Citrus reproductive biology from flowering to fruiting

Citrus reproductive biology is characterized by peculiar processes such as self-incompatibility, parthenocarpy, and nucellar embryony. The understanding of citrus flowering mechanism is quite important since it will lead to control of production quality, efficiency, and timing of crops. In cultivation and breeding programs of citrus, the flowering behavior is strictly related to juvenility and alternate bearing. In citrus fruit, the failure of the sexual reproductive process (e.g., female and/or male sterility) in parthenocarpic cultivars results in seedless fruits. In contrast to other fruit crops, sterility can be considered a benefit to avoid the presence of seeds, which is one of the main quality parameters for fresh citrus fruit consumption. Here we review the current state of knowledge about the genetic control of reproductive biology in several citrus and its closed related species.