Research has been carried out in the UK to identify varieties of oilseed rape (OSR) that are more attractive to insect pollinators, such as bees.

In recent years, some beekeepers have suggested that hybrid varieties of OSR may provide inferior nectar for pollinators, compared with traditional open-pollinated varieties.

Scientists at Rothamsted Research, the University of Exeter and Newcastle University tested whether the amount and quality of nectar produced by glasshouse-grown oilseed rape plants varies between crop variety, and – more fundamentally – between three conventional breeding systems used to create the varieties.

The researchers demonstrated that, while the amounts and sugar content of nectar were similar in varieties within the same breeding system, they varied between the breeding systems.

Professor Juliet Osborne, of the Environment and Sustainability Institute on the University of Exeter’s Penryn Campus in Cornwall, said: "We got the idea for this study from beekeepers".

People approached us to ask if we knew why some varieties of oilseed rape didn't seem to give as good a honey crop from their hives as they expected.

The nectar and pollen produced by rape’s distinctive yellow flowers provide a key source of nutrition for insect pollinators. The UK and Ireland have around 250 bee species, including the domesticated honey bee.

In the pollination study, varieties produced with three different methods were tested. The scientists compared OSR varieties representing open-pollinated (OP), genic male sterility (GMS) hybrid and cytoplasmic male sterility (CMS) hybrid breeding systems.

Dr. Jonathan Carruthers from Newcastle University explained: "We measured a range of floral traits in varieties of winter OSR, grown in a glasshouse, to test for variation within and between breeding systems. Specifically, we quantified 24-hour nectar secretion rate, the amount, concentration and ratio of nectar sugars per flower, and the sizes and number of flowers produced per plant from 24 varieties."

Benefiting pollination and crop production

Analyses of the data demonstrated that the amounts of nectar and sugar varied between the breeding systems, being significantly greater in GMS hybrids than in CMS hybrids and open-pollinated varieties. The researchers concluded that plant breeding could be used to create crop varieties with pollinator-friendly traits, benefiting both pollination services and crop production.

Osborne said: "Differences in nectar might not be the only reason for variable honey yields, but the research does show that we shouldn't assume all oilseed rape crops are going to provide the same resources".