Pollen-pistil interaction influence on the fruit set of sweet cherry

- Flowering period, compatibility relations and fruit set of sweet cherry were assessed.
- Full bloom synchronization was related to better pollen growth throughout pistil.
- Pollen arrested growth in the middle part of pistil following self-pollination.
- Pollen-pistil interactions determine the final fruit set.
- Compatible pollinizers for each cultivar are recommended.

Pollination success and final fruit set of sweet cherry depends on self- and cross- (in)compatibility relations among cultivars in orchard. The objective of this study was to determine the compatibility relationships and to select pollenizers for the most important Croatian sweet cherry cultivars, 'Gomilička' and 'Stonska'. Phenological observations, pollen germination, pollen tube growth and fruit set were assessed following self- and cross-pollination treatments in two flowering seasons. In general, we found overlap of flowering periods of all cultivars included in the study, but low synchronization was observed for the full-bloom period among traditional cultivars, particularly 'Stonska' (early cultivar) and 'Tugarka' (late cultivar). There was a significant difference in fruit set among the type of pollinations and pollen donors. 'Gomilička' and 'Stonska' are self-incompatible, and cross-pollination is necessary for good fruit set. According to the overlap in flowering time and fertilization level in 'Gomilička', cross-pollination with 'Garnet', 'Isabella' and 'Starking Hardy Giant' was more effective than that of the traditionally grown cultivars 'Stonska' and 'Tugarka', and introduction of these cultivars as pollenizers is a good choice that can provide regular and abundant fruit set. Despite the different S-allele combinations of traditional cultivars, overlap in flowering time with some of the introduced cultivars, and favourable climatic conditions, we found also significant effects of pollen-pistil interactions in the style and ovary on the dynamics of pollen tube growth and final fruit set. Inter-incompatibility reactions between cultivars were not observed.