Pollen tube behaviors in self-incompatible and self-compatible Citrus cultivars

To observe pollen tube behavior in the pistils of ten self-incompatible Citrus cultivars, bud pollination, delayed pollination, self-pollination and cross pollination were carried out. In self-pollinations of self-incompatible cultivars, pollen tubes were perfectly arrested in the stigmas and styles by 6 days after pollination, while in three self-compatible and 19 cross-compatible pollinations pollen tubes penetrated into the ovaries by 4 to 8 days after pollination. Various abnormal behavior and morphology of pollen tubes were observed in both incompatible and compatible pollinations, but were less common in the compatible ones. In the pistils of self-incompatible cultivars self-pollinated two days before anthesis and two days after anthesis, the self-incompatible pollen tubes ceased to grow in the stigmas and styles, while in the pistils self-pollinated 4 and 6 days before anthesis many pollen tubes reached the ovaries. However, numbers of pollen tubes penetrating the ovaries were different in different cultivars. In the pistils of self-incompatible cultivars self-pollinated 4 days after anthesis, pollen tube growth was enhanced to some extent, while in those self-pollinated 6 and 8 days after anthesis pollen tubes could not detected probably because of the degeneration of the styles. These studies suggested that in the pistil of self-incompatible Citrus self-incompatibility initiates 6 days before anthesis and increases up to the day of anthesis and that some of the cultivars have a common S allele that controls self-incompatibility.