How to choose the best pollinizer cultivars for ‘Conférence’ pear (Pyrus communis) in Belgium?

Pear (Pyrus communis) is the most important fruit crop in Belgium and ‘Conférence’ represents 90% of the pear production. ‘Conférence’ is self-incompatible and requires cross-pollination to develop fertilized fruits. We therefore compared seven pear cultivars (‘Dicolor’, ‘Doyenné du Comice’, ‘Joséphine de Malines’, ‘Seigneur Espéren’, ‘Sweet Sensation’, ‘Triomphe de Vienne’, ‘Williams Bon Chrétien’) adapted to Belgian conditions in order to identify valuable pollinizer cultivars for ‘Conférence’. These cultivars were used as male parent in hand pollination experiments with ‘Conférence’ and the resulting number of fruits was assessed. Fruit size and weight were measured at harvest. Moreover, to evaluate the pollination efficiency of these cultivars and their attractiveness for bees, we analyzed their pollen and nectar production and composition. Pollen is one of the prime nutrient resources used for bee larvae and nectar represents the major source of sugars for bees. Regarding fruit production, the mean weight and size reached 103-154 g and 50-61 mm respectively depending on the crossings. The largest fruits resulted from the pollination of ‘Conférence’ with ‘Triomphe de Vienne’ or ‘Doyenné du Comice’. The cultivars differed in their pollen and nectar quantities and compositions. The mean number of pollen grains per anther ranged from 2,200 for ‘Dicolor’ to 4,600 for ‘Williams Bon Chrétien’. Pollen viability was high whatever the cultivar (60-92%). Pollen polypeptide concentration was variable (31-107 µg mg-1) while amino acid concentration was high and stable (346-390 µg mg-1) among cultivars. The nectar sugar content per flower varied between 52 µg for ‘Seigneur Espéren’ to 255 µg for ‘Conférence’. Pear cultivars produced therefore pollen of high quality regarding amino acid content while their nectar production was poor in sugars. Bee attractiveness might differ among cultivars and needs further research to optimize orchard management.