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 13 and K11-8 as pollen receptors, and two almond cultivars Tuono (self-compatible) and D5 (self-incompatible), a peach cultivar HolouYazdi, and GN15 (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 45 to 86% 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. KD13 × D5 (self-incompatible (with 9.6% and K11-8 × D5 (self-incompatible) with 7.63% showed the highest percentage of pollen tube penetration but KD13 × Tuono and K11-8  ×Tuono with 1% and 2.12%, respectively, had the lowest pollen tube insertion into the style. Ninety days after pollination, the crosses of KD13 × KD5 and K11-8 × D5 showed the highest percentage of fruit set (48.90 and 42.45%, 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.

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

Fertilization , Hybrid , Prunus dulcis , Self-incompatibility