Effects of cross-pollination, self-pollination, and natural pollination on golden apricot (Prunus armeniaca) fertilization and embryogenesis

Golden apricot (Prunus armeniaca) achieved a fruit setting rate of 62.30% after artificial cross-pollination, as against 56.77% for natural pollination by bees. Self-pollination produces no fruit, indicating that this particular species is self-incompatible and infertile. We used fluorescence microscopy to examine the pollen tubes of golden apricot plants at regular intervals after artificial cross-pollination with a mixture of pollen from 'Katy' and 'Golden Sun' apricots, natural pollination, or self-pollination. All experiments took place in a greenhouse. Our observations showed that pollen from the same plant was capable of germinating on the stigma and growing through the style, but when it reached a point 3/5 of the way down the style, at around 96 h post-pollination, the pollen tube appeared to bend backwards. This behavior appears to be characteristic of species with gametophyte self-incompatibility. Dissections of golden apricot embryos suggested that, after cross-pollination, pollen grains germinate normally, grow through the stigma, and enter the ovary to complete the fertilization process. A diploid zygote is formed at 19 days after pollination. It subsequently forms an embryo that in turns globular, heart-shaped, and torpedo-shaped at 31, 35, and 42 days post-pollination, respectively. Eventually, the cotyledon is formed at 46 days post-pollination. Our results provide a reference that will facilitate future cultivation of this species under greenhouse conditions.