Pollination Effects on Fruit and Seed Development in ‘Comice’ Pear1

Abstract Cross-pollination increased fruit set, fruit size and seed content of ‘Cornice’ pear ( Pyrus communis L.) in 3 large orchards without pollenizers. Supplemental self-pollination was equivalent to open pollination in its effect on fruit set and size. Low female fertility of ‘Comice’ could not be accounted for by early ovule degeneration or frost injury. Pollen transfer by bees was observed to be low in 2 orchards, with 36 and 41% of seedless fruit the result of open pollination. In comparison, only 6% of open-pollinated fruit were seedless in the orchard of greatest bee activity. Seedlessness was due to seed abortion during early fruit development. Classification of aborted seeds as to size at time of abortion revealed that in most fruits a minimal amount of seed growth occurs, although fruit retention does not require the presence of fully developed seeds. Fruit size was positively correlated with seed content, although this relationship was less pronounced in fruits with high seed count. The importance of seed development before abortion and of fully developed seeds in fruit set as well as fruit size is shown.