Resistance to race 1 of Kabatiella caulivora in subterranean clover (Trifolium subterraneum L.) cultivars and breeding lines

Twenty-eight cultivars and 106 F-6-derived breeding lines of subterranean clover ( Trifolium subterraneum) were screened in the field for their response to clover scorch disease caused by race 1 of Kabatiella caulivora. Eleven of the cultivars, including Denmark and Goulburn, were classified as resistant. Breeding lines with Denmark parentage had 55% of progeny with resistance, while those of Goulburn had only 19% of resistant progeny, suggesting different modes of inheritance. Selection for resistance to race 2 of K. caulivora in the F-4 generation markedly increased the probability of selecting F-6-derived lines with resistance to race 1, suggesting linkage between genes for resistance to both races.