Different factors involved in the low fruit set of mango (Mangifera indica)

Abstract

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.