Occurrence and variability of sexual polyembryony in olive cultivars

• The occurrence of polyembryony in olive is described here for the first time.
• 24 olive cultivars and 5287 seeds were screened to find polyembryony.
• Polyembryony in olive is a low-frequency but cultivar-dependent phenomenon.
• It is of a sexual origin and is due to monozygotic cleavage after normal fertilization.

The occurrence of spontaneous sexual polyembryony is described and characterized for cultivated olive (Olea europaea L.). We screened seeds from 24 olive cultivars and found significant differences in the frequency of polyembryonic seeds between them. Cultivar ‘Cornicabra’ and, especially, ‘Meski’ yielded the highest ratio of polyembryonic seeds (1.6% and 3.0%, respectively), indicating that polyembryony is a low-frequency (0.95% of 5287 observed seeds) but cultivar-dependent feature in olive. Polyembryonic seeds consisted of two and eventually three embryos with a normal endosperm. Simple sequence repeat (SSR) markers were used to characterize the nature of the polyembryonic seedlings. DNA profiles indicated that polyembryonic seedlings in olive have a sexual origin because their profiles were identical and distinguishable from the mother parent. Therefore, polyembryony in olive is of a sexual origin and is due to monozygotic cleavage after normal fertilization. To the best of our knowledge, this is the first evidence of polyembryony in olive and its occurrence in a representative number of cultivars.