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We examine the current knowledge about the abscission of fleshy fruit, in particular with regards to the development and function of the abscission zone (AZ). While tomato is currently the main model species to elucidate the mechanisms of fleshy fruit abscission, most studies on tomato focus on the development and function of the pedicel AZ, which is involved in both flower and ripe fruit abscission. However, the localization of the AZ within the pedicel is not the most common location of the AZ for fleshy fruit. Fleshy fruit can have one or more AZ, which can be found in different locations within the inflorescence and fruiting structure and fulfil different functions. In fact, most of the fleshy fruit species examined thus far have more than one AZ, which can be found at the boundary between the fruit and pedicel (often referred to as the calyx AZ), within the pedicel as with tomato, at the juncture of the pedicel and peduncle or at the juncture between peduncle and shoot/branch. In addition, the different AZs may be activated or function at different stages of development, under different environmental conditions, or have a completely different purpose, such as the abscission of fruitlets or mature fruit. Together, our current knowledge about AZs suggests that while there are similarities between different AZs in different locations or from different species, not all AZs are created equal, which may be reflected in the underlying molecular mechanisms that control their development and function.

Background The outer cell wall of the pollen grain (exine) is an extremely resistant structure containing sporopollenin, a mixed polymer made up of fatty acids and phenolic compounds. The synthesis of sporopollenin in the tapetal cells and its proper deposition on the pollen surface are essential for the development of viable pollen. The beginning of microsporogenesis and pollen maturation in perennial plants from temperate climates, such as peach, is conditioned by the duration of flower bud dormancy. In order to identify putative genes involved in these processes, we analyzed the results of previous genomic experiments studying the dormancy-dependent gene expression in different peach cultivars. Results The expression of 50 genes induced in flower buds after the endodormancy period (flower-bud late genes) was compared in ten cultivars of peach with different dormancy behaviour. We found two co-expression clusters enriched in putative orthologs of sporopollenin synthesis and deposition factors in Arabidopsis. Flower-bud late genes were transiently expressed in anthers coincidently with microsporogenesis and pollen maturation processes. We postulated the participation of some flower-bud late genes in the sporopollenin synthesis pathway and the transcriptional regulation of late anther development in peach. Conclusions Peach and the model plant Arabidopsis thaliana show multiple elements in common within the essential sporopollenin synthesis pathway and gene expression regulatory mechanisms affecting anther development. The transcriptomic analysis of dormancy-released flower buds proved to be an efficient procedure for the identification of anther and pollen development genes in perennial plants showing seasonal dormancy.

Very little has been published to date on seasonal spatial variability of produc-tion in fruit crops, and most papers refer to data collected post harvest. This work analysed field information recorded within-season (fruit growth rate) and at harvest (crop load, fruit size, fruit ripening) in 2008 in two commercial apple (Malus domestica Borkh.) orchards in the Ferrara province, Italy. In high-quality apple production systems, manual refinement of chemical thinning is a must, but growers lack a methodology for assessing the efficacy of thinning treatments and to assist further management decisions, such as irrigation levels, for example. The within-season data were used to provide assistance in management decisions taken by growers and/or consultants throughout the season. The goal was to assist in improving the efficacy of management to ensure high production while maintaining as high yields as possible. The relationships between the within-season and harvest measurements were analyzed using both traditional and spatial statistical techniques. Maps of crop production/ quality parameters and fruit growth were generated by punctual kriging with a global variogram on a common grid. Within-season monitoring provided more robust estimations of the fruit load per tree than traditional methods, which underestimated fruit load, leading to more appropriate thinning. Monitoring fruit growth rates also provided good estimations of fruit size distribution at harvest and permitted better satisfaction of the target market. Useful information could be obtained by interpretation at the block (orchard) scale, however, a spatial analysis at a sub-block level appeared to offer the opportunity for differential management. The work presented is intended as a proof of concept of this methodology, the satisfactory results from which signal that it may be not far from large-scale adoption.

The environments where apple and peach originated are very different in terms of water availability and evaporative demand. This likely determined the evolution of different strategies against drought stress, with ensuing effects on the growth mechanisms of their fruit. This work compares the seasonal biophysical mechanisms of apple and peach fruit growth via an analysis of the vascular and transpiration in/outflows on ‘Gala’ apple and ‘Red Gold’ nectarine fruit. Due to their lower surface conductance, apples attain lower transpiration rates during the season, which are reflected in their lower xylem flows, as these are directly related to transpiration. By contrast, phloem flow is always comparable between the two species both in terms of daily amounts and daily patterns. It is striking that peaches exchange much more water than apples, but receive the same amount of phloem sap. This might be related to the different strategies adopted: apples unload assimilates actively and phloem-to-fruit hydrostatic pressure gradients are of relatively low importance. On the contrary, although the mechanism of phloem unloading in peach fruit is still unclear, some results suggest that it may be partly passive, at least during the cell expansion stage. As fruit turgor pressure is negatively related to transpira¬tion rate, the high water loss of peach fruit may be the way to lower water potential and to create the hydrostatic pressure gradient needed to promote passive unloading of assimilates. Therefore, the high surface conductance and transpiration rates of peach fruit appear to have a key role for fruit growth. This feature may be the consequence of the higher water availability typical of the south-east of China, from where most of the peach genetic material derives. Similarly, the growth strategy of apple fruit, based on low surface conductance, seems related to the dry environment (Kazakhstan mountains) where the apple species originated.