The term vertical resistance was first used by J.E. Vanderplank to describe single-gene resistance. This contrasted the term horizontal resistance

Horizontal resistance

In genetics, the term horizontal resistance was first used by J.E. Vanderplank to describe many-gene resistance. This contrasts with the term vertical resistance which was used to describe single-gene resistance. Raoul A. Robinson further refined the definition of horizontal resistance...

 which was used to describe many-gene resistance. Raoul A. Robinson

Raoul A Robinson

Raoul A. Robinson is aCanadian/British plant scientist with more than forty years of wide-ranging global experience in crop improvement for both commercial and subsistence agriculture...

  further refined the definition of vertical resistance, emphasizing that in vertical resistance there are single genes for resistance in the host plant, and there are also single genes for parasitic ability in the parasite. This is a very important phenomenon known as the gene-for-gene relationship

Gene-for-gene relationship

The gene-for-gene relationship was discovered by Harold Henry Flor who was working with rust of flax . Flor was the first scientist to study the genetics of both the host and parasite and to integrate them into one genetic system...

, and it is the definitive character of vertical resistance.