Reproductive Biology of Mango (Mangifera indica) in a Mediterranean Climate

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. INTRODUCTION In mango, even after adequate pollination, a very small proportion of the flowers are able to set fruits, due to a massive drop of flowers and developing fruitlets (Davenport and Nuñez-Elisea, 1997). This is especially important in areas such as Southern Spain, where climatic conditions are very different from those in the area of origin of the species, often resulting in erratic bearing. The knowledge about the reproductive biology of species of agronomic interest (Herrero, 1992) and its relation with environmental conditions (Hedhly et al., 2009) is relevant in order to optimize production. But in mango, in spite of the importance of the crop, surprisingly very little is known on its reproductive biology. In this work, in order to study the ultimate causes behind this massive flower and fruitlet drop under a Mediterranean climate, we studied the process that goes from flower to fruit in mango, characterizing its phenology in the field and reproductive process under the microscope.