Screening for ‘resistance’ to Spotted Wing Drosophila (Drosophila suzukii) in strawberry and raspberry accessions

The invasive fruit fly, spotted wing drosophila (SWD), is one of the most serious pests in soft fruit production worldwide. This is due to the females' ability to pierce the intact skin of ripening fruits and lay eggs, resulting in considerable crop loss. SWD has been able to migrate quickly within the past 20 years aided by the movement of infected fruit material between continents. The pest was first detected in the UK in 2012 and is estimated that the current cost of mitigation and the crop loss due to damage is £20 - £30 million p.a. to the UK industry. Current mitigation measures include pesticide applications, high labour inputs involved with careful plant husbandry and regular picking of waste fruit, which must be carefully disposed of to prevent the fly returning to infect the crop. This project aims to identify strawberry and raspberry germplasm with reduced susceptibility or even resistance to SWD which would alleviate growers' reliance on control strategies including chemical plant protection products. There is variation between cultivars for differences in fruit characteristics such as skin thickness, sugar content, shade of colour and flesh firmness which may have an impact on the attractiveness of fruit to SWD. By identifying strawberry and raspberry accessions that are less susceptible to SWD, we can help develop breeding lines and less sensitive cultivars for the benefit of producers which currently suffer large crop losses resulting in large volumes of waste fruit. Furthermore, this project will provide invaluable information to breeding programmes and generate preliminary data for future research.