1. School of Biological, Earth and Environmental Sciences Univ. of New South Wales; Kensington NSW 2052 Australia
2. School of Plant Biology The Univ. of Western Australia; Crawley WA 6009 Australia
3. Dep. of Agric. and Food Western Australia; Kensington WA 6151 Australia
4. Dep. of Agric. and Food Western Australia; Merredin WA 6415 Australia
5. Precision Agronomics Australia; 9 Currong St. PO Box 2418 Esperance WA 6450 Australia