Do floral resources influence pollination rates and subsequent fruitset in pear (Pyrus communis L.) and apple (Malus x domestica Borkh) cultivars?

tPear and apple are among the main fruit crops worldwide. These species can be planted in mixed orchards,and they both depend on insect pollination for fruit set. As pollinating insects are attracted by the floralresources, we investigated nectar and pollen production and chemical composition in four pear (‘Con-corde’, ‘Conférence’, ‘Doyenné du Comice’, ‘Triomphe de Vienne’) and five apple (‘Braeburn’, ‘GoldenReinders’, ‘Jonagored’, ‘Pinova’, ‘Wellant’) cultivars commonly grown in Belgium. We also investigatedwhether insect flower visitation rate and pollination efficiency are linked to floral resource quantityand quality. The pear cultivars flowered one week before the apple cultivars in early spring, and theirflowers were about six times less visited by insects. The visitors foraged more on the pollen of the peartrees and the nectar of the apple trees. Pear flowers produced higher volumes of nectar than appleflowers (1.3–3.2 l vs. 0.4-0.6 l), but with lower sugar concentration (9.6%-10.8% vs. 28.3%-36.4%). Pearflowers also produced fewer pollen grains per anther than apple flowers (2425–4937 vs. 3284–7919),but these had higher polypeptide (346–362 g/mg vs. 216–303 g/mg), amino-acid (40–77 g/mg vs.12–18 g/mg) and phytosterol (21–47 g/mg vs. 15–43 g/mg) concentrations. The foraging behaviorof the insects is thus better explained by nectar and pollen quality rather than quantity. Despite thedifferences in flower visitation rates, pollination of both species resulted in valuable fruit production.