Host-Parasite Interaction in Flax Rust—Its Genetics and Other Implications

Cultures segregated for pathogenicity, the ratio of avirulent to virulent cultures approximated the 3:1 expected if virulence on each was conditioned by a pair of recessive genes. On Ottawa 770B, 2 pairs of genes may have conditioned pathogenicity. Fifty-four pathogenic races were identified from the 67 cultures. Host-parasite interaction in flax rust may be explained by assuming a gene-for-gene relationship between rust reaction in the host and pathogenicity in the parasite. Pustule type, the criterion of both reaction and pathogenicity, is conditioned by specific pairs of genes, one in the host and the other in the parasite. In flax and the flax rust fungus, 25 such pairs of genes have been identified.…