Bee pollination services and the enhancement of fruit yield associated with seed number in self-incompatible tangelos

Abstract

Insect pollination services substantially enhance global major crops in terms of fruit quantity and potentially quality. Even Citrus crops, which have been supported by broad breeding programs and well-established agrotechniques, depend on pollinators to achieve high yields. In this study, the effects of pollination services on the production of ‘Lee’ and ‘Nova’ tangelos were experimentally assessed in north-eastern Brazil. The associated flower visitors were surveyed and the visitation pattern on tangelo flowers was described and quantified in the experimental orchard. Both cultivars were self-incompatible and mainly benefited from pollination services provided by honeybees, which was responsible for more than 90% of floral visits. Under this scenario of local pollination, fruit production was enhanced by 12% compared to that obtained from hand cross-pollination (intra-cultivar crosses), probably due to the several visits a flower received during anthesis involving multiple pollen parents. However, fruit size and weight achieved similar values in open pollination and hand cross-pollination. A high number of seeds per fruit was also attributed to bee pollination, which indirectly impacted fruit weight positively at least in ‘Lee’ tangelos. ‘Nova’ produced larger and heavier fruits than ‘Lee’. These differences in fruit traits between cultivars may not occur due to divergence of floral characteristics because ‘Nova’ and ‘Lee’ had similar floral traits. Nevertheless, the presence of other cultivars, avoidance of high number of clone plants and adequate pollination management in planted areas are required for plenty production of ‘Lee’ and ‘Nova’ tangelo.