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5 Pags. The definitive version is available at: https://www.ishs.org/ishs-book/1231, Mango (Mangifera indica) is a tropical fruit tree originated in southeastern Asia, which is cultivated in regions with tropical and subtropical climates worldwide. Mango cultivation has significantly increased in the last decades, often spreading to areas where environmental conditions are not the most favorable for optimal fruit set. In this work, we describe the reproductive biology of mango in the coastal areas of southern Spain, the furthest region from the equator where mango is produced commercially at a significant scale. As in other regions, mango trees produced several inflorescences per tree with hundreds to thousands of male and hermaphrodite flowers, depending on the cultivar, but only a very small percentage of the flowers are able to set fruits due to a massive drop of flowers and fruitlets. Although about half of the flowers in the inflorescence are male flowers and, consequently, contribute to this massive drop, a high proportion of the hermaphrodite flowers were not receptive to pollen germination. In receptive flowers, the characterization of the pollen tube pathway within the pistil showed chalazogamy. A detailed study of the ovules indicates that a high proportion of them showed degenerated embryo sacs, both before and after fertilization. Paternity analysis with molecular markers showed a high proportion of embryos resulting from self-pollination in orchards planted with a single cultivar. However, without pollination restrictions, the offspring shows a higher proportion of genotypes resulting from cross-pollination, suggesting preferential cross-fertilization. The variable response of this parameter, together to the variable proportion of hermaphrodite/male flower ratio, also obtained in response to environmental conditions, suggests a reproductive plasticity in this species., This research was supported by the Ministerio de Economía y Competitividad – European Regional Development Fund, European Union (AGL2012-40239 and AGL2013-43732-R) and Gob. Aragón A-43. V. Pérez was supported by a Cabildo de La Palma-CSIC PhD scholarship.

The importance of mango growing contrasts with the paucity of information on its reproductive biology. In this work, the reproductive biology of mango was studied in the subtropical conditions of the Southern Spanish Mediterranean coast, using the cultivars ‘Osteen’, ‘Kensington’, ‘Kent’ and ‘Keitt’. In order to establish the appropriate developmental coordinates during the reproductive phase, phenology was studied from the start of the blooming season to fruit harvest. Also to detect the reasons behind the low fruit set in mango, pollen tube pathway and fertilization were analysed, using microscopy techniques. A good proportion of the flowers were male and dropped soon after anthesis. Pollen grains readily germinated, pollen tubes reached the base of the style within one day, penetrated the ovule through the nucellus and reached the embryo sac three days after pollination. Endosperm nuclei soon developed, but the embryo remained in a quiescent stage. A good proportion of the ovules degenerated at different stages of development. Temperature had an effect on pollen performance, and low temperatures hampered pollen germination. Finally, a compatibility assay was performed, showing no differences between self and cross pollen tube growth in the style. However a paternity analysis, with microsatellite markers, showed significant differences in outcrossing rate depending on the availability of pollinizer trees.

Trabajo presentado en el XXVIII International Horticultural Congress on Science and Horticulture for People (IHC2010): International Symposium on Plant Physiology from Cell to Fruit Production System, celebrado en Lisboa (Portugal), del 22 al 27 de agosto de 2010, Cherimoya (Annona cherimola Mill.) is a subtropical fruit tree with an incipient but promising commercial production niche in subtropical climates. However, the expansion of this crop from its areas of origin has taken place without its natural pollinating agent and crop production relies heavily on hand pollination. Erratic yields are often obtained without apparent causes, and they could be related to the lack of knowledge on the biological requirements of pollen in this species. Since pollen performance in the pistil is dependent on previous pollen development in the anther, here we perform a study on the influence of temperature and water content on final pollen development stages and, as a consequence, on pollen performance in A. cherimola. The results show a significant influence of temperature and relative humidity on pollen performance. These results provide biological support for adequate pollen handling to optimize production in this species., Financial support for this work was provided by the Spanish Ministry of Education (Project Grants AGL2009-12621 and AGL2010-15140), INIA (RF2009- 00010), GIE-Aragón 43, Junta de Andalucía (FEDER AGR2742), and the European Union under the INCO-DEV program (Contract 015100). J.L. was supported by a grant from Junta de Andalucía.

Low fruit set in fruit trees has been traditionally related to weather conditions. In apricot, flowering takes place in winter or early spring, when adverse meteorological conditions can influence the pollination process and subsequent fruit set. The blooming period usually lasts one to two weeks in most cultivars and locations. Thus, external conditions can strongly vary over this period, and flowers in the same tree could have different conditions during their development depending on the time of anthesis. In order to evaluate whether the capacity of flowers to set fruits is affected by the time of anthesis, in this work flower development and fruit drop have been characterised in early and late flowers of the cv. Moniqui. Flowers from both populations were hand-pollinated with compatible pollen. A set of flowers were weekly counted in marked branches from anthesis to harvest. Another set of flowers were collected at anthesis, weighed and anatomically characterized. Fruit set in early flowers was considerably higher than in late flowers. These differences in the capacity of flowers to set fruits between early and late flowers were associated with differences in the size of different floral structures. Results are discussed in terms of the implications of floral differences at anthesis in the subsequent fruit set.

Financial support was provided by FEDER-CICYT (AGL2003-05318-C02-00 and AGL-2006-13529-CO2-00/AGR) and by Grupo Consolidado de Aragon A-43 (DGA). C.J. was supported by a fellowship of INIA.

Cherimoya (Annona cherimola Mill) belongs to the Annonaceae, a basal Angiosperm family that includes a number of tropical and subtropical fruit tree species. Cherimoya shows protogynous dichogamy, a common characteristic in Annonaceae, where female and male structures do not mature simultaneously. Moreover, flowers of the same genotype usually open synchronously and, consequently, transfer of pollen between different flowers of the same genotype is difficult. This mechanism has been assumed to prevent self-fertilization and to encourage cross-pollination and has clear implications both from a plant breeding perspective and in an agronomic context. Inadequate pollination is one of the most important factors that limit commercial production of cherimoya resulting in low fruit set and in the production of misshapen fruits. This is due to the lack of overlap between the male and female stages and the expansion of the crop to areas outside its native range in absence of its natural pollinating insects. As a consequence, hand pollination is a common practice for commercial production. In spite of the implications of this isolating mechanism, its efficiency has not been previously evaluated. In this work, we evaluate stigmatic receptivity under the microscope and natural outcrossing rate using molecular markers to test the paternity of the seeds. The results obtained show that stigmas can still be receptive when the flowers pass to the male stage and that a surprisingly high proportion of the seeds produced are the result of self-fertilization. The results are discussed in terms of the implications of these results both in plant breeding and in an adequate crop handling.

Apricot (Prunus armeniaca L.) trees bloom early and frequently encounter periods of freezing temperatures from budbreak to fruit set. Thus, important damages are produced by low temperatures in buds, flowers and developing fruits, and crop losses due to frosts after dormancy are usually more important than those due to frosts during winter. In this work, freezing injuries associated with low temperatures during and after budbreak were studied under orchard conditions, for several years, in apricot 'Moniqui'. Symptoms in different phenological stages, from budbreak to several weeks after bloom, have been examined in the days following the frosts. Likewise, the evolution of the affected organs has been followed to establish the influence of the frosts on the fruit set and crop. At flower budbreak, while external symptoms were not observed, freezing temperatures caused clear internal damage. During the pre-bloom and bloom period, clear external and internal symptoms were observed in several floral structures in the days following the frost. Finally, in developing fruits, a clear relationship has been established among the early external symptoms observed in the epidermis in the first few days after the frost and the damage in the developing seed, the arrest of fruit growth and the subsequent fruit abscission.