Breeding system in Olea ferruginea Royle (Oleaceae): comparative performance of staminate and perfect flowers in reproductive assurance

Olea ferruginea, a wild widely distributed species of the olive lineage, exhibits andromonoecy with protogynous perfect (hermaphrodite) and staminate (male) flowers. The present communication elucidates the differential performance of staminate and perfect flowers in reproductive assurance. The flowering chronology and function of perfect and staminate flowers in the breeding system were investigated to understand the breeding behavior of the species. In terms of breeding behavior, pollen from staminate and perfect flowers was used to establish their role in breeding system under different pollination treatments. Results indicate higher pollen viability, germination, and pollen tube growth of staminate than perfect flowers. Results from pollen counts and morphological investigations show slight differences in both types. The species is self-incompatible which is indicated by pollen germination, the average number of pollen tubes in the style, and the fruit set following self and cross-pollination. Hand cross-pollination improves natural fruit set, especially when pollen from staminate flowers was used. Although the relict role of attracting pollinators cannot be fully discarded, it is suggested that the main benefit supplied by the formation of staminate flowers in olives is to promote male fitness by raising pollen output at the population level.

Automated summary

Olea ferruginea, a widely distributed wild olive species, exhibits andromonoecy with staminate and perfect flowers. This study investigates the differential performance of staminate and perfect flowers in reproductive assurance. Results show higher pollen viability, germination, and pollen tube growth of staminate flowers. The species is self-incompatible and hand cross-pollination improves natural fruit set, especially with pollen from staminate flowers.