About 10% of yield is lost due to foliar disease (BBRO annual report 2015-16). Good fungicide resistance management is needed to prevent losses and costs increasing. Most beet crops receive one or two fungicide applications, with 80% of treatments using a co-formulation of two modes of action (MoA): azole (de-methylation inhibitor; DMI) and strobilurin (quinone outside inhibitor; QoI) (Garthwaite et al, Fera 2014). Resistance to azole or strobilurin fungicides (e.g. Trkulja et al, Crop Prot. 2015; Vaghefi et al. Plant Dis. 2016) has been reported for Cercospora beticola from other countries in recent years, but the resistance status of UK C. beticola, powdery mildew and rust is not known.
There are now many reports, from a range of crops, of pathogens developing resistance to more than one MoA. This BBRO project is part of a wider levy/industry collaborative project testing new strategies for the management of resistance developing concurrently against two or more MoA, using field experiments and modelling on septoria as a test pathosystem. A review of experimental evidence on resistance management (van den Bosch et al., 2014 Ann. Rev. Phytopath.) showed that good anti-resistance strategies are effective across different pathogens on a range of crops. Results from the collaboration can therefore inform guidance to beet growers.
Outcomes / Key Message For Growers And Industry
- Virus yellows resistant or tolerant varieties will play an important role in future ‘Integrated Pest Management’ strategies aimed at reducing the damaging effects of virus yellows on sugar beet crops with few pesticides available to control aphid vectors.
- Virus yellows tolerance QTL have been identified by our research group, which exhibit a significant decrease in canopy yellowing and a yield benefit in the presence of virus.
- Virus yellows resistant and tolerant sugar beet material has been generated which has high potential for development in future breeding programmes.
- This project has significantly accelerated the development of virus yellows resistant and/or tolerant sugar beet varieties for the future.