Pollinizer' Effects on Olive Seed Set, Size and Abortion

Olive is a self-incompatible species that usually produces one-seeded drupes, although double-seeded fruits and seedless fruit due to seed abortion may occur. This study evaluated the effects of different pollinizers on seeding pattern in three self-incompatible cultivars: 'Arbosana', 'Koroneiki' and 'Sikitita'. Fruit and seed set, seed abortion, double seeding and seed weight were analyzed. Maternal effects were confirmed with significant differences between cultivars. 'Sikitita' produced a higher-than-expected proportion of double-seeded fruit, whereas 'Arbosana' and 'Koroneiki' produced fewer. In contrast, 'Koroneiki' showed a higher incidence of empty endocarps, while 'Sikitita' produced fewer. Paternal effects on seeding pattern were generally not significant, although marginal differences were observed in 'Arbosana' and 'Koroneiki' depending on pollination treatment. Some pollination crosses were more successful, with 'Sikitita' pollen fathering most seeds in 'Koroneiki' and 'Arbosana', with reciprocal success for 'Arbosana' pollen in 'Sikitita'. A striking discovery was that different fathers often sired twin seeds within one single fruit. Finally, seed number affected fruit development. Thus, total seed and endocarp mass increased as viable seed number did. Fruits with aborted seeds had smaller stones, whereas stones enclosing two seeds were heavier. Seed, endocarp, pulp and fruit weights were positively correlated across cultivars and pollination conditions.