Who advanced the gene for gene concept of disease resistance and susceptibility

Flor advanced the gene-for-gene concept of disease resistance and susceptibility.
In 1942, Harold Flor deduced that a single gene of this fungal pathogen was responsible for the ability of the fungus to cause disease on the flax plant.
He also determined that this gene in the fungus corresponded to a particular resistance gene in the flax plant. This interaction was called the gene-for-gene theory.
It states that (specificity) genes in the pathogen that determine pathogenicity have a one-to-one corresponding match to (specificity) genes in the host that determine resistance.