The effect of autumn and spring temperature on fruit set and on the effective pollination period in apple and pear

Abstract

Under completely controlled conditions fruit set and the effective pollination periods (EPP) of apple cultivar ‘Golden Delicious’ and pear cultivar ‘Doyenné du Comice’ were evaluated as affected by autumn temperature (9°C and 24°C, apple; or 10°C, 14°C, 17°C and 22°C, pear) in combination with two spring temperatures (13°C and 19°C, apple; or 13°C and 17°C, pear). In apple the low-temperature period started just after the end of bloom, in pear the two temperature treatments were already applied in February when the trees were still in rest. In apple and pear there was no effect of the autumn temperature on fruit set. In apple, although bloom temperature was the same, the EPP was extended when the temperature was lowered just after bloom, resulting in a better fruit set in that treatment. There was no severe fruit drop (‘June drop’) between 3 and 6 weeks after full bloom in apple. In pear, fruit set was clearly lower at 17° than at 13°C; the length of the EPP was 4–6 days at 13°C against 2–4 days at 17°C. A marked fruit drop occurred between 3 and 6 weeks after bloom in pear. The data are discussed in terms of a differential effect of temperature on ovule longevity and rate of pollen tube growth.