OLIVE SEED SET AND ITS IMPACT ON SEED AND FRUIT WEIGHT

Abstract

Pistillate olive flowers bear at anthesis four viable equally sized ovules. In spite of that, olive fruit is typically a one-seeded drupe. Preliminary observations, however, disclosed that some cultivars sometimes form fruits containing two seeds. In this study we compared seed set on five olive cultivars and we found maternal (cultivar) and paternal (pollen) effects on seed set. Up to 14% of Hojiblanca fruits from open-pollination were two-seeded while only 4% and 1% were found in Arbequina and Sevillano. No biseeded fruits appeared in Picual and Frantoio. On the contrary, Sevillano produced 46% of fruits with aborted seeds. Paternal effects on seed set could also be verified. In general, a higher percent of biseeded fruits developed under cross-pollination while empty endocarps were more often found under self-pollination. Presence and number of seeds per fruit affected fruit and seed size on cv Hojiblanca. Fruits containing two seeds were heavier due to heavier pulp as well as heavier endocarp and seeds. Though total resource allocation in seed development was higher in two-seeded fruits, each seed from biseeded fruits weighed less than single seeds. Results reveal pollination as a useful tool to improve not only fruit set, but also fruit size and fruit uniformity in olive.