The breakdown of vertical resistance due to the development of a new physiological race is

The breakdown of vertical resistance due to the development of a new physiological race is the Vertifolia effect.
The Vertifolia effect is a well-documented phenomenon in the fields of plant breeding and plant pathology. It is characterized by the erosion of a crop's horizontal resistance to disease during a breeding cycle due to the presence of strong vertical resistance, characterized by the presence of R genes.