1. a F. A. Janssens Laboratory of Genetics, Katholieke Universiteit Leuven , Willem de Croylaan 42, B-3001 Heverlee, Belgium
2. b ZENECA Agrochemicals, Jealott's Hill Research Station , Bracknell Berkshire, RG42 6ET , U.K.
3. c Danisco Biotechnology , Copenhagen , Denmark