Self-compatibility and cleistogamy in Japanese plum

Most Japanese plum cultivars are self-incompatible and to produce fruits require cross-pollination with compatible cultivars coincident at flowering. However, a small number of Japanese plum cultivars have been described as self-compatible. In this work, self-(in)compatibility and cleistogamy have been analyzed in the Japanese plum cultivar ‘African Rose’ by combining controlled pollinations and microscopic observation of flowers. One tree was enclosed in a mesh cage before blooming to avoid pollination by insects. Several branches in the caged tree and also in trees outside the cage were selected and marked as a control. The experiment was made during two years. Self-incompatibility was evaluated by controlled self-pollinations in a set of flowers in the caged tree. Fruit set and fruit drop were characterized in both self-pollinated and control flowers until harvest. Additionally, cleistogamy was evaluated in another set of branches, by determining the presence of pollen grains on the stigma and pollen germination in flower buds collected at four phenological stages before flower opening. The presence of pollen tubes reaching the ovary in pistils from self-pollinated flowers, and fruit set observed after self-pollination as well as the showed that ‘African Rose’ behaves as self-compatible. The synchrony between anther dehiscence and stigma receptivity before flower opening, which resulted in self-pollination without pollinator intervention, indicates that this could be the first reported case of cleistogamy in Japanese plum.