneously from all ovular structures and callose is layered at the chalazal end of the nucellus. The size of the secondary ovule does not change significantly from anthesis to degeneration, and callose starts to accumulate 5 days after anthesis. Likewise, this process occurs independently of pollination. These results are discussed in terms of the implications of the starch content of ovules in fertilization success and ovule fate.& k w d : Key words Apricot · Ovule abortion · Ovule development · Starch · Prunus armeniaca& b d y :

Stone fruit trees of genus Prunus, like other temperate woody species, need to accumulate a cultivar-specific amount of chilling during endodormancy, and of heat during ecodormancy to flower properly in spring. Knowing the requirements of a cultivar can be critical in determining if it can be adapted to a particular area. Growers can use this information to anticipate the future performance of their orchards and the adaptation of new cultivars to their region. In this work, the available information on chilling-and heat-requirements of almond, apricot, plum, peach, and sweet cherry cultivars is reviewed. We pay special attention to the method used for the determination of breaking dormancy, the method used to quantify chilling and heat temperatures, and the place where experiments were conducted. The results reveal different gaps in the information available, both in the lack of information of cultivars with unknown requirements and in the methodologies used. The main emerging challenges are the standardization of the conditions of each methodology and the search for biological markers for dormancy. These will help to deal with the growing number of new cultivars and the reduction of winter cold in many areas due to global warming.Agronomy 2020, 10, 409 2 of 32 (2.4 million t in 0.4 million ha), almond (2.2 million t in 1.9 million ha) and sour cherry (1.2 million t in 0.2 million ha) [2].Stone fruit trees, like other temperate woody species, need to accumulate a cultivar-specific amount of chilling during winter to overcome dormancy and then experience warm temperatures to finally flower in spring [3][4][5]. These conditions the adaptation of species and cultivars to each region [6] and it is the main drawback for their extension to warmer latitudes [7]. Knowing the temperature requirements of a cultivar can be useful for growers to anticipate the future performance of their orchards and to design new orchards taking into account the predicted global warming [7][8][9]. In this work, the available information on chilling-and heat-requirements of cultivars of the most cultivated stone fruit crops (almond, apricot, peach, plum and cherry) is reviewed, paying special attention to the approach used for the determination of breaking dormancy, the method used to quantify chilling and heat temperatures, and the place where the experiments were conducted. There is extensive information available about chilling and heat requirements that has purposefully been omitted from this review. We have only included those studies that a) obtained results by using an experimental methodology (i.e., transferring shoots into a growth chamber sequentially during winter) or computational/statistical approaches that relate flowering dates to temperature data over a sufficiently long time series, and b) quantified chilling and heat temperatures using the common models (Chilling Hours model, Utah model or Dynamic model for chilling requirements, Growing Degree Hours for heat requirements). Dormancy: Definition and DescriptionStone fruit tr...

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