SEEDLING AND ADULT-PLANT EVALUATION OF RACE VARIABILITY IN LEPTOSPHAERIA-MACULANS ON BRASSICA SPECIES IN AUSTRALIA

Seedling and adult plant studies were used to identify the race struct ure of Leptosphaeria maculans (the cause of blackleg) on oilseed Brass ica species in Australia. Host-pathogen interactions using a set of 12 differential host lines identified 14 seedling races and 7 adult plan t races. There was little relationship, however, between seedling and adult plant reactions to individual isolates, indicating that seedling and adult plant resistance are under different genetic control. While non-specific adult plant resistance was observed in the B. napus line Jet Neuf, host-pathogen interactions confirmed the existence of race- specific adult plant resistances in other differential lines.