Affiliation: | (1) Department of Agricultural Sciences, University of Bristol, AFRC Institute of Arable Crops Research, Long Ashton Research Station, BS18 9AF Bristol, England;(2) ZENECA Agrochemicals, Jealott's Hill Research Station, RG12 6EY Bracknell, Berkshire, England;(3) School of Pure and Applied Biology, University of Wales, PO Box 915, CF1 3TL Cardiff, Wales |