Optimizing sunflower yield: Understanding pollinator contribution to inform agri-environmental strategies

Context

The agricultural intensification due to global increased food demand has harmed pollinator communities worldwide. However, some of the economically most important oilseed crops, such as the sunflower, depend on pollinators to produce seeds. While self-fertile varieties have undergone genetic selection to guarantee productivity, the pollinator-dependence levels and the economic contribution of pollinators have not been fully estimated.

Objective

Here, we aimed to explore floral and pollinator constraints limiting the agricultural yield of sunflower varieties most frequently used in the Iberian Peninsula.

Methods

Pollination experiments were undertaken to analyse the pollinator-dependence level of 12 varieties under controlled conditions and also under natural conditions in 23 fields of two Spanish agricultural regions. The selfing ability and economic contribution of pollinators were estimated by comparing bagged and open-pollination treatments.

Results

Our results showed that the degree of pollinator-dependence is highly dependent on sunflower variety, with impacts on production and productivity outcomes, e.g. individual plant yield values varied between 0.188 and 0.692. Several varieties could self-fertilize and produce seeds regardless of pollinators. However, outcrossing significantly increased seed set in most varieties with increments up to 0.341. Overall, a trade-off between the number and weight of seeds was observed. Under natural field conditions, pollinators significantly increased overall sunflower production, although differences were observed among regions (increment of 275 kg/ha in Burgos and 382 kg/ha in Cuenca), with an associated economic outcome.

Conclusions

The self-fertilization ability and the level of pollinator-dependence vary according to the intrinsic reproductive traits of the variety analysed. Although some varieties are able to produce seeds despite the absence of pollinators, the sunflower clearly benefits from insect pollination. The landscape context and the availability of pollinator communities influenced the final crop yield and the economic outcome.

Significance

Combining landscape-restoring interventions with the cultivation of self-compatible varieties during at least the first years of implementation may be a solid additional agri-environmental strategy to maintain production levels and economic outcomes, which may particularly mitigate effects of pollinator and biodiversity losses mainly in highly simplified agroecosystems.