Abstract
Self- and cross-compatibility of pollens and the effects of pollination and gibberellins on fruit set, physiological drop, growth, and maturation of 'Le Lectier' pears were investigated to clarify the characteristics of fruit bearing.
1. Self-pollinated pollen tubes stopped growing at about 4 mm below the stigmatic surface, whereas cross-pollinated ones reached the base of the styles within 3 days after pollination.
2. Fruit set of self- or non-pollinated flowers was under 15%, whereas that of crosspollinated ones exceeded 40%. Treatments with both 200 ppm GA3 sprays one day before pollination and GA3+4+7 paste applications 5 weeks after pollination increased fruit set of both self- and non-pollinated flowers to 30%.
3. Physiological fruit drop ("June drop") in self- or non-pollinated group reached a maximum 3 weeks after anthesis, thereafter the rate of abscission was relatively high for 4 more weeks. Fruit drop of the cross-pollinated lot reached a maximum 5 to 6 weeks after pollination. Fruit drop of GA-treated flowers from all pollinated groups exhibited a wave of abscission similar to that of the cross-pollinated control lot.
4. Fruits resulting from cross-pollination were larger at harvest than were those resulting from self- or non-pollination. GA applications resulted in longer fruits with a protruding calyx and hastened chlorophyll degradation compared to the non-treated control fruits. Fruits of the self- or non-pollinated groups contained a few or no seeds, whereas, those of from the cross-pollinated lot had 7 to 8 seeds per fruit.
5. The time of ethylene evolution during the ripening period was advanced by GA treatment.
6. Emasculation had no effect on fruit set and development.
These results indicate that the pollen of 'Le Lectier' pear is highly self-incompatible and the cultivar has a weak tendency to form parthenocarpic fruits. GA induces the setting of parthenocarpic fruit and stimulates fruit maturation possibly by advancing the time of ethylene evolution.
