Funding for this research was provided by:
Biotechnology and Biological Sciences Research Council (BB/M016900/1)
Received: 5 December 2018
Accepted: 31 July 2019
First Online: 16 August 2019
: The authors declare the following competing interests: G.J.H., G.A. and C.F. are employed by Syngenta. The other authors declare no competing interests.