Effects of pollen source on pollen tube dynamics and fruit set in two almond promising genotypes

In this study, a pollination experiment on almond species was conducted about the pollen tube penetration in the pistil with a fluorescence microscope and the rate of fruit formation by the controlled pollination in the orchard. These species included two new almond genotypes of KD ۱۳ and K۱۱-۸ as pollen receptors, and two almond cultivars Tuono (self-compatible) and D۵ (self-incompatible), a peach cultivar HolouYazdi, and GN۱۵ (hybrid between almond and peach) as donor pollen sources. This experiment was conducted in an almond orchard with six-year-old trees at Kamal-Shahr Horticulture Research Station in Karaj, Iran. The results showed a significant difference among pollen sources for in vitro pollen grain germination. The pollen germination percentage ranged from ۴۵ to ۸۶% in the cultivars and genotypes under study. There were significant differences among crosses for the rate of pollen tube penetration in different parts of the style. KD۱۳ × D۵ (self-incompatible (with ۹.۶% and K۱۱-۸ × D۵ (self-incompatible) with ۷.۶۳% showed the highest percentage of pollen tube penetration but KD۱۳ × Tuono and K۱۱-۸  ×Tuono with ۱% and ۲.۱۲%, respectively, had the lowest pollen tube insertion into the style. Ninety days after pollination, the crosses of KD۱۳ × KD۵ and K۱۱-۸ × D۵ showed the highest percentage of fruit set (۴۸.۹۰ and ۴۲.۴۵%, respectively) as compared to other pollinizers. It was determined that the fruit formation was mainly influenced by the pollen source and therefore the source of pollen had a decisive role in the final fruit set. As a result, it is important to choose the right pollen source in the breeding programs before recommending the cultivation of new almond varieties.

Keywords:

Fertilization , Hybrid , Prunus dulcis , Self-incompatibility