1. School of Biology and Environmental Science; University College Dublin; Belfield; Dublin 4; Ireland
2. Johnstown Castle Research Centre; Teagasc; Wexford; Ireland
3. Oak Park Crops Research Centre; Teagasc, Co; Carlow; Ireland
4. Department of Botany, School of Natural Sciences; Trinity College Dublin; Dublin 2; Ireland
5. Institute of Biological and Environmental Sciences, School of Biological Sciences; University of Aberdeen; 23 St. Machar Drive; Aberdeen; AB24 3UU; UK